: 500 V864 - is this even theoretically possible?

07-08-04, 12:02 AM
This might be a crazy thought, but since the 368 V864 and the 500cu in Cadillac engines are of the same family, I wonder if it is even remotely possible to take a 500 block and use the 368 valve solenoids & covers, along with a throttle-body fuel injection system & '81 DFI computer and make a 500 V864? Would the main computer even notice a difference to make it not work? If this worked, I would think you would have plenty of power in an 80's Fleetwood or Deville and still get some gas mileage when all that power isn't needed. Heck, the thing might even have some power in 4cyl mode without having to switch back to 6cyl when encountering a slight breeze! Is this crazy or possible, and do you know of anyone who's tried it???

07-08-04, 05:00 PM
Yes it is crazy, but it's that good kind of crazy!

I have no idea if it would be possible but it sure would be fun to try. I hope you get some good input on this question because you have my curiosity raised now as well.

Steve B.

Night Wolf
07-09-04, 12:03 AM
yeah, that is definitly something to look into more... I can see it now:

"yeah, not only does this 8.2L, 500 cubic inch big block Cadillac have 400hp and 500ft lbs of torque.... but with variable displacement, I get 30mpg on the highway with a 3-speed auto..... yeah, sucks that your hybrid gets only 10mpg more then this beast.... "

those numbers are very easy to get on even a mild build from a 500 too :D

08-04-04, 06:36 AM
Firing order will be a problem.

08-06-04, 04:22 AM
It's just a solenoid that releases the pivot point of the rocker arms so the valves stay closed. The mechanics there aren't a problem. I don't know anything about the computer control of this system, so I can't comment there.

In an article in a 80 Popular Science it says highway economy jumps from 16-18 to 24-27. That translates to 19-20mpg highway if a 500 was done the same way, which is pretty damn good.

08-17-04, 10:33 AM

08-17-04, 10:42 AM
This subject came up on the mts board awhile back. That person was considering using a switch to control the solenoids. Also GM's new "displacement on demand" engines go directly from 8 to 4, they say it's much simpler, smoother and easier on the engine. One complaint that many owners had about the v8-6-4 was that the engine vibrated a lot in v-6 mode, so they eliminated it in their latest variable displacement system.
I believe all 368s used stud-mounted rocker arms too, so that may be a problem. I don't know if the v-8-6-4s did this, but GM's new system closes both valves on the deactivated cylinders, so when the pistons rises with both valves closed, it compresses the air trapped in that cylinder, which pushes on the piston when it starts going back down, which helps turn the crank. Otherwise, the "extra" pistons and rods would just be along for the ride, making the other cylinders work harder. I don't mean to lecture, I just find this subject extremely interesting!

08-17-04, 09:26 PM
I have been looking into this for a while.

Food for thought, maybe we can put our heads together and come up with something....

1. You can open an exhaust valve full time in 4cyl mode and pump fresh intake air in the exhuast. (how much reversion will occur?)
2. You can open an intake valve and keep the exhaust closed and pump air in the intake. Might be confusing pressures in the intake, but then again, a internal supercharger?? Hmmmmm
3. You can keep them both closed. Pump vacuum...
4. You can close only the intake valve (like GM does).
5. You can create a bypass channel that vents the cyl through the head into the exhaust.
6. Use the Sturman Digital Valve and electronically control the valves (my choice!), but lots of design work here! Fancy ECM, and you get bet you will be dealing with patent issues.

On the valve idea of #4, look at a rev kit, and then create something to move out of the pushrod path so the valve doesn't open, but the rev kit will keep the lifter in the bore.

Maybe some sort of way to "unscrew" the rocker arm nut like you were taking the rocker off. Again, need to hold the pushrod in place and keep the lifter in the bore, using some modified rev kit or something.

A channel bypass valve with a solenoid control to open and close the bypass port when going into 4cyl mode. Still need to cut fuel to those cyls. So either EFI or butterfly valves in the intake would be needed. Don't need anything big, just something to be able to withstand normal combustion temps and pressures when driving normal, and then to open and bypass the air as the piston comes up. Head mods here, but this may have some benefit too in being more standalone and not mess with the pushrods/valve/lifters.



08-17-04, 09:28 PM
864's work by having the solenoid release the fulcrum of the rocker arm, and the valves stay closed. With a 500, you'll probably have enough power even in 4cyl mode that it would be more possible to drop 6cyl mode.

08-18-04, 12:04 AM
864's work by having the solenoid release the fulcrum of the rocker arm, and the valves stay closed. With a 500, you'll probably have enough power even in 4cyl mode that it would be more possible to drop 6cyl mode.

i think that would be very fun to build this type of engine
and put it in some kind of street rod or classic truck.
but insted of going with the dfi use a carberuator !,
and find a carberated 368 and swap heads, and make some kind of switch set up to activate the solenids,
that might work. :lightbulb

08-20-04, 01:34 PM
I think it would be better for both valves on the deactivated cylinders to be closed at all times. That way, the compression action would overcome the enertia generated by the weight of the rising piston and rod, then the compressed air will push the piston back down, rather than the crank having to pull it back down. The effect of all these things combined would be that the engine would not "know" that it has four "extra" pistons and rods hanging on the crank, it would not "feel" their weight, therefore, even greater highway fuel efficiency.

08-21-04, 05:33 AM
The problem with building an engine like this is that the solenoid actuated rocker arms are on 368 heads. I've never seen the heads up close, and have no idea if it would be possible to run the rocker arms on a 500 head, another idea would be to run a 368 head on top of a 500, 368s only have a 4.057" bore, but 425 heads (4.082" bore) have been run on 500s before, the valves are smaller than stock 500 valves, so high end performance would be diminished. Not to mention I don't know the volume of the combustion chambers, so compression will be affected.

08-21-04, 10:50 PM
Maybe the valvetrain could use something similar to Potter's stud mounted rocker system.
Everything on a 368 head is tiny compared to a 500 or 472 head. I think the chambers are 66cc but I'm not sure.

08-21-04, 11:32 PM
I have seen these heads up close at the junk yard on a 1981 eldo
and i took the solonoids off they are only held on with 2 bolts ,
i wish i had pics to post but i dont,
the push rods appear to be the same length and size as the non solonoid valves .
i dont think it will be possible to mount the rocker arms from the 368 on the 500 heads(no bolt holes cast on the heads)

hope that info helps,

10-23-05, 11:23 PM
I found an idea to address the mounting problem for these rockers on Al's site here is what he said:

"I just took a quick glance at both style heads. My first thought would be to start with a set of castings with no A.I.R. hump down them. #552 or #950.
Then I would look at machining down the height of the stock rocker mount pads. I would install a moly bar straight across all the lowered rocker pads.
Drill and tap new bar to accept the original V4-6-8 rocker assemblies.
Mount sytems styled like this have worked for many aftermarket Cad rockers. They work well."

Has anyone been successful in mounting this system yet? - Justin

terrible one
10-23-05, 11:45 PM
So this could actually work...sounds like a great project! I am really excited to hear your progress! Are you going for it?

10-24-05, 03:37 PM
Ya this could work, and you could save alot of gas in the process lol. I am trying to find out more info so I can try it on my 484. I wonder if anyone has been successful in converting this setup to their 472/500? It would be a sweet setup. I also was wondering if you could rig it up on a switch to kick it into v4 on the highway. - Justin

10-28-05, 03:57 PM
Not Sure If Anyone Is Looking But I Know Of A Running 1981 Coupe With The V8-6-4 For Sale In Pa For $300. Also Just Saw A V8-6-4 Motor Only On Ebay For A Buy It Now Of $75.00 And You Pick Up

10-31-05, 09:57 AM
I love the idea, love to hve it in my car!

11-01-05, 06:06 AM
A bunch of guys on the CB7 board have been discussing this and looks like one's going to try it. We'll see how that goes.

terrible one
11-01-05, 07:32 AM
Yeah they sure are. I really hope he does try it.

11-14-05, 09:55 PM
Just a quick mockup to see if mounting the 368 valve train is feasable to a 425/472/500 engine. Non A.I.R. heads will be a bunch easier because of more clearance.

Night Wolf
11-14-05, 10:11 PM

someone is making it work!


dosn't the 425 use a T-pedistal while the 368 had 2 bolts? THAT is what I don't understand.... how did you get them swapped over?

The only parts I have from that 368 are the 4 selonoids, IIRC the rocker arms that go with them, and the valve covers... no pushrods, or none of the other rocker arms etc... that was back in NY and I doubt that car will be there if I ever go again.... so I sure hope I have enough parts.

Can you please go into more detail...

I remember I was told there was no way those will fit the 425/472/500 heads because they use 2 bolts vs 1 (or visa verca) and that another hold would have to be drilled and tapped in the head.... but it looks like you are doing it pretty easy....

Night Wolf
11-15-05, 12:50 AM
Thanks! I'll defintly check that out tomorrow.... getting late now :)

good stuff....

11-17-05, 12:39 PM
I Have A V8-6-4 Car That The Motor Will Be Coming Out Of Very Soon!!! If Anyone Is Looking For Parts, Computer, Whatever. Also Have A 1982 Coupe With A Knocking Buick V-6 Up For Grabs, Body Is Excellent Missing Grille Insert And Trunk Lid Is Dented. And Last But Not Least Have A 78 Sedan Minus Motor, Trans, And Driveshaft If Anyone Needs Any Parts Off Of That One Let Me Know And I Will Check Them Out, Previous Owner Began To Disassembly With Extreme Disregard Under The Premise Of Building A Demo Derby Car. Interior Not Too Busted Up For The Year, Door Panels And Seats Good, Light Blue Leather. Call Rich 484-695-0944 In Eastern Pa.

Night Wolf
11-17-05, 05:13 PM
Eastern PA, damn, why can't I be in NY again.

'82 Coupe with the Buick V6? that is RARE!

how much of the '78 sedan is trashed, whats left and what is the interior color? do you have pics?

About the V8-6-4, if nobody else will grab them, I would be interested in the 4 selonoids and both both covers, all the rocker arms and hardware that goes along with them too..... BTW does it run? why is it coming out of the car?

11-17-05, 06:26 PM
Remember to also get the spacer for the aircleaner or else the snorkel will hit the valvecovers.

11-17-05, 09:47 PM
78 sedan - just took a close look at it basically the interior is all that is good they knocked the mirrors off with a crowbar and just banged up just about every panel on it

82 coupe - grill and trunk lid will be taken off, motor knocks and trans is "iffy" another trans with it listed in classifieds as well

81 coupe- just the v-8-6-4 for sale it idles perfect but has no power on road, was going to check into timing and 8-6-4 setup malfunction but found the 425 instead
email me for pictures at a19chevelle70ss@aol.com

01-12-07, 07:28 PM
hey everyone im new to this forum (im on lincoln vs cadillac) i have a 71 eldo 500. and i intend to do the cylinder deactivation idea. i have been to the junkyard and have started taking heads off of an 81 368. i can also compare these to what i believe is a 500 in the same lot. does anyone know if the 368 heads can be ported by any reasonable amount and or if the valve diameter can be increased it dosnt look like there is much room to work with. the compression will be too high im assuming if u just bolt them strait on, so i will see if using two gaskets and or using different pistons will fix this im goin for 10.5 to 1 if i can. any info would be appreciated thanks

01-13-07, 04:58 AM
I honestly doubt anyone has seriously looked into 368 heads in terms of performance.

01-13-07, 05:35 PM
i posted that message before i saw what CLAY88 did with his adapter plate. i dont have enough privlages to send private messages yet. if you see this CLAY88 please tell me if you think 1970 AIR heads from an eldo could be used. i will try to find some pictures of some if u need them
Also does anyone know if anything was done to address the fact that if the valves are deactivated right before the spark plug fires the mixture will ignite and not escape(ouch) or did the computer deactivate the hei for a split second or some other thing to counteract this or does it not matter if this happens? any input greatly appriceated.

01-14-07, 06:07 AM
If that happens it will just be a compression stroke instead of an exhaust stroke and will act as an 'air spring.'

01-14-07, 10:41 AM
yeah ur right, i wasnt thinking about it right thanks also i found out there was no AIR in 1970-68 so i wont worry about it. but im still interested in the adapter plate. i havnt been able to find one online yet

01-20-07, 05:45 PM
alright everyone. I am going to do install 368 heads on my eldo 500 to achieve the 4 cylinder mode. because as of now the adapter plate is still a prototype and i got the heads cheap.

to get the right compression, i am going to use multiple gaskets that will have a sparse layer of jb weld between them. if necissary i will make extra thick intake gaskets out of cork. it wont perform extremely well but i might just have the same power i started with because i have 120 cc heads @8.5:1 compression and even with my many gaskets i will have a gitch over 10:1. so althought ill have smaller intake and exhaust, ill have more compression.

anyway on the 368 heads there are these spacers between the spark plugs and the heads. they make the spark plugs stick out alot. u cant see the terminal from inside the champer just a hole in the funky spacer thing. Does anyone know what these are? for some reason the 81 engine was Inundated with sludge, any one know about that either?

Ted in Olympia
01-21-07, 11:31 PM
What cc do 368 heads have?

I think it will ping like crazy with double head gaskets.


01-22-07, 10:42 AM
368 heads have 66 cc heads 68-70 500 heads have 76 cc heads im seeing how much a machine shop will charge to make the valve tgrain adapter if they want more than i got im gonna use the 368 heads i just want it so that i can use 93 octane (or less, haha)
no one knows about the funky spark plug spacers?

Ted in Olympia
01-22-07, 08:40 PM
66cc wow! This is going to be hard to run on any pump gas and if you use double gaskets the quench will be terrible.

The 68-73 engines had the 76cc heads. I would think if you want to do this, and I think you put a lot of thought into it, it would be best to start with a 71-73 500 engine with 76cc heads and 8.5 to one compression. Or you can get these pistons for your engine.

I have not seen 368 heads but I heard the ports are very small. If you get a chance to cc the intake and exhaust ports it would be interesting.

For the 500 with 120cc heads the intake 184cc and the exhaust 120cc


01-22-07, 10:54 PM
as far as i knew the 76cc heads are from 68 to 70, and are 10 to 1 compression im told that ihave the 120s that the motor came with. any way i was wondering about the quench. that is a good point. but until i know it wont work, i still am tempted to try it because i asked a couple machine shops how much adapting the valvetrain with a plate (like clay 88 is trying to do) would cost, 500 bucks or more. the cost of trying the heads is 115 bucks. unless someone thinks it will explode or something as far as i know if it dosnt work it will make bad noises and run bad mabey pop a gasket but will this damage anything other than the heads? which are expendable

01-23-07, 04:52 AM
If the quench is bad it will knock and could trash the whole motor essentially. If you had an older motor that came with 76cc heads (68-73, ted is right) then you could try the 66cc heads on premium pump gas. If you have a 74-76 motor with 120/126cc heads you better try running E85 or straight alcohol (which means carb work) or it will pop.

Ted in Olympia
01-23-07, 08:37 PM
The 71-73 came with 76cc heads but had a large dish in the piston to bring the compression down to 8.5. So if you started here you would be safe with pump gas. I have a couple of 71 to 73 engines around here if you were in the Northwest.


01-24-07, 12:12 AM
HAA! thats great. now knowing that i looked up what the dish was in ccsfor 71-73, its 47ccs. plugging in this new information into an online compression calculator means the compression from the 66 cc heads gives me9.3 to 1 compression. well within a safe range and i dont have to use more than one gasket. i wondered why it was being so hard... thanks for your help it makes more sense now guys

although i am confused about one thing thats a side issue.... if i have 8.7 compression why does the sticker say to use 91 fuel? it used to be my grandfathers car he says he used to put cheaper stuff in and it was ok but i was afraid to try it. no i wont be leaving texas for awhile yet

01-29-07, 02:13 AM
no one knows about the funky spark plug spacers?

This discussion is way over my head, but the first thing I thought of was anti-fouling spacers. I guess they help by sparking outside the compression chamber? I think I read about them when researching engine knock.

02-04-07, 09:18 PM
ok guys the head and exhaust gastkets will be here in a couple days and that weekend i will install the 368 heads and deactivation hardware. and then.....well see

02-09-07, 03:25 AM
Keep us posted.

big block fiero
02-12-07, 09:50 PM
I have tried this deactivation concept on my 500 powered fiero.what happened was my engine is built with .519 lift. The 8/6/4 rockers have a shutter that locks out the movement of the pivotal axis on the rocker arms. That shutter from locked to unlocked allows a pivotal axis varience of only about 1/4". to make this work with the 1.6 ratio rocker i would have to limit my valve lift to about .380 wich would trash my total horsepower production.

so to keep it simple I cut the throttle shaft on my two barrel throttle body.I shut off four injectors to one plane of the dual plane manifold then open just one barrel of the throttle body.

displacement on demand as done recently by the carmakers does so by changing oil pressure at the lifter. these lifters allow proper funtion with a greater amount of valve lift. if you were to try a cam with more lift this system would malfuntion as well.

Your lift will allways be governed by the design of the deactivator travel.If you try to get to much out of it the valves wont shut to create the air spring.At that point you may as well do what i did wich may not offer the fuel savings you were expecting. Mine also has purpose for the car to sound like it has a four cylinder motor because my 500 caddy motor is concealed and the car looks stock.

02-13-07, 08:21 PM
so to keep it simple I cut the throttle shaft on my two barrel throttle body.I shut off four injectors to one plane of the dual plane manifold then open just one barrel of the throttle body.

Hmmm, interesting. Let us know how that works. Just thinking through the basic physics, I don't think it will work as well as leaving the valves closed.

I noticed that the V8-6-4 system would limit total lift when I was looking at it first. Have you tried disassembling it to see how much room there is to alter the deactivation part? It is possible that you would be able to modify it to accept greater lift by grinding the slots deeper on the bit that is rotated by the solenoid.

Another idea is to run it on all 8. Make it kinda like variable valve timing. Your lift would be substantially reduced and valve timing as well. Only thing I would worry about is that the rocker would be slamming into the deactivation parts since the valve would only start opening mid-way through the cam ramp when the lifter is really moving. Basically you'd be bypassing the opening/closing ramps on the cam like having the valve lash super-loose. It's a thought, but use at your own risk...

big block fiero
02-13-07, 11:45 PM
It is true that my deactivation method doesnt create a good air spring hence not able to deliver the fuel economy of a system that closes the valves. If someone figures out how to increase the travel (ive studied it and it would be a tough complex job) I would like to purchase a rocker set and i have cores.If theres enough travel there would not be any slamming effect when the valves are closed making an air spring and with the valves turned on the motion would use the ramps of the cam.

The Ape Man
02-17-07, 09:54 AM
Mine also has purpose for the car to sound like it has a four cylinder motor because my 500 caddy motor is concealed and the car looks stock.

Why not use a large sound system with a recording of a Honda with coffee can exhaust? Put a couple Electrovoice horn speakers in back of the grille.

big block fiero
04-08-07, 08:40 AM
I have discovered that altho the fulcrum travel is only 1/4" that is enough to accomodate .520 lift and even a little more so I am back on this project with the airspring feature as of 4/8/07

04-09-07, 10:38 PM
I actually own an 81 Coupe DeVille with the V864. If you can get everything to fit mechanically you'll have to find someone to hack/reprogram the ECU. When it goes into 4 or 6 cyl modes the dead cylinders do act like an air spring. After one full 4 stroke cycle finishes then it operates like an air spring.

6 cylinder mode does indeed shake a little bit, but with bad motor mounts it feels much worse. They couldn't do much for the balancing in 6cylinder mode.

The system monitors engine load and speed and the 3rd gear switch on the transmission. Most people that hate the system put a switch on the dash that breaks the circuit to the switch on the transmission as the system will only operate when it's in 3rd gear.

The other problem is fuel metering - with more displacement you'll need more fuel. The ECU also compensates for different cylinder modes (it lowers the amount of fuel being delivered depending on which mode it is in) so that would have to be reprogrammed for the displacement as well. This is why I mention reprogramming the ECU.

Edit: The best mileage I've recorded was 24.3 MPG on a 600km trip. My last trip I was a little more heavy footed and I still kept it around 19-20MPG.

04-10-07, 06:59 AM
Actually, any modern fuel injection system shouldn't have much problem handling the cylinder shutdown. If you switch off the ground wires to the injectors that feed the deactivated cylinders then there will be no fuel going there and the computers feedback system (through the O2 sensor) should manage injection to the remaining cylinders and keep the mixture correct. Of course, this system would rely on a manual switch to go into 4 cylinder mode. I think that everybody converting to this has given up on the 6 mode, as has GM with their current cylinder deactivation system. There are vacuum switches available though that could make the system automatic if one wanted to work with that. Look for a torque converter lockup kit.

04-10-07, 08:02 PM
The system on my '81 is far from modern... throttle body with 2 big injectors... I doubt that it just turns one completely off.

Most modern fuel injection systems will balk if you break the circuit at the injector. They'll set a failure code and go into limp-mode. I wonder if aftermarket EFI could be programmed to deal with this.

There are set limits that the ECU can adjust the mixture. Outside of that the fuel maps need to be reprogrammed. We're talking a fairly large jump in displacement for the stock system (368 -> 500) so it wouldn't run properly. That's all I was saying.

04-11-07, 07:41 AM
Who's talking about using the stock injection system? I had thought pretty much everyone wanting to swap on the cylinder deactivation system was using a carb or aftermarket EFI anyways and a manual switch for deactivation. You are right about the factory EFI being pretty poor on that car (slow processor speed), and that is one of the big reasons attributed to the system not being very successful. Obviously the deactivation idea is quite valid as it is widely used today (finally!).

Cutting out half the injectors would definately set an error code, but the rest of the computers inputs would still register in the normal range so it should be able to cope just fine. Most error codes do not trigger limp mode, which is why you see so many people driving around with a check engine light that comes on occasionally and never do anything about it (not that I advocate this!) The GM ECU's are pretty throughly hacked, so adapting a system off of a TBI equipped truck (the 454 motors would be ideal) to a Caddy would not be that big a feat and has some distinct advantages over an aftermarket EFI system.

If using TBI and you limit it to 8-4 operation. Just cut one injector - the way a dual plane intake is made each injector feeds four cylinders. The four that get cut are either being fed by one plane of the intake or the other. So in 4 cyl mode you would just have one side of the intake go 'dead'. No air would be moving through it (valves closed) and no fuel in it (injector off). This is why I say that the original system probably cuts one injector (under four cylinder operation). It is the absolute easiest way to achieve the goal. The fuel requirements of the other four cylinders have not changed at all, so the original map should be fine. If things are slightly off, the O2 sensor will tell the computer and it should trim mixture accordingly.

Six cylinder mode would be difficult to achieve with TBI (aside form the '81 system) because you would want to run one injector normally and the other at half rate. But the computer on most TBI systems wouldn't know this, so it would be running both injectors at 3/4 rate and two cylinders would be running with 50% more fuel than they need and the other four would be getting only 75% of what they want. Pretty crappy way to run. Probably could be fixed with some programming wizardry, but note that the modern deactivation systems have dropped the six mode entirely.

For point injection, the principle is the same but here 6 cyl mode could actually be achieved easily except for that pesky vibration thing. You cut air and fuel to two or four cylinders and the other cylinders really don't know what has happened. They are still drawing in their air charge and getting the fuel they need because the computers feedback system keeps the a/f ratio correct and fuel is being injected to each cylinder individually instead of to groups of cylinders.

04-11-07, 07:30 PM
Eh, I thought someone mentioned the stock system. My memory sucks bad though, and I don't feel like reading the last 6 pages of posts to find out.

In the case of using a different EFI on the car and cutting the circuits to the injectors, may as well put a piece of tape on the check engine light. :)

05-06-07, 01:02 PM
ok guys sorry i havn't posted in a long time.

i was going to simply install the 368 heads i have onto my 500 so that i could try 4 cylinder mode (sure it wasn't going to have as much power but i had to try) but i ran into a little problem

the gaskets for the 368 heads leave some of the gasket exposed to direct flame because the 500 bore is so much bigger and the 500 gasket doesn't cover up some of the water jacket passages and burning lots of water doesn't work so well

so does any one know 1. if the gasket will handle open flame?
2. if i could make it do this somehow how long

3. where can i get some custom gaskets made without spending a fortune(is there a way to make your own?)
4. if there has been any progress made with the adapter plate to allow this hardware to be put on 500 heads

5. how does this system work( i know how it works in principle but i cant see how the solenoids keep the valves from opening i just dont want to spent money on blind faith i want to see how this functions

any input appreciated thanks

05-07-07, 11:21 AM
I'm not sure I can help on the headgasket, but I do know that some engines have copper headgaskets available. It seems that a copper gasket could have the bore cut out larger. The downside is that I have heard copper gaskets are more tempermental to sealing - they want a very flat surface, some sort of sealer is usually used and retorquing the gasket may be necessary.

As for the rockers, it's pretty simple. Look carefully at the fulcrum of the rocker arm and specifically the part that is turned when the solenoid engages (you can push it in by hand) and the slotted plate beneath it. Under normal running, the raised areas on the part controlled by the solenoid line up with the solid areas of the plate beneath it so the rocker functions normally. When the solenoid rotates the part, the raised areas come over the slots in the plate beneath it. When this happens, the fulcrum of the rocker arm is free to move upwards when the pushrod moves upwards. What happens is that the entire rocker arm pivots at the valve tip and the valve never sees enough pressure to open it. There is a reasonably strong spring at the rocker funcrum so it is a bit hard to do this by hand, but that spring is needed to provide some downward pressure on the lifter so it stays in its bore.

06-03-07, 11:30 AM
well i figured out how to get the 368 heads not to leak water but it is a moot point because i have been told ( and suspected) that they will create so much pumping loss that i wont just lose power ill be losing mileage as well.
it looks like making the system work on 500 heads is the only way.
oh i read this and as i understand it, it wont work

"If using TBI and you limit it to 8-4 operation. Just cut one injector - the way a dual plane intake is made each injector feeds four cylinders. The four that get cut are either being fed by one plane of the intake or the other. So in 4 cyl mode you would just have one side of the intake go 'dead'. No air would be moving through it (valves closed) and no fuel in it (injector off). This is why I say that the original system probably cuts one injector (under four cylinder operation). It is the absolute easiest way to achieve the goal. The fuel requirements of the other four cylinders have not changed at all, so the original map should be fine. If things are slightly off, the O2 sensor will tell the computer and it should trim mixture accordingly."

in saying that the requirements of the other 4 cylinders havnt changed you are correct but the dual plane intake feeds the right and left side separately, right? But the engine makes a v4, not an inline 4 in deactivation mode so cutting off one whole side would mess it all up. i would go with a carb but im using port efi for other reasons so now i have more to deal with but it shouldn't be too hard, once i spend alot of money that is hehe

06-05-07, 09:14 PM
but the dual plane intake feeds the right and left side separately, right?

Nope. The dual plane intake feeds every other cylinder in the firing order from each side. Basically, it works perfectly for how the V4 mode is implemented.

06-06-07, 12:09 AM
upon closer inspection, it seems i am wrong. it does seem that the intake feeds the cylinders in that manner. i stand corrected.

The Ape Man
06-07-07, 04:29 PM
This thread has been going on forever. You folks have reached the BIG issue. All the factory intakes will not behave properly in the 4 cylinder mode except for the factory 8/6/4 intake. Take a look at one sometime. Quite interesting as are the exhaust manifolds. You want performance from a 500 and then economy by making it a 250. That cannot be done with the big intake. One has to suffer. Either use the puny plumbing from a 368 or the stuff from a 500. Of course the 368 intake will limit power with the 500. Maybe there is a way around this... Another issue is to see exactly what the modulated displacement does to modulate the EGR valve while activating cylinders. A very nasty ping happened on 8/6/4s when cylinders were turned on.
Seems like an overdrive transmission would be a proven way of increasing fuel economy and making it pay off. Still it would take a long time to recoup all the $$$ unless it is a daily driver.

06-08-07, 12:50 PM
All the factory intakes will not behave properly in the 4 cylinder mode except for the factory 8/6/4 intake.

My 472 intake feeds cylinders 1-6-4-7 off one 'plane' of the intake, which are the same cylinders that are running in V4 mode. Since I have not milled down the center of my intake, the venturis on the other side of the carb will not see any air flow and thus not dispense any fuel so I don't see what the problem would be. Whenever I have seen a V864 car in the junkyard, the intake looks like a dual plane TBI intake, so if you have some special knowledge about "secret passages" that GM cast down in there please share!

The Ape Man
06-08-07, 03:08 PM
The factory 8/6/4 intake is designed to feed 4 cylinders and be fuel stingy. The 500 is designed to feed 8 with cruising economy. Not too much rocket science needed. You cannot simply drop draw to half the cylinders and expect the best design to look the same. It looks the same in at the junkyard? Well it isn't.
The 368 intake ports are much smaller. Have you ever seen the inside of a 368 exhaust manifold? Those are quite a bit different than the 425/472/500 also. The theme is keep flow velocity up at lower flow rate. As I said, the FI 368 intake makes a lousy performance part on a 500. The whole idea here is to start out with a large engine and cut it back for gas mileage. In doing so the performance will be severly degraded is using a 368 injected intake. The 4 cylinder economy will be lost is using a 500 intake.
Maybe someone will actually get one up and running and post results. I'm not holding my breath. This thread is almost 2 years old, not the first one on the subject and nobody has one on the road yet.
Maybe someone can actually prove me wrong by building instead of typing.

06-09-07, 11:22 AM
Disagree on your reasons. The 368 intake and exhaust has to have smaller runners whether it uses a V864 system or not. It is simply a (much!) smaller motor and using the 472/500ci intake in a stock application would diminish throttle response and low end torque.

The beauty of shutting down cylinders is that the draw is NOT reduced it is INCREASED, and this is why economy is increased. A 500 (or 368) cruising down the highway only needs to make a very few hp to keep the car rolling. To make so little power out of such a huge engine takes alot of throttling which means that the actual pressure inside each cylinder is very low. This hurts efficiency tremendously. When you cut 1/2 the cylinders completely out of the picture you have to *increase* the throttle opening to maintain the same total power output. In fact, I'd say that the power produced *per cylinder* from the operational cylinders should roughly have to double. This means less throttling on the operational cylinders, higher cylinder pressures and more efficient combustion leading to your economy gain. What this means on the intake side is that the runners which are still being used will see more airflow than they usually would while cruising.
No, I wouldn't expect four cylinder economy out of a 250ci because 4.1L is more the size of a large V6 and equal to alot of modern V8's. But, if I could gain even 1-2mpg that is a big gain when I get 10-15mpg right now. No, I don't expect it to pay for itself, but that's not the point. If I cared about cars paying for themselves, I wouldn't have fixed the AC, added Guidematic headlight controll, fixed the cracked taillight lens or switched to a leather interior - I'd be driving a 15 year old Metro that I bought at an impound auction. This is a hobby for me and I want V864 on the car because it would be cool and it would be even cooler to have a beautiful car like this that hits 25mpg on the highway one day so this is just one piece of the final goal.

While I agree that I can't find evidence that anyone has actually driven a Caddy with a retrofitted V864 setup, there is a member on "the other board" who has successfully mounted the 368 rocker setup to 472 heads. Last I read there he was working on EFI to go on it. Personally, I'd run it with a carb and work out EFI later but that's his choice. As for myself, I recently graduated college so I will soon be getting a real paycheck and can start affording the machine shop bills to adapt the system to my own set of heads.

Still, sitting around writing that you don't think it will work and giving very few details on why is not the right kind of attitude to take. I've got a mechanical engineering degree, so please don't worry about confusing me with technical details. I have no problem with your opinion, but please elaborate on any problems you see so that those of us who do think it will work can overcome them.

The Ape Man
06-09-07, 08:08 PM
Thanks for the narrative. I almost forgot about how the whole thing worked. Sorry you don't agree. If anyone ever gets one of these going then maybe someone will start looking at intake manifold designs for V engines and what would happen if 1/2 of the pulses were no longer there. Hint: This series of engines ran much better with port injection as the intake manifold runners ran a long way uphill. V engine intake manifold design includes more than getting the mixture from the carb flange to the intake ports. Balance in extremely important. Each cylinder should see similar flow velocity. As proven in engine tuning circles, flow and balance is a major factor in performance and economy. I'm saying that an intake manifold designed to work an 8 or 4 cylinders at 6 liters will not also be able to deliver reasonable performance at max throttle on an 8 liter engine and vice versa. You are pretty close on the 1 or 2 MPG figure. A good guess. That's about what the system was good for on a steady roll at 60 MPH. We can both "sit here" and pontificate for another 2 years. The answer will only be a byproduct of someone actually getting one of these working. I can design a perpetual motion machine and convince a whole bunch of people to by stock in my company. Stranger things happen every day. Too bad about that nasty conservation of energy rule.
Congratulations on your degree. Please take it easy on some of the older, experienced engineers that you might be working with. Those guys might not seem to know anything at all for the first few years.

09-02-12, 12:48 AM
Digging this back up. After years of looking i finally scored some v864 parts from an 81 cadillac i found at the junkyard today. Incase anyone hasn't seen this there is a guy in Sweeden named Peter from the cadillacpower forum that pulled this off years back. The guy is getting some pretty good gas mileage with this setup and from what I've heard it's possible to get 30mpg from a 500 with this setup and properly turned EFI. This is going on a future build of a 500 that I have but definitely the hardest part seems to be fabricating an adapter plate to get these rockers to bolt up.


09-02-12, 12:58 PM
I'd like to see more people doing it. I got a set of parts too, althought I don't know if I got everything I would need. All I took were the solenoid assemblies and the valve covers. I wonder how high you could go with a 425, port injection, and a super high overdrive to get the rpms down close to 1,000 - 1,200 at 65. Or maybe 55 would be better since you wouldn't want to go lower than 1,000 I would imagine. And what if you could do it with a #10 cam. Now I'm likely dreaming...

09-04-12, 11:12 AM
I wonder how high you could go with a 425, port injection, and a super high overdrive to get the rpms down close to 1,000 - 1,200 at 65. Or maybe 55 would be better since you wouldn't want to go lower than 1,000 I would imagine. And what if you could do it with a #10 cam. Now I'm likely dreaming...

These engines ( at least the 425 ) operate more efficiently at a constant between 2000 - 2500 rpm, within the "cruise" range. Engine speeds below that, and efficiently suffers because of the loads on the engine. Installing overdrive will move this engine out of it's cruise range.
There is now another option, converting to natural gas. There is a company that makes conversion kits, but I don't know how one would adapt NG to these engines. I have seen the advantages of using LP propane in a internal combustion engine and thought that was astounding. NG would be an advantage along the same lines.

09-04-12, 11:55 AM
I see a lot of people say that about the cruise range, and I understand, but then I wonder, whats the best cruise range for the car as a whole? I mean, if you're just on a flat or going down a hill, without much load, wouldn't it still use less gas at 1,200 even though it's a less efficient rpm? Even without variable cam timing, ls engines for example can cruise as low as 1,500 or 1,600 and get great mileage, and I doubt that's their peak efficiency rpm. Or maybe it is.

09-05-12, 10:07 AM
Never having been to Sacramento, I'm not sure what terrain you have there. Here, in the Berkshires, we have hills, so engine load is a constant variable. These engines are more efficient on I-90 where engine speeds are in the 2000 - 2600 range. When traveling on local roads, I can get better fuel efficiency on roads that allow higher engine speeds at more of a constant. I might not have to stop as often, due to intersection stop lights, on the secondary roads, but gas mileage will suffer due to pulling the car weight up small grades out of it's cruise range.

The Ape Man
09-08-12, 04:49 AM
The 500 cruises great at 1200 RPM geared to 60 MPH.

30 MPG out of a 500? Please. The 6 litre DEFI modulated displacement never got even close to that. Maybe in an aerodynamic 2,000 Lb vehicle.

The guy on utube had really high compression and alternative fuel. A 500 runs really well with high compression and will idle slower than the alternator will start charging if adjusted that way.

09-08-12, 06:56 PM
On his website - which is hard to find - he claims to have gotten 27 mpg on gasoline. Could have meant imperial gallons, but maybe not.