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139K views 238 replies 45 participants last post by  Capt Fiero 
#1 · (Edited)
Okay folks, it's getting close to crunch time with the turbocharger...Had you thinking, huh?

Anyways, this project is still a little off from actually starting, but I now have most of the pieces in place for the project to begin.

4.9 turbocharger, stage one indicates that the turbo will be placed on an existing engine/transmission combo without an actual rebuild. I will be running no more than 6 psi of boost, and will try to get away with not using an intercooler. We'll see how it works out. I am well aware what this might mean for my engine and tranny, but I feel that it will be good for tuning purposes in the long run for the second stage...

The 4.9 turbocharger, stage two, will include the 4.9 liter Cadillac engine (4.5 was considered for a split second) with ported/polished heads and intake; possibly more cam; new moly-chrome piston rings and general rebuild specifications. Overall, the stage two engine will be pumping around 260hp/300lb.ft naturally aspirated. I will add about 8 psi of intercooled boost which will make the engine perform in the 360hp range...I hope.

The second stage transaxle will be rebuilt and bullit proof and I will attempt to have a 3.73:1 final drive ratio. I have to study the tranny more, but I hope I can make those aforementioned changes.

So back to stage one. I have the following items for this project:

GM-3 IHI 6.5 liter diesel turbocharger. It is used and will probably need a rebuild in the bearing area, but for $76.00, I couldn't pass it up. I'll let everyone know if it needs a rebuild or not when I get it next week via UPS.

I have the MSD boost timing controll system with an MSD digital-6 ignition. These items will help combustion and timing while under boost.

I have two Deville exhaust manifolds (front and rear) and a cross-over pipe. They need some welding and an adapter fabricated for the turbo to attach to, but this won't be an issue...I hope.

Auxiliary fuel system minus the actual controlls (piggy-back ECM). I am going to do one of two things here: use an old TBI system for extra fuel needs; or I will make a new fuel log and use two or more auxiliary fuel injectors for fuel needs. An extra fuel pump and some cutting will be necessary, but they're taken care of...Minus the cutting of the fuel tank.

I am going to go with the Megasquirt system for now, which will set me back by a couple hundred (actually $140.00 for the complete DIY kit)...Unless someone hacks the Caddy ECM before I purchase it.

Extra exhaust tubing. I have plenty around in the garage I have just rented. It shouldn't be an issue.

That's it for now as far as supplies. I will also add a bypass valve so that the boost won't blow anything up when I take the pedal off the floor. And perhaps an electronic wastegateb to keep good controll of the boost I'll be running, which will be considered a rather small amount...We'll see how that works out.

As for the general reader: there are only a select few people here on this form who's technical advice will be heeded. They know who they are, and are welcome to help me out if possible. If you don't have anything positive to say, then don't say it: this is my project and I'll won't listen to your negatron views! :nyanya:

I am not concerned if people think this is a crazy idea: I don't care and if you don't have any good technical advice, read on...If you decide to flame or otherwise put this project down, I simply will not respond: your opinion won't even be considered valid. If you have valid advice and/or comments, type away. Remember, this is a community project that everyone will enjoy in the end. People want to see this done and IT WILL BE DONE!

That's it for now. This thread will be here for a while, and may even get burried due to my personal time constraints, but I'll keep everyone posted and will post pics of the items and project as soon as I recive more space for attachments.
 
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#127 ·
if you visit the pennock's fiero forum, there has been alot done to the 4.9L caddy engines for performance, including turbo charging...there is alot of info on the type of engien mods you are doing to the 4.9L.. unfortunately, because the 4.9L cadd engines dont use a knock sensor, youll have to use an entirley different computer if you plan to use more than 6 psi boost... visit www.fiero.nl

post on the group about what you wnat to do.. there several hotrodding build up threads for the 4.9L engines and also some about turboing it as well.. take care
 
#132 ·
stickpony said:
heres a thread that tells how to build up the 4.9L , including a cam change to the delta cams .496 lift cam, head work where the intake valves were increased in size, and an allante intake manifold was used http://www.fiero.nl/forum/Forum2/HTML/061613.html

Thanks for the great link!

However, when I do my 4.9 rebuild (after stage 1 install is complete), I will not be looking to increase the compression ratio with the Northstar pistons. I will likely do some combustion chamber work to lower the compression ratio to run a little more boost. I have an idea for about an 8.5:1 comprssion ratio when stage 2 is finished running closer to 10 psi of boost.

As for the components I will likely use for stage 2:

Ported and polished heads. Aforemetioned work to lower CP ratio.

Roller rocker arms with Allante steel supports. 1.6:1 rocker ratio will be used, and stock is 1.6:1 ratio.

Camshaft...I might get away with just higher lift while leaving duration and such alone so I don't have to worry about ECM changes...Am I able to do that with a regrind for just lift? Put it like this, I can change to a 1.7:1 rocker ratio to increase lift without doing any ECM changes. The ECM work is needed only for profile changes...I think.

New internals are a must! Chrome molly rings are good and I installed a set in my '87 Seville 4.5 liter engine.

I like that Allante intake setup. I would be willing to change things around to run with an Allante EPROM and such. Wiring is the key here...I also know a place that will sell me an Allate intake (upper and lower), valve covers, rocker support bar (steel), and fuel rail for $250.00.

Then run 10 pounds of boost...Yeah, that sounds about right!

N0DIH said:
Does it allow for a knock sensor input? In my really disasterous experience, pinging is piston lightening deadly. Being I don't have a EST module car anymore, I can't play and experiement with adapting the ESC module to the 4.9L V8. I would love to. (anyone got a 90-95 4.9L car to donate/loan for a while while I test?) I need to connect an oscilloscope to the EST line to the module and see what is on it, and then determine how ot interfere with it to reduce timing when pinging is heard. Also need to find a knock sensor that is tuned for a 4.9L. That may be more difficult.
Tom, unfortunately it does not. There is however a knock sensor kit that can be plugged into an engine drain plug or what have you from Jegs. They run at about $150.00 or so. They don't do an automatic retard that I'm aware of, but it does alert you of detonation and you can thereofre use the MSD to retard the timing scale for boost. From what I've seen, that would be the single best investment that I could get away with.
 
#133 ·
For stage II I would like to see more like 8-8.2 compression. More boost is worth far more than higher compression will ever get you.

Something to consider is ditching the Cadillac ECM. But you lose some cool FDC functionality. That is a downside. But if you go something like a LT1 (pre 96) ECM, or a L98 TPI computer (TPI 350 and TPI 305 ECM's like HEI's, where LT1's like Optisparks, unless you can adapt a 360 degree crank position sensor to the HEI or to the front of the engine), you gain full aftermarket support. And they have knock sensor inputs too. You need the fast speed of the automatic knock retard, believe me, working with mine running the way it did, with 7.5:1 compression and 7.5 psi boost with knock retard, with me pushing the timing as high as 93 octane would allow, pinging still would get you when you didn't want it to. Like at 120 mph when you try to cruise and vacuum advance kicked in!!! RATTLE CITY. I had to be at WOT or no throttle to maintain 120. I know why GM was so bloody conservative on that engine. The ECM in the Cad doesn't know anything different. Sure, no vacuum adv, but it will think there is no reason not to up the timing at light throttle at 100+ mph.

And the knock sensor is specific to the frequency of the cyls. The wrong sensor would be someone deaf to the engine. So you may need to get an array of sensors to try and connect an oscilloscope to so you can measure pinging. One will work better than others. I wonder if you can use a microphone to analyze the engine sounds in pinging.

A good friend of mine is a head guru would be glad to give you some tips to lower compression safely. Grinding the wrong thing on the heads can make for poor flame travel. Take some good pictures of the chambers on a 4.5/4.9 and send them to me, I will see him soon. Or even Blaze might see him sooner.

Olds guru's like to use Ford 351 Roller Rockers (302 too?) for the Olds V8's. Cad 4.x engines LOOK to be nearly identical to the Olds in rockers. You can likely easily adapt them to the 4.x. 15hp boost on any 4.x. Cost, maybe $150. I think you can get 1.7's. Cam regrind will keep duration very very close. The smaller base circle of the came needs to be examined in the block. If the lifter goes too low you can run into issues with lifter bosses breaking due to excessive forces. I don't know the 4.x lifter valley that well. Turbos love lift, they are not so caring of a lot of duration. Keep it low, a 200/200 cam in a GN is a "big" cam. So keep it down, more like stock should be fine. The turbo will greatly broaden the powerband where you don't need it. If you are racing, then it matters. This is street power. The smaller cams will make the boost more restrictive at higher rpms, as with the valves open less of the time there is more backup, where a larger cam allows for more time to pack the cyls with more. And more sudden open plenum area such as the cyl, drops charge temp a little bit more.

Turbo's don't need tuned intakes, they can make the engine peaky. But do give it as much flow as you can, it will use it. The more plenum volume the less need for intercooling. How many semi's do you see with intercoolers? None. How many with aftercoolers? All. Design for aftercooling. It is basically adding a large plenum area after the turbo exit that allows some room for the turbo boosted air to expand into some, causing the air charge temp that was heated by the adiabatic heating/cooling of the turbo to cool down some. This will help overall a lot. Almost like coming out of the turbo into an intake like the GN Regals only with a larger plenum top area than the GN had, but keeping the same size runners. You want velocity way up. I would honestly bet that a creative nut could adapt a Buick 3.8 or 3800 intake (need 2 to merge) together to make a V8 intake that would support a sweet intake for the 4.5L/4.9L.

I'm still sticking to no intercooler with 10 psi and lower. There isn't as much heating, so the added intake track for the intercooler increases lag time, and there isn't as much need to cool the charge off. Example, if the boost increases the charge temp to 150 degrees F, and it is 75 degrees out, you can only hope if 100% efficiency, to drop it to 75F. We know we won't get that, so it will maybe only cool it down to 100-125 degrees. Not much savings here for the large expense and difficulty plumbing it. Higher boost levels? Yes, defineatly worth it. When you are heating the air up to 200-250 degrees, you have to have it, and it is very worth it.

Nitrous is an awesome intercooler.... The super cool gas temp makes intakes nearly frozen at speed. And then the additional power is fantastic.
 
#134 ·
Tom, the reason I was thinking about the Allante intake is the exact reason you've stated: the plenum will help cool the charge air temps...Am I right?

Also, here is a picture of the combustion chamber from an HT-4100 cylinder head. The 4.5 and 4.9 liter heads are exactly alike in the combustion chambers...

See what can be done here. There seems to be enough material to lower the compression ratios to your idea of 8.2:1 or so.

Let me ask you this as well: you stated that the lower compression ratio would'nt take too much power away. What are the exact losses you would expect if it was lowered to 8.2:1? If we are dealing with an engine with a higher lift cam, roller rockers, Allante intake, and head work (the whole 9 yards on the heads), you're saying that the compression loss would be minimal? Please let me know...

Here is the picture of the head combustion chamber:
 

Attachments

#135 ·
I will have to consult a friend of mine for more info, as he is a cyl head guru.

But what I do know:
1. This is a high swirl "heart shaped" chamber. There is mixed theories on whether or not you should destroy the swirl properties under high flow applications.
2. Do not mess with the quench area, the flat part that is opposite the sparkplug, it will invite a hiding place for fuel to hide and not have access to the flame front, which will cause HC emissions to skyrocket. As well as fuel not exposed to the flame is not making you HP.
3. I think initially I would widen the area around the valves, unshroud them, especially around the intakes. You should be able to gain some good Cc's there. As well as enhancing airflow around the intake valve.
4. CC the heads first, and then shoot for 6 cc to reduce 1 point of compression. If I remember my math right.
5. Avoid shaving heads, unless you have to, as it invites higher compression.
6. The square block around the spark plug is unqiue to the chamber performance, but I don't remember exactly what, I'll let you know when I dig it up.
7. Avoid excessive grinding of the valve seats. This causes the valve to recess sllightly in the chamber (which does lower compression slightly) but creates a delay time for the air/fiuel mixture to start flowing. There is additional shrouding created.
8. Do not stack head gaskets to reduce compression. this is a terrible invitation for blown gaskets, especially with blown apps.
9. I have been planning on building a low buck flow bench. Let me know when you are ready to start grinding and I will let you know what I have in the works.

the general rule of thumb is 1 compression point is as much as 4% hp increase/decrease. with 1 psi boost you might gain more like 5-10% increase. Consider for every 14.7 psi is double the CID (2 atmospheres), so your 4.9L is now a 9.8L. You'll need some extra fuel....
 
#136 ·
yeah thats cool.. to lower the compression, youd want to get some quad-4 pistons, they fit and will give you about 9:1, of course getting some head work done will lower it slightly more, 8.6-7 to 1, thereabouts.. I woudl HIGHLY recommend geting LT1 1.94 in. intake valves for this when you get the head work done.. get new exhaust valves too
but for a 12 valve 6 cyl 3.8 buick...order them new
 
#137 ·
An odd thing with turbo engines I have noticed over the years. They all seem to have small valves. I have never seen a factory production turbo with large valves.

My 301 Turbo: 1.75 Intake 1.5 Exhaust (my particular car, 290 RWHP)
GN Turbo: 1.75 Intake, 1.5 Exhaust (245HP stock, easily to make 400+ with stock long block)

Honestly, with the boost, valve size may not matter at all. I guess if you are going all out, 15+ psi boost, sure, the valve will become a restriction to the flow, raising boost when it shouldn't be (backpressure in the intake tract will make the turbo back up and activate the wastegate early, thus lowering overall cylinder boost pressures)

Maybe increase exhaust valves on the exhaust, but until boost gets up, don't mess with them. BUT, OTOH, boosted engines often have sodium filled exhaust valves. The 301, not sure, they are fat suckers, enough room they probably do, the 3.8L Supercharged Ford, the 2.3L Turbo Ford, both do. Not sure on GN, probably does.

So, do consder that. If you are swapping valves, look for the necked down valves that have more flow around the valve, but keep with the Severe Duty versions if at all possible. Turbocharging is serious business. (more for Phase 2 not Phase 1) High mileage valves can be a risk.
 
#139 ·
of course, you could always go for the biggest normally aspirated 4.9L ever! hehehe... if you shave the heads .050, and use Northstar pistons ( use the stock sleeves, just have them bored .040 ), you'll get in the neghborhood somewhere of 11.5 to 12:1 compression.. of course, pump gas is useless at this compression unless you use a different ECM entirely, one with a knock sensor of course..have a custom built valvetrain, and a very high lift cam...
 
#140 ·
I am not that familliar with the dimensions of the Quad 4 pistons, but you don't want to mess up the quench. You can mess with the other side, but the quench area is cruicial to helping manage and eliminating pinging. Typically around 0.040". Alum rods increases that by around 0.040 to 0.080. And if it has 4 valve relief's, are they in the correct position for the 4.9L? Same with N* pistons. BEing the 4.9L shares pistons with the 3.4L Chevy V6, pistons and rings should be plentiful and cheap. Sick puppies like me read websites like KB-Silvolite.com. It is interesting to find out what works with what...

stickpony said:
yeah thats cool.. to lower the compression, youd want to get some quad-4 pistons, they fit and will give you about 9:1, of course getting some head work done will lower it slightly more, 8.6-7 to 1, thereabouts.. I woudl HIGHLY recommend geting LT1 1.94 in. intake valves for this when you get the head work done.. get new exhaust valves too
but for a 12 valve 6 cyl 3.8 buick...order them new
 
#141 ·
You know what I've just realized? We're getting nowhere fast with this project! There has been about 140 posts pertaining to pistons and camshaft changes that I will not use at all for stage 1 :bonkers:

Let's get back to topic here and start to figure things out. I mean Christ, it's just another engine with the same characteristics that almost every other V8 has in terms of moving parts...So I'm not getting all fancy. It's just a tune before the real deal if you please...

Ok, for stage 1:

a.) No intercooling whatsoever. Tom has stated time and again that for 6 simple psi that it won't be needed.

b.) Fuel. I'm just going to order the Megasquirt self-programmable system and get with it. I have most of what I need and will run with an auxiliary TBI system to add more fuel. I'll add the extra fuel pump and lines too.

c.) Timing. So I'll keep factory settings of 10 for idle. The MSD boost timing controll can take care of the rest.

d.) Turbocharger. I would like to have the compressor map done, but I really feel that the turbo I have will suffice for now.

e.) Tubing and pipes. I'm installing the turbo via the crossover pipe from a Deville. There will be Deville front and rear exhaust manifolds feeding the crossover pipe, which will in turn feed the turbocharger.

f.) Boost level controls and a blow-off valve. Done. The turbo I have has a dual-port wastegate system and the boost control should work out fine.

All that is really needed is for me to order the Megasquirt and build it. Welding pipes and other things together is easy. Or at least I hope so.

Okay people, let's get with it here. If I'm going to blow this thing up, let's do it in style!!!
 
#142 ·
Funny you should mention it, I was actually looking at the title to the thread last night, thinking, we are not posting at all about Stage 1! But the bunny trails were cruising on and on....

You are right, the MSD BTM and 4-6 psi boost to start (keep boost low initially) with a simple mechanical wastegate, unless we have $$ to get an electronic one and make a knob inside the car (which would be nice to help save the engine if boost is suddenly too high, maybe make an ESC module control the wastegate instead of the timing control) A way to monitor pinging should be seriously considered. GM put knock sensors (ESC) on 3.8L's, Turbo 301's, and various other cars. Look for G Bodies with V6's and the ESC module is on the pass side fender. Snag a few of them. Get some various knock sensors, 4.6L N*, 2.8L Chevy (if they have), 3800, 3.8L, 3300, 1.8L Turbo 4, 2.0L Turbo 4, etc. You may need to experiement with the one that is most sensitive. Install them one in each block coolant drain. Closer to the cyls is best. Becareful removing those drains! It is an aluminum block, so it might not come out easily.

Plan out where the turbo can do, how to get exhaust to it and away from it (likely on top of the trans, that is where Pontiac put it on the 1988 SSE Turbo Bonneville prototype), obviously the air box is removed, build an abundance of heat shields you WILL need them, a little goes a long way on a heat shield. You can drop temps 50 degrees with 1/2" air between the source and the thing you are protecting.

Calculate the boosted airflow requirements. If the turbo is at 14.7 psi, you are double the CID. Make sure the TBI unit will flow enough air for you, at 7.5 psi you are ballpark 450 cid. You may need a 454 unit, stock maybe, maybe a little porting. You don't want it to be a boost restriction and having it backing up the intake tract. I need to look at the allante intake more (is that Stage 1 or 2?). Make sure there is some plenum under the TBI. Being the 4.9L isn't a high revver, the 454 TBI is probably sufficient, for stage 1....

I am wondering if the MS is best saved for Stage 2 and use my idea to trigger extra fuel for stage 1. Simple, cheap, and very effective.

Does anyone know if the Cadillac PCM will handle a 3 bar MAP? And has anyone broke the programming on it? Does anyone have any friends at GM in handware or software engineering that might be willing to answer silly questions like that?

You should not need anything special on wastegate with that low boost. Like an extra exhaust pipe, etc.

When I was pondering turboing my 3800, I was looking at bringing up the exhaust to the turbo right off the factory crossover, and then return it back to the cat converter in the stock pipe with an extention. Just weld off that nasty back side crossover on the 3800. (Thrasher Engineering makes a replacment that isn't so bad, for you guys with a 3800) Odd thing, the 3800 has a 2.3" crossover pipe, the 4.9L is smaller, like a 2" or 1.75". Maybe you can adapt the 3800's pipe.

Oil supply, oil pressure sending units with a T work, but not always sufficent flow. The closer you get to the oilpump the better. If you can up oil pressure, DO SO! Oil drain back. Drain must be lower than turbo exit. The intake may work, you might need to drill a hole in the backside of the intake to drain into the lifter valley.

Being we already have an engine oil cooler, that is good. Either monitor oil temps or go synthetic. Even with me changing oil very often, the oil didn't survive enough to save my rod bearings. So it is low cost bearing insurance. 15W40 may be sufficient though.

Turbos LOVE cooling engines and cold air induction. A cold day will give you a ton more power than a warm day.

Insulate the exhaust pipes going up to the turbo. Spools faster and reduces underhood heat. But, non stainless pipes may not live as long.
 
#143 ·
N0DIH said:
Funny you should mention it, I was actually looking at the title to the thread last night, thinking, we are not posting at all about Stage 1! But the bunny trails were cruising on and on....

You are right, the MSD BTM and 4-6 psi boost to start (keep boost low initially) with a simple mechanical wastegate, unless we have $$ to get an electronic one and make a knob inside the car (which would be nice to help save the engine if boost is suddenly too high, maybe make an ESC module control the wastegate instead of the timing control) A way to monitor pinging should be seriously considered. GM put knock sensors (ESC) on 3.8L's, Turbo 301's, and various other cars. Look for G Bodies with V6's and the ESC module is on the pass side fender. Snag a few of them. Get some various knock sensors, 4.6L N*, 2.8L Chevy (if they have), 3800, 3.8L, 3300, 1.8L Turbo 4, 2.0L Turbo 4, etc. You may need to experiement with the one that is most sensitive. Install them one in each block coolant drain. Closer to the cyls is best. Becareful removing those drains! It is an aluminum block, so it might not come out easily.

Plan out where the turbo can do, how to get exhaust to it and away from it (likely on top of the trans, that is where Pontiac put it on the 1988 SSE Turbo Bonneville prototype), obviously the air box is removed, build an abundance of heat shields you WILL need them, a little goes a long way on a heat shield. You can drop temps 50 degrees with 1/2" air between the source and the thing you are protecting.

Calculate the boosted airflow requirements. If the turbo is at 14.7 psi, you are double the CID. Make sure the TBI unit will flow enough air for you, at 7.5 psi you are ballpark 450 cid. You may need a 454 unit, stock maybe, maybe a little porting. You don't want it to be a boost restriction and having it backing up the intake tract. I need to look at the allante intake more (is that Stage 1 or 2?). Make sure there is some plenum under the TBI. Being the 4.9L isn't a high revver, the 454 TBI is probably sufficient, for stage 1....

I am wondering if the MS is best saved for Stage 2 and use my idea to trigger extra fuel for stage 1. Simple, cheap, and very effective.

Does anyone know if the Cadillac PCM will handle a 3 bar MAP? And has anyone broke the programming on it? Does anyone have any friends at GM in handware or software engineering that might be willing to answer silly questions like that?

You should not need anything special on wastegate with that low boost. Like an extra exhaust pipe, etc.

When I was pondering turboing my 3800, I was looking at bringing up the exhaust to the turbo right off the factory crossover, and then return it back to the cat converter in the stock pipe with an extention. Just weld off that nasty back side crossover on the 3800. (Thrasher Engineering makes a replacment that isn't so bad, for you guys with a 3800) Odd thing, the 3800 has a 2.3" crossover pipe, the 4.9L is smaller, like a 2" or 1.75". Maybe you can adapt the 3800's pipe.

Oil supply, oil pressure sending units with a T work, but not always sufficent flow. The closer you get to the oilpump the better. If you can up oil pressure, DO SO! Oil drain back. Drain must be lower than turbo exit. The intake may work, you might need to drill a hole in the backside of the intake to drain into the lifter valley.

Being we already have an engine oil cooler, that is good. Either monitor oil temps or go synthetic. Even with me changing oil very often, the oil didn't survive enough to save my rod bearings. So it is low cost bearing insurance. 15W40 may be sufficient though.

Turbos LOVE cooling engines and cold air induction. A cold day will give you a ton more power than a warm day.

Insulate the exhaust pipes going up to the turbo. Spools faster and reduces underhood heat. But, non stainless pipes may not live as long.

Thanks again for the info Tom. I am sorry if I sounded like a jerk with my last post, which was not singling anyone out, I was just a little buzzed and was wondering where I am getting with this project I have been promising for close to a year now...

I was checking out that 4.9 buildup thread and I seen the most interesting thing that I would like to use. They had a set of 4.1 liter exhaust manifolds in the picture that appear to be stainless, and they are the same material that I have on my '87 Seville, only those are made for the cross-under pipes. I'm just not too sure how the flow would work out should I decide to use those instead of the cast iron manifolds. I have a set of Deville exhaust manifolds laying around along with a cross-over, but they seem to be the cast iron manifolds. The cross-over is stainless I believe...I would much prefer the header look of the 4.1 liter manifolds as well.
 
#144 ·
Absolutely not, I agree, we got off on some good bunny trails thought! I think we all tend to go with the flow of the thread, almost Ralphlike...

I haven't take a look at the 4.1L stainless, if they are like the Olds 5.0L "Y" stainless, they might be a good choise if they are a bolt on. For Olds, they only work on 7A heads with the tiny exhaust ports (althought they DO have the more desired fully divided center 2 exhaust ports, which is rumored to pick up 30 hp on an modifed engine, I would guess more like 15 myself....). A little trick to manifolds is to go too big on headers or manifolds to allow a block to reversion. The exhaust pulse is larger once it gets in the pipe, and then when the pressure pushes it back or the cyl tries to suck it back, the pulse will get partially stopped at the port exit. free power though less diluted chamber. Ok, NOx might go up slightly, but who cares, right?



illumina said:
Thanks again for the info Tom. I am sorry if I sounded like a jerk with my last post, which was not singling anyone out, I was just a little buzzed and was wondering where I am getting with this project I have been promising for close to a year now...

I was checking out that 4.9 buildup thread and I seen the most interesting thing that I would like to use. They had a set of 4.1 liter exhaust manifolds in the picture that appear to be stainless, and they are the same material that I have on my '87 Seville, only those are made for the cross-under pipes. I'm just not too sure how the flow would work out should I decide to use those instead of the cast iron manifolds. I have a set of Deville exhaust manifolds laying around along with a cross-over, but they seem to be the cast iron manifolds. The cross-over is stainless I believe...I would much prefer the header look of the 4.1 liter manifolds as well.
 
#145 ·
illumina said:
Tom, the reason I was thinking about the Allante intake is the exact reason you've stated: the plenum will help cool the charge air temps...Am I right?

Also, here is a picture of the combustion chamber from an HT-4100 cylinder head. The 4.5 and 4.9 liter heads are exactly alike in the combustion chambers...

See what can be done here. There seems to be enough material to lower the compression ratios to your idea of 8.2:1 or so.

Let me ask you this as well: you stated that the lower compression ratio would'nt take too much power away. What are the exact losses you would expect if it was lowered to 8.2:1? If we are dealing with an engine with a higher lift cam, roller rockers, Allante intake, and head work (the whole 9 yards on the heads), you're saying that the compression loss would be minimal? Please let me know...

Here is the picture of the head combustion chamber:

negative... 4.5L heads from 1990, '89 and later allante engines, and 4.9L engines are the same. 4.5L TBI engiens' heads arent as good
 
#146 ·
N0DIH said:
I am not that familliar with the dimensions of the Quad 4 pistons, but you don't want to mess up the quench. You can mess with the other side, but the quench area is cruicial to helping manage and eliminating pinging. Typically around 0.040". Alum rods increases that by around 0.040 to 0.080. And if it has 4 valve relief's, are they in the correct position for the 4.9L? Same with N* pistons. BEing the 4.9L shares pistons with the 3.4L Chevy V6, pistons and rings should be plentiful and cheap. Sick puppies like me read websites like KB-Silvolite.com. It is interesting to find out what works with what...
N* pistons are a very common hotrodding upgrade for the 4.9L engines..the "quench" area that you speak of on the N* pistons, 4 concave little etchings on the surface of the piston,is actually notfor that, but to create turbulence in the combustionchamber, which leads to cleaner, more efficient burning for the fuel. I was talking to BUd of Bu'd outback, a specialty shop out in arizona that specializes in hot rodding the 4.9L and N* engines, and he was telling me that gM originally put those concave 1/4-moon shaped etchings on the head around the outside of thevalves, but too many test heads were failing and cracking because of the lack of available space on the head because of having 4 valves per cylinder, so they put them on the pistons instead. anyways.. the N* pistons will actually burn cleaner than the 4.9L pistons. I dont know how well the quad 4 pistons will burn, but i talked with a friend who puts 4.9L engeins in fieros, he did the quad 4 piston swap, and said that the compresison is actually 8.5:1 without head work if you use the quad 4 pistons.
 
#147 ·
stickpony said:
negative... 4.5L heads from 1990, '89 and later allante engines, and 4.9L engines are the same. 4.5L TBI engiens' heads arent as good
I don't know where you got that I said what heads are better than the other, and I also don't know where you got that either. The picture posted was a sample for Tom to take to his friend, as the head design in the combustion chamber is the same.

Speaking of which, I don't know if you realize this or not, but the combustion chamber design is the same for all 4.x heads. I have taken enough of them apart and rebuilt them to know this. The only difference between the TBI heads and the MPFI heads are the intake water passage area, and perhaps better oil return from the MPFI heads. It really isn't possible to use the 4.1 liter heads for a MPFI intake manifold because of the water passages. Other than that, they are made of the same material and have the same basic combustion design, which is all that I stated. If you happen to re-read my post before you actually make a statement against it, make sure you get what I said right.
 
#148 ·
Also, though I appreciate the link to the 4.9 buil-up, I am not going to use a single Northstar/Quad-4/whatever piston in this stage, or in stage 2. The information given pertains to an engine being built for natural aspiration, not turbocharging.

My aim for stage 2 will be to lower compression ratio for more boost, not raising it to blow my engine during boost. So let's consider the Northstar piston upgrade a closed matter and get with what needs to be done for stage 1.

Thank you :eek:
 
#149 ·
IIRC, the N* pistons were close to the 4.9L, but not the same, but I don't remember which way. I'm checking KB-Silvolite.com for more details. Another concern is the valve relief angle. Again, I don't have the details of the 4.6 and 4.9L on this.

For some serious reading on pistons and engines, take some time and read at http://kb-silvolite.com/ and look for the tech pages. The ones on Quench are very interesting.
 
#150 ·
#151 ·
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