View Full Version : Buildup a V8 like a high revving 4 popper?

01-19-07, 11:47 PM
I have had (yuk!) to drive a 03 Toyota Matrix for the day, and my gosh, it runs 2900 rpm @ 75 mph!! It has 4.5x gears and OD. It is weak below 3600 rpm, but revs all the way up to 7000 rpm.

So, take my Fleetwood, drop in 4.56 gears, take a LT4 HOT Cam with 1.6 rockers, port the heads slightly to flow better at 6000 rpm (being reasonable)
and compare it in drivability and manners.

All these little dinky 4 cyls have cruise rpms below 3000 rpms and have too large cams for good cruise rpms. But yet they get decent mpg all things considered.

So if we built a 350 LT1 the same way, or better yet, a L99, how would it do?

01-20-07, 09:01 AM
With the right cam and a rev kit, it would scream! 'Course you'd need a much higher stall converter to use it, and mileage would be dismal.

01-20-07, 10:53 AM
I have always wanted to build a 260 Olds, can't tell you why....

But might be better to build a L99 (265 Chevy). Parts are cheap, engines are unwanted, and it is factory EFI.

Lets see, LT4 HOT Cam in an L99, 3000 rpm stall with a lockup, 4.56's or maybe 4.11's for economy, LT1 heads if they are larger than L99 (keep compression as high as you can, 11:1 or so), and put it in as light of a car as I can find, say a 85 Cutlass or so, maybe a 78, they are lighter. Lighter is better....

The Ape Man
01-20-07, 12:31 PM
Pick an engine with low recriprocating mass. That's where brands like Mercedes really outshine Amerikan engines. Put some $$$ into the parts.

01-20-07, 01:36 PM
I think Lunati makes a crank for first gen. SBC that weighs something like 45 lbs. If you want a high-revving V8, what about a Chevy 302? One of the most underrated engines ever built.

01-20-07, 02:07 PM
You can make a 302 LT1 with a 350 block and a 265 crank. Even use the longer L99 rods and make it a 5.94 rod motor.

01-21-07, 12:58 PM
Oh man, that would rev to the moon! But then you'd probably want a manual with a screamer like that.

01-21-07, 01:14 PM
4.56's and a 6 speed manual. Ideally the ratio of the of the M22 would be sweet.

I would probably shoot for a Nash 5 speed or the replacement 6 speed and keep like 3.23's in it.

01-22-07, 05:53 PM
I've been half-following this thread and I've got to ask the question, why the heck would you want to do this? The reason these sport compact motors need to rev is because that's the only way you can make power out of small displacement. The whole reason for a big V8 is to make torque and HP at low revs and low stress levels. The original Honda S2000 made 240 HP out of 2.0 liters (121 cu in). that's impressive until you look at the HP and torque curves. The entire power band was between 7000 and 8000 RPM, which means you're constantly rowing the shifter. Some people like that sort of thing. Power went rigth down the toilet on either side of the HP peak. Even worse, peak torque was something like 160 ft-lbs. My STARTER MOTOR has higher torque than that. Peak HP and torque numbers sound impressive, but for real world driving you care about the area under the curve.

Finally which engine will last longer - a 121 cu in four cylinder making 240 HP or a 350 V8 making 250 HP? Which one costs more initially? Which one costs more to maintain? Which one makes 400 ft-lbs to go with that 250 HP?

High-reving V8s are common. Drag racers regularly spin SBCs to over 7500 RPMs. 500 cu in Pro Stock motors run over 10,000 RPM. Why would you want to do that on the street? Nitrous or forced induction is a much easier way to achieve the same effect, with much more usable torque besides.

01-22-07, 08:27 PM
The '67 Camaro is a great example of fun on the street, with the aforemetioned 302 Chevy. Now you're correct in saying that high-revvers don't last as long, and that's true; bearing wear increases by squares, so an engine at 9000 rpm sees 49 times the wear as an engine at 2000 rpms. But a high-revver with a manual can be a blast, especially if it's a V8 and has a little torque to it.

01-23-07, 12:43 AM
The goal would be to make a very wide rpm range engine. Honestly we are all stuck in a world of a idle to 5000 rpm engine, but why not make a V8 that is following the pattern of a 7500 rpm small displacement engine? Those 4 cyls may not last like a V8, they do last a fairly long time.

Everyone paints these 4 cyls like the engine my sister in law had in her Matrix that is a measly 1.8L and makes 140 hp as a engine that is so undrivable that it isn't useable, but that is far from the truth. Sure, it is is quite shift happy, but explain to me what happens at lower cruise rpms when port velocity is lower and less A/F is needed to maintain cruise, how would fuel economy be? But honestly, if the cruise rpm is sub 3000 rpm (at 75) and built well, why would it NOT be a decent runner? Giving it a rpm range that is broader and is more useful. We aren't getting the greatest ratios in the trans, so why not make the engine broader?

I still say keep CID up, 5L or better, cam it to match the gearing, say 224@0.050 or better, decent lift, on a 112 or narrower, I prefer a mech roller, lightweight pistons, balanced to 4gms or better, etc. Sure, it won't have as much low end torque as a stock cam LT1, but look at it this way, we have 4.10 or 4.56 gears and that will make up a lot of low end power. And with the newfound top end power, with 4.56's will scream.

01-23-07, 09:59 AM
The goal would be to make a very wide rpm range engine. Honestly we are all stuck in a world of a idle to 5000 rpm engine, but why not make a V8 that is following the pattern of a 7500 rpm small displacement engine? Those 4 cyls may not last like a V8, they do last a fairly long time.

There are several problems with this. First, it is VERY, VERY difficult to build a gasoline engine that has a very wide useable RPM range. As I noted, small engines with high HP numbers tend to have very tiny power bands. If you tune the intake and exhaust tracts for the high end and install a cam to match, the engine is a dog at low RPM. The classic example of this is the Ford 351 Cleveland. The 4bbl heads actually have ports that are too large for the street. The 2bbl heads make more power and torque in regular use, but Ford needed to sell the big port heads to qualify them for racing. Most new engines use variable geometry intakes and variable cam timing to achieve a wider useable power band. This adds major dollars and increases the likelyhood of something breaking.

Second, the larger the displacement, the greater the internal stresses. These stresses go up exponentially as RPM increases. If you go with a short stroke to minimize crank stresses then you need a large bore to get the displacement. This results in a heavier piston that you are constantly accelerating and decelerating at each end of the stroke. Go the other way and use a small bore with lightweight pistons and now you have a monster stroke with large rotational inertia and high bearing loads. It's a no-win situation. Either way, if you beef up the parts to handle the stresses, the added mass increases the stress even more. It's a visious spiral. High RPM race motors (like the 10,000 RPM, 500 cu in Pro Stock motors I mentioned previously) use extremely expensive internal components to get light weight and high strength.

And now let's talk about the valvetrain. Again, the technology exists to run pushrod motors well over 7,500 RPM. You need roller lifters, rev kits, very stiff valve springs, etc, etc. Keep in mind that at 7,500 RPM each valve opens and closes more than 60 times A SECOND!. Yes, you can use OHC, but that's got it's own set of problems.

Bottom line is that the only replacement for cubic inches is rectangular dollars.

01-23-07, 12:12 PM
Speed costs money. How fast do you wanna go?