old motorhead

iTrader: (10)

Thinking of destroking my LS2 with a 4.8L truck engine crank. Motor will have an MP122 Maggie supercharger on top. I'm thinking the maggie will make similar power no matter the engine size. Only have "X" amount of air to work with. Why not go a little smaller on engine size? Hoping for a little better fuel eco as well as longer engine life. Am I way off base here?

KCS

iTrader: (20)

Coonass350

iTrader: (19)

im with this guy.. dont do that

408firebird

iTrader: (1)

Wouldn't you be able to rev higher though?

stroker_SS

Rev limit is a function of the valvetrain not the bottom end.

Hans Grüber

iTrader: (2)

This would reduce your displacement to 5.35 L or 329 ci.

I really don't see the point of this.

old motorhead

iTrader: (10)

The points are:

I want to use the Aluminum LS2 block that's sitting in my garage

I don't need, nor do I want, 6L of displacement.

Looks to me like it's easily doable. Stock 4.8l crank and rods along with stock type 6.0L pistons would do it.

The shorter stroke, longer rod combo would lessen the need for a high dollar bottom end. I think it would last longer under boost/higher rpm.

Again, the supercharger I'm using won't make any more power with more cubes.

Please, if this subject irritates/aggrivates or is insulting to your intelligence, please accept my appologies. Just ignore it. It will soon go away.

However, if you do have something to add, I'm all ears.

G Engines

IMO This isn't a bad idea at all, look at all of your nascar engines they all run this same concept of big bore short stroke and make good hp. I have D-stroked quite a few 400 chevy's going as small as 347 ci. and it still made 940hp on the dyno. I do feel that with only having a 122 maggie on it it will actually help your supper charger become more efficient with the smaller ci. due to the fact it wont have to work so hard to fill the cylinder volume.

jmilz28

iTrader: (13)

So long as it's not going in a heavy car, I think it would really scream - like a 69 Z28. You may get good mpgs with proper (small) cam selection, like an ls6 cam maybe?

Overall, I think it's a real waste and you're giving up power and torque for no reason. If you just want something different, with some interesting character, give it a shot - it may well be a shitload of fun. Just make sure you have good springs and pushrods.

02camaroburn

iTrader: (1)

I'm intersted in the results

Phantom

iTrader: (16)

Been thinkin of doing this myself. Let us know what you come up with

Hans Grüber

iTrader: (2)

How much power are you planning to make and what kind of supercharger are you using?

This probably will not be a cost effective way to run a high rpm engine since you'll need to spend a lot on the valve train either way.

I doubt there would be a significant difference between a 3.268 and stock 3.622 stroke crank anyways in terms of high rpm reliability.

If you're going 7000 rpm+, aftermarket rods would be a good idea anyways. For the uncommon 4.8L rod length, this would add more cost.

I was not insulting you.

Reducing displacement is really only done when one is restricted by the racing class that they run in, the old 302 Camaro, the current 5.5 L GT2 Corvette (next year 5.0L).

If you were competing somewhere where you had to run stock displacement, you could use the 4.8L crank in a stock 4.125-in LS7 block and get 5.7L or 349 ci. I think this is what Katech did in the original CTS-VR's.

old motorhead

iTrader: (10)

Supercharger is an MP122 Radix. It will pump enough air for about 550rwhp reliably. With slightly above average heads, small blower cam, and bolt ons, you don't need a whole lot of cubic inches to use all of the air the MP122 will pump. The torque will be there just fine. It won't come in as quick as a 6.0L, but it will be tire roaster in a 3500lb ride.

I'm not looking so much for a high rpm screamer, more looking for something that will make the power reliably and effeciently (with stock parts) for a long time. The shorter stroke and longer rods should be easier on the bottom end. Also, it should use less fuel for every mile traveled.

I'm not looking for a max effort build. I think I can put this thing together pretty cheap, have good power, and still be smooth and effecient when the cruise is set.

old motorhead

iTrader: (10)

A gentleman proposed a trade in a PM. The PM disappeared. I don't remember who sent it. Not interested in a trade and I'm sorry for the confusion. I hope whoever sent the PM reads this.

KCS

iTrader: (20)

Well, if you don't even want ~35 more cubic inches, then I guess this is a moot point anyhow.

However, one thing to note is that cramming the same amount of air, into a smaller space, will typically increase cylinder pressure and put you closer to the detonation threshold, requiring a higher grade of fuel for the same amount of power. The question here is, could the expense of higher octane fuel, or a water/methanol injection setup, negate the supposed fuel economy of a smaller engine? Is there better fuel economy in a smaller supercharged engine, making the same power as a bigger supercharged engine?

Also, what you are doing does not require a "high dollar" bottom end, although I wouldn't attempt it with stock pistons. You can use any stock crank, stock connecting rod combo, so why not enjoy ~35 more cubic inches? It's not a reliability issue, I assure you that. The stock LS2 crank and rod will last as long as you want. The tune and the quality of the machine work will have exponentially greater influence on the reliability of the engine than this rod ratio.

Old SStroker

Because you aren't looking for huge torque, and probably can't use it as you mentioned, I like the idea of the budget 329. If it makes peak power at say 6000, 550 fwhp is about 210 psi BMEP, very doable with the huffer. With some very well modified 243 heads, 550 hp is doable NA on a 329, albeit at a higher rpm and a lot less dirveabilty.

The bottom end, with upgraded rod bolts, is plenty strong. Obviously, the engine should be designed as a complete package: heads, cam valvetrain blower and octane you want to use. OEM lifters and rocker arms are also good. This helps kep the cost reasonable and allows you more of your available budget for headwork. The better the head the less cam and boost you need with a blower. That's heresy to many folks, but not to the engine.

Hans was correct about how GM Racing/Katech got he original 5.7 L CTS racing engine. It also would spin to near 8000 with hydraulic lifters.

Good luck with your project.


Jon

IH8FORD

iTrader: (6)

It was me, no problem thought I would ask before I bought a bare ls2 block.

blackhawk400

iTrader: (1)

I've been told to forget about going this route several times. But I still want to see it done, successfully, and on a reasonable budget. Good luck on the build!

Taspeed

iTrader: (1)

if you do it my understanding is that the deck height and piston height are not the same on the 4.8. You can use the crank, but the rods are not right to get the piston to the top of the bore. I believe they are longer or something. You can't just stab it together. I thought of this years ago, but never followed through with it. Your looking at custom length rods and custom pistons at the very least. other than that everything else should come together. I don't think you'll make the hp your thinking though. Good luck.

Scoggin Dickey

iTrader: (34)

I always thought about doing this, but in the end I couldn't find any real advantages. If you want the cool factor of having the short stroke setup it may be worth it, but cool factor is really the only advantage. Less cubes will not equal better mileage. You won't be able to rev it higher, as the valvetrain is the limit rather than the bottom end. You will strain the bottom end more to make the power with less cubic inches. I think in the fuel economy area it's moot and it won't make much difference. As far as engine life goes, if it is set up well it will last, but the full displacement setup is probably safer than the same power on the smaller displacement setup.

If this is a setup for the truck in your sig, I honestly think you would be stepping down from what you currently have. I'm not a "more cubes is always batter!" kind of guy either, as I have considered something like this myself. I just do not believe the de-stroking option is advantageous for this situation.