N2OBaby

It seems like now since the LSX race block and the LS7 have gained some popularity that larger bore pistons maybe cheaper to buy.

I was wondering apples to apples comparison(same cam,cr,boost,Procharger F1-A) if a 4.13 inch bore engine with a 3.825 stroke would run better than a 4.03 bore with a 3.622 stroke(FI application)?

What do Ya'll think?

Phil99vette

iTrader: (11)

What are your goals? Why would you use a 3.62 or a 3.825" stroke crank? I would build a 4.125 x 4".

N2OBaby

My thoughts are I want 10.20's-10.70's from a (TH-400) GTO/Monte Carlo SS '93-'02 Camaro.

This is what I am saving/planning for(I am leaning more towards the GTO).

I hear a popular bore size is 4.127 is this better than 4.125?

Phil99vette

iTrader: (11)

Any of those builds are more than you need to get to your goals. I'm partial to alot of torque.

pwrtrip75

iTrader: (8)

Why not just use a stockish 5.3-6.0 if thats all your looking to get out of it?
You're sizing out nuclear warheads to go gopher hunting.

slowlsx

iTrader: (28)

^^ what he said, that's alot of motor for the times your looking for. AES sells a forged 327(5.3) for 2599 I think that would be perfect and reliable for your goals

HydroStream6

iTrader: (16)

How much $$ ya got saved? I'd sell my car for the right $$$. 2004 GTO, 49k miles, garage kept, driven only in nice weather, mint... runs mid low 10s as it sits. Should go 9s with some better tires and a more aggressive tune.

87silverbullet

iTrader: (11)

^^^ There you go. Save yourself some headache and expense.

LSX-coupe

iTrader: (1)

Aes is building me a 4.130 x 3.8 motor right now. Most builders I have talked to say that LS motors love bore more than stroke.

AES Racing

iTrader: (6)

You can build a better piston with less stroke and it doesn't pull the piston out the bottom of the bore with 3.8/3.825 crankshaft.

Also end up with a stronger crankshaft with less stroke.

AES Racing

iTrader: (6)

We're coming out with combination 410ci, 4.130" x 1.200" CH, main use for LSX or sleeved blocks.
First piston order we made is pre-sold.

bore size it doesn't really matter I choose 4.130" bore cause few people come to me with a block that is already been run at 4.125" bore size, with a piston .005" larger will be able to fix any nicks, scratches, out of round or taper the bores may have.

When we torque plate hone LS7 block it ends up measuring 4.126, bit much for a 4.125 piston that may measure 4.120 on the skirt. Rather just hone LS7 block to 4.130".

In order to run 10.20 shouldn't need anything over 400ci, our 390ci setup with D1SC shoudl get you there and hopefully in the 9s.

N2OBaby

HydroStream6 it sounds like you have got a great setup.

It pains me visibly to type these words.

I recently signed papers with a business partner to acquire a 50% share in two homes for rehab/resale.

Once these close I will have three homes in process.

The first home is in move in condition and available for sale currently.

N2OBaby

I had always heard with FI large bore engines with shorter(not real short) strokes makes less low end torque to be compounded by the blower.

Thanks to all of Ya'll for posting here.

I see much more than I did before.

Shawn @ VA Speed

iTrader: (3)

generally speaking, if you have 2 engines of the same displacement, the long stroke smaller bore will go faster at the track. the longer stroke gives you a much wider powerband with more usable power.

let's look at the pros and cons of each


short stroke large bore

pros

bigger bore allows the heads to breath much better
shorter stroke allows for a taller piston and better rod to stroke ratio
shorter stroke gives you a stronger crankshaft and doesn't load the bearings as hard


cons

bigger bore means thinner cylinders which equals more bore distortion and blowby
bigger bore means less area between the cylinders making the possiblity of blow head gaskets greater
shorter stroke raises the rpm range-higher rpms equals more valvetrain issues(which fi engines are harder on valvetrain components to start with)
shorter stroke means less tq, less tq means a looser converter and more slippage in an auto,also slower spool times
shorter stroke means smaller power band


small bore long stroke

pros

smaller bore-less bore distortion,more area between the cylinders,less head gasket issues
longer stroke-more tq,faster spool times,wider power band,lower rpm range,tighter converter. (better valvetrain control)


cons

long stroke-weaker crank,more bearing load,rod to stroke ratio not as good,shorter piston

compromise on cylinder head flow.



let's look at the cons of the long stroke engine


weaker crank-yeah maybe a little, but you have to be really cranking alot of power to figure this out-same with the bearing load. If you use the proper parts there will be no issues

rod to stroke ratio-who cares, if the pistons are made right and the cylinders are round you won't have an issue,unless you trying to do something stupid like put a 4.250 stroke in an iron block,but that's a no no anyway.

Shorter piston- once again as long as you don't get stupid and run the correct ring pack and design the piston properly ther will be no issues.


my 2 biggest likes on the long stroke is lower rpm(i don't like beating up the valvetrain) and more tq. Lets face it,unless we are racing a 2200lb car,we need tq. To the guys that say they have too much tq, i say no,you just need to figure out how to get the car to work better.

turbo'd stang

You can get there either way. Personally....I'd go with something simple and not try to reinvent the wheel.

FlashLCD33

iTrader: (8)

Thanks for taking the time to write that out Shawn, makes a lot of sense

madmax4499

iTrader: (3)

Yes very good Shawn, with all that info what is the answer for the perfect FI engine for what most people talk about on here. most want the infamous 1000-1100rwhp race car they can drive on the street at 800+ on pump gas. I read for hours at a time, everyone has an opinion. some do it with stock parts, some with high end builds. what are the magic numbers? to get all the benefits with as few drawbacks as possible. We all know if you blow hard enough an LS will make great power. what in your opinion is the best all around set up.

N2OBaby

Big thanks to both Fraser Semple of AES Racing and Shawn @ VA Speed.

The new AES 410 cid package sounds great but their 370 & 390 sound good also.

LSX-coupe

iTrader: (1)

What about a PD blower on a short stroke engine are we looking at a lot less low end torque? Reason i ask is that most PD blowers will make ungodly torque down low anyways. Pros and Cons the same then?

N2OBaby

With a 260+ lb driver and a 4000 lb car I will need Torque but I don't want to burn through a rear set of M/T ET Streets every 2 weeks.

Everything in moderation.