Engine displacement=8(pi)*((Bore^2)/4)*stroke.....Thus leaving me with a 4.00" stroke and a 3.9694" piston bore. This project is souly ment for nostalgia purposes....but I needed some imput as far as proper stroke to piston size. What was the original...and what forged parts are available.

 

If you absolutely HAD to have that CI, i would probably use a 3.9" stoke and then bore a 6.0 iron block to whatever was required to achieve that exact displacement.

 

Mine is a 3.905 bore and 4.125 stroke. Most people don't like this set up because of the extended stroke (unsquare).

I agree with Z28mcCrory in saying that I would stay with the stock stroke and either get an LS2 (or resleeved LS1) and bore it out to its appropriate bore.

 

Not necessarily a stock stroke (3.622), but a 3.9 stroke. It would be big money to get over a 4" bore. A stock LQ9 block could be slightly overbored to 4.0xxx to achieve 396ci exactly i think.

 

More than likely I would resleeve....but I wanted to try and avoid any custom machining as far as piston diameter....What do you mean by "unsquare"?

 

If you are going to get it resleeved, you are going to have to have machine work done.

As for squareness, it is often thought as being better to have a bigger bore than stroke. Tons of topics on here if you search.

 

ROCNDAV...I just noticed your 396 Lunatic stroker...what pistons/bore/stroke/rods did you end up going with?

 

I purchased the complete rotating ***'y as a kit from Lunati:

http://store.summitracing.com/partde...rsview=sku&Ns=

 

Just take a page from Chevrolet. Build a 402 and call it a 396.

 

I would say Over and Under square. If you have a square engine your bore and stroke will be the same i.e 4" bore 4" stroke 4/4=1

Oversquare would be when your bore is larger than your stroke.

i.e. LS1 3.62" stroke with a 3.90" bore, or you can determine if you divide the 2 numbers bore over stroke. You must have result larger than 1 to be over
square. 3.90/3.62 = 1.07

Undersquare would be when your bore is smaller than your stroke.

i.e 396 stroked LS1 with a 3.97" bore and a 4" stroke.

3.97/4.00=0.99 Result is smaller than 1 therefore undersquare.

Arthur

 

What are the advantages and disadvantages of under and over square.

 

Erik Koenig built me a 3.9 stroke 4.0 bore 396 Nitrous motor. Works great !!

 

There really is no power advantage to either design. Where they differ is in how that power is produced. Usually, a 'stroker' (undersquare) makes it's maximum hp/torque #'s at a lower rpm. An oversquare motor of equal displacement can produce the same power, but would require much higher rpm to reach the power band.

 

So basically your talking about stoke vs bore....the small the stroke the higher the RPM you can turn due to the decrease piston speed...meaning higher power band, verses a bigger stroker motor.

 

You bet.

 

Have a machine shop offset-grind the stock crank to a longer stroke and bore a 6.0L iron truck block to get the rest of the cubes.

 

The closest I think youre gonna get is to use a 5.3 litre block and use a ls1 3.960 piston (which scoggins sells) and a 4 inch bore crank with a 6.125 rod...that make like a 394ci. Or you can go stock bore 6.0 iron block with the same crank and rods as above...thats a 402...But honestly if your gonna spend the money to put a motor in a car i would do something thats gonna make some big power. like an iron block 414 or something...Utilize the new 4.125 and 4.200 cranks in the 6.0 iron block with a common piston like a 4.030

 

yes you can get a 396ci out of a LS1/6 block
383-4.000 stroke
396-4.125 stroke

 

4.135 bore x 4.250 stroke and 7300 rpm limit. big stroke big rpms need air

 

Just use a iron block, with a 3.9 crank, its standard parts no real funky stuff. He did ATVRacers motor about 3 years ago.