Bryan Wilkinson

iTrader: (1)

I am curious. With all of these 408ci and 402ci motors out there like the Scoggin Dickie, and others, how is everyone dealing with the piston at the bottom of the sleeve on the 4.00" stroke.

On a C5-R block, this is not a problem because the sleeve is 6.00" long and the block is built for the 4 inch stroke to accomidate for this.

On a 6.0 Iron block, if you go 4" stroke, the sleeve is only 5.5" long. When the piston comes down at BDC, the piston is extremely close to the bottom of the sleeve and rocking will occur. So a off the shelf piston will not work reliably.

On the LS2 block, the sleeve is 5 5/8" long. When I ordered my new pistons, the company that made them was extremely concerned, about the 4 inch stroke in the iron block, at their recommendation they wanted me to move to the LS2 block had me move to custom made pistson to insure that the piston would stay as far in the sleeve as possible on BDC and prevent piston rocking at the bottom of the sleeve. The more the piston comes out of the sleeve, the more force will be placed on the sleeve when it is pushed back in.

I am curious if anyone else has addressed this.

Armageddon

iTrader: (41)

I'm not sure if you've posted this in the internal section yet, but you might find some additional help there. Personally, I've never heard of this, but I'm not stroked and it probably does exist.

ddnspider

iTrader: (26)

then why dont people with ls1/ls6 blocks have a problem when they install a 4" crank?

Tony Mamo @ AFR

iTrader: (13)

What you are refencing is a situation that needs to be addressed, but it is more of an issue with 4.125 and 4.250 stroke LS1's (obviously less "popular"). The key with ANY stroker regarding piston rock at the bottom of the bore is precise piston to wall clearance, and the shape the piston manufacturer designs into the "barrel" shape of the piston skirt. With longer stroke engines, a better designed piston (perhaps not a shelf piece) can make more power due to less rock and better stability (subsequently better ring seal) with a well designed piston.

I wouldn't worry too much about it with a name brand piston and a 4" stroke....you should be fine.

Tony M.

Ben R

I agree with Tony here.

Blown408

iTrader: (4)

So my 408 with Diamond pistons should be OK?

bigdsz

iTrader: (1)

What is the sleeve length on the LS1/LS6?

Bryan @ Speed Inc.

iTrader: (19)

i have a 402 that routinely runs up to 7k rpm and never had one problem... i think it would be more of an issue for the really long throw cranks...... but not 4" imo

CAT3

iTrader: (9)

Is it not offset also by the longer 6.125" rod? I would think the 6" rod, with 4" crank would equal disaster.