Gearhead6s

does anyone have any information on building a 402ci LT1?
i've searched a few times but haven't found what i'm looking for.
i can build a 402.1ci with a 4.00" bore and a 4.00" stroke but i can't find forged pistons that are for stock bore size. would it be better to go with a larger bore and shorter stroke? the problem there is that cranks usually skip from 3.875 to 4.000. the 3.875 crank with a 4.060 bore yeilds a 401.3. i guess you could call either one a 402 but i would think the 402.1 would be more true. has anyone built a 402? i thought i saw something that Lingenfelter built a 402 or 421 or something like that.
how you any of you experts recommend doing it? and please don't tell me to just do a 355,383,or 396 because i like to do things differently. i am looking for a block to get started with as i type this. i think i have everything else except the cam figured out and i think i am just going to get a custom grind to meet my needs. any input on a 402 LT1 would really help me, thanks a lot guys.

rskrause

The cylinders are thin on LT1 blocks, and many blocks suffer from "core shift" such that the center of the bores are shifted away from their intended location with the result that the walls are even thinner than designed. Older production blocks had thicker cylinder walls and more careful casting. As a result, it's not generally a good idea to take a Gen II LT1 block more than 0.030" over but the older Gen I production blocks are usually ok to 0.060" over. Gen II's can be sonic checked for bore shift and may be safe to go more than 0.030" over. We checked mine and I went 0.040" over, but the block is also partially filled.

Rich Krause

frmula1

how did you work that, and still have the car running cool for street driving, with a % filled waterjacket?

Perry93TransAm

If you fill it to the bottom of the freeze plugs you should have no problems on the street. You could also put steel plugs in the deck then drill a hole through them , have the block decked and strengthen it mucho as well.

rskrause

Like Perry said, by filling just to the bottom of the freeze plugs it's not usually a problem. Actually, it makes the oil run hotter more so than the coolant. And generally, hot oil is better provided the correct viscosity is used and it doesn't get too hot.

Rich Krause

Gearhead6s

so if i stuck with the stock 4.00" bore and went with a 4.00" stroke then i should be ok right? i know i have to clearence the oil pan rails and other parts of the block for such a larger stroke but as long as thats not a problem then i should be good to go right?

marshall93z

is this an lt1? i didnt know you could get 4 inch stroke for the lt1'S

Gearhead6s

yes its an LT1 as far i know you can use a standard small block 350 crank in an LT1 a Lunati, Eagle, Scat, and i'm sure a few others make 4.00 cranks.

Injuneer

Mark Montalvo ran a 4.125" crank in his LT1 421ci stroker. You can get a 4.00" stroke LT1 409ci short block off one of the engine builder sites.

I think going "exactly" for 402ci is a bit obsessive, and maybe not the best thing to do. You are going to have to use the existing bores exactly the way they are, and if its not a brand new block, that's a mistake. The bores need to be cleaned up. You can buy custom made pistons in virtually any bore you want, so 4.00 forged pistons can be had... you are just paying a premium for them. Seems odd to either risk a poor quality rebuild or pay extra for custom pistons, just "to be different".

Gearhead6s

Thanks Injuneer thats the exact type of answer i was looking for. i was thinking that it would be difficult to find a super clean block with a 4" bore that didn't need any clean up with out buying a new one. i will price a few blocks from work to see what i can get a new one for but it looks like i will be going with something like a 405 or a 409 depending on how much the bore has to go over.the unique factor was just the original drive to do a motor this size, i would never let a factor as trivial as that compromise the integrity of my engine. if i get lucky and find a super clean block or the money for a new one then i will be going with the true 402, but if all that don't work then it will prolly be a 409. thanks for the help guys.

LT5

Not a 402....but this 396 looks very promising....

https://www.cantonracingproducts.com...et_thunder.pdf

shoebox

This thread is 13 years old and the guy sold his car 5 years ago and left the site. Why dig this up?