I plan on doing a nice blown 358. I dont see many people going 40 over when doing rebuilds. I see 355's then 383's. Is there a reason for this. Will I be running into wall thinning problems if I go 40 over? Thanks for you help guys!

 

.030 overbore is a more common dimension, but .040 should not have a substantial effect on power output or cylinder wall strength.

Are you doing this because your block will not clean up with a .030 overbore? I would not personally bore any larger than you have to. Rings & pistons are more common at .030 over, so why not use them?

.060 is the practical overbore limit & is not recommended unless you intend to save a worn block. Starting at .030 gives you the potential to bore 1 more time, whereas starting with .040 may not allow for clean-up a second time.

 

http://web.camaross.com/forums/showt...threadid=50326

that thread has great info on it
one guy says he's cracked blocks at 4.060 and to keep it under 4.050....

another guy has heard of an lt1 at 4.1" bore

 

I am at 0.040" over, but that is not my choice for a blower motor. When we did the shortblock it was already 0.030" over and I couldn't locate a fresh block in a timely way, so we went with it. I am doing a rebuild this winter and plan on 0.010" over. My belief is that the cylinders on an LT1 are already pretty thin-walled. So the extra beef should promote better ring sealing with more hp and less tendency toward overheating.

Unless it's already 0.030" and you don't want to procure another block, I'd keep it at 0.030" over or less. If you go 0.040" over you will be unable to reuse the block without going to pretty radical overbore.

Rich Krause

 

The problem of the block being a thin walled casting is concern enuf, but the larger concern is the variation of the wall thickness in not just block to block, but also in the same block. Plus, the inherit thin area that adjoins each cylinder.

 

Isn't .040 over a more expensive piston size? Thats what I was interested in at first but I was told that it required more expensive pistons. Remember, these will be blower pistons.

 

If you are talking "high-end" pistons (which you should be) you will pay very little more for a "custom" than an off-the-shelf piston.

Rich Krause

 

rich, i see your sig, and that thing must be a monster! what's ur average track time? hp?


--shokor--

 

Well, the hp is there, but the times aren't all that impressive. This is mainly becuse the car is a "loaded" convertible with no weight reduction measures. It weighed 3,810 without the nitrous system. We me aboard and the nitrous system it should exceed 4,100lbs! Highest dyno was 733rwhp and my best ET was 10.77 with best mph 135. Next year (don't they all say that) there will be another 200rwhp and better traction, but it will be even heavier due to a full cage The goal is 9's with full emissions, acessories, interior, etc.

Rich Krause

 

I definately plan on using high end pistons. Either JE or SRP. I'm gonna stick with stock rods and a stock crank. I think i'm gonna go ahead and go .040 over so if I blow it up, i'll at least have a little room to work with.

 

SRP are not "high end" pistons. JE's are

 

Hi Jordan,
Don't you run a 401 LTx engine? I assume it is a 3.875x4.060, is that correct? If so, have you had any problems with it? I have a 396 LTx engine that needs on the stand that needs to be rebuilt and I was thinking of going 4.060" to clean it up. I would appreciate hearing some of your experiences on this subject.
Thanks,
CT