I was just wondering cause all you ever hear about is the classic .030 383. I just wanted to know if there was a problem in going bigger.

 

I've heard people say that the cyclinder walls would be too thin and you might get to much cyclinder wall distortion or something like that..., generally .030 is as far as you can practically go w/o hurting the blocks lifespan...

 

I wouldn't go >0.030" over under most circumstances on a stock LT1 block. Cylinder walls are pretty thin on modern castings anyway. On the old cylinder blocks (from the 60's and 70's) 0.060" was very feasible. I went 0.040" over on my current motor as a matter of expediency, and it's worked out ok. But the additional <2ci you gain from going 0.030" to 0.040" isn't worth the potential problems, IMHO.

Rich Krause

 

Yea from what Ive read on GM blocks 1980 or newer you shouldnt go very big, but then again I have a '88 305 block .040 wth no problem.

But the block that Im using i a 70 somehting block that came out of an RV, so it should be tough as nails. Its one of the ones that say 10/20 by the cam bore, which means 10% tin 20% nickel. Im going at least .040 but Im undecided on whether I should go .060 because If a break a piston or something I prolly wont be able to just bore out any damage on the block.

 

Even on the early blocks I would be careful. If there is a good machine shop near you just have them sonic check the cylinders. Of course, that just brings up the issue of what is the minimum acceptable thickness. Reccomendations vary between 0.200 and and 0.250" minimum on the thrust side.

Rich Krause

 

Hmmmm...Sonic check Ive never heard that one before. What does that do, tell you how much metal you have between hte bore and the water jacket?

 

Yep, uses high frequency sound (ultrasound) to meausre cylinder wall thickness.

Rich Krause