.60 over block for STS turbo set-up

I was wondering if going .60 over would be to much for a STS set-up or to much on the street. I dont plan to spray. I can get a cheap deal on a .60 block. Just wondering if I should build that up or just go with a 355. I want to run up to 15psi

.060" will be fine. I'm running .060" at 20 psi making more power than an STS can.

I'd wait for a block that can go 30 over or less.

Technically you're okay with a .060" over. Your walls are obviously thinner and there is a higher risk to breaking the block of course, but that comes with the high-boost territory.

The biggest downside otherwise to starting with a .060 block is if you have everything done to this block like some fill, convert to 4 bolt mains, prep the thing etc etc and then break something and gouge the cylinder wall it means there really isnt any more you can do for it and you have to start all over.

If you start with a stocker and bore .020 over you can rebuild the block several times over most likely. A stock bare block is usually in the $100 range, so I wonder what your deal is and if its already had prep work to it.

When I learned that some are successfully running .120" over, I felt fine about running mine .060".

Mike

When I learned that some are successfully running .120" over, I felt fine about running mine .060".

Mike


And I've seen more than a few break at 060 over (had one fail personally), in NA applications. Just because guys are running 120 over doesnt mean it's smart. :D

And I've seen more than a few break at 060 over (had one fail personally), in NA applications. Just because guys are running 120 over doesnt mean it's smart. :D

I've been fooling around with race engines for a long time and have NEVER seen a block split down the cylinder bore. I've seen cracked deck surfaces and blown out main webbing, etc. . . but not a broken bore. The difference in hoop stress between a .250" cylinder wall and .235" cylinder wall isn't going to cause it to suddenly crack straight through. If yours failed this way, then something else was very wrong.

Mike

For those who say 60 or 120 over is ok on a stock block with high boost, explain just how thin a cylinder wall can be before causing problems?

Rich

According to Bill Jenkins, author of "The Chevrolet Racing Engine", the cylinder wall should be more than .215" thick. The 3 LT1 blocks I've measured start out at .250", give or take. This means you could go to .070" and stay within his specification. As far as .120" goes, I wouldn't do that with boost, but it has been done in NA applications. That leaves .190" wall, but according to David Vizard you can go all the way down to .170".

I've been fooling around with race engines for a long time and have NEVER seen a block split down the cylinder bore. I've seen cracked deck surfaces and blown out main webbing, etc. . . but not a broken bore. The difference in hoop stress between a .250" cylinder wall and .235" cylinder wall isn't going to cause it to suddenly crack straight through. If yours failed this way, then something else was very wrong.

Mike

Actually, sorry Mike, there wasnt anything else wrong. The block was machined perfectly, and was run for awhile at 30 over with no problems whatsoever. It was again checked and adjusted as necessary when it went 60 over. It was a racing engine (circle track motor), but even after 60 over initially it never had any overheating issues, was never starved for oil, and was never overheated. The motor had always seen perfect bearing wear, or lack thereof of any wear. A cylinder just ended up letting go. It wasnt because of ring or piston damage, or improper install of either of the above. We found nothing in the oil that could have caused the damage. It turns out that particular part of the block was just ever so thinner than the other cylinders, but certainly still within "spec". Maybe it's because it was a race engine. Nonetheless, it wasnt an ultra high compression engine (right arounf 11:1) and it was run on race gas. Anyways, I just prefer to have the thicker the better. It is always just a safety margin.