Like I said in another thread I am going to rebuild my engine.

There are some schratches in the walls so I must overbore it.

Is is now a 4.020 bore, I know I can bore to 4.030 but what is the max?

Thanks and greetings,


Erik.

Not sure what the max bore is, but my 350 is now .060 and no problems.

.060 on a pre '87 GM block is about the limit. I believe aftermarket blocks can take more.

I think -- I think somebody sell's .080" over 350 pistons so go from there.

I sure wouldn't order a set before sonic checking the block I wanted to try to use them in!!

pdq67

scratches in the bore?

The bore doesn't have to be absoluely perfect.

engines will run fine for most every use with some gouging in the cylinders.

Agreed to what hhot has to say. FWIW the only blocks we will machine to .060 over (without sonic testing) are the 454's. When we do sonic test the 350 blocks there is maybe 1 in 10 that we are comfortable boring out to .060 over, and we avoid exceeding .040" over if at all possible.

Agree with Rust an hhot... I mike'd the cylinders on my last rebuild and found a max of .003 wear so I just had it clean up and put it back together with new rings and bearings. The cylinder hone cross-hatch pattern in my block was still visible so I'm wondering if that's what you are seeing as scratches? I've never seen .080 over pistons in a 350 and certainly wouldn't want to run them. Some very few lucky ones get away with .060. IMHO

Agreed to what hhot has to say. FWIW the only blocks we will machine to .060 over (without sonic testing) are the 454's. When we do sonic test the 350 blocks there is maybe 1 in 10 that we are comfortable boring out to .060 over, and we avoid exceeding .040" over if at all possible.

I agree

agree'd. i think muskegan still makes .080 pistons as well as a few others,, but why?? another block choice would be better insurance. the thinner you make the cylinder walls from excess boring,, the more power you loose to loss of ring seal from the cylinder walls flexing and chances of the bore splitting. if you can run it again at .020,, it will be stronger than at .040 or .060 over.
i've done lots of .080 over 250's,350's and .125 over 307's in chev,,, and 240/300/302 fords in a production rebuilder environment years ago,, where every block that can be salvaged is just that,, salvaged. but i wouldn't go that far oversize for anything over stock. just not worth the risk unless all your parts, machine work, and labor are free. although the success rate was fairly high,, there's always that odd chance.........
jmo.

I have taken the engine apart and it is not a schratch but is a crack..........


F...K F...K and something more.......

Also the journals are schratched....

So I am looking for a new block with a forged crank....some suggestions??


Greetings,



Erik.

Heck guy..

Please consider one sleeve and I figure the scratches on the journals are just concentric rings so they should clean up fine if you want to have your crank turned under?

AND I have even just dropped a crank back in UNTOUCHED on new stock bearings and used stock rod bearings too and kept right on going!!

Sure she's loose, but whatever, she ran fine for me!!

pdq67

.060 is pretty much it... i have seen a few go .080... but only a very small handful

Fwiw, I think S-O-M is selling all 8-cylinder's sleeved back to stock bore blocks, but only in kits...

pdq67

my engine is .60 over and gets hit with a cheater plate,no problems and car runs too cold actually.

I went .020" over on my 400 build. The smaller the better.

If you are looking for a new block to build, I would highly recommend getting a factory roller block. Then you can easily get roller cam performance for cheap and have a 1 piece rear seal.

we are at .040 on our 400. it will be making some serious power.