.020 or .030 overbore?! ---

[alwayscode390]

My engine is getting ready for a full rebuild. It has 67k miles on it....should I go for the .020 overbore or the .030 overbore?

I have only heard of .030 before, but see a few people running the .020 ... is that because they are rebuilding low mileage vehicles and just wanted to keep the block as thick as possible between pistons? Thanks ---

 

[Luke]

Re: .020 or .030 overbore?! ---

It really depends on the condition of the cylinders im pretty sure that .030 is the most common though. It may not even need to be bored out, a GOOD machine shop should be able to tell you if even a hone would be enough. IF it were me, i wouldn punch it out unless its needed

 

[dgoodhue]

Re: .020 or .030 overbore?! ---

I have only heard of .030 before, but see a few people running the .020 ... is that because they are rebuilding low mileage vehicles and just wanted to keep the block as thick as possible between pistons? Thanks ---

Yeah that may play a factor. I have heard some 4.3 block you can't go over 0.030 and most of them you can't get anymore than 0.040 safely. So 0.030 over block might only allow for one rebuild.

 

[Foot Performance]

Re: .020 or .030 overbore?! ---

i would probably go as little as possible but just honing the engine to me is not the way to go especially for longevity and performance becuase when you bore and engine you set a clearance between the piston and the cylinder wall and if there is any kind of mileage like 60k is defintally enuff ( i biuld race care motors that dont see 2000 mi and i will hone rering and go) that clearance is much larger than a couple thousandths but the rings will be put out there so far you may have problems with high rpm oil burn and later down the road ring gougin do to carbon build up but .010, .020, .030 it does not matter unless you want to keep this blokc for aslong as possible then if rebiulding again later go .020 that way you still have some meat left for the next time

sorry for the spelling

 

[alwayscode390]

Re: .020 or .030 overbore?! ---

Wow, I didnt realize that they are only good up to .040 . I may just put off buying my pistons until the machine shop tells me where to go with it. I would LIKE to be able to do another rebuild after this one someday.

How come .030 is common with the small block chevy's. Can they take more meat out....or are they in the same boat as us? ( I thought THESE 4.3's would be meatier ) ---

 

[dgoodhue]

Re: .020 or .030 overbore?! ---

Wow, I didnt realize that they are only good up to .040 . I may just put off buying my pistons until the machine shop tells me where to go with it. I would LIKE to be able to do another rebuild after this one someday.

How come .030 is common with the small block chevy's. Can they take more meat out....or are they in the same boat as us? ( I thought THESE 4.3's would be meatier ) ---

Also note some 4.3 won't take 0.040. Anyways to answer your question lots of SBC can go as high as 0.060

 

[sleepy]

Re: .020 or .030 overbore?! ---

Just listen to what your machine shop says about boring. Mine was good at 020.

 

[bezerk]

Re: .020 or .030 overbore?! ---

these blocks are cheap, and the .030 is the cheapest.
i wouldn't worry about it

 

[Don W.]

Re: .020 or .030 overbore?! ---

Go with what the machine shop says as mentioned. But think about it .030 is only .015 worth of metal. IMO if the block can't handle that it's a problem. All IMHO.

 

[JSM]

Re: .020 or .030 overbore?! ---

,030 just cleans up 95% of blocks so it has become common overbore. Like others said let machine shop tell you.

 

[dgoodhue]

Re: .020 or .030 overbore?! ---

these blocks are cheap, and the .030 is the cheapest.
i wouldn't worry about it

Personally I am just going to get another block for my truck, so I don't have to worry about screwing up my original number matching block.

 

[tytom]

Re: .020 or .030 overbore?! ---

.020 over it will just have the advantage of having more cylinder wall left after boring...odds are, You wont be able to go .030 over from .020 over on the next bore, because it will rarely clean up with just a .010 cut...sometimes it does, but often it doesnt...so You may be in for a new block either way, imo...

 

[Aeroking]

Re: .020 or .030 overbore?! ---

just dropped my spare block at the machine shop, and the machinist said that .010 should clean it up, he recommends .020. But after searching Summit for pistons, it looks like the most commonly available size is .030 over.

Any opinions??

 

[EcSy#2671]

Re: .020 or .030 overbore?! ---

just dropped my spare block at the machine shop, and the machinist said that .010 should clean it up, he recommends .020. But after searching Summit for pistons, it looks like the most commonly available size is .030 over.

Any opinions??

Look at RPM they have .020 SRP pistons