2G Bore out or not

[Victor1]

Should I bore out a std block to max to get the most compression off a 4g63 virgin block or stick to std compression?

 

[Cruciatus111]

Boring the block will not raise the compression of the engine. The only way to do that is to get Pistons that have a lower dish volume. When selecting your compression ratio you also have to think about your goals of the car, if this is for a street daily driver then a 9.0:1 would be good without going too crazy, but if it's for a race only that gets high octane race gas then you can go a bit higher in the compression ratio

 

[CrackedDSM]

Get the block checked out by a reliable machinist, and if he says the cylinders aren't warped or out of round, just go with a good set of fresh pistons in your favorite flavor and go. If you're asking a question like this, I would recommend just keep it OEM. Read, read, read, and top it all off with more research. Find out and learn everything you can, start slow, take baby steps, and enjoy what you HAVE, and not what you are DREAMING about.

 

[Victor1]

Sorry i guess I should have mentioned that; I was not only boring out the block but also thinking of changing piston configuration

Get the block checked out by a reliable machinist, and if he says the cylinders aren't warped or out of round, just go with a good set of fresh pistons in your favorite flavor and go. If you're asking a question like this, I would recommend just keep it OEM. Read, read, read, and top it all off with more research. Find out and learn everything you can, start slow, take baby steps, and enjoy what you HAVE, and not what you are DREAMING about.

Every build I see now has a bored out spec; and with the mileage on these engines now it would seem that it would be the best to just bore it out.

 

[CrackedDSM]

I've seen some virgin blocks test out really well and stay standard bore, but usually it's just safer to bore it .020" over, especially with an aftermarket forged piston, so you know for a fact your P2W gaps are within spec, due to the different expansion rates of the different metals these companies use VS OEM. That, plus you can guarantee it'll seal with an overbore, VS just throwing stock pistons in a standard bore hole and hoping. Not impossible, but it's easier for the machinists to guarantee their work.

 

[steve]

You bore the block to correct for wear. To make sure that the cylinders are round, "square", and the proper size for the piston clearance required.

The difference in displacement between the stock bore and the max bore is less than that of a typical weed wacker.

You can find pistons of various compression for standard and standard oversizes.

As mentioned the "right" compression ratio depends on the expected use.

 

[Victor1]

I've seen some virgin blocks test out really well and stay standard bore, but usually it's just safer to bore it .020" over, especially with an aftermarket forged piston, so you know for a fact your P2W gaps are within spec, due to the different expansion rates of the different metals these companies use VS OEM. That, plus you can guarantee it'll seal with an overbore, VS just throwing stock pistons in a standard bore hole and hoping. Not impossible, but it's easier for the machinists to guarantee their work.

I have recently come across a set of ross pistons that are std bore thinking id like to use them but may end up boring it out to .20 since those parts are coming up and getting cheaper than std

You bore the block to correct for wear. To make sure that the cylinders are round, "square", and the proper size for the piston clearance required.

The difference in displacement between the stock bore and the max bore is less than that of a typical weed wacker.

You can find pistons of various compression for standard and standard oversizes.

As mentioned the "right" compression ratio depends on the expected use.

I agree i havent really thought of increasing the compression other than the occasional bigger turbo and the need to help spool it.

 

[steve]

Check your block first, then select the pistons.

Once the metal is gone there is no replacing it.

 

[Victor1]

Thats my thoughts exactly; has anyone sleeved the 4g63 block with any success?

 

[steve]

Has anyone sleeved the 4g63 block with any success?

http://www.dsmtuners.com/threads/cy...leeving-merged-9-7-block-bore-cylinder.58914/

It's possible, they do it to the fork lift versions of the 4G63 but for our uses I'd consider that block junk unless it was the last one in the world.