how far can i bore?

zookcruzr · Post by **zookcruzr** » Fri May 09, 2014 9:37 pm

I can get my hands on new cylinders and rings that are 50 thou over.
I know 40 is common. I'm concerned that 50 might be to big and jeopardize the integrity of the block as I will be taking it off road and doing a lot of highway driving.
Does anyone know if my concerns are valid? Preferably from experience.
I have read they do crazy stuff in the USA for the ea81 engines in planes but they lose to much power down low under load.

steptoe · Post by **steptoe** » Sat May 10, 2014 7:32 am

do you really expect to get any value out of an extra ten thou over forty - other than brag value ? I think it is much the same with head shaving - how much extra comp ratio would 20 or even 40 thou off an EA81 head really give, and would it be found that much better on a dyno ?

I have gone 40 thou (1.0mm) oversize twice now and got a really good little EA81 each time - compared to an unknown quantity engine before....

Gannon · Post by **Gannon** » Sat May 10, 2014 9:14 am

how much extra displacement does the 1mm oversize provide?

zookcruzr · Post by **zookcruzr** » Sat May 10, 2014 8:26 pm

It's not the fact I want 50, it's more the fact I can get cheap cylinders and rings that size.

YouTube · Post by **El_Freddo** » Sat May 10, 2014 8:40 pm

You mean cheap pistons and rings? Or are you buying a block that's been bored out to 50 thou oversize?

Cheers

Bennie

zookcruzr · Post by **zookcruzr** » Sat May 10, 2014 9:05 pm

Cheap piston and rings. Henley's or something. My father in law who is a mechanic said they're good quality. So if they're cheap enough and it's not to big of a bore I'll get them.

YouTube · Post by **El_Freddo** » Sat May 10, 2014 9:32 pm

40 thou is usually the first re-bore to go with. I don't see why 50 thou would be an issue for a first rebore on the block.

Cheers

Bennie

RSR 555 · Post by **RSR 555** » Sun May 11, 2014 12:34 pm

First is 20thou (0.5mm) then 40thou (1.0mm) but I've not heard of any 50thou pistons, so they might be from something else or someone had them specially made up.

As for using 50thou Pistons, it depends on what you're doing with the car. If you plan on doing some 4WDing and hard work, then I'd say try them but don't expect too much from them, as you'll find the engine will run hotter.