Increasing Bore on 16V Bigport

[Bluterus]

I'm currently rebuilding my 4AGE Bigport and the number 1 bore in the cylinder block has some rust from sitting around.
I was going to bore it out using 20 thou oversize pistons but I'm concerned about the lower compression.

Any problems anyone else has experienced? Should I shave the head or run a thinner head gasket?

[Skylar]

Woah, can we take a step back here?

If you have a larger bore, the swept volume increases right? and the combustion chamber volume stays the same. Wouldn't that mean an increase in compression with the head gasket thickness being constant?

This is assuming you have standard replacement pistons, not some lower compression piston.

Lastly, I have half mil. oversize standard replacement pistons in my 4AGE. It seems to go fine.

[Hen may possibly be a nut]

Sklar is right. If anything compression will increase very slightly, but here we are talking about 2/5 of 5/8.

There are more important things to spend your time thinking about.

Hen

[Bluterus]

Cool cool. I've never worked on Toyota motors before just Fords so I'm in a new ball park.

I thought that the pistons made up part of the combustion chamber thats why they have the valve relief grooves in them. So by increasing the size of the pistons I thought would increase the size of my compression chamber thus giving lower compression.

Thanks for clearing this up guys.

I wanted to keep stock sized pistons but because of the pitting in the cylinder I will most likely have to go to a 20thou oversize.