New member

[910Bluebird]

Hi Guys,

I am an older guy from Melbourne into older Nissans.

I am building my first engine and looking for technical assistance and knowledge.

Can anyone tell me if its better to increase head to piston clearance by machining the head or machining the piston?

I have adequate valve clearance and want the best option.

Thank you.

Gavin

[KiwiRS4T]

Hi there. Depends on what you want to achieve.  Why do you want to increase the clearance when you already have enough? It would be pretty hard to do by machining the head. People who want to decrease the compression ratio usually try a thicker head gasket ...but low CRs are so last century!

[910Bluebird]

Hi  KiwiRS4T,

Thank you for the reply. Whilst I have adequate valve clearance, I only have 0.4 mm clearance (0.016 in) piston to head around the edge of the combustion chamber with the head gasket installed as the head has been machined a few times. The block has also been decked a couple of times so the new forged pistons the engine builder purchased for me come out of the block by almost 0.6 mm (0.023 in). I am currently at about 10.7 to 1 compression and I want to keep the compression up as much as possible.

Thank you.

Gavin

[KiwiRS4T]

Hi Gavin

Would think that you could take a bit off the pistons without too much trouble. If you tried to excavate the head I would think it very hard to do without upsetting the flow characteristics  and also difficult to have each combustion chamber the same.

[PranK]

Welcome Gavin! 

[910Bluebird]

Thank you guys.

Kind regards

Gavin