Building an A15 engine, but won't be able to measure the block for a long while.

Does anyone have accurate measurements on if the pistons come below the deck or flush with the deck at TDC? If so by how much?

Also what is the piston dish CC (has offset dishes in the pistons)

Engine is factory spec.

Thanks

They are flush with the deck. CCs for offset-dish pistons vary as there are three different ones

Any idea if the CC of the different piston dishes is on the forum? Had a look and couldn't find anything.

http://datsun1200.com/modules/mediawiki/index.php?title=Piston#A15

The G34 piston is probably the most common however the dish CC is not listed

The H97 piston has 6.5mm deep offset dish (CC not listed). This deep dish is used with the short-valve head

Other piston dishes range from 2 to 7 mm deep

Quote:

Are you trying to find the static compression ratio of your engine build? If so my recent experience on my A12 proved the numbers in the wiki incorrect for CCing a cylinder head. A brand new NOS H72 head I have never milled, never on a motor, never built worked out to 41 cc’s .

I think the wiki says 25 to 30 mL so I found relying on that info completely inaccurate for figuring out the compression ratio of this motor. Best to physically see the piston in the block and the head individually.

As an example the H 72 head I’m using is 25 mL and it’s been milled substantially, to the point where I need to use index washers on the spark plugs to clearance the piston tops as they’re forged And actually stand above the deck.

Overall my point is just do it physically so you know with certainty what it is you’re putting together.

Good luck!