Kent Deck Height

[Chipv]

I have a new block and am looking for recommendations for deck height. I’d like to leave a little material in case it needs a repair in the future.
thanks
Chip
Crossle 62

[bob darcey]

It's not an answerable question. Assuming you're building an uprated motor for your FF, the compression ratio limit is 9.3:1. The variables are the piston choice, your connecting rod length and your actual bore and stroke. You need to put those components together, cc the volumes and do the math.

[EACIII]

Chip,

I have a graduated beaker with stand you could borrow if you decided to do the cc thing.


Ed

[jrh3]

I’m surprised no one has suggestions. There are lots of resources describing how to calculate clearance. A used Felpro head gasket I just measured at 0.038-40”. Some suggest 0.035-40” is a conservative safe clearance. YMMV. Trial assemble the lower end and see what you have, deck to your liking.

[Chipv]

I guess the better question is how compression ratio is measured by SCCA and how they use the mins and maxes in the GCR for things like valves and bore diameter.


I do have a calculation which aligns pretty well with what you folks are saying. Right now I get 8.208 to get 9.3 vs a delivered height of 8.225. (I shouldn't be surprised by this number since Jake Lamont says the standard deck height is 8.210)


For each extra .001 of height looks like a loss of about .022 of ratio. I'm just going to have to decide how much I want to give up for re-surfacing.


Volume at TDC is comprised of the volume of the piston dish and valve reliefs (measured with a syringe) the annular volume around the piston above the top ring, and the cylindrical volume above the piston to the deck. (both calculated)


I have a Ford gasket that measures .040 and a Fel-Pro that measures .038 uncompressed. Which makes me wonder about the measuring procedure because the GCR says only approved gaskets may be used which goes without saying but I think the implication is they will not measure the volume of this but rather check that it is an approved gasket and assume something for its compressed height.


Thanks for the feedback. I just wanted to get this chat out there. I couldn't find anything on APEX on this topic so anything people can share is helpful.