mx5cartalk.com

Hi All

I'm currently running an 1800 engine in my MX5 2f race car and for some stupid reason I assumed the guy who completed the head work would have shaved the head in order to increase the compression however he did not.

I know the standard head is 133.8-134 mm what I don't know is what is the minimum height before valve hit piston? I'm currently running the Wisco high compression pistons and a mild-ish cam at 265deg duration and peak cam lift of .34892 inch.

Assuming that I have the pistons flush with the top of the block and running a standard head gasket does anybody know what is the maximum I can take of the head?


If nobody know does any body know where I could get such information?

Any help would be greatly appreciated.

Neil

20 thou is a safe limit but I'm pretty sure many have gone more with no problems.

i dont know much about head shaving, that is all i recall

Check the big forum (www.miata.net forum) for more info- There's tonnes on this

^^

He's an idea's man!

Daz 27 wrote:rip the head off, put some soft putty on the valves, fit the head back on, turn the engine over a couple of times by hand, rip the head off again & measure how thick the putty is.

Best and most accurate way to do it, even if someone has the exact same combo then dialing in the cam timing can change the clearance. Better to take some extra time now to avoid the possibility of a sump full of piston pieces and valve heads.