piston cylinder clearance

[Frankensteinz2]

Hey guys,

I am curious what you more experienced z guys have to say about piston to cylinder clearance. I sent my engine to the shop and they told me i should have .002 clearance. He told me my worst piston is .004 and that with cast iron pistons, that was excessive. I looked in my engine book by Monroe and he says .002 is standard, however max clearance is .009. Can I stick with these pistons for daily driving or is this too much?

One other thing, I bought a stock cam from MSA and they get theirs direct from Nissan. (I had to pay premium but I believe this will not be a softer after market cam) I am curious if my old rockers look fine would they be ok to stick with or should i get new?? I am told they are pretty forgiving. Plus they are like 27 a piece!!!!!!!!!!!!

I am trying to save some cash but not if i am going to loose quality. However i don't won't to spend if i don't have too.

Thanks Frankie

[Phred]

Cast piston clr. is generally .002 for a new piston/bore. Most used engines that are out there and running fine, probably have around .004 like yours. You stated your worst clr. is .004, so that will not be a problem for an older street engine. I must point out that I would never attempt to put an engine together with .009 clr. That is way out of line. More important on an old piston is the ring land clr. That's the clr. between the ring and groove when the ring is installed. A new piston will generally have about .0015 to .0025 ring land clr. If you have anything over .005 land clr. your engine will probably smoke, as the ring will flex and flutter and not seal well. If you replace the rings, at minimum, make sure to ball hone ( flex hone) the bores.

If you have a new cam, send in your Datsun rockers to have them resurfaced. This will save you some money and they will work great. I have even used resurfaced rockers on race engines with no problem.

Phred