killab18

Hey whats up. i tore down my cobra motor.

i noticed that like 3 of the cylinders had a big piston to wall clearance. like an 1/8th inch. this seems like alot.

I have been searching for over a week now and cant find any answers.

what should the stock piston to wall clearance be? I want to try and get away with using stock bore pistons.

and on forged pistons, if you keep it stock bore, do they come slightly larger due to running a tighter piston to wall clearance? or will they come exactly the same size as my stock pistons now?

Im trying to keep the price down on this rebuild. the hone on the cylinders was just done about 1000 miles ago. previous owner honed it, new rings. new bearings.

but the 3 cylinders look like a big gap.

well any help will be great. here is a pic of what im talking about. hard to really see but hopefully you get what im talking about.

pcs

in the service manual it says the
max taper in a bore 0.0002in
out of round service limit is 0.0008in
bore diameter coded red 1 3.5539-3.5544 in
coded blue 2 3.5544-3.5549 in
coded yellow 3 3.5549-3.5554 in
piston to bore clearance limit is 0.0008-0.0018 in

killab18

what is the deal with the coded red blue yellow stuff?? im sorry if i dont know. im an import guy who builds nissans. first v8 im doing.

but yea my piston to bore is ALOT bigger than that.

killab18

what is the deal with the coded red blue yellow stuff?? im sorry if i dont know. im an import guy who builds nissans. first v8 im doing.

but yea my piston to bore is ALOT bigger than that.

off to the machine shop for them to measure my bore and see what size pistons i need.

now do they make like a stock piston that is .020" over?

pcs

not sure what the codes are for? i didnt look it up in the book.
they do make 20 over pistons as well. are u just doing a stock rebuild or are you going performance oriented?

killab18

we dont know yet. im trying to see cost of everything.

i know that they make oversized pistons. but they are usually aftermarket ones and forged. which in return are pretty expensive.

i dont know if this car will ever see any type of forced induction so im trying to weigh out pros and cons and if it seems likely for a supercharger/turbo setup is in the future.

so im asking if your able to get stock pistons oversized. like whatever the stock pistons are made out of.

i know its not ideal but my pockets arent huge and this rebuild is already going to be about a $1000 even using all my stock parts.

i dont know if your answer was yes they make oversized pistons that are not forged. or yes they make oversized pistons. implying that companies make them. i.e diamond, cp, je....

but i dont want to use stock bore due to the big p/w clearance.

so im just trying to price things out both ways. i can get rods for a great price but i cant find pistons for any cheaper than about $600

pcs

well just reuse what u can and buy what you have too, pistons. good luck and keep looking to see if you can get a good deal on those pistons.