Hey guys,

I'm rebuilding a 402 for my '71 Camaro, and I was hoping some of you may have some info I need.

According to my book it says that the piston to cylinder clearance is .0035" MAX.

Now after measuring what I have, it is sitting at .005" Now do you really think the extra .0015" is going to make a huge difference? This isn't a race engine, and I plan on buying file to fit rings to the gaps will be perfect. And I do plan on the very occasional SMALL shot of NOS. I was thinking that the extra clearance may help in a juiced situation? I don't want to have excess piston slap/noise so I am just being sure. This block is already sitting at .060 over the stock 402 size. (4.157" now)


Any info or thoughts on this?


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1971 SS 402 BB
1970 Chev 3/4 ton 402 BB
1997 Z28 (11.43@127MPH)

My Videos Page (http://www.angelfire.com/bc/sscamaro/videos)

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I would say that is a bit much. A forged piston is definately gonna make some noise when cold. The other thing to look for is if the bore has a taper to it. If the bore size changes as the piston moves up and down in the cylinder, this will weaken the sealing effectiveness of the ring. Not a good thing.........Rich

What pistons are they, cast, hypers, slotted forged or drilled forged? Are the pistons showing signs of collapse or are they as new? No doubt it will be noisey and require a proper warm up prior to using, but may very well work for you seeing as you're next piston option is a custom unless by chance the block with take another .093" overbore to 4.250".

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

They are just a cast piston. Not sure of the brand. I pulled the engine apart for inspection, decided to rering & bearing it.

I honed out the cylinders and now this is where I am at. The pistons are like new yet. I really don't want to dish out the large $$$$$$ for custom pistons as nobody makes them any bigger than .060 over.

Hmmmmm what to do.

I'm just worried about the noise. http://www.nastyz28.com/ubb/frown.gif

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1971 SS 402 BB
1970 Chev 3/4 ton 402 BB
1997 Z28 (11.43@127MPH)

My Videos Page (http://www.angelfire.com/bc/sscamaro/videos)

My Home Page (http://www.angelfire.com/bc/sscamaro)

.005" piston to wall on a cast piston is dangerous territory, you stand a chance of breaking a skirt off. How many passes would you say you made with the hone per cylinder?

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)