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A15 piston-to-bore clearance
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Motor was honed out and stock pistons were measured by machine shop and read as follows:

Piston 1 2.9922
Piston 2. 2.9926
Piston 3. 2.9924
Piston 4. 2.9929

All the bores read between 2.9940-2.9941

Clearance is

1. 0.0018
2. 0.0014
3. 0.0016
4. 0.0011

Nissan specs are 0.0009-0.0017. Engine is being built back to stock standards combined with a mild cam regrind from Isky, GX head and dual Hitachi's. Do I need to be concerned about #1 piston bore being out of tolerance that could lead to oil consumption or low compression?

Posted on: 2016/7/22 5:01
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Re: A15 piston-to-bore clearance
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I'd guess it won't cause low compression or oil usage, that depends mostly on how you set your ring gaps and how you CC the head/piston dish. Might cause a tiny loss of power or increased wear over the next 100,000 miles. More piston slap? Datsun tolerances are already higher than Detroit of the same era, so it probably won't hurt

Maybe you can swap pistons around until they are all in spec

So the machine shop measured everything and still got it out-of-spec -- which happens all too often. That's why I prefer to do it myself

Posted on: 2016/7/22 5:13
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Re: A15 piston-to-bore clearance
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He said to swap out Pistons 1 and 4 since the #4 piston cylinder typically runs the hottest. Is it ok to move pistons around?

Posted on: 2016/7/22 5:16
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Re: A15 piston-to-bore clearance
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Another option I have is using Pistons from another A15 block that I have to get within tolerance. Would it be ok to use Pistons from another motor?

Posted on: 2016/7/22 5:53
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Re: A15 piston-to-bore clearance
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It's OK to move pistons around, they should all four be the same

But from another A15, the pistons may differ. There were at least three different pistons designs used by A15. CC the dish to see if they are the same, then weight the piston to see if they are the same manufacture

After moving them around the engine should be re-balanced except if the pistons weigh exactly the same

Posted on: 2016/7/22 6:32
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Re: A15 piston-to-bore clearance
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Ok thanks DD. I'll weigh and cc the pistons from both motors and come up with the best 4 pistons to get within tolerance. They appear to be the same. The motor I am working with is from a 1981 210 car. The other motor is from a 1982 210 car. Where can I find the piston-to-bore clearances in Tech Wiki?

Posted on: 2016/7/22 15:11
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Re: A15 piston-to-bore clearance
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http://www.dprracing.com/scec.html just in case you need to coat skirts to get tolerances up

Posted on: 2016/7/23 3:54
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Re: A15 piston-to-bore clearance
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These motors are very forgiving of "bonus tolerance"
She'll be sweet as mate.

Posted on: 2016/7/23 12:24
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Re: A15 piston-to-bore clearance
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I could be off here but if you add the clearances to the piston dimensions you get 2.994 for every cylinder. Wouldn't you just be moving the issue from one cylinder to the next?

I'd run it and not worry as only #1 is outside the tolerance and it a rely is. My poor tired A12 race motor had way more than that and it still pulled over 7000, the bores were so bad I had to got to 1mm oversize.

Tom

Posted on: 2016/7/24 0:02
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Re: A15 piston-to-bore clearance
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Correct Tom. All the pistons are slightly different in size based on what my machinist measured. So #1 piston will be a little loose. Doug gave me some specs from the 1981 Datsun shop manual (.0010-.0018)and all my pistons are within tolerance with #1 being on the upper end. Machine shop guy said to put the smallest piston in #4 cylinder since it usually runs the hottest. Not sure how accurate that statement is. Maybe I am overreacting based on some comments posted. Motor came out real clean and like the look after having it cleaned at the machine shop. Does it have to be painted or will it start showing surface rust? No harsh chemicals used because I preserved the cam bearings. Rings and gasket set have been ordered. Tri metal Clevite bearings received from ebay. I have had to pick all of this up from different sources. Its been a real challenge finding quality parts.

Attach file:



jpg  specs.JPG (154.33 KB)
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jpg  cylinder.bore.jpg (58.98 KB)
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jpg  block.jpg (115.51 KB)
20677_57942d76a0d0e.jpg 960X720 px

jpg  block.1.jpg (76.53 KB)
20677_57942d82bfe3f.jpg 720X960 px

jpg  block.2.jpg (97.33 KB)
20677_57942d8e17f33.jpg 960X720 px

Posted on: 2016/7/24 4:01
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