Engine/Machinist questions

[blcknspo0ln]

Ok so the block is at the machinist and he says everything looks good to go. Rod #1 will be reconditioned, piston skirts are lightly sanded with 600 and the block is being honed. I had a couple questions on specs and would like some more insight from you guys.

Big woo recommended these specs:

0.0020 on the rods
0.0025 on the mains

As for ring gap, I was doing a lot of research and ross mentions .004 x bore +.004 for turbo app. on their rings. As an example through Ross:

3.625*.004 = .015 (for nonturbo)
3.625*.004+.004 = .019 (for turbo)

My machinist recommended running .0065 per inch of bore so in that same example it would be :

3.625*.006 = .02175
3.625*.0065= .0235625

Not looking at the bore size, since I don't remember what he told me off hand, is the difference from the ross recommended of .004+.004 to the machinist recommended .0065 (which is a difference of .004) make that big of a difference? I know gap is very important, so what spec would you recommend for the rings?


Lastly, .006 for PTW clearance is the ross recommended gap. I will ask again what my machinist measured and would like to know what the standard is and what is considered too tight and too loose.

Thanks guys!
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[outkastracing]

that is a big difference. when i did mine if i remember right for a stock application is .019. i'm running arias pistons and they reccomend going a little more im actually at .023 and have'nt had a problem. now the reason for this is when your boosting and putting pressure on the pistons the rings expand so if you give it a little more your taking the risk of your rings lapping them selves which is not good, and will cause damage to the block!! hope that helps!

 

[Freerevving]

If you are using ross pistons, use their ring recommendations only... The expansion rate of the piston is a little more important than the expansion/behavior of the ring... If you're worried, you can go as much as .005 over on the top ring only... but .002 should be plenty (on top of the added .004)

.022 should be plenty on the top ring

 

[blcknspo0ln]

Thank you guys. I just got news from my machinist so here are the results:

All specs are within +- .0003 of each reading:

mains : .002
rods: .002
PTW: .006

top ring : .021
middle ring: .021 (a little looser than top ring)

I'm VERY happy with the competency of my machinist and he's been understanding 100% of the way.

As a discussion with big woo for future searches:

"First off are you working on a 4G63 motor, if so then standard bore is 3.346, and .020 over would be 3.366."

If so, the ring gap should be 3.366*.004+.004 = .0175 for a .020 piston. It is also recommended that the piston ring for the first ring is a little tighter than the middle ring. So it should be bore*xxx for the first ring and bore*yyy for the second.

 

[Freerevving]

considering the specs you provided, and despite my advice above, I would just go .020 on the top ring but .021 is pretty much the same.

Middle ring specs are definitely best if following the ring manufacturer's recommendations, as rings behave differently... Mahle calls for a tighter-fitting middle ring, but one could still go looser if he wishes

 

[VETTE_50_TH]

For my application for my engine, wiseco rec. a .004 clearance. He said you could tighten it up by .0005 if you coat the skirts, which i didnt, so i went .004. So anything under 50 psi at my comp ratio would be perfect the guy from wiseco said.

James

 

[estoyaqui30]

Who is the machinist that you are using, I would like to find one local that I could use in the future.

Jason

 

[blcknspo0ln]

I went to Rob @ Edwin Automotive in Parsippany, NJ. He did work that far passed my expectation and is a good guy. Tell him Tom referred you.

Rob Hutton @ Edwin Automotive: 973-263-0807

 

[VTEC_THIS]

I agree with Tom. I recently had my block built by Rob - no complaints here. Rob's an honest guy and a good machinist.

 

[estoyaqui30]

thanks, I appreciate that. I will be thinking about doing a shortblock in the near future. Possibly a 2.3 stroker.

Jason