Max out of the hole

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user-30257

Re: Max out of the hole

Post by user-30257 »

sccagt1racer wrote: Wed May 16, 2018 6:34 pm I'm assembling a ls engine for a friend and from my calculations its going to be .012 -.015 out of the hole. I have a .051 head gasket right now and could go thicker if needed. How much is too much out and what is the min quench I'll be safe at. Ive been told .038 -.040. Its a ls6 with a wiesco forged piston. wiesco 6.125 rod and stock crank. Its going to see a max rpm of 7200 road race car.
Too much would be when the top ring comes out.
sccagt1racer
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Re: Max out of the hole

Post by sccagt1racer »

Being out of the hole is not a problem any more. The block was over bored by the machine shop and is now scrap. Thanks everyone.
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Re: Max out of the hole

Post by B Original »

Connecting rods, crankshafts, wrist pins, and pistons do not stretch but is a certain amount of deflection to be considered? Depending on component weight, and centrifical forces of the RPMs? Or would this deflection be negligible?
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Re: Max out of the hole

Post by cjperformance »

Headguy wrote: Fri May 18, 2018 1:28 am
sccagt1racer wrote: Wed May 16, 2018 6:34 pm I'm assembling a ls engine for a friend and from my calculations its going to be .012 -.015 out of the hole. I have a .051 head gasket right now and could go thicker if needed. How much is too much out and what is the min quench I'll be safe at. Ive been told .038 -.040. Its a ls6 with a wiesco forged piston. wiesco 6.125 rod and stock crank. Its going to see a max rpm of 7200 road race car.
Too much would be when the top ring comes out.
:lol: so true
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Re: Max out of the hole

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B Original wrote: Fri May 18, 2018 6:47 am Connecting rods, crankshafts, wrist pins, and pistons do not stretch but is a certain amount of deflection to be considered? Depending on component weight, and centrifical forces of the RPMs? Or would this deflection be negligible?
In any material stress results in strain, however little. That said, squish change from static cold to dynamic hot is the cumulative result of the thermal expansion of the block, crank, rod and piston (from pin bore to crown) plus possible piston rock and the inertial loads on the moving parts. Going too tight can sometimes be deduced by a sudden increase in blow by above some RPM limit, as the top rings are unloaded by the pistons striking the head.
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Re: Max out of the hole

Post by grant6395 »

Built a 472 cid sbf 6.400 rod/ 4.250 stroke. She's WAY out of the hole. Lol. .120 cometic.
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Re: Max out of the hole

Post by tonyg64 »

Does anybody taper the top land slightly to stop scuffing on the change of piston direction?

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Re: Max out of the hole

Post by MadBill »

If the piston was 3.0" tall and the skirt clearance 0.005", the maximum 'tilt' would only be 1/10th of a degree, so the top of a 0.300" high land would only come about half a thous. closer to the wall than the bottom.
The reduced top land diameter to accommodate expansion due to the possible ~ 500°F. crown temperature is usually quite generous*, so, no. (*The resulting crevice volume is a discussion-worthy topic.)
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