l92 head valve/piston clearance

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Jan 14, 2016 | 12:46 AM

gareth12

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l92 head valve/piston clearance

Long long time reader first time poster.

I have an l76 (dod delete) in a s13 nissan with comp cams
281LRR HR13 (231/247 .624). Im going to pull the heads off again in the coming weeks to fit the tie bar lifters i should have fitted from the beginning.

I plan to port/valve job/mill the heads while im there - i hate pulling things apart to put them back together with the same power!

Australian motor, 10.4:1 comp. hoping to deck it .030 to push it to over 11:1. I have heard to watch clearances with these heads, my long winded question is will I be fine with .030?

I'm also wondering what pushrod length i will need as i would like to knock it over in a week i have off work, but i'm thinking i will really need to assemble it and then get some pushrods ordered.

Thanks

Jan 16, 2016 | 12:05 PM

chevyfanaddict

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I hope someone comes in here with answers cause im on the same path as you I believe

Jan 17, 2016 | 03:54 AM

Quick Ranger

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What is your current PTV clearance? That will dictate how much you can mill the heads.

Jan 17, 2016 | 04:54 AM

gareth12

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Not sure, i wont know that until i pull it out and pull a head off and check it. But its a stock motor with the afformentioned cam, so i figured someone would know.

Jan 17, 2016 | 07:19 PM

speedtigger

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Quote:

Originally Posted by gareth12

If this is the camshaft you have: http://www.compcams.com/Company/CC/c...csid=1411&sb=0

I would not recommend milling the head any or using a thinner head gasket without checking the piston-to-valve clearance very carefully first. On an LS3 that camshaft would likely have about .040-.050" piston to valve clearance on the intake valve. If you have a dished piston, you may have a little more, but you need to check.

Jan 18, 2016 | 01:41 AM

gareth12

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Thanks speedtigger, yes thats the cam. They are factory flat top pistons. Gee that is already pretty close stock. How much clearance is neccecary between piston and valve? Naturally i can hand rotate it with some plastigauge but would i be right in saying that even with my PAC 650 valve springs the valves could extend further when the engine is actually running?

Jan 18, 2016 | 03:24 AM

gareth12

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Ok, did some reading, seems .080 is pretty much the accepted minimum clearance, hard to believe a stock LS3 is half that?

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Jan 18, 2016 | 07:12 AM

speedtigger

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Quote:

Originally Posted by gareth12

Ok, did some reading, seems .080 is pretty much the accepted minimum clearance, hard to believe a stock LS3 is half that?

A stock LS3 with a stock camshaft has plenty more than that.

As for the minimum acceptable, it is true that the old standard is .080" intake and .100" exhaust. But, that does not seem to be the trend with the LS community. LS enthusiast often run as little as half that much. And, as long as everything is under control, most seem to do it without problem. I have run .040" intake and .060" exhaust successfully and others less.