Setting rocker arms
Thread Starter
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Setting rocker arms
Gday people, ive just had my heads done up and put them back on the car today, should have it all put back together sometime tomorrow.
I am wondering what i should set the rocker arms at after zero lash, i know what the service manual says, but it assumes all is stock, which is not my case.
I dont know what cam is in there, it was there when i bought the car. The lift height at the lifters is about .320 intake and about .345 exhaust. Rocker arms are Crane Cams gold race 1.6:1, and the springs are doubles and also Crane Cams parts.
Thanks in advance
I am wondering what i should set the rocker arms at after zero lash, i know what the service manual says, but it assumes all is stock, which is not my case.
I dont know what cam is in there, it was there when i bought the car. The lift height at the lifters is about .320 intake and about .345 exhaust. Rocker arms are Crane Cams gold race 1.6:1, and the springs are doubles and also Crane Cams parts.
Thanks in advance
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The only advantage to zero lash, is that the lifters can't pump up. If the plunger is already at the end if it's travel, then it can go no further. The disadvantage is that the lack of preload allows for no self-adjustment for wear. Any increase in the lash(?) will start to make noise. Unless you rev your engine to or beyond the pump up point for your combination of parts, there is no reason for zero lash.
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: Feb 2005
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From: The Motor City
Originally Posted by Casethecorvetteman
I am wondering what i should set the rocker arms at after zero lash, i know what the service manual says, but it assumes all is stock, which is not my case.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
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From: Kempner Texas
Anyone else read where TPIS is recommending NO LESS THAN TWO FULL TURNS from zero and, also, has gone as far as THREE FULL TURNS on their engines?
Sounds way over the top to me. Anyone tried that yet?
Jake
Sounds way over the top to me. Anyone tried that yet?
Jake
Drifting
Joined: Aug 2002
Posts: 1,475
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From: Speedo Indiana
You DO NOT want to go three whole turns. Here's how you do it... If the motor runs, let it warm up with the valve covers off. As soon as you see oil seeping out of ALL of the rocker arms, shut the motor off. Then disconnect the coil and bump the motor starting with cylinder #1 until you see either rocker arm compressing the valve spring fully. At that point loosen the rocker arm over the NON COMPRESSED spring until you can spin the pushrod between one of your fingers and your thumb. As soon as you are not able to easily spin the pushrod between your fingers, simply retighten the rocker arm one-half turn. Obviously after you tighten down this rocker arm you need to bump the motor until the rocker arm you just adjusted is now compressing its spring fully, whereby you now adjust the other rocker arm for said cylinder. After this cylinder is completed, repeat this proceedure for each cylinder. Don't forget to reattach your coil wire.
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Le Mans Master
Joined: Feb 2005
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From: The Motor City
Originally Posted by JAKE
Anyone else read where TPIS is recommending NO LESS THAN TWO FULL TURNS from zero and, also, has gone as far as THREE FULL TURNS on their engines?Jake
bottom of this pic. shows the page number and catalog reference:
Last edited by mseven; Nov 7, 2006 at 02:26 PM.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by mseven
Comp Cams used .030 as the recommended ammount of pre-load. When I measured that equaled 3/4 of a turn past zero. I have read here on the forum that others prefer 1/2 turn past zero.
With a rocker arm stud with 20 threads per inch, one turn of the nut equals .050" movement. Three quarters of a turn, .75 X .050" = .0375". Close.
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Le Mans Master
Joined: Feb 2005
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From: The Motor City
Originally Posted by CFI-EFI
With a rocker arm stud with 20 threads per inch, one turn of the nut equals .050" movement. Three quarters of a turn, .75 X .050" = .0375". Close.RACE ON!!!
Last edited by mseven; Nov 7, 2006 at 02:43 PM.
Pro
Joined: Nov 2002
Posts: 737
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From: Charlotte MI
Originally Posted by Casethecorvetteman
Gday people, ive just had my heads done up and put them back on the car today, should have it all put back together sometime tomorrow.
I am wondering what i should set the rocker arms at after zero lash, i know what the service manual says, but it assumes all is stock, which is not my case.
I dont know what cam is in there, it was there when i bought the car. The lift height at the lifters is about .320 intake and about .345 exhaust. Rocker arms are Crane Cams gold race 1.6:1, and the springs are doubles and also Crane Cams parts.
Thanks in advance
I am wondering what i should set the rocker arms at after zero lash, i know what the service manual says, but it assumes all is stock, which is not my case.
I dont know what cam is in there, it was there when i bought the car. The lift height at the lifters is about .320 intake and about .345 exhaust. Rocker arms are Crane Cams gold race 1.6:1, and the springs are doubles and also Crane Cams parts.
Thanks in advance
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Assuming 3/8" fine thread studs, one turn is .041" and change. I've never done the math for the 7/16" studs. W/O looking at my tap and die set, I don't know if they have a different TPI or not. The type of lifter can make a difference. For instance, CC has a lifter that they absolutely state should only be preloaded a very few thousanths, maybe .005" or so tops, can't remember the exact number. I've run my stock LT1 lifters with anywhere from 1/8 to 1/2 turn. Never noticed any difference in noise or performance. It has been shown though that running minimum practical preload is good for a few HP on a dyno up high. I generally run mine at 1/4. I like to minimize the chances for any problems should pump-up occur.
Jake and Mick, what kind of lifter is TPIS stating that adjustment for? (I didn't check the link yet) I can only assume that it is required for a particular lifter design.
Jake and Mick, what kind of lifter is TPIS stating that adjustment for? (I didn't check the link yet) I can only assume that it is required for a particular lifter design.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
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From: The Motor City
Originally Posted by Corvette Kid
Jake and Mick, what kind of lifter is TPIS stating that adjustment for? (I didn't check the link yet) I can only assume that it is required for a particular lifter design.
The earlier post of their catalog is reference to setting lash for hyd. rollers across the board, no other special settings are listed.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
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From: Kempner Texas
Originally Posted by TONYDEE64
You DO NOT want to go three whole turns. Here's how you do it... If the motor runs, let it warm up with the valve covers off. As soon as you see oil seeping out of ALL of the rocker arms, shut the motor off. Then disconnect the coil and bump the motor starting with cylinder #1 until you see either rocker arm compressing the valve spring fully. At that point loosen the rocker arm over the NON COMPRESSED spring until you can spin the pushrod between one of your fingers and your thumb. As soon as you are not able to easily spin the pushrod between your fingers, simply retighten the rocker arm one-half turn. Obviously after you tighten down this rocker arm you need to bump the motor until the rocker arm you just adjusted is now compressing its spring fully, whereby you now adjust the other rocker arm for said cylinder. After this cylinder is completed, repeat this proceedure for each cylinder. Don't forget to reattach your coil wire.
After all the years I've spent twisting on Chevy engines, I was taken aback by the most recent information from TPIS. In fact, TPIS included dyno graphs supporting their "new found" setting recommendations.
To be flat out frank about it, they fly in the face of what we have, over the years, learned to be normal parameters.
I caution, lets' not have a NIH (Not Invented Here) mentality and, out of hand, discount what TPIS is proposing until and unless we've actually put their recommendations to the "test"
I'm not resistant to change, as long as the change gives positive results.
They jury's still out on this one.
Jake