Correct preload for an LS1?
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Installing the rockers right? If they're adjustable you want to get to top dead center on that cylinder and then get to zero lash (push rod becomes difficult to turn with fingers) - meaning no slack in the system, yet no preload. Then you want to go an additional 1/4 to 1/2 a turn and you're done.
The stockers, or non-adjustable ones just require a torque down to 22 lb/ft. (My Yella Terras said 25 lb/ft) The manual has a special procedure that you can follow after adjusting both intake and exhaust on cylinder 1 (stock cam). I can give it to you if you need it. For an aftermarket cam I feel safer just getting each individual cylinder to approximately TDC then torquing... I just think compressing a valve spring will skew the torque readings.
The stockers, or non-adjustable ones just require a torque down to 22 lb/ft. (My Yella Terras said 25 lb/ft) The manual has a special procedure that you can follow after adjusting both intake and exhaust on cylinder 1 (stock cam). I can give it to you if you need it. For an aftermarket cam I feel safer just getting each individual cylinder to approximately TDC then torquing... I just think compressing a valve spring will skew the torque readings.
Thread Starter
Burning Brakes
Joined: Apr 2006
Posts: 976
Likes: 1
From: Lincoln NE
I've already replaced my cam and used 7.400's. This is the standard size that TSP sells. It was what they suggested at the time of sale.
the cam is a 228R btw. I didn't think anything more about it. THe install went fine and got it tuned... valve train is kinda load but i'm told that was normal.
My buddy just did a cam swap and put down some really low numbers for hsi cam. Torquer V2. from TSP. Used the same 7.400 rods in his. Put down 360 with all the supporting mods. This is the exact same dyno i put down over 380 with my cam. So we started looking around and found that his preload is really high. Can't remember the exact number but i think it was in the low 90's.
after watching this i got curious and popped the valve covers off mine and measured a preload of 66. I've done alot of research online to find out what the idel preload is and i can't find a common answer.
one of my buddies who's been building engines for years said the magic number is usually around 30. i've found numbers ranging from 30-90. to me that variation is huge. TSP suggested 40-60. in that case i'm outside their suggestion and on the high end. So before i go buy another set of rods i want to clarify what the correct preload is.
the cam is a 228R btw. I didn't think anything more about it. THe install went fine and got it tuned... valve train is kinda load but i'm told that was normal.
My buddy just did a cam swap and put down some really low numbers for hsi cam. Torquer V2. from TSP. Used the same 7.400 rods in his. Put down 360 with all the supporting mods. This is the exact same dyno i put down over 380 with my cam. So we started looking around and found that his preload is really high. Can't remember the exact number but i think it was in the low 90's.
after watching this i got curious and popped the valve covers off mine and measured a preload of 66. I've done alot of research online to find out what the idel preload is and i can't find a common answer.
one of my buddies who's been building engines for years said the magic number is usually around 30. i've found numbers ranging from 30-90. to me that variation is huge. TSP suggested 40-60. in that case i'm outside their suggestion and on the high end. So before i go buy another set of rods i want to clarify what the correct preload is.
Thread Starter
Burning Brakes
Joined: Apr 2006
Posts: 976
Likes: 1
From: Lincoln NE
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Rocker Adjustment
The rocker procedure calls for 1-1/2 to 1-3/4 turns plus 1/8 turn lock-down. With 1.8 rockers, us 1-7/8 final location this comes out to 0.120" of lifter pre-load based on a 3/8-16 thread.
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Thread Starter
Burning Brakes
Joined: Apr 2006
Posts: 976
Likes: 1
From: Lincoln NE
contradictory preloads is all i seem to find... I dont' understand how there can be so many "standards" or "correct answers" to what should be a pretty cut and dry answer.
I'm honestly starting to believe no one knows the answer and it's kinda a grey area.... 8 years ago i could understand there still being questions but dangit my car is almost a decade old.. heck some C5's are. How is it i keep getting different numbers????
I'm honestly starting to believe no one knows the answer and it's kinda a grey area.... 8 years ago i could understand there still being questions but dangit my car is almost a decade old.. heck some C5's are. How is it i keep getting different numbers????
Last edited by N0TDADYS_98; Jun 14, 2007 at 11:12 PM.
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Ah, I see you were talking in like.... thousandths of an inch. Yeah, in that case I don't know. I agree, there's no real "truth" to setting the preload. I've seen so many different ways to put on rockers it's downright confusing. It seems most people throw 'em on and if it works... they stick with it. I'll see how mine runs very soon... I ordered +0.025" by the cam grinder's recommendation.... and I have Yella Terra non-adjustables. I had to use the shims as without them the pedestal wouldn't touch the cylinder head, lol. 
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
contradictory preloads is all i seem to find... I dont' understand how there can be so many "standards" or "correct answers" to what should be a pretty cut and dry answer.
I'm honestly starting to believe no one knows the answer and it's kinda a grey area.... 8 years ago i could understand there still being questions but dangit my car is almost a decade old.. heck some C5's are. How is it i keep getting different numbers????
I'm honestly starting to believe no one knows the answer and it's kinda a grey area.... 8 years ago i could understand there still being questions but dangit my car is almost a decade old.. heck some C5's are. How is it i keep getting different numbers????
Last edited by vettenuts; Jun 16, 2007 at 08:34 AM.
Thread Starter
Burning Brakes
Joined: Apr 2006
Posts: 976
Likes: 1
From: Lincoln NE
thanks for the replies guys. I believe my buddy gets his new rods today. we are going to drop him down to .04ish i don't have hte numbers infront of me. will report back with the difference in performance both at the wheels and the behavor of the valve train... better he take the walk in the dark than me...
I think as mentioned above; If you slam them in and it runs then great leave it be seems to be the way things are done. I would have never thought to investiage this until this happened to him... makes me wonder how many other people that are disappointed in their numbers at teh dyno and track couildn't correct their problem with a simple rod swap....
I think as mentioned above; If you slam them in and it runs then great leave it be seems to be the way things are done. I would have never thought to investiage this until this happened to him... makes me wonder how many other people that are disappointed in their numbers at teh dyno and track couildn't correct their problem with a simple rod swap....
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
thanks for the replies guys. I believe my buddy gets his new rods today. we are going to drop him down to .04ish i don't have hte numbers infront of me. will report back with the difference in performance both at the wheels and the behavor of the valve train... better he take the walk in the dark than me...
I think as mentioned above; If you slam them in and it runs then great leave it be seems to be the way things are done. I would have never thought to investiage this until this happened to him... makes me wonder how many other people that are disappointed in their numbers at teh dyno and track couildn't correct their problem with a simple rod swap....
I think as mentioned above; If you slam them in and it runs then great leave it be seems to be the way things are done. I would have never thought to investiage this until this happened to him... makes me wonder how many other people that are disappointed in their numbers at teh dyno and track couildn't correct their problem with a simple rod swap....
