Comp R's Extremely Sensitive to Preload

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Nov 20, 2003 | 10:19 AM

LS1x2

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From: hou

Comp R's Extremely Sensitive to Preload

I just recently rebuilt my shortblock and swapped the cam and lifters as well. The 5.7L heads are milled .030". I was running stock lifters with a 7.350" pushrod without excessive valvetrain noise. I am running stock rr's. Upon initial startup the valvetrain was extremely loud. I thought it was the lifters pumping up but it wasn't. I could wiggle a few of the rr's by hand with the motor off. I swapped in some 7.4" stock pushrods and the vavetrain got nice a quiet. The problem was it sounded like the motor only had 2 valves. think some valves were hanging open a bit. The car ran fine, but i am sure it would have died at high rpm. I then shimmed the rocker up .025" last night using the 7.4" pushrods still. It is almost right. 1 rocker on each side is a tad loose with the valve all the way open. It looks like I'll end up extremely close to zero lash and a quiet valvetrain with some .015" shims. I recommend some adjustable rr's with these or have fun shimming them 3-4 times like me

Nov 20, 2003 | 10:43 AM

CHRISPY

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How much are the adjustable rockers?

thanks,
Chris

Nov 20, 2003 | 10:53 AM

LS1x2

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From: hou

Well you have alot of choices but you need valve cover spacers, etc. Usually you are out $1k when it's all said and done!

Nov 20, 2003 | 11:39 PM

Jabroni

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From: Orlando

Strange. Unless I've been reading prior posts wrong, I thought everyone was saying the R's were not too sensitive to preload. Hmmm. Half a turn or so and they were good. Did I misunderstand this?

Nov 21, 2003 | 12:37 AM

Nickn20

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or you can use some 7.25 pushrods? hehe I have some for sale if you are interested

Nov 21, 2003 | 07:37 AM

LS1x2

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From: hou

Quote:

Originally Posted by Jabroni

Strange. Unless I've been reading prior posts wrong, I thought everyone was saying the R's were not too sensitive to preload. Hmmm. Half a turn or so and they were good. Did I misunderstand this?

They are wrong. So far I have used 7.35 pushrods(loud as hell), 7.4(a little to tight), and 7.4's with a .025" shim(little too noisy). They seem to be sensitive down to .010". I am thinking with a .015" shim they will finally be just right. They don't pump up like a stock lifter so there is less room for error on the preload.

Nov 21, 2003 | 12:34 PM

Chris99WS6PWTMET

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From: Orange Park, FL

Speaking with Comp Cams I was told that the recommended pre-load is .000 to .005. I spent alot of time getting mine shimmed properly since it is almost impossible to use a dial indicator with a magnetic base on our aluminum blocks. With a TR224, 7.4 PR's, and .015 milled heads mine came in almost perfect at .030 shims.