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Charter Member
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Discussion Starter · #1 ·
My car has idled for a while now and I think I need to adjust the valves. I ear a few at higher rpms, but my main concern is the lower temp reading I am getting on the #5 header tube. It is about 100 degrees cooler. However, I have heard that coating variances can cause temp variances on the headers.

Hear is my setup:

Ford lifters (new)
Comp Hi-Tech pushrods
Harland Sharpe rockers
Cam is 248/254 @.050 609 lift.

After zero lash how much of a turn should I add? I have heard anything from 1/4, 1/2 and 3/4 of a turn.

thanks
 

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Premium Member
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18,135 Posts
I generally use a hair less than 1/2 a turn. That seems to work every time. I also use Ford lifters.
 

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Former Roadster Owner
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1,861 Posts
Using an up and down motion to feel for zero lash (rather than twisting)I'd tighten them exactly 1/4 turn, and no more.

Here's how I do it:

Pick a pair of valves / lifters to adjust. Watch the exhaust lifter (or valve/rocker etc). Rotate the engine in the direction its intended to run. this would be clockwise in say a 302.

When the exhaust valve begins to open (or lifter pokes out of bore) stop and adjust the INTAKE valve/lifter.

If you're working with a hydraulic lifter type cam, I'd suggest a 1/4 turn of preload as soon as you've felt 0 lash on the push rod between the rocker and the lifter. I also would use the up/down motion rather than the twist method on the pushrod.

After you've set the intake valve, you're going to keep an eye on that intake rocker or lifter. Rotate the engine again, this time let the intake valve open all of the way and then begin to close. When the intake is almost closed, stop, and adjust the EXHAUST just as you did the intake previously.

Continue this process and work your way around the engine until you're finished. It takes a few valve pairs to get use to, but you'll find it quite simple once you've practiced a few times.

-dan
 

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Discussion Starter · #4 ·
Dan-
Can you explain the logic that dictates 1/4 turn vs 1/2 turn? Are there some variables that would mean some applications would need more or less than 1/4 turn?

Thanks for the input.
 

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Super Moderator
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1/2 turn here. That is what my cam manufacturer told me
 

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Former Roadster Owner
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I recommend 1/4 turn because I know it works without (well, much less) the possibility of hanging a valve open. Zero lash is not concrete. Meaning, while one guy does a 1/2 to 3/4 turn of adjustment from what he calls Zero lash, and ends up with .050" of preload another guy will do the same and end up with .110" and has a few valves that won't seat properly.

So...I say 1/4" because the likelihood of someone having a problem is much less than if I recommended 1/2 to 3/4 turn.

If 1/4 turn seems to create noisy rockers, then go back and run them again with 1/2 turn. Personally, I run 1/4 turn, and I've always been happy with the results.

There's nothing wrong with 1/2 to 3/4 turn, but what you're really looking for is .020" - .060" lifter preload.

-dan
 

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FFCobra Fanatic
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I go 1/2 turn from 0 lash. Rare you will need to go back because of a noisy liftr. Think 3/4 to 1 turn is a bit too much. Check the preload with an indicator with 1 full trun and you'll see why it getting to the max.
 

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section 8
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5,136 Posts
The temperature variance could be a mixture issue, Dan is right about the valve lash .020-.060 .Mount your dial indicator ,loosen the rocker arms for number one , run the nuts down until they just touch . Touch dial indicator to pushrod end of rocker set to zero, adjust down .020-.060. Looser is better things grow when they get hot . You'll find that .020 is very close to 1/4 turn. The easiest way to picture this is with the intake off , then you can watch the plunger of the lifter go down as you tighten the nuts . No need to pull the intake just for that . But if you have a spare engine or something and need a visual aid . The factory used bolt down rockers with no adjustment and let the lifter take up the slack . I don't know how much the max plunger movement is but you could test on an old one . Hope this helps , bob
 

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Junior Charter Member
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212 Posts
I would think the amount you turn the adjuster depends a lot on what rocker arm studs you have. A 3/8"-24 stud would provide a 0.020" displacement for a 1/2 turn while a 7/16"-20 stud would move 0.025" for the same 1/2 turn. These values could then be used to calculate the movement at the pushrod end of the rocker arm. Using typical 1.6 ratio rockers, lifter preload would be about 0.040" and 0.050" for a half turn. A 1/4 turn would still be within the 0.020"-0.060" spec. for either stud type. Perhaps at the edge of the spec. for 3/8" stud though.
-Tony LaBoy

[ August 04, 2007, 11:34 AM: Message edited by: Tony LaBoy ]
 
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