Pushrod Length Results
09-28-2011, 08:29 PM
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Pushrod Length Results I used the EO/IC method using a comp cam adjustable pushrod and came up with the following:
A 7.325 pushrod = 1 1/2 turns to 22 lb./ft w/Lifter preload ~ .0705
A 7.350 pushrod = 1 3/4 turns to 22 lb./ft w/Lifter preload ~ .0822
Thinking about going with the 7.350... thoughts?
A 7.325 pushrod = 1 1/2 turns to 22 lb./ft w/Lifter preload ~ .0705
A 7.350 pushrod = 1 3/4 turns to 22 lb./ft w/Lifter preload ~ .0822
Thinking about going with the 7.350... thoughts?
09-30-2011, 09:00 AM
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I used this procedure:
With my stock pushrod I got about 2 1/8 turns to 22 lb./ft. So I adjusted my adjustable pushrod to 7.325" and 7.350" to achieve 1 1/4 to 1 3/4 turns. Did I not measure correctly?
1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...
09-30-2011, 11:04 AM
#4
Since you have the adjustable, why not do a direct measurement to zero lash then add your preload. Otherwise, you are estimating. I also calculated numbers based on your turns and find you are getting more preload then you think. You have to correct for rocker ratio when you do that.
09-30-2011, 03:39 PM
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Ok heres what I came up with that way. Turns is the number of turns on adjustable pushrod.
8 turns; At snug, ticking
8.5 turns; At snug, ticking
9 turns; At snug, lite ticking/goes away
9.5 turns; At snug, lite ticking/goes away
10 turns; Ticking goes away at snug
10.5 turns; Ticking goes away at snug
11 turns; At snug, no/very lite ticking
11.5 turns; At snug, no ticking
12 tuns; At snug, no ticking
For snug, I turned the rocker bolt till I felt Resistance then stopped. I thought I had this figured out, but now I'm lost again.
8 turns; At snug, ticking
8.5 turns; At snug, ticking
9 turns; At snug, lite ticking/goes away
9.5 turns; At snug, lite ticking/goes away
10 turns; Ticking goes away at snug
10.5 turns; Ticking goes away at snug
11 turns; At snug, no/very lite ticking
11.5 turns; At snug, no ticking
12 tuns; At snug, no ticking
For snug, I turned the rocker bolt till I felt Resistance then stopped. I thought I had this figured out, but now I'm lost again.
09-30-2011, 04:54 PM
#7
You may be compressing the lifter. Go back to 8.5 turns where the adjustable was know to be loose with a small tick. Then gently lift the rocker tip (not too hard or you can compress the lifter plunger) and use a feeler gauge to figure out the gap between the rocker tip and the valve stem. Let's say you get 0.010" feeler gauge thickness. Multiply by the rocker ratio and this will add 0.017" to the pushrod length, or about 1/3 turn (0.017/0.050). Next, lengthen the adjustable pushrod by 1/4 turn (slightly less than the computed value based on the feeler gauge). Re-install and check (gently to make sure you don't compress the lifter). You should be at zero lash or very close and a small feeler gauge may fit. Bottom one it you have to very gentle making the measurements, especially if the lifters are new as the plungers will move very easily.
Hope this makes sense.
Hope this makes sense.
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10-01-2011, 05:30 PM
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8 3/4 turns, feeler gauge measurement was .015. Multiplied by the rocker ratio equals .0255. Which bumps up the number of turns to 9. So 9 x .05 + 6.8= 7.25 Adding preload(.080) gets me to a 7.33 pushrod correct?
At 8 7/8 turns I got .008 on the feeler gauge.
At 9 turns the feeler gauge(.0015) wouldn't quite fit.
At 8 7/8 turns I got .008 on the feeler gauge.
At 9 turns the feeler gauge(.0015) wouldn't quite fit.
