BadAssFast

iTrader: (2)

I may have an incorret push rod length when we did heads/cam...we will be measuring next week after the holidays...what are possible indications if using a 7.4 and it should be 7.35 or something else?

MadBill

One would be rapid guide wear, due to excessive side loads from rocker tip scrub.

BadAssFast

iTrader: (2)

Thanks any sounds...like intermittent valve noise? Ex sounds great until warm or sounds noisy cold and better when warm?

MadBill

No, don't think you could count on any sound clues. You'd have to use a Moroso pushrod checker or measure and minimize the 'sweep' of the arm across the valve stem via an adjustable temporary pushrod.

Bombguy99z28

Too short and you will have the pushrod 'bouncing' up and down. Too long and you have too much preload, won't get compression. Unless it is a proven combo that you have confidence in I would always use an adjustable pushrod to determine correct pushrod length. Especially if using aftermarket rockers/lifters.

BadAssFast

iTrader: (2)

Interesting stuff...AFR says we need to use a 20lb test spring too in order not to affect lifters. All this inquiry since I have intermittent valve tick...real odd. Push rod length is probably not the culprit, but we'll check everything carefully.

Beast96Z

iTrader: (21)

Install a test spring, color the valve tip black with a marker, re-install rocker arm, then roll the motor over several times by hand. When you remove the rocker, there will be a line across the valve tip where the rocker was riding. That line should be in the center of the valve. Any line to the bottom side is to long, anything to the top side is to short.

bigdsz

iTrader: (1)

Pushrod length does not determine wipe, only preload. Proper preload is about one turn or about .040. If you are at 1 3/4 or 2 turns preload is too much and lifters can pump up. Wipe is determined by shimming the rockers.

Viper

iTrader: (6)

I thought one turn on stock rockers is .060 being that each quarter turn is .015.

Regardless, I can say different length pushrods DO make different noises. A 7.325 was much louder than my current 7.350. IMHO.

John02SS

iTrader: (47)

You sure about that buddy? I'm pretty sure it is the other way around. Get the swipe looking right with pr's and then adjust preload with shims.

John

BadAssFast

iTrader: (2)

Bump thanks - seriously we will be pulling valve covers off Sunday or Monday and checking over retorquing and trying all these great suggestions. BTW to be more specific...

AFR 205 (#1510 Heads)
FMS FM13 114 Cam
7.4 .080 Futral Hardened Push Rods
Manley Nextek Springs (380 lbs?)(Whatever Futral sells)
The Titanium Retainers that were on the AFR heads (1.8")
Stock 1.7 Roller Fulcrum solid tip Rockers

Byter

iTrader: (1)

Setting the wipe is used to find the correct VT geometry and should be done at ZERO LASH. You use the pushrod checker to set different lengths until you get the correct wipe (basically in the middle of the valve stem). Once that is done, you go about setting the preload.

With non-adjustable rockers, it's a little different because (without shims) your geometry is set if you torque the rockers according to spec (i.e. the relationship of the rocker to the valve stem is set). Changing the length of the pushrod will only change the preload on the lifter. Now, once you introduce shims, the geometry changes.

What does it mean? My guess is that the stock geometry from GM with the NA rockers is fine. If you buy a set of aftermarket heads, you hope that they engineered them and installed the correct valve stem lengths to keep the geometry correct when using a stock setup. If it isn't, then you must use shims to get the geometry correct (by using the wipe method at 0 lash). After that, you break out the dial indicator with a pushrod checker and start playing with preloads for your specific lifters.

Since I switched to adjustable rockers, all this is a lot easier. With a felt tip pen and a dial indicator, I can set the wipe and preload to anything I want.

If I could only find the sweet spot for these damn Comp 850 lifters...

bigdsz

iTrader: (1)

The only time push rod length affects valve train geometry is when you use solid lifters.

BadAssFast

iTrader: (2)

I'm glad I have a competent mechanic and a cold beer. (The beer for me .)

SILVERZZ28

iTrader: (3)

Man I already gave you lessons. You musta failed though