methods of adjusting preload on hydraulic lifters

[1 FMF]

for those who have played with valvetrains, what are you're thoughts, advice, or procedures for setting lash and/or preload on hydraulic lifters?
I asking mainly about American pushrod motors, ford/chevy v-8, running flat tappet or roller, hydaulic (not solid) lifters.
I've read things from various sources. Most recently was current issue of chevy hi-performance magazine, where the guy gets new crane rockers and a stud kit, and they elaborate on how they initially tighten down rocker nuts to 22 lb-ft, then turn engine over 1 revolution by hand, wait 30 minutes for bleed down, find zero lash, rotate 1 rev again, wait another 30 minutes, then adjust zero lash again, THEN tighten down rocker nut 1/4 turn for preload.
I've read and heard many different ways and arguments on how you don't have to wait for lifters to bleed down during the procedure because they're job is to adjust automatically. I've also heard you need to do this with the engine warm to account for expansion, and then the other side of that is you don't because again they're hydraulic and adjust automatically.
And the chevy hi-perf article made no mention of setting zero lash with the lifter on the base of the cam (i.e. completely off the lobe).

and yet again, i have an engine building book and they mention that the best, and only way, to set preload (although during a rebuild) is to set zero lash with lifter on base of cam, then set preload to 0.020-0.030 inch depth using a dial caliper. Going from memory, I think the spring inside most hydraulic lifters can be compressed, with no oil in them, to 0.060". So setting the preload at 0.030" depth allows for 0.030" of movement for expansion and pump-up. This seems the simplest approach with the exception of needing a caliper.

anybody have any experience or words of wisdom to share?

 

[punisher]

Pushrod engine with adjustable rockers, street use- Lifter on base circle, "0" lash + 1 turn. For high rev situations where you are running the engine on the edge of lifter/valve float, "0" lash + 1/4 turn. That being said, always check your rocker geometry, especially with roller tip rockers. Differing your lash/preload will move that roller on the valve enough to cause misery in some situations.

Ask 10 different people and you will get 10 different valve lash/preload adjustment instructions.

 

[TooManyWheels]

1FMF - Punisher has it right, and that also is roughly equivalent to the method of your last paragraph.

I see no logic at all to the first method, unless it is some bass-ackwards way of compensating for not being on the base circle. But as far as I know, if you aren't on the base circle when doing the adjustment, you have no frame of reference to use as a starting point.

 

[mechtech]

Racers will preload a little less, like 1/4 turn, so if the valves float, the lifter won't pump up when compensating and have a valve head hit a piston.
Preload is very useful for valve train geometry.
You want the rocker to ride, or slide, evenly from one side of the valve stem to the other. Many times the rocker tip starts it's rolling/sliding action offset from the valve stem centerline. This causes wear on the valve guide, and less than optimal lift.
You can normally get better contact while still be in a properly preloaded condition. There is a range that is perfectly fine.

 

[TooManyWheels]

In reference to using a caliper to measure, that is an awful lot of work for little or no benefit, especially when you consider the error induced if you aren't experienced at that kind of thing.

A beginner will get better results faster if he measures the threads per inch (same as turns per inch) of the stud, translates that into decimal inches per turn, than figures how many turns are needed to get the desired preload.

 

[Shannow]

I used to get the cylinder at it's TDC (about to fire, so therefore well and truly on the base circle).

back the rocker right off, and spin the pushrod with my fingers, while tightening the lash until I just felt drag. Then tightened one flat.

 

[Hirev]

quote:

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they elaborate on how they initially tighten down rocker nuts to 22 lb-ft, then turn engine over 1 revolution by hand, wait 30 minutes for bleed down, find zero lash, rotate 1 rev again, wait another 30 minutes, then adjust zero lash again, THEN tighten down rocker nut 1/4 turn for preload

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That is scary to me.

Ok, Lets look at a common SBC 3/8 - 24 thread pitch. 24 threads per inch. 1.000 divided by 24 is .0416 so this is your preload at 1 turn. Divided .0416 by 4 and you get .0104. .0104 X 3 is .0312. So 3/4 of a turn on a 24 threads per inch thread is .0314.

Now the problem is a stock SBC Hydraulic lifter is dimensioned as far as valve train geometry for 1 turn preload (.041). Valve train geometry will be effected when you go out of the net figure of 1 turn preload. There are aftermarket lifters that can correct this some. But the problem is you really need to check your valve train geometry. When you start talking 1/4 or 1/2 turn .0208 or less preload.

Best method of adjusting valves.... especially long duration cams is the running direction method. Hint..if your not sure of running direction bump your starter.

One cylinder at a time.

Turn the crank in the running direction until the exhaust pushrod begins to move upward opening the valve. adjust the intake nut at this point.

Rotate crank in running direction until the intake pushrod moves all the way up and goes past the top until it is 1/2 to 2/3 of the way back down adjust the exhaust nut at this point.

Have you thought about just using a solid lifter cam? If you don't get to aggressive with lift and spring pressure they are not that bad.

[ July 01, 2005, 03:17 AM: Message edited by: Hirev ]