Predator valve adjustment help

Provff26

New member
I know not many people run predators yet but we do at our track. It was low on compression when cold so we adjusted the valves to factory which is 5 and 7 thousandths(int/exh). Not sure if this is supposed to be a cold or hot adjustment. The manual didnt specify. What do you guys set them to if there are any that run them. We are using stock valve springs btw
 

flattop1

Dawg 89
plenty run them .
I would say most are a little tighter. did you check them before adjustment? if so what were they at? The valve adjustment can be a lttle trickey with the compression release. couple ways, at tdc and the other method I do not quite remember but it is when one valve is closing and when one valve is opening. hope some one chimes in with that method as it does seem to be a bit better.
 

Provff26

New member
They were at 3 and 4 before. But this was cold. And the engine was ten lbs down on compression. We alsp did my brothers he gained 15 lbs compression also cold. But im thinking now that it wasnt right to check ot cold and may have revwrse effect when the engine heats up. Im just at a loss
 

flattop1

Dawg 89
should be able to tighten up to near zero. as long as valve stays shut it should not leak . .005 or
.010 it should not gain compression via valve lash adjustment. typically they gain clearance as they warm up.
 

metalmagic

New member
X2......i run my son's at 0 lash with 1:3 rockers with no trouble at all.... They gain about 2-3 thousandths when they warm up
 
I think the Predator is the same as a Clone and has a exhaust relief lever built into the cam, this just makes it easier to crank. But would probably give you false compression readings. jmo
 

Kart43

Member
While turning the crankshaft the correct direction, watch the intake valve will close as the piston rises, just before the piston reaches TDC you will see or feel the exhaust valve bump open, roll the engine a few more degrees and you are now ready to check your valve clearance. You should do this with the engine cold, with your thumb and finger rotate the push rod as you tighten the adjuster down, tighten until you cannot turn the push rod. back off a few degrees until you can turn it again. Lock it down with the lock nut. check push rod again, do both valves at the crank position.
 
While turning the crankshaft the correct direction, watch the intake valve will close as the piston rises, just before the piston reaches TDC you will see or feel the exhaust valve bump open, roll the engine a few more degrees and you are now ready to check your valve clearance. You should do this with the engine cold, with your thumb and finger rotate the push rod as you tighten the adjuster down, tighten until you cannot turn the push rod. back off a few degrees until you can turn it again. Lock it down with the lock nut. check push rod again, do both valves at the crank position.

^^Exactly.
 

Zach Jaynes

New member
While turning the crankshaft the correct direction, watch the intake valve will close as the piston rises, just before the piston reaches TDC you will see or feel the exhaust valve bump open, roll the engine a few more degrees and you are now ready to check your valve clearance. You should do this with the engine cold, with your thumb and finger rotate the push rod as you tighten the adjuster down, tighten until you cannot turn the push rod. back off a few degrees until you can turn it again. Lock it down with the lock nut. check push rod again, do both valves at the crank position.

^^Exactly.


I ran across this while researching about assembling my first motor this week. I'm in no way trying to dispute or question this method, just trying to gain understanding. Why is this particular crankshaft position used to check the valve clearance and how do you know that? Before I read this I was trying to get .003" lash (per the cam card specs) and the problem that I was having was even with the valve closed I could rotate the crank a few degrees and go from probably .003" to ..30" without the valve ever moving. So, I'm gathering that you guys prefer this method described above over getting too technical on the exact amount of "measured" lash. On this note, again just trying to learn, what does more or less lash effect? Sorry for the newbie questions. I'd love to hear back on this from you guys if you don't mind.

P.S. This is a hemi predator that I'm working on.

Thanks,

Zach
 

Kart43

Member
You are adjusting the valve clearance on the base circle (closed portion) of the camshaft. It sounds as if you are adjusting the .003 while on the compression realease, you turn it past the compression release and you have excessive clearance. OR if you are turned past TDC in the correct direction of rotation it sounds like you have missed the cam alignment to crank marks.
 

rkcarguy

New member
Typically in a liquid cooled engine the valves get hotter as the engine heats up( and need space for the valve to grow and still seal), some engines require .018" clearance cold. On these clones, the growth in the aluminum air cooled head actually makes the valve clearance increase as they get warm, so many run as close to 0 as they can when cold to take advantage of every bit of lift the cam can offer.
 

CRT29

New member
You can also adjust the valve timing by increasing or decreasing your valve lash. I'll give up a couple thous of lift to get the correct timing. Esp on the exhaust side. Makes a huge difference.. JMO
 

95 shaw

Site Supporter
plenty run them .
I would say most are a little tighter. did you check them before adjustment? if so what were they at? The valve adjustment can be a lttle trickey with the compression release. couple ways, at tdc and the other method I do not quite remember but it is when one valve is closing and when one valve is opening. hope some one chimes in with that method as it does seem to be a bit better.
The method to adjust on the base circle of the cam.

Turning in the direction the engine runs;

As the exhaust starts to open, adjust the intake valve.

Turn further in the same direction;

After the intake has opened completely and just starts to close, adjust the exhaust.

No danger of being on the compression release.

Works for any engine requiring the valves to be adjusted on the base circle of the cam.
 

Fly

Member
Why are you adjusting the valves on the base circle? On automotive engines I have always adjusted valve lash at tdc of firing stoke intake & exhaust.
Why would these engines be differant.
 

95 shaw

Site Supporter
A look at where the lifters are sitting in the cam at tdc of will answer your question.

The engine in question in this thread uses a rpm deactivated compression release which holds the exhaust valve open near tdc on the compression stroke.
This requires a precise method of finding tdc.
On the correct stroke.
Which also places lifters on the base circle of cam.

The method I've given provides easy visual confirmation of being on base circle of cam, with no chance of being at wrong tdc. Or compression release creating artificial excess lash on the exhaust valve.

In the end, it's about using a simple and consistant method for adjusting valves.
Both methods adjust valves on the cam"s base circle.
 
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Fly

Member
Interesting, but using a rpm deactivated compression release which holds the exhaust valve open near tdc on the compression stroke.
Does that not hurt performance, by lowering compression. Does anyone machine that off.

OK fellows I did my research & see how that thing works by a spring. I have been a motor head all my life. But just shows there is
always things to learn. That thing only works at low RPM. Cool do you guys that race these leave it be? or remove it & use a remote
hand held starter?

Fly
 
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mike97760

Site Supporter
Most classes dont allow remote starters, And if youre man enough to pull start one I would be afraid to run into you in a dark alley. All of our open motors are electric start but our clones, box stocks stock appearing and superstock must be pull start.
 
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