valve clearance issues

[Anonymous]

i check the valve clearances on my '68 200. The #2 exhaust and #3 intake had very low clearances, like 0.02. since the car is using hydraulic lifters i'm a little confused about why this clearance needs to be checked and what to do about it. i know the shop manual says to use 0.060 shorter pushrods but i haven't seen anyone who sells thoses?

any help is appreciated.

-evren

 

[CZLN6]

Howdy Evren:

Engines with Hydraulic lifters should have zero clearance and a slight preload.

Older engines can develop clearance with time and wear and sometimes sticking lifters, but that is not good and is usually signaled by the audible clicking. The solution is to tighten clearances by replacing your non-adjustible rocker arm assembly with pre-'65 adjustible rockers and pushrods.

Using the shorter, but impossible to find pushrods would only make the matter worse. What you need is a slightly longer pushrod. FoMoCo originally made the shorter pushrods to accomodate for head milling and OEM shim type gaskets. Your problem is that you have more clearance then the hydraulic lifters can compensate for.

Adios, David

 

[Anonymous]

Hi

thanks for the reply.

the shop manual has a part about checking the clearance in which you are supposed to push down on the pushrod and bottom out the lifter then check the clearance. otherwise the rockers are touching the valve tips. so i realize that the clearance with hydraulic valves should be zero. but the shop manual for some reason talks about pushing the push rods down and checking the clearance. the shop manual says that the clearance should be between 0.065 and .206, something like that. i'm really confused by the whole thing. should i just disregard this? anyone know why this check would be necessary?

-evren

 

[Falcon62]

Evren - Ideally, you want your hydraulic lifters centered in their travel, so, if the range is .065 - .206, you would want your clearance to be somewhere around .1355. As long as the clearance is between these two numbers, the hydraulic lifter should maintain a zero lash condition.

If you find you have too much clearance, the lifter plunger can no longer take up the slack, and you end up with tappet noise. Then you either replace your pushrods with longer ones, or as David suggested, replace with an adjustable rocker assembly and matching pushrods.

Hope that helps! 8)

 

[DYNOED250]

mabie its there just to confuse u. it could b there to measure pre load on the lifter..... but thats a weird way of doing it.
in my engines i have ran no pre load on lifters, just enuff to take up the slack, that way at high revs the lifter can not pump up, and hold valves open.

 

[Anonymous]

i have too little clearance on two valves - what can i do to increase that clearance? i think the rest of the valves are right in the middle of the range, so they're good. will i have lash problems if i don't fix the two "bad" valves?

also the engine was just rebuilt, i'm putting it together now. the pushrods, lifters, and the whole rocker assembly are brand new. i bled the lifters but maybe i need to check these clearances after the engine has been run a bit?

 

[DYNOED250]

r these two valves sunken at all in the head giving u a tighter clearance.
these two lifters might b full of oil and arnt allowing u to bottom them out to check them properly.... compressing a lifter thats full of oil is pretty hard

 

[Falcon62]

EDIT It's possible you aren't fully bleeding down the two lifters in question. Other than using shorter pusrods to gain necessary clearance (establishes proper lifter pre-load), you could shim your rocker assembly .040 - .050", but then you might have too much clearance on the remaining valves.

I think I would doublecheck the two questionable valves and go from there. If the clearance comes up the same again, then it might be prudent to check and compare the stem height of those two valves against the others.

 

[Falcon62]

mabie its there just to confuse u. it could b there to measure pre load on the lifter..... but thats a weird way of doing it.

This is the method Ford recommended for checking proper lifter pre-load on non-adjustable rocker assemblies since the mid-60s. They even had a special tool made just for this practice. You are right, it does take time to fully bleed down a lifter.

 

[Anonymous]

i feel like we're almost talking on the phone with the quick replies. thank a lot, i really appreciate you guys helping me out especially with the quick replies from everyone. the only down side is that i can't get any work done cause i just keep thinking about the car
and writing back

i think you're right i think the problem is the lifter are not going down. i wonder if i these two were not bled properly (by me of course) or if the other 10 were not bled properly. i check them a couple of times and got the same result, the lifter doesn't budge barely at all. i know about that special tool but i don't have it of course, i just pushed down on the pushrod end of the rocker with the wood end of a screw drive handle, so it would be hard for me to apply a lot of pressue on the lifter so i may not be able to get them to bottom out.

i may just go ahead with the rebuild and assume this is okay? unless this could be a serious problem? what do you guys think?

 

[Falcon62]

Well, if you're just using the end of a screwdriver handle, then you probably didn't get them fully bled down. This is one reason I do not pre-prime a hydraulic lifter before installation, the other being I like to use an adjustable rocker assembly and it makes it more difficult to detect the slight drag while spinning a pushrod and adjusting the rocker.

It will probably be just fine to continue with the rebuild. Most people don't even bother to check lifter pre-load on non-adjustable rocker assemblies.

 

[Anonymous]

yeah will do.

thanks again for all the help everyone.

-evren