Valve adjustment for Ford 302 after head gasket replacement
GSmith7585
me to pull the pushrods before pulling the cylinder head off. Putting it back
together, I reinstalled the pushrods for the valves and got NO compression-ie.
the pushros were holding the valves open. I back off on the rocker arm nuts
and the valves close and I get compression. But the nuts seem loose to me-I'm
worried that in this condition, they'll come off. This valve train is not
adjustable-the manual talks about getting longer or shorter pushrods for
adjustments but this seems extreme to me. Also, the compression was lower in
all cylinders than before I replaced it (was getting 150 before and 120 now).
Does a head gasket like this need to be run in before you get higher ratings?
I ran the compression tests cold, before the engine could run and before I
bothered to put everything back together. Am I doing this right?
Greg
Bob
pushrods. Also you might try tightening the rocker arms down and waiting
overnight before checking compression. Sometimes it takes a while for the
lifters to bleed down.
Bob Knutson
"GSmith7585" <gsmit...@aol.com> wrote in message
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Dean Dardwin
No you're not. There is a very specific procedure to adjust valve lash.
Either get a service manual or enlist the services of a mechanic.
Whatever you do, do NOT attempt to start the engine or you may do quite
a bit of damage.
Dean
Jonathan Ward
Greg-
I had the exact same problem about 15 years ago after a head rebuild.
Chances are it's your valve springs, assuming the head bolts are at
the proper torque. That, or you have some lifters that have stayed
pumped-up. I'd put it together and run it for awhile, then re-check
the compression.
Head gaskets seal from the time they are torqued properly -- no run-in
possible or needed. Adjusting valve clearance by changing pushrod
lengths is only necessary when extensive milling has been done to the
head and/or deck.
If you have to, you can service the valve springs (and change the
valve stem seals while you're at it) on an assembled engine using an
air hold fitting (made by Lisle and KD Tools, to name two) and a
topside spring compressor that uses the rocker stud as its pivot
point. Rotate the engine until both valves are closed on each
cylinder, pressurize the combustion chamber using the air hold fitting
and your compressor, and you can take the valve train apart without
having the valves drop down into the head.
If you want to be conservative, pull a few valve springs off and have
them tested for compression at a machine shop. Also check the spring
height. Alternatively, just buy a new complement of springs and
seals, and change them all out.
GSmith7585
compression this morning. Also, I learned the rocker arm nuts are torque to
18-22 Ft-Lbs. Still reading lower on the compression but I'm going to retorque
the head today-I may not have cleaned the bolt holes well enough or lubricted.
Thanks!
shiden_kai
"GSmith7585" wrote
That sounds reasonable. I see this happen all the time. Often
when you dis-assemble and re-assemble the valve train, the
lifters pump up and take a few minutes to bleed down. I've seen
more then one tech that I work with start tearing the engine back
apart because they figure they did something wrong. If I can
catch them in time, I grin and tell them "relax, let it run for
a few minutes". It's worse when you have had antifreeze intrusion
into the engine oil, this seems to make the lifters even more sticky
then usual.
Ian
Jeff Deeney
: That sounds reasonable. I see this happen all the time. Often
: when you dis-assemble and re-assemble the valve train, the
: lifters pump up and take a few minutes to bleed down. I've seen
The easy solution is to replace all the lifters while you have the
engine apart. They are only $2/each. If you have large miles on the
engine, it's a good idea anyway. With fresh lifters (no oil in them),
they are easy to compress down and measure lash. I built a simple tool
to loop over the rocker arm & compress the lifter.
On a recent Ford 460 top end job, I had to fiddle with the
shorter/longer push rods. What a pain. It seemed like the sizes of
rods available either put me at the top or bottom of the acceptable
lash. I ended up adjusting exhaust valves toward the maximum lash,
since the exhaust valves end up working their way up into the valve
seats over time.
-Jeff Deeney-
Rex Burkheimer
has a parkerized finish good for breaking in one (1) lifter. Each lifter has
a convex crown good for breaking in one (1) cam lobe. If you put a new
lifter on a cam lobe that has already worn in to the first lifter, it must
start the break-in process over. Except now it doesn't have metal to spare.
The likely (but not certain) result is a cam lobe that fails prematurely.
Having said that, if you have a lifter that just flat won't pump up, you
may have to try just dropping in the one replacement. But first I think I'd
see if I can take it apart (snapring) and clean the internals with solvent
(carb cleaner). Often the period of running flat will have the internal
plunger bottomed out hard and unremovable. Check the surface that rides on
the cam with a straightedge. If the convex surface is flat or concave,
discard the whole thing. If it looks good, reassemble and reinstall.
Hopefully it will now pump up, and you can consider yourself lucky.
--
Rex Burkheimer
Parts Plus Marketing Director WM Automotive Whse., Fort Worth TX
"Never attribute to evil that which can be explained by stupidity" -George
Pyle
"Jeff Deeney" <nos...@thank.you@PROBLEM_WITH_INEWS_GATEWAY_FILE> wrote in
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Dean Dardwin
Most cam manufacturers will tell you it is perfectly acceptable to install new lifters on an old cam, assuming of course, that the old cam is within service limits for lift. What is never permissible is to install a new cam and reuse old lifters; if the cam is new it must be installed with new lifters, preferably from the same manufacturer. If the old lifters will be reused, they must go back on the same lobe. Same deal with pushrods and rockers. Hydraulic lifters generally last as long as the cam unless the engine has been seriously neglected and severe sludging results. In those cases, installing new lifters may be an acceptable, if short term, solution.
The proper way to deal with hydraulic lifters is to soak them in a can of oil overnight so oil is everywhere it should be but to NEVER work the plunger in an attempt to force them to fill before installation. Doing so will at least make setting the proper lash near impossible; at worst, damage the valve train.
If the proper cam lube is used, proper lash is set, and the engine primed, the first start will result in a minimum of noise and wear.
Dean