Valve stem seal replacement. A learning experience.

[Grandma’s 68]

Valve stem seal replacement and lash adjustment

There are obviously innumerable posts on these subjects, so I apologize for proliferating.

I have been resurrecting a 1968 c10 that has been parked since ‘87. Spent too much money making it drivable already. It has an 1981 engine from a G30 bread motorhome.

Got the truck in the air conditioned garage earlier this year and started tackling the smoke on starting problem. Here are my experiences to help other novices...

Valve stem seal replacement

Got the Felpro valve stem seals listed on Summit site as apparently for this ‘81 engine; SS72527 for intake and SS72526 for exhaust.

Started by trying the compressed air method to hold the valves up.

Picture 1.

With 100psi dialed in, my little pancake compressor was almost running continuously. As I had not done this task before, I did not know how long each cylinder was going to take, so I aborted this method in favor of the more time consuming (but fail safe) system of stuffing rope in the piston chamber and manually cranking the engine to compress.

Picture 2.

I intended to use the Lisle 36050 Valve Keeper Remover and Installer Kit
Lisle 36050 Valve Keeper Remover and Installer Kit

There are a few issues with this tool for my 350 engine. It can work, if you have enough room to get a good swing with a big mallet (which you probably don’t as my brake booster was in the way), but main issue is reinstalling the spring keepers. Smashing with a hammer will almost certainly dislodge and damage the upper ‘square’ oring seal located just below the keepers. I suspected this and then proved it when I re-removed the spring with the replacement, more gentle, OEM tool.

OEMTOOLS 27040 Valve Spring Compressor

The o-ring the Lisle tool displaces and splits is shown below.

Picture 3.

So I continued with the OEM tool.

Picture 4.

Now this OEM tool needed a bit of adjusting with a hammer to grab the spring better. Even then I felt more comfortable with the help of a zip tie. Another design flaw is the little tommy bar to tighten the screw. It’s loose and inevitably it slipped out. I couldn’t find it anywhere, so fearing the worst that it somehow fell into the intake manifold, I justified the next gadget.
Industrial Endoscope, ScopeAround 1080P Dual Lens Inspection Camera, 16.5ft Waterproof Borescope 4.5” Screen Snake Camera with 6 LED Lights,Semi-Rigid Cable, 32GB TF Card (PU Bag)

Now that’s a cool tool. Thankfully I found nothing in the manifold.

I bought another complete stem seal kit just for the square o-rings to make up for the Lisle damaged one, so plenty of spares now.

Lesson learned: I’d say avoid the Lisle tool, use a slower, gentle spring compressor unless you decide there is no need for the square orings. If you’re not in a hurry then the rope method is quite relaxing, compared to the noisy compressed air, non failsafe, method.

I still have some lingering questions. There were fragments of the original 40 year old square o-rings, but no trace of the white and blue ‘umbrella’ seals which come in the replacement set. Were they possibly not fitted at the factory? Are the umbrella seals optional? Are the square orings below the keepers optional if you use umbrella seals?

Valve lash adjustment

This was a nightmare. I didn’t do a lot of research prior to this job as the chassis manual was pretty clear and straightforward. So I followed the GM chassis service manual which said 1 full turn after getting slop out.

I put it all back together supremely confident, but shockingly no combustion at all! The starter sounded bad was obviously ancient (likely from ‘81). It also seemed like it wasn’t turning over very fast. Bad coincidence I thought. Looking up the part number online the starter was obsolete and replaced by 4 other starters. All 4 of those were also now also obsolete, but without any replacements! Took it to AutoZone who said it failed all 3 tests. I put the new, much lighter, starter on. Messed around getting all the old oil cleaned up down there to help identify future oil leaks, and needed to shimmed it to get the 1/8” clearance to the flexplate. Found a tooth was missing.

That’ll be another project whenever the transmission is pulled.

The truck sounded better while turning over, but same result. No combustion.

After more online research it seems ‪1/4 to 1/2‬ turn is arguably ’typical’ valve stem adjustment. So, I reset all the valves again at 1/4. She did fired up but ran like crap. Fearing I had screwed up pushrods with the 1 full turn, I happen to discovered the distributor lockdown had not been tightened after being professionally replaced (professional mechanic = amateur mechanic who takes money). I thought the smoking gun was me accidentally moving it. Checked the timing, couldn’t get it running good, couldn’t get to the 4deg the chassis manual says. Something must still be wrong with valve adjustment, possibly me bending something!

I read more clearance adjustment articles and one said to wait a couple of minutes for the hydraulic lifter to reset. Lightbulb moment. I was probably not creeping up on the lifter at full extended up position. I could get pushrod wiggle, but didn’t realize the spring/hydraulics are so slow to react. I was probably tightening down too much then backing off and setting the rocker too quickly. Understanding that the goal is to get the hydraulic lifter somewhere mid stroke was key, plus understanding lifter hydraulic bleed off.

I undid all the rockers completely and used the unnecessary shiny new starter to turn it over (without spark plugs) with the goal to pump oil through the lifters. Left them a while more and was then careful not to over tighten the rockers, creeping up gently to the no wiggle point. Kept to just 1/4 turn beyond that, although the manual would indicate 1 turn gets you to ‘center lifter plunger’.

I also changed from the chassis manual method of #1 at TDC and doing various cylinders intake or exhaust. I found that required a bit more concentration than expected. I found the EOIC method much simpler to implement. Cranking the engine with spark plugs out is pretty easy and looking at the pushrod/ rocker is reassuring knowing where the cam is for each cylinder.

Picture 5.

Runs great now. Time will tell if 1/4 turn is too little.

Lesson learned: Make sure hydraulic lifters are fully extended and creep up on the actual tightening. Don’t necessarily follow the GM manual!

[Davidf]

Shoot, trying changing valve stem seals on a BMW V8 (I have done it twice) and what you did will seem like a walk in the park.

I found the best method to set hydraulic valve lash is (from valve closed and rocker loose) tighten the nut while turning the pushrod with your fingers. Once you feel the push rod become harder to turn, then tighten another 1/2 turn and you are good. All you want to do is preload the lifter spring slightly which in turn compensates for temp and wear. The hydraulic portion simply firms it all up while the engine is running.

[RustyPile]

I worked 32 years as an automobile mechanic, did countless valve stem seal replacement jobs.. The tool I used for "heads on engine" seal replacement is this one.. https://www.summitracing.com/parts/oes-25064

Also, I might add -- don't be afraid to move things out of the way, AC compressors, brake boosters, throttle linkage, miscellaneous brackets, etc.. Having room to work makes the job go easier and faster...

[Peanut74]

Nice write up. I normally I use air to hold the valves in place while I change the seals. The tool I used to change out the seals was like the one sold by Summit and worked great.

Never heard to the rope trick to hold the valves in place. I will have to add that one to my list of methods.

I once had a brain fart and took off the keepers of all the valves at the same time. Yep, sure did and yes I had to pull the head to retrieve the valves that fell down inside the cylinder.

[Davidf]

Might be worth mentioning that the SBC is an interference engine. So, if you ensure the cylinder you are working on is at TDC, then you cannot loose the valve into the cylinder.