Replacing valve stem seals

Walter Clark

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It seems hard for me to believe there isnt already a topic on this in this forum...

I am replacing the valve stem seals in my 94. The car doesnt have high mileage (<40K) but there is evidence of oil leaking past the stem seals after the car is parked, especially on the intake valves. Also, upon removing a few seals, I noticed the rubber is very hard compared to the new ones I acquired from Viper Parts Depot...well they are at least 29 years old so no great surprise. And when removing them, once unseated from the head they didnt feel especially snug on the valve stem compared to the new.

The primary tool I am using is the Powerbuilt Valve Spring Compressor Tool. As it is a mount-on-the-existing 3/8-24 rocker stud tool for most Ford and Chevy engines, I needed an adapter stud that screws into the 3/8-16 tapped boss in the head for each rocker arm and into the 3/8-24 thread in the tool. I did this using an adapter from McMaster-Carr catalog number 91344A57. It is handy compared to a typical rocker arm stud in that it has an integrated nut which permits me to tighten it (slightly) into the head before installing the compressor.

I am putting each cylinder at TDC and using 100PSI shop air to pressurize each cylinder in turn using the hose of my leakdown tester. (by the way so far I am seeing under 5% on each cylinder).

Some of the keeper/retainers are unwilling to just release with the compressor so I am using a 1/2" drive deep well socket and hammer to tap the retainers after pressuring the cylinder and before mounting the compressor tool. I can tell when it has been loosened because the sound it makes when striking it changes from a sort of boing to a thud. Boing is the valve opening for a moment and the keeper holding tight. Thud is the spring and retainer moving and the valve staying closed.

Once the compression tool is installed on the stud (not fully seated, but usually less than half a turn off) it is easy to compress the retainer and pick the keepers with a magnet. The swing of the arm is obviously going to be limited when doing this job with the engine in place and heads on but I was able to adjust the spring compression foot downward enough to not run into any limits before being able to remove or install the keepers. It is also helpful to get the bottom of the central shaft of the tool as close to the rocker boss as possible, so I dont recommend using a stud with a lot of unthreaded length between the 2 threaded parts, or adding a nut to the stud as these will require that you push the lever even lower to compress the spring.

After removing the keepers I turn the tool 90 degrees CCW to be clear of the spring and retainer and then remove them. Then using a long nose pliers based tool I made some years ago for my 16V VW engine, I pull the old seal. The seals are kept im place by a molded ridge inside the seal slipping into a groove in the valve guide, so the effort to remove it is in compressing that ridge by pulling up on the seal. A couple times I was only able to lift the seal a little with my tool but that opens a space between the bottom of the seal and the spring seat that small prybar can slip into and lift the seal until it comes free of that groove.

I am oiling each new seal with a couple drops of my engine oil and putting it on the valve stem. I am able to fully seat the seal by just pushing with my thumbs. The first couple times I used a tool I made that resembles a nutdriver and was sort of surprised it is this easy going on. Some other engines (VW and Toyota) I have done, require I tap the seal home with a small hammer and suitable tool or sized socket. I am sure it would be harder if I installed them dry, but I dont like doing that since pushing it home can more easily tear the ridge around the inside of the seal.

Then it is a matter of reinstalling the valve springs and retainer, repositioning the compression tool, pushing down and installing the keepers then removing the tool and adapter.

At the moment I have 7 of the 10 cylinders done and it gets easier with each cylinder as I get the sequence and technique down.

Having not done a Viper before, these have been my biggest challenges:

1) Finding a tool that works and doesnt cost well north of $200 (I dont really plan to do this again so buying a professional grade tool seems foolish is something lower in cost will work fine).

2) Adapting the tool I did end up selecting to the head. There are in fact studs for other engine applications that should work as many engines that use studs will put 3/8-16 in the head or block and a 3/8-24 for the nut to hold the manifold, rocker arm, alternator, etc. The Dorman 675-003 looks like it will work, and I have a couple on the way to take a closer look, but it lacks the built-in nut which can be handy.

FWIW I tried using a couple other compression tools but they didnt work out. First was a gear puller/spring compressor style tool, that I already own, with J arms. It will not grab the inner spring so isnt of much use. I looked for alternatives on the web ands they all seem to have similar short hooks and a few even say they dont work with dual spring setups. Next I tried a tool made for Chevy LS engines that bolts down to the rocker bolt bosses and uses a jack bolt with slotted plate and nut to compress both the intake and exhaust springs as a pair. The main issue with this is the LS must use a smaller diameter valve spring or the valves are space much further apart since the part of the plate that holds the jack bolt is more than 1/4" wider than the space between the Viper springs. Also this particular tool angled the jack bolt at a fixed 10 degrees and the Viper valves are canted 19 degrees so it would not have compressed the springs evenly along the valve stem axis and the retainer probably would bind against the valve stem at some point. I saw another similar product that put the jack bolt on a pivot that would address the angle issue but did not get it so I dont know if it also might be too wide to go between the valve springs.
 
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Dan Cragin

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If the car is smoking on start up and oils is getting down the guides,
most likely just changing seals will not fix this.

When I get an older car like this, first thing I do is drop the oil pan and check
a couple rod bearings, if they are good then I do a leak down test. If the
on a warm motor or 10% or less (crankcase pressure), then I move onto the
heads.

Best to pull the heads and have them redone, those seal seldom go bad
on the stock heads. If the heads have been redone, then there could be other
issues, pull them off and send them out to be checked.
 

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