I need to replace my valve stem seals and o-rings and would like to know if someone can tell me what the standard size (11/32" or 3/8") is for the L98 engine. Also what would the standard rocker arm stud size would be (3/8" or 7/16"). Thanks so much.

 

I believe the stock rocker stud is 3/8ths on an L98. I don't recall the valve stem diameter, If you ask for the valve seals /orings for your year and model car at the parts counter, you should get the right ones. By the way, I just did mine . What a PITA but worth it! :cheers:

 

3/8" is the standard stud size. I think my valve stem seals were 11/32".

 

Though your '85 exhaust valve assembly differs (it has a cap & rotator assembly) from that of the intake valve both have the upper & lower valve seals.

I got a set of upper O-rings & lower seals from my Chevy dealer for about $50-$60.

It might be a good idea to also replace the keepers to avoid the chance of a dropped valve.

 

How did you replace 'em?

Heads off?

Air line into plug hole?

Rope in cylinder?

What?

I am just starting a cam/springs swap.

 

I did mine heads on with an air fitting in the plug hole and valve spring compressor. The hard part was removing the valve covers. On the driver's side, I had to remove the air pump pulley so that I could back out (not remove completely) the mounting bolt that interfers with the valve cover removal. I also had to remove the perimeter studs that attach the valve cover (mine is an iron head with perimeter studs and nuts). Only other thing was that I used a differential pressure gauge to bleed air slowly into the cylinder so as not to cause the piston to move down in the bore from TDC. This also gave me the opportunity to check my cylinder leak down rate (true measure of compression sealing). This is not necessary but you could use any kind of valve to meter the air pressure in slowly. Sometimes the keeper doesn't want to release before the air pressure seal is broken. If that happens, reseat the valve and let the pressure come back up(70 to 80 psig). Try lightly tapping on the retainer as you apply pressure with the valve spring compressor. A magnet is ideal for removing the keepers . Then just remove the nut, rocker retainer, spring and old seal /o ring and replace. Adjust valve one turn past zero lash and you are done with that one. Repeat 15 more times after turning each subsequent cylinder up to TDC on compression stroke.
It's not that hard but it sure is time consuming and tedious. Good luck!
:cheers:

 

Thanks for that, sounds like I may as well take the heads off, its the header removal that bothers me there though, but then I could do a clean up and port the heads a little. Sounds like a PITA whatever though.

Wish I was a rich B and could pay some other mug to do stuff like this.

Ah well - We was poor, but we was 'appy.

 

IMHO

Don't remove the heads, and don't use air. Use a piece of rope. If your valves are really gunked up, they won't let go of the retainers. You need the pressure of the rope, against the face of the valve (held in place by the piston) to push up on the retainers. Definitely buy a magnetic pick up tool, to retrieve the retainers once they do let go.

The job's not that hard, assuming the valves and the retainers part ways.

Good luck with it.

:cheers:

 

I've heard of the rope in the cylinder technique. I just haven't tried it. I would think that a clean braided nylon rope would be best since it is less likely to shed fiber into the cylinder. I still like to use air pressure because it can also be used as a measure of cylinder condition/sealing. BTW, If I was rich I would still do my own work; one cause I enjoy it and two If the work is not done right , I have no one to blame but myself. Good luck! :cheers:

 

And THREE: We ALL know you can't even pay GOOD money to get good work THESE days!!!
I do ALL my own work, from adding fluids to zaino and EVERYTHING in beteween.
That's from A-Z. Bumper to Bumper,top to bottom.
Had a 35x40 shop built just to maintain these Vettes (and my other vehicles)
But I like to call it 'Jim's Corvette Garage'.

I do GOOD work and I CAN afford to pay someone else to do it.
In the past I always came out feeling like I had a 'screw me, I'm stupid' sign pasted to my forehead after I paid for sehx with those quick buck guys out there that didn't know peadoody about what they were doing.

So, I do whatever necessary MYSELF and when I'm finished I can say "MAN! That Job Looks Beautiful!! And, I KNOW it's perfect because I DID IT.

And FOUR: I just LOVE working on these Vettes. It gets me up and away from these computers for a little while. (software engineer)

If you want to spend MOST of your time working on your Vette, get yourself two or three of them. They're almost worse than children. Always NEEDING something. :) :yesnod: :lol: :)

Good luck with your valve seal job.. it's not that hard, just a little messy.

Oh, I'll give you a little tip on your valve adjustment after you have changed the seals:

With the engine cold, I take NEWSPAPER and put them along the edge of the head just above the exhaust. This catches any oil it'll throw out when you crank it up and do the final valve lash adjustment.
You can let it run long enough to adjust the valves before the exhaust will burn the newspaper. (It only takes a few seconds per valve to readjust them)