82TransAM84

Hello everyone,

I have a question for you, as I didn't find an answer with the search option.

I have to change my valve stem seals on my car (Pontiac Trans AM 1984 with the stock V8 305 4bbl Rochester carbed engine, aka LG4).

So I need to choose the correct valve seals, and for that, I must know the stock size of the valve stem. I looked in my shop manual and didn't find something interesting. There are blank concerning the valve stem diameter in the "engine specifications" section of the shop manual.

I read somewhere 11/32 in is the standard stem diameter on stock Chevy V8 SB. Is that true and does it apply for my car ??

My other questions are which type of seals must I choose ?? As there are different type : positive, o-ring and umbrella.
Does it depend of the type of valves ??

And, just before the finish, which material is the best for a stock engine, except the rubber from GM ?? Viton, Teflon, Nylon ??

Thank you all for you help !!

Sonix

iTrader: (1)

A 3rd gen in france? cool!

I believe the 11/32", standard diameter is what you want.

I'm only replying to stir others into replying, as I don't really know a lot about this.
First of all, you're only replacing these to stop leaks? no perf upgrades at the time?
Umbrella seals are stock, I *think* you need machine work to use positive, but they work way better. As i'm tearing down some 993 heads now, I got the idea they have umbrellas, and o-rings...? maybe those cheesy little o-rings on the valves are something else...?
anyway, hopefully someone else more knowledgeable will chime in...

ede

the positive seals work best, the o ring seals are pretty worthless, i like to use the positive seals and o ring seals both

82TransAM84

Yes, and it's not the only one

Yeah, I plan just to stop the blue smoke that happens sometimes.
It's not too bad but it bothers me a lot to have a smoking car.

And yes, I don't plan to do some upgrades, I try to keep my engine as stock as possible. I think the day I want to improve the performances of the engine, I will stick to a 350

So, it is possible to combine both type of seals ?? That's good to know !!

Concerning the umbrella seals, can't they block the springs if they remain stock too ?? I heard they work well but with a dual springs setup.

Thanks for your help !!

ede

i don't like umbrella seal, but they'll work, but you can't use them and psoitive seal at same time. the umbrella and positive seals go down around the valve guide boss, the o ring goes near the top of the valve stem.

82TransAM84

I think I will follow your advice about the use of both positive and o-ring seals. Is there a brand and seal kit you would recommend ??

Do you think, as Sonix said, that I will have to mod something if I want to use them ??

Thanks a lot !!

82TransAM84

Hello,

Sorry to bother you again

I would like to know if there was a stock standard outer valve guide diameter on the 82-84 LG4 engine heads ??

I saw in my shop manual there was only one type of heads used on all the F-Body V8 engines from 82 to 85

So if someone know it, can you post it here please ??

Thanks a lot !!

Sonix

iTrader: (1)

certain positive seals require milling the valve guide to fit them. I heard fel-pro's vitons are some of the only positive type that DO NOT require machining. May want to confirm this, but sounds like an easy choice...

Yea, there wasn't a lot of choices of heads from the factory, I think they're taking about the "416" castings" . If you want more info, do a search on 416 heads...

I'd think whoever would be selling you these seals would know what the valve guide OD would be... (unless this is going to be an internet order, then...)