Like most of us with the TPI. The valve seals have gone on a L98 in a GTA i picked up. Planning to do the replacement with the heads on the car. I picked up the pictured comp cams valve seals as replacements but they say for a triple spring and will need the valve guides machined? I am not trying to get into all that and would like to just replace them with a drop in replacement that will hold up better than the originals. Does anybody know which seals would be for my 350 TPI without machining?

 

Just get the Fel-Pros. I know they work on an L98 with zero modification. I think Fel Pro has a couple different options, spend the extra $ and get the good ones. The seals are cheap but it is very labor intensive to do with the engine in the car.

 

I get that. I guess the confusing part is that there only seems to be intake seals and no exhaust. Anybody know if this engine didn’t come with exhaust seals?

 

I went through this deep dive about 2 months ago. You buy two sets of those. One for intake and one for exhaust. The factory used those little o-rings in the beginning of time or both intake and exhaust. Then they learned they failed miserably. Somewhere along the way GM started using umbrella seals (plastic cones) on the intake and those failed with little bits of plastic all in the oil pan. Then GM decided to go with those above; but to be cheap they left the o-rings of the exhaust side these scenarios. The internet consensus: if you want to believe what you read is use those valve stems seals on BOTH sides, just in-case.
The way I read it, the intake (obviously) generates vacuum so that oil on the stem gets sucked down the valve guide and you get a "puff" of smoke as the o-ring, and umbrella seals deteriorate. The exhaust side (obviously) allows air out so the oil on the stem is pushed out into the valve cover if the valve steam/ seat is crap. I had to even break out the trusty "How to Rebuild Your Small Block Chevy" Book as reference on this question as the FEL-PRO Engine gasket kit came with (o-rings, umbrella seals, and the valve stems above - but only for the Intake side).

But I am not an expert - this is what I figured out and used two sets when I installed new springs on my rebuilt heads.

Perhaps Sofa, Skinny Z, or Fast 355 will help us out with their wisdom.

 

Appreciate the response. Are you thinking use the intake on both sides? They make an exhaust kit ss72526. But they don’t look like they would do much. I got a set of ss72527 for the intake but I want to do this right when I get in there.

 

No one wants to do things twice; especially I get older, I loathe repeating the same thing over and over. From what I read on some old threads here, use those seals (ss72527) on BOTH sides "just in case", and toss out the rubber O-rings at the top of the valve stem. My logic (flawed as it is) the factory used the O-rings on both exhaust and intake since the beginning of the SBC (55 first production) so obviously there was need to keep the oil from running down the stems on the exhaust side.You can return the ss72526.

 

The .530" seals require the guides to be machined. Stock guides are a good bit larger than that, like .625" or so. Butt if you're getting the guides cut down ANYWAY for whyever, don't bother with those; get the PTFE ones. They're MUCH better in every way.

The O-rings went into the retainer before the keepers. The order of assembly with those was: seals on the guide, valves in the guide, shims locators & springs on the seat (unless the seals get in the way in your particular setup, in which case, reverse those 2 steps), retainers on the springs, compressor on the retainers, O-ring over the stem and past the keeper grove far enough to let the keepers on unmolested, keepers, compressor off. All the O-ring did was to prevent oil that accumulated on top of the retainer from running down the stem.

I would note also, the exhaust ports have vacuum in them at least some of the time, especially with headers. Needless to say, any oil that gets into exh ports, will cause mystery smoke; because you can have smoke, LOTS of it, butt completely clean plugs. A very perplexing mystery, hard to pin down the source, when that happens.

Put the FelPro intake seals on both int AND exh. The reason they don't spec em for the exh is that extreme temperatures can degrade them. In most situations they'll be fine though. Fuhgeddabout da O-rings. They are as useless as **** on a chicken.

 

That is what I needed to hear. Thank you everyone.

 

My car has been doing it since 5,000 miles. It's a prelube. Still runs fine at 80,000 miles, 40 years later.. I would never do the seals unless I pull the heads.

 

Use the Fel-Pro and use the little plastic sleeve the give you so they slide over the valves without tearing the seal. I always put the O-rings on, do what you like with them.

 

I used the O-rings in addition to the umbrella seals too. I used the SS72877 High Temperature ones for the exhaust.