[AdamIsAdam]

Hi all. I'm going to keep this simple. I posted a long thread over at CP.com that you can read more here if you like.

Basically, I want to know EXACTLY how to install both the O-rings and valve stem seals on my stock 68 350 (#17 heads). Factory manual states 0 rings used only, so that's what I did. But I'm getting a big puff of blue smoke at startup, and am going through a qt of oil in about 200 miles! Prior to my installing the cam and new springs, I was getting some puffs of smoke, but not going through any oil!

My felpro gasket kit cam with valve stem seals that look like #2 in this picture.


I didn't use them as I was told I didn't need them, just o rings.

Can I use those rubber umbrella seals with my stock valves? WHAT ORDER do the parts go in? Rubber umbrella seals first, sliding all the way down to the head, then put o ring in to the lower groove (lower= away from hood), then put spring assembly back in.

This right?

ONE LAST THING: I can't get #7 springs off because brake booster is in the way. I have two spring compressors. There is nearly no clearance between valve cover and booster. Anyone have a compressor that works in such tight spaces?

TIA!

[AdamIsAdam]

Buying new springs today. How about these: Crane CRN-99838-16 ? They're in stock. The crowler 68404s are not in stock at my local speed shop. Any thoughts?

[screamingchief]

Buying new springs today. How about these: Crane CRN-99838-16 ? They're in stock. The crowler 68404s are not in stock at my local speed shop. Any thoughts?

Easy one first,the only crane springs I avoid at all costs are their "single with damper" #99840-16 springs,those are junk!!!

Now the crane #99838-16 are Ok I guess,but a bit "stiff" over the nose when compared to the crower #68404-16 springs,and often that added pressure is unnecessary and just adds to any potential "wear related issues",the seat pressures are nearly the same between those two springs,but the cranes have a higher spring rate (438 lbs/in vs. 338 lbs/in) thus the additional open pressure.

I myself would advise finding somebody who can get the crower springs,or buy them direct from crower if needed,JMO/FWIW.

Now the valvestem seal deal,first point to clarify,are the guide bosses machined for the "positive" style seals to begin with?

Some heads are,some are'nt.

Can I use those rubber umbrella seals with my stock valves? WHAT ORDER do the parts go in? Rubber umbrella seals first, sliding all the way down to the head, then put o ring in to the lower groove (lower= away from hood), then put spring assembly back in.

Ok,now to point out the mistake,a common one at that,lets forget the umbrella seal for the moment and go right to the O-ring seal,you cant install the O-ring before installing the retainer,it just does'nt work right that way,it usually damages the seal or just pushes it down on the stem where it wont seal,the entire spring assembly needs to be compressed with the retainer in place and then the O-ring is slipped into the groove and the locks installed and the spring compressor is released,I know this sounds counter-intuitive,but that's how it has to be done or you will likely have issues.

Also if you use just the O-rings,you almost hafta use the sheet metal spring shields as well,or too much oil gets on the stem and you get the oiling issues you mention.

[AdamIsAdam]

Now the valvestem seal deal,first point to clarify,are the guide bosses machined for the "positive" style seals to begin with?

I don't know. How can I tell? got any pics? I believe my 68 350 is (was) 100% stock and original. The shop manual says only the 350HO, 400 and 428 used the umbrellas, not my motor.

I did install the o rings first then slid the compressed assembly over it. I was careful when I did it, and actually pulled the first few to make sure it didn't push the o ring out of the slot. I could see how that could happen. But I guess you're right since I'm having heavy oil consumption now.

But bottom line is if my valve stems are just one straight tube, it's o rings only?

As for the springs, I REALLY wanted to do them tonight! No one stocks them in my area! argh! Looks like it's a Summit deal and wait.

THANKS fir the info!!!

[AdamIsAdam]

http://www.cranecams.com/pdf/10g.pdf

Got it! Now I understand. It's not the valve stem that's machined, it's the head (valve guide)!

Comprendo!

Now all I need is a spring compressor that somehow fits below the brake booster! I have two that don't fit.

[Jack Gifford]

It sounds like you're getting on the right track now. Now that you know what "machined guides" look like, are yours machined for seals? If so, I'd go ahead and use the seals that you have that are like your #2 picture (or like #3 or #4 if you like).

As others do, I've always installed the O-rings after pressing the retainer down.

A minor point about terminology, but it could eliminate confusion in future discussions of stem seals-
The four seals you pictured are collectively known as "PC style" seals. It's a 'historical' name, because Perfect Circle was the first mass marketer of them back in the early sixties. Theirs were one-piece Teflon (your #1 picture looks like one), and the early ones gave such seals a bad name for a while. They sometimes didn't have enough compliance to follow the stem surface, sometimes caused stem wear, and sometime worked too well (!), not allowing enough lube on the stems. All modern "PC style" seals seem to work good, with most builders shying away from the still-available all-Teflon ones.
"Umbrella" seals are a different design- I don't know if they were ever OEM in Pontiacs. Other brand engines have used them a lot. They are one-piece elastomer (rubber?) and slip over the stem like a PC-style. But instead of fitting tightly onto the head, they merely "ride" the valve stem. So they provide "shielding" from direct oil spray, much as the Pontiac spring shields do.

Where your brake booster's in the way- you could cobble up a crude compressor, as I've done for various OHV engines. A piece of stiff flat plate (minimum 1/4" steel or 3/8" aluminum) about 1 1/2" wide and a couple of inches longer than a rocker arm, with a hole to fit loosely over the rocker stud, and a U-shaped cutout in the end toward the spring. Take the pushrod out, set the tool over the stud with legs of the 'U' on the retainer, and select a metal block to sit between the tool and the upper rocker cover rail, such that about 1/2" of stud shows through the tool. Use a common hex nut on the stud to push the tool down and compress the spring. As you first start to tighten, stop and hammer-tap on the retainer end of the tool to break the taper-fit of the locks in the retainer (much less 'drama' than putting gobs of force on before they break loose!).
[If you're like me, the next step is to go back to the beginning and open up the 'U' shape a little larger, to allow removing the locks!]

[AdamIsAdam]

This was an awesome post! EXTREMELY helpful! Thanks!!! It all makes perfect sense to me.

Yes, per my shop manual, in my year Pontiac did use those floating umbrella shields on the 350 HO, 400HO (and 400 4bbl) and 428 motors, but not on my 350.

So one question: can I buy those umbrellas and just use them since they don't require any machining?

As for your home made tool, that's exactly what I need. I have an old skid play from my jeep that I could cut up. It even has the U slot for where it bolts on. This is just how the original Pontiac tool is pictured. I wonder why they don't make them this way any more.

Thanks again. And P/N and store info on those Umbrellas would be great!!!

[Kenth]

Pontiacs name of the "PC-seals" in the (1968) service manual is "umbrella type valve stem shields", and they are NOT floating, they are located on the end of the machined (if machined) intake valve stem guide.

Her you can see the difference of a machined versus non-machine valve stem guide:

[Mr. P-Body]

Adam,

Screaminchief and P-Jack have pretty much nailed the whole deal for you. The "technically correct"name for the "PC" seals are "positive" seals ("positive" retention). Fords and Dodges used a LOT of the umbrellas in olden times. Fell out of favor in the '80s, as emmissions-related issues surfaced at a higher rate than before.

One thing no one pointed out, was, if you installed the "O" rings before the retainer, and the retainer didn't move the seal down, they are probably aftermarket retainers. Stockers WILL push the rubber down.

A few years back, we had an "issue" with a pair of '68 heads. The bosses were not machined for seals, and it sucked oil badly. Since then, it has been our policy to ALWAYS install positive seals on Pontiacs.

FWIW

Jim

[AdamIsAdam]

Thanks all. Finally great info with pics! When my new Crower springs arrive tomorrow, hopefully I'll put them in then.

I'm fairly certain my entire engine was original. Stock springs, oil shields, retainers, etc.

I was able to slide the retainer over the o ring, but VERY carefully. It was a snug fit which is why I'm aware of it. I put the first one on and did move the o ring. I then removed the compressed spring/retainer, repositioned the o ring, and did it again. Like I said, i just had to do it very showly and carefully. But I guess that even at that, it either moved or scatched the o rings in such a way as to give me excessive oil consumption.

I have an extra set of o rings so I'll re-do the whole process. If my heads are machined to accept the PC umbrellas, I'll use them. If not, I'll just go O rings installed properly.

On the off chance that my heads are machined (someone once told me that they'd seen a few `68s machined), do I simply push down the PC seals first using a tube or two screw drivers carefully, and then install the springs, then o rings? in that order?

[Jack Gifford]

Originally Posted by AdamIsAdam

... If not, I'll just go O rings installed properly.

... do I simply push down the PC seals first using a tube or two screw drivers carefully, and then install the springs, then o rings? in that order?

That's the correct order. I wouldn't use screwdrivers on the seals, though- it's easy enough to find a piece of tubing to use. And don't forget to use the thin plastic protector cap that comes with the seals, to prevent seal damage as they pass over the stem grooves.

I tend to agree with Mr.P-Body, that's it's almost foolish to not use positive stem seals. As someone else said, the O-rings were intended to work in conjuction with spring shields, which most of us don't use because of their tendency to break in performance applications. Even if your guides aren't machined, you can buy a simple dedicated cutter from any of the cam companies. The cutter pilots in the guide, so all you need is a good portable 1/2" drill to drive it. I don't know a current price, but it's got to be a lot less than taking the heads to a machine shop.

Kenth- Sorry, I didn't realize Pontiac used the "umbrella" terminology for positive seals. I was trying to explain the "common" terms that almost everybody uses.

[AdamIsAdam]

Hmmm. But I can't get a drill on to cylinder #7 without removing the brake booster.

New cam, so new springs, so no more splash shields, so need positive stem seals, so...

It's like the old lady that swallowed a fly or whatever. hehehe

[Mr. P-Body]

Adam,

A drill won't do it "in the car". The heads must be disassembled so the pilot can use the valve guide to stay straight. You can't modify the bosses with the valve in place.

Jim

[AdamIsAdam]

Update: It's making a lot more sense now because I just spent an HOUR doing cylinder #1. Yes, that's 30 min per spring! argh.

My guides aren't machined to accept the positive seals, so that's out for now.

When I took off one of the springs, the o ring was a bit twisted, but it's hard to tell if that's how it was or I did that removing the spring and retainer.

Now that it's apart, I was able to see that the retainer is verly slightly tapered! THAT'S why you need to put the o ring on after the retainer is on. But that's much harder than it sounds, especially with the spring compressor in the way!

I used a lot of oil and slid the first retainer over the o ring. It worked as I took it off and on to check. the second one didn't work that way at all, so I got the spring compressed enough to get the o ring on and gently push it down with a small screwdriver. Being VERY careful not to cut the o ring. I think it worked well.

But I guess the thing to do is use some vacuum hose or something to push the o ring down, eh?

Oh, and I tried making the tool out of 1/4" metal to get springs under the brake booster off. I'm not sure I can do it. I think I cut my tool/metal piece too short. But I'll try. It's not easy in there! So hard to get the springs to compress enough to work in there. I can't seem to get the compressor to grab the bottoms of the springs when it's on the head.

Input and tips welcome. I'm stopping for tonight to think about it more before proceeding.

(PS, even with compressed air, I got lucky when I tried to remove both springs. I broke the air seal and the valve fell down! down, but not in! WHEW! Piston must have been up a bit! Time to take a break!)

[Kenth]

This is what you´ll need:

http://store.summitracing.com/partde...0&autoview=sku

And see that the piston is UP in the cylinder you´re working on.....

[AdamIsAdam]

how does that tool work? does the small circle go over the rocker arm stud? then I use it like a pry bar, pulling the bar towards me, which pushes down on the spring?

I just did the other springs on that side and it was easy. But I don't know how I'm going to do #7.

[AdamIsAdam]

job is done! made the tool (a friend had it made at work) out of thick steel. All springs and o rings replaced and motor is buttoned up and ready for firing today. (It was midnight when I finished so I gave the neighbors a break.)

Thanks again for the suggestions.

[AdamIsAdam]

Originally Posted by pontiac jack

Where your brake booster's in the way- you could cobble up a crude compressor, as I've done for various OHV engines. A piece of stiff flat plate (minimum 1/4" steel or 3/8" aluminum) about 1 1/2" wide and a couple of inches longer than a rocker arm, with a hole to fit loosely over the rocker stud, and a U-shaped cutout in the end toward the spring. Take the pushrod out, set the tool over the stud with legs of the 'U' on the retainer, and select a metal block to sit between the tool and the upper rocker cover rail, such that about 1/2" of stud shows through the tool. Use a common hex nut on the stud to push the tool down and compress the spring. As you first start to tighten, stop and hammer-tap on the retainer end of the tool to break the taper-fit of the locks in the retainer (much less 'drama' than putting gobs of force on before they break loose!).
[If you're like me, the next step is to go back to the beginning and open up the 'U' shape a little larger, to allow removing the locks!]

My friend made this for me. It worked great. We needed both sets of hands, but we got `er done!

Oh, and this is what happens when you run those OEM splash shields with aftermarket springs:


I recovered every piece that broke off. I pieced the shields back together to be sure.