72 C10 SBC 350 - Valve Seals (Stock)

[Rich72C10]

Hi guys,

My C10 72 SBC 350 was rebuilt a few months back and I am getting a bit of startup smoke. It's not horrible, at least at the moment - burns off quickly and does not do it again until it has had time to sit a number of hours or parked overnight/few days. The passenger side blows the most on startup, just enough smoke for me to start up the engine, get out of the truck and see it.

The worst offender is #8 spark plug by far (photo attached). But for comparison, I have attached #1 spark plug too, best of them (say around 1k miles on them). I have attached photos of one of the heads before and after valve & spring install - so they can be seen for what that is worth.

So, I know there is a O-Ring but is there or is there not suppose to be umbrella seals on a 72 SBC 350? Oh then there is the Valve Spring Shields with O-Rings.

Basically, what are all the bits for oiling sealing that needs to be in place?


PS: My bother did admit when he 1st started the valve install, the engine guy with him helping made him stop, as he was doing something wrong and had to start over.

[Rich72C10]

It looks like my question(s) on seals was pretty much answered here in this thread Request: GM Valve spring experts

1. SBC 350 of 72 only rolled out with O-Rings
2. Later Umbrella seals came out (some used Fords). Both can be used at the same time.
3. If you add umbrellas, they would only be used on the intake side, I believe but unsure.
4. Unless the your old heads have been machined for positive seals, you can't use them.

[Getter-Done]

x2

[Rich72C10]

Well, I dropped my baby off to the shop down the street and walked home in about 10 minutes (they are that close). The shop is highly recommended and highly reviewed. I actually remember when the shop was built about 15 or so years ago - very clean and organized. When I told them I wanted Fel-pro seals, they responded, well that's all we use. So that gave me warm and fuzzies.

Also having the TH350's pan seal replaced, it is lightly seeping fluid. After parking, I get perhaps less than 1/2 cap of fluid on my garage floor. Not bad but annoying...

[Rich72C10]

Got the truck back today and early too! Seems my brother mucked up a few of the seals. Also, these new seals were nearly hard as a rock. So odd being less than 2k miles since they were installed. But no worries, all new ones installed plus umbrella seals to back them up!

Also, the transmission pan was redone with a rubber one they say is a lot better than the cork one that was one it (I told them whatever is the best). Plus proper sealant (not RTV, duh). So far, dry under the truck but they give a 1 year 12k warranty on their work.

Oh, the new seals used for the O'Rings and Umbrellas are from Fel-Pro!

[cadillac_al]

Good shop. We have a good shop in town that puts umbrellas on sbc's so I try to too. Although....I will probably go pc seals from now on.

[Rich72C10]

PC Seals? I assume you mean positive seals? That is what they recommended but that would take my heads to be machined to accept them and I knew I could not get those. If I had known a little more about O'Rings, Umbrella and Positive seals - I would have asked my brother to have this done (the machining) when the motor was being rebuilt.

But on to my TH350, which is off topic of this thread but its my thread so I'll forgive myself. It seems my leak from my pan has moved up to the shifter or perhaps that is easier seen now that the pan is dry. Something is up with the seal for the shifter linkage :'(

Now the question is, if it is the seal did the tranny guy replace it or not replace it when it was rebuilt back last May. If replaced, was it mucked up or is there wear/burr/groves that is causing fluid to get by the seal. Ugh... questions, questions, questions. I sooo hate leaks!

[Bigdav160]

Shift shaft seal is a common leak area when parked. It will look like a pan gasket leak.

Your builder probably forgot to put it in or buggered it up. Most guys use a special little removal tool rather than disassemble the whole park linkage to get the shift shaft out. Lot's of times removing the shift shaft will wreck the bore in the case. Inevitably there's a bur on the shaft.

[Rich72C10]

The pan was most definitely nearly leaking all around, though that is not to say the shift seal wasn't before to and they where mixed up. The pan leak would run on the transmission cover and was basically wet on nearly ever bolt around the pan.

The speedometer, while not actually making a drop stop is wet around it.

So I'll take her back to the shop tomorrow. Hopefully they don't see a need to replace the shifter shaft, since that will mean pulling the pan off again (but in for a penny, in for a pound).

For the speedometer, I will suggest if it is the aluminum bullet one go ahead and replace it with the steal one and a new speed gear. Read a lot about that bullet and then wear grove patterns on the gear. I am guessing that if it is not making a drip now, it will soon enough.

[Rich72C10]

new shift shaft, speedo gear with their seals - TH350 is leak free (and yet another pan seal and new fluid)! As a side bonus, the bounce I had in the speedometer is all gone too - smooth as silk as it goes through the MPH readings!

Man, its nice not seeing drip, drip, drip .... puddle of Transmission fluid!