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350 remanufactured and put in the late 90's by previous owner, my plan is to measure the valve stems and the guides. The heads are 75 or later 333882 castings and I know these are prone to cracking and not very good performance heads, it runs fine and I'm not going to replace them.
I'll report back sometime over the weekend with the dimensions I come up with.
You can use stock O-ring seals. They come free with every overhaul gasket set known to man. There is only one style. Hot rodders throw them away every day. If you keep those stock metal spring umbrellas with factory retainers in there they will work great for a number of years.
I've never disassembled a SBC head that had O-ring seals, where more than half were not either missing or crumbled in your fingers. I personally prefer umbrella seals such as Comp Cams Viton® seals instead of the o-ring seals. (Manley, Dart, Edelbrock, etc, all offer Viton® umbrella seals) http://www.jegs.com/i/COMP-Cams/249/518-16/10002/-1
If you get the correct ones, no machining of the head needed.
Even basic umbrellas' are better than the o-ring seals in my opinion.
You can get about a hundred cheap "O" rings for a dollar or better ones like the Vitons for $20+ for 16 seals. A whole lot easier to install also. Comes with a protector sleeve to slide seal over valvestem before spring is in place.
With "O" rings the spring is compressed then add the seal. Not fun.
I don't plan on using just the o-rings...I just need to make sure I get the correct ones....I don't really know what SBC these heads came on originally so I figured I would measure to make sure.
Thank Ya'll for the advise....I'm headed to the shop now to get some measurements.
They are 11/32 stem diameter. Looks like it has umbrellas in there already. If you go with umbrellas, you may want to loose the steel umbrellas and maybe get regular spring retainers instead of those heavy valve rotators. Might wanna consider beehive springs and retainers. Old valve springs belong in the scrap metal bin in all cases...
Last edited by derekderek; 01-14-2018 at 02:03 PM.
I don't plan on using just the o-rings...I just need to make sure I get the correct ones....I don't really know what SBC these heads came on originally so I figured I would measure to make sure.
Thank Ya'll for the advise....I'm headed to the shop now to get some measurements.
Brian
Brian the heads you have (333882) were used from 1970-80 on 350, 400 cuin small blocks. They should have 1.94" intakes and 1.5" exhaust valves with 76 cc chambers.
Taking measurements is a sure way to get the correct seals. Most places like JEGS, will list the seal measurements by valve stem diameter and valve guide boss, outside diameter.
There should be no need to run both types of seals, either the umbrellas or the O-ring seals. If you do decide to go with O-ring seals you can also get them made of Viton® rubber. These will last much longer that the original rubber o-rings ever did.
Here are the measurements, the exhaust only had an o-ring and it wasn't brittle....The intake had both. The guides/ stems seemed to be Ok no play when trying to move them back and forth.
I drive like a grandma so as long as what I have will run fine I don't plan to upgrade for performance.
How about a search on Summit Racing? Gaskets & Seals, Valvestem, Yr, make, model, engine, stem dia. 11/32. Here is where Summit puts it in decimal which I belive is 0.343? Double check.
Goes on to ask if machining is required? Click on NO!
I ended up ordering the seals from Alex's Parts but not the ones shown above. They had Viton fixed seals for 11/32" stems and .562 guides, other than color they look like the VS-562FKM posted above.
Brian, the reason that I recommended the VSS-408 is because it has an expanding band on the lower part of the seal. This allows the seal to fit over a a wider variety of valve guide bosses snugly.
On factory as-cast heads the outside of the boss is not machined so the bosses can vary somewhat as you discovered (.5660-.5675). This isn't a lot, but with a fixed band, the seal is less forgiving . On machined guide bosses, with the correct seal, fixed band fitment is much more consistent. The seals are Viton®, so just be careful when installing them and you should have no problems.
I went with the fixed because of the outside dia. they are only .670 the adjustable ones with a guide boss of dim. of .5675 would be .7555 and one of my springs measured .7365 inside, that had me a little worried about interference. If the fixed ones won’t go on I have to try the adjustable. I really do appreciate all the advice it gave me the guidance I needed to dig in and figure out what I hope works best for these heads.
I went with the fixed because of the outside dia. they are only .670 the adjustable ones with a guide boss of dim. of .5675 would be .7555 and one of my springs measured .7365 inside, that had me a little worried about interference. If the fixed ones won’t go on I have to try the adjustable. I really do appreciate all the advice it gave me the guidance I needed to dig in and figure out what I hope works best for these heads.
Gusto...You were right I should have gone with the adjustable ones....I spent most of the day trying to figure out how to get them to go all the way down onto the guide boss.....No luck even trying to knock them down with a socket the top rubber gets all buggered up. I even tried to heat them up...Nope...Finally I decided to trim some of the rubber off the inside...They would go on enough that they didn't hit when the rocker arms....But the little grabbing arms on the POS valve spring tool I bought just tore them up.....Needless to say I had a very unproductive day.
why did you feel you needed valve seals anyway? your heads had been done at some point and umbrellas were added to the orig o-ring setup. so you had double seals on the intake and standard on the exhaust. you claim to be a grandma driver and not hot rodding. is it a smoker, or what? and are the heads off the engine?
Yes it smokes on start up after it has sit for a few days....I figured the seals were the issue. I started a thread on here a couple of years ago and the consensus was valve seals.
I have only checked two cylinders so far and the seals looked good on both....So I may have other problems thats causing the smoke.
The heads are still on the engine.....and I hope this doesn't turn into a "While I'm at it..." maybe time to buy a borescope if the smoke doesn't stop after I get these seals on.
I had the umbrella seals on my Iron Eagles. When I removed and took the valve train components out of the heads, several had crumbled and the pieces ended up either in the oil pan or lying inside the springs. Point is, they crumble too. The heat, oil and gases do a number on them just like the o-ring seals.
Your valve spring package may determine your seal options. From Comp Cams: "The O-ring seals use the standard retainer and oil splash shield. The umbrella seals are normally used when a larger-than-stock diameter spring is used (single-spring pkg). In the case of a double spring, the positive stop PTFE seals are used. For triple-spring applications, use the smaller-diameter Viton® seals.".
I would go with the positive stop OR (Manley) viton seals over the umbrella seals. Also, be sure you check the valve guide bosses to be sure the seals are compatible. I went with a new set of the PTFE seals with my retro-roller with dual springs (outer spring and inner damper spring). If you change camshaft type (ie. from hydraulic flat-tappet to hydraulic roller), update to the correct spring pressure springs as they need to be matched to ensure the lifters ride properly on the cam.
NOTE: PTFE and Viton seals may necessitate machining of your valve guide boss. From the Manley Viton seal part for SBC: "Requires machining the top of the valve guide with a special .530 in. diameter cutter.".
01-11-2018, 11:03 PM
What valve seals do I need....?
You can get about a hundred cheap "O" rings for a dollar or better ones like the Vitons for $20+ for 16 seals. A whole lot easier to install also. Comes with a protector sleeve to slide seal over valvestem before spring is in place.
Most places like JEGS, will list the seal measurements by valve stem diameter and valve guide boss, outside diameter.
