After 28 years of smoking I finally have time to replace my 270's valve guide seals and.... realizing whoever rebuilt the engine 30 years ago couldn't be bothered to put any in. None of the valves have grooves for the little O ring. There are no umbrella seals either. I noticed the intake valve springs have a solid round disk on top of them. Two of them were broken. Haven't found the missing pieces. My spare 248 engine does NOT have these solid disks. So here are my questions: Which umbrella seals will fit? Are the solid disks necessary? What is the proper name for these little solid disks? I realize if I don't put these disks back in then I will have to adjust the valves. Last but not least.... A good source for parts!! None of the places I bought parts from 20-25 years ago exist anymore. Thank you!
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
I don't own a GMC, but if it was me, I would buy a GMC parts manual that covers your year engine, then do a parts identification. Find the part numbers then search the Internet for information or suitable replacement parts. Egge is a good place to start. Valve guides need some lubrication. You don't want to risk using the wrong seals that leads to valves seizing in the head.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
I had a 235 head redone and the machinist used umbrella seals that clipped into groves in the guide and had spring-type seals around the valve. Had it apart after 40,000 miles and found no stem wear and the seals still apparently good. I bought a set for another head for 283 Chev V8 which fit over factory 235 stems haven't tried them on the guides yet.
1951 3800 1-ton "Earning its keep from the get-go" In the DITY Gallery 1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
Valve guide seals are not a substitute for proper guide to valve stem clearance. It's also possible to seal things too well, resulting in the guide running dry, and wearing rapidly. When that happens, there's not a seal made that will control oil loss, regardless of its design. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
As an alternative, have your machinist install bronze valve guide liners in your existing valve guides. These are old heads, prone to cracking, so you want to be gentle with them. I no longer try removing the stock valve guide unless absolutly necessary. Have not done it for quite a few years now. I dont like to pound on the heads to get them out and in. The liners are much easeier on the head and minimize the chance of initiating a crack.
From there, the machinist should be able to machine the tops of the guides for PC (short for Perfect Circle) style Teflon seals. Your machinist can then dial in the right amount of clearance between the stem, guide and seal to make sure the valve gets sufficient lubrication. If you look closely at the next to last photo you can see the blue Teflon seal. That head is currently installed on a 261 that I ran down the historic beach bend kentucky dragstrip this past weekend at the trifive nationals, shifting at 5800 rpm. My son and I made 20 passes this year, 25 last year. Does not smoke one bit, and the valves get just the right amount of lubricant.
I had bronze guides, not guide-inserts, installed with PC umbrella seals last head rebuild. The results have been good. As I said up-thread, at 40,000 miles no stem wear.
1951 3800 1-ton "Earning its keep from the get-go" In the DITY Gallery 1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
I had bronze guides, not guide-inserts, installed with PC umbrella seals last head rebuild. The results have been good. As I said up-thread, at 40,000 miles no stem wear.
