The Stovebolt Site Forums The Shop Area Engine Shop As the crank turns, Part III

So I go to my new machinist yesterday to pay for my 235 head. He had to surface the head another .010" cuz he said it was .006" warped. I asked what the hell, as the head had been cut .030" in '97. Shop says that the head had been shaved on an old machine, which introduced a "bow" into the center of the head due to a worn surface machine. OK, I'll buy that.

He removed the umbrella seals and installed new o-ring seals. He said that was correct for a street engine. Said valves, guides, and hardened seats done in '97 were OK.

He also said that the head was trying to drop a valve. HUH? I said. Seems that the Comp Cams inner/outer springs I was using didn't fit the stock valve retainers correctly. The inner spring was grinding away at the stock retainer, and could cause a lock to pop loose. So he installed the correct Comp Cams retainers with new locks, machined the spring seats in the head, ground the valves, surfaced the valve stems, checked the springs, and set the installed height on all valves.

So if any of you guys use dual-wound valvesprings on your 235/261, you have to use the Comp Cams retainers and have the spring seats machined to accept the inner spring. Or risk dropping a valve. How many of y'all knew that one???

He is also going to CC the head so we'll know the compression ratio.

Question- My '54 (pre-898) head has now been shaved at least .040". How will this affect my valve-to-piston clearance and valvetrain geometry?

Chip

It sounds like you finally found a good machinist who knows what he is doing.

Chip,the valve to piston clearance wasn't a problem on a 235 and a 261 I assembled with after market cams The 235 had a Clifford 260 cam and the 261, the M4F. the 235 had .030 saved, and the 261 had 20 off the head and 30 or so off the block.At maximum overlap, both engines have .070 valve to piston clearance.If your engines pistons have close to zero deck clearance, its best to check out the clearance.The 40 thousands head shave may alter geometry slightly , but with the valve assembled to the correct height,you won't notice anything.
I use single springs, Buick I think, they work ok for 4500 rpm.When I bought the Clifford cam years ago, they recomended dual springs. The springs and retainers sold to me were wrong!! they didn't seat properly on the head (too small diameter) in fact their own springs didn't seat in their retainers.. Many phone calls to Clifford and they wouldn't admit to the problem.I replaced then on my own and tossed the Clifford retainers and springs in the scrap barrel.

What kind of valve stem seals is everybody running? Am I gonna suck oil early using only 0-ring seals? The shop guy said I could have the head machined for teflon seals, but that the total lack of oil would wear the guides early.

I like the umbrella seals, cheap, no machining needed, and no oil consumption problems . The stock O rings are ok, Chevy used them on 6 and V8's for years.

One place I have to disagree with your mechanic is on the seals. The umbrellas are a far better designed seal than the o-ring. The o-ring will work good for a few years until they harden and you start getting a little blue smoke when you start the engine. It's really not a problem as far as engine life, though.

Chiphead,

Personally I do not like the O-ring seals, they really let us down sooner or later, and as the guides looses, they can do nothing to stop the oil coming down. If You can use the umbrella, go for it. You can even leave the O-ring and the umbrella. Or You can use the teflon. But the fact that it will induce valve guide wear is really a fact, and when the guides get really loose, it will not stop the coming down oil. And it may happen before You think it should happen.
Now if I were You, and considering the engine type, i'd go for the umbrellas. Just the 0.02.

He said the umbrellas might not fit with the new spring retainers and .420" lift. He still has the head, so I will ask him again about it. I hate that puff of smoke when I crank up. Should I ask for umbrellas on just the intakes, or all the valves?

Chip

Chiphead,

At least on the intakes, but if possible to use on them all, it's better. There are some models, intended for use in Furd small block engines that are made in a smaller diameter, so they may fit, just check out the stem diameter.

ghip you tell JEFF i want 10%commission on your work .i like jeff and should have reffered him in the begining ..