1954 chevy 235 intake valve sticks after rebuilding the engine. patrick's 251 cam Sealed power valves Cast iron guides Brad Penn oil New oil pump - melling Fresh gas Valve lash at 0.012 both intake and exhaust Valve to stem clearance Intake 0.0016/ Exhaust 0.003, ran for 15 mins and #2 intake stuck open. Opened clearance on valve guides to Intake 0.0021/ Exhaust 0.003, 42 miles later - #3 intake stuck open. All intake valve stems are scored. Need help
I never did much high performance work on these engines but my first thought is were the guides replaced and why cast iron instead of bronze? Are you using valve guide seals? If so, you might not be getting any lubrication. These engines were designed for low rpm and a higher lift cam and higher rpm will create more friction. Lead in the gasoline might have helped lubricate the valve stems. Are the rocker arms putting sideways pressure on the valve? Others who have done more high performance work on these engines might have a better answer.
Cast iron guides were stock and really do not need a lot of lube. But it sure as hell sounds like a lack of lube ,bronze guides MUST have enough lube or they will stick for sure. Next thought how is your geometry ,are you side loading the valves?
Not using valve seals, just o-ring on valve stem. Valve train: Sealed power lifters and MPR32 pushrods, stock rocker arms, looking at the Rocker arm "wipe" across the valve stem it is very close to the middle. Also evidence of valve stem rotation... Looks like geometry is good. I'll try to attach a picture here....
How critical is the valve guide hight above the head... we have ~ 3/4 inch, read somewhere need to be 15/16" intake/ 1" exhaust
It looks very dry in the second picture. That's a very short time for a valve to stick. The assembly lube should last longer than that. What does the machine shop that did he head work say?
Machine shop thinks we're not getting enough lube to the valve stems. We're talking about 1. Pinching off the return on the rocker arm shaft 2. Put Bronze liners in the intake guides and changing the exhaust guides to bronze. 3. Setting the guides to 1954 Shop manual Specs, as close as possible, Patric's 251 cam has higher lift. Intake Max Cam lift = 0.28909/ net valve lift = 0.43364 Exhaust Max Cam lift = 0.28854/ net valve lift = 0.43281 4. open the valve stem to guide clearances another 4/10th on both intake and exhaust. Getting experience, keeping an open mind, we're both trying to figure this out. Sure does run sweet when she runs!
You might try posting this situation over on stovebolt.com, there's a lot of Chevy 6 knowledge over there. I'm scratching my head, sounds like you're doing everything right. Good luck! And, keep us posted. Edit: Since these are intake valves that are sticking, I'm wondering about the fuel in the tank, has it been sitting there a long time while the engine was in the shop? You might try draining out the tank, refilling with fresh gas, maybe even a can of Marvel Mystery Oil until things get broke in good.
I was going to ask about the gas too. Actually not the gas itself...I've seen valves stick even after all the old gas was supposedly flushed out, as if there was varnish in the bottom of the tank that was getting dissolved into the new gas and still getting deposited on the valve stems and guide bores. Maybe check to see if there's sludge/varnish still in the tank. Good luck.
Had bad gas mess the valves on a small block with a fresh set of heads. Had to drive the valves with a brass mallet. Soaked everything in a 5 gal berrymans carb bucket to cut the scum.
Just remember with brass/bronze guides they need more lube than cast ,or they will stick for sure. Good call on old fuel ,if bad the first thing will be sticky intakes.
You could try some 2 cycle oil in the gas. I don't see bronze as needing more lubrication. They are used in electric motors with no lubricant at high speeds. They will wear faster without lubricant but they won't gall the steel. I wonder how much thermal expansion the intakes see. It would seem they stay cooler than the exhaust valves which is why the exhaust guides have more clearance.
If the tank has old gummy fuel in it drop it and boil it out. Fresh gas in a dirty tank will dissolve the shellac and you will still have issues. Modern gas will go sour in as little as 3 months or so.
Electric motors do not use the same kind of material as engine valve guides. They use "OILITE" oil inpregnated material. I have seen more that one engine with poor valve stem lubercation with stuck valves were someone tried to use bronze for guides.
There are 4 different rocker arms used, they must be in the proper positions. The rocker shafts must be in there properly with the open ends in the center, plugged ends out on the outer ends. Check to see if oil is making it up to the shafts.
You probably did this already, but just in case, relative to the oiling issue, did you prime the oil pump before starting the engine (distributor removed, flat screwdriver bit attached to electric drill)? You should see plenty of oil flowing to the head assembly as you spin the oil pump. Also one of the head bolts is specially drilled for oil passage, it needs to be located properly in the head.
put half a quart of Marvel Mystery Oil in the gas tank and the crankcase. Works wonders on sticking valves and gummy fuel system deposits.
While this should have nothing to do with the sticking valve(s), It looks like your springs are installed upside down. Tighter wound coils should face down. Just an observation.
Bonjor, Check your rocker arm shafts for correct installation. There is a flat ground on each half of the shafts which should face up. If they are not you will not have proper oiling in the upper end. You can see the flat if you look closely, I had a similar problem on 4-6 until I rotated the shaft.
Thanks for the input. Here are some results so far. Rocker arms - checked, they ar in the right location according to the exploded view in the shop manual, also, they line up pretty good with the push rods and valves. Ran the oil pump with a drill before starting the engine for the first time, oil flows out every rocker arm weep hole, doesn't gush, just flows. Looking at some videos on the web, looks like the oil is flowing about as good as the others. None of my head bolts have a hole, this may be a problem. reseaching to see which one and hole size. I'll let you know what I find out. Rocker arm shafts have holes that feed the rockers with oil, the holes are oriented down, rocker shaft hold down bolts go through the shafts so they can only go holes up or holes down, found the holes down on disassembly, reasoned that's how they need to be to provide oil to the bearing point on the rockers, loaded on the bottom. Valve Springs - We put them back like we found them, however, I believe you are correct, they're upside down... thanks. Measured the Intake and Exhaust guides height above the head .. Exhaust 0.0650/ Intake 0.795. Book says Exhaust =15/16/ Intake=1.00 could this cause a problem with valves sticking? So far 1) head bolt doesn't have a hole 2) guides are installed too deep 3) varnish in gas
The infamous head bolt with the hole in it is ONLY used when you have a '59 - '62 block and you want to run '58 or earlier rockers. You also have to install plug (part no. 376479) to force the oil into the bolt. There's info in the later shop manuals on how to do it - but since you have a '54 - you never had one. An old rebuilders trick was to not install the stem seals until the engine had run 500 miles or more. The oil flow you describe while turning your oil pump with a drill sounds about right, these earlier blocks don't flow a lot of oil upstairs. The guides being too deep seems to me to have the potential to be the problem. This is just a guess but wouldn't they be likely to be a lot hotter the closer they are to the combustion chamber? Anyway, good luck! And, keep us posted.
How much material has been taken off the head and block? take alot off, and you will want to shim the rocker stands and check for valve to piston clearances. Oil flow to rockers sounds fine. Drilled head bolt isn't an issue. Manually oil it real good before startup. Nothing wrong with using the O rings or iron guides. Just make sure the guide tolerances are correct, valves aren't bent, and that the head of the valve is hitting the seat properly. Make sure the valve locks aren't bottoming out on the tops of the guides. Make sure the pushrods are the correct length.
Back to the question about guide height: It is quite often necessary to shorten the top of the guide to accommodate higher than stock lift cams, however if they were just driven in farther to accomplish this you could be hanging up the valve at the port end. .205" and .287" extra guide hanging down in the port could quite possibly interfere with valves closing. If you can look in the port(s) it should be fairly easy to tell if you have a problem. Another possibility would be that the guide or guides don't have enough press in the cylinder head and have moved or are moving while engine is running.
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