Projects Ford 312 head valve not coming up to proper height

Well I have no chicken in the fight but personally I'd either contact the shop that "built" the engine if it was built in a shop or I'd be pulling the heads to inspect everything on the inside.
A few points that were made previously that need to be addressed or corrected.
1. Old gas if there was indeed old gas in the tank and that doesn't mean several years anymore it can mean as little as a year or less. The unleaded gas and even worse the Ethanol gas deteriorate and turn to varnish that in turns turns to a gummy then hard carbon on the valve heads when you run it in an engine. I've got one sitting out here now that I thought all the old gas was drained out of when I dumped a couple of gallons of gas into it to start it but there was enough left in the tank to screw the valves up. That means the heads have to come off as there is no magic dribble the elixir down the valve stems to cure it. Your bud's scope may show that or excess carbon on the pistons where there should be no carbon.

2. Valve adjustment. What lifters does it have? solids or hydraulic? Most if not all of those earlier Y blocks came with solid lifters from the factory and the valves have to be adjusted correctly.
3. This may be the most important, Oiling to the rockers, an engine that has run for several minutes should show plenty of signs of oil to the rockers and the general consensus is that we don't see any signs of them oiling.
Rocker oiling, or lack of it= rocker arm shafts not installed correctly. Head gaskets not installed correctly so that the oil passage is in the correct spot. Oil passages in the block or head plugged with crud that didn't get cleaned out.
4. Guides too tight or the valve stems not being oiled before being installed? yep either is a possibility.
Myself I'd bite the bullet and pull the heads and check every last thing over from the block out. A few bucks for gaskets is pretty cheap compared to really breaking the engine because something that could have been found and fixed wasn't because you guys didn't want to pull the heads.

 

X2!!

 

The new gas with ethanol starts to break down in about three months without any stabilizer in it. We have had newer vehicles bend valves at the school from being gummed up by fuel deposits


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I see oil next to the drain back hole in the picture This is not a SBC shaft mounted rocker use way less oil than ball rockers. Y block rocker shafts are not under pressure only fill with oil one reason to pre lube valve stems on assembly Takes a while for them to get oil.

 

You do? Looks way dry to me, there should be oil covering everything, by that I mean every thing, the boltheads and rockers look completely dry, the tops of the valve retainers &c., don't show any oil.

 

ALL y blocks have solid lifters.

 

You would be surprised at how long a Y block will run with not a drop of oil getting to the rockers. and dry rockers will not stick the valves. Ive had them that didn't oil a drop . but to be fair they got aplenty of oily blow by fumes. And if you ran external lines the worn shafts & rockers would robb the oil pressure. So I added a grease fitting and filled a grease gun with 90 weight gear oil. When they started getting dry I would with the engine running pump the rockers full and drive another 100 miles.

 

I would expect a stuck valve to result in a bent pushrod, which doesn’t seem to be the case. Also, since this is shorty after a rebuild, dirt left in the guide during the assembly process is the most likely cause of stuck valves, not old gas in the tank.

The statement that the engine ran ok until an attempt to restart it after refueling, and a reference to having to cool it down would suggest that the engine may have been run low on coolant. If that did happen, it’s likely that the exhaust valve seat (if they were installed as part of the head rebuild) collapsed because of high hoop stresses when the engines, low on coolant, was shut down and the coolant drained from the heads to below the top deck.

A quick peek with the borescope should reveal if the insert did, in fact, drop. There should be excessive lash when tha lifter is on the base circle.

 

Here's an update with some info
1.92 heads were planed, new hardened seats installed by a machine shop. I have my own equipment to grind and lap and ream valves. New Oversize valves were used and lubricated, no guides installed. Installed new original springs and seals, along with new rocker shafts ( lined up correctly)and machined rockers, all adjusted to .020" cold and .019" hot. Also new solid lifters and cam that would be stock. Everything is receiving oil,.. It's just clean and zero miles. Old gas was drained previous; this gas was 6 months old, with see thru filter clean and clear. Ran beautifully on initial startup, probably 2 hrs breakin, then first road test . Gave it half throttle at 20mph and pushrod fell off with #5 exhaust valve sticking open. Took the valve spring off and with inspection camera in the spark plug hole, and valve stem as low as it goes while holding on with visegrip, spinning it freely and observing with the camera. Seems no obvious bent valve, with minimal stem clearance. I can pull the valve up about 1/2" before increments of binding, and gets very tight near seating. Seat seems to be in position. Been trying to flush valve stem with light oil and Seafoam and air pressure, but slow going. It's a possibility the valve stuck down and the piston tapped it, but nothing obvious shows with the camera.

 

Yep the piston kissed the valve and bent it. with rebored guides and a new valve it wouldn't take much bend to make it not return to proper height. I would of pulled the head a long time ago.

 

So, Is this apart yet?

 

Was the valve to guide clearance measured? Should be measured in three places, if so what was the clearance?


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It probably would not be obvious while assembled. Even upon teardown the piston valve contact may not be evident but upon disassembly of the head will become apparent.

 

The info above describing increased difficulty in lifting the valve as it nears the seat sure points to a bent stem.

Oversize stems, I assume? If that's the case, then see below......

 

So after taking the valve spring off and lubricating the tip with WD40, A/TF, and Seafoam and working it with a visegrip and forced air down the stem, things were going slow. So hooked an electric drill to the valve tip and worked it gently until it loosened up. Put the spring back on and got full compression back and runs as great as before the pushrod fell off when the valve got stuck in the tight guide. I had confidence that nothing was really wrong or broke. I learned a few things from all the feedback. I now use 1/2 a Seafoam in the oil, and the other 1/2 in the tank. I also pinched off the rocker overflow by 50%, and see how that goes. So thanks to all who gave opinions and their experience free of charge.

 

Please include some long term report and thank you for the information you have gave back already Sir.

 

Sounds good

 

The fix in every scenario so far will require removal of the head Six days and running.

 

Agreed. I hope it gives a warning again before really bad things happen.

 

all's well that ends well!

Were the oversize valve stems hard to get?

 

I remember running 348 chevy valves in Y blocks stronger valves and larger stems let you ream loose guides to larger size.

 

Thanks

 

Hello here’s the 312 purring nicely!! Enjoy: