Cylinder Head Questions

[Pritchard]

I have a '74 2.0L stock engine.

Recently discovered low compression on one cyl. I have dropped the engine and removed the suspect head. The valves on that cylinder are seated below the surface level of the compression chamber. Actually the intake valve is flush w/ the chamber and the exhaust valve is below the chamber surface. Is this what y'all are talking about when you say "dropped valve seat?" Also, the pushrods in this head have a beautiful ring worn into them approximately where they enter the head. This groove is just about the same length as the throw of the rocker arms. I would guess that some of whatever is missing in the head got situated where the push rods enter the heads and machined this ring. This ring is about 3/8" long and 1/32" deep. I realize that I need to replace the push rods, but money is running out. Can I get by with these for a while, as long as they are straight, until I donate some blood for more money?

I have another question. To removed the head for cylinders #3 & #4, a piece of the lower engine tin needs to come out. This is the piece that helps direct the air flow down thru the oil cooler. It seems the only way to remove this piece is to remove the oil cooler. I'm planning on removing the cooler anyway to replace the seals, but I wasn't going to do this just yet. Do I have any options other than removing the oil cooler?

Back to the valves. Did I read correctly that the sodium filled exhaust valves have an indention on the top of them and that they usually don't need to be replaced?

Thanks for listening and providing advice and info. to get me this far.

PRITCHARD

[JP Noonan]

See if Pelican has some used pushrods for ya. Cams, lifters, push rods, and rockers all mate wear, but it's only critical on the cams and lifters. Without looking at them I'd guess they're O.K. for the time being, and I "THINK" you can put new ones in later with the motor in.

A "dropped seat" is one that has come loose from the head. It at least blocks the valve from sealing. At worst it jams the valve completely open so the piston hits it, somtimes this breaks the valve head off, holes the piston, jams the valve into the head, etc. A "burnt" valve is one that couldn't shed it's heat to the head (wasn't seating completely) so parts of the valve start to burn off. The valve looks like small "peices of pie" were cut out of it.

Sodium vavles can be re-ground, but like anything else it depends. If the vavle is past it's margin, if it is stretched, bent, cooked, or worn under size it can't be re-used. It is the luck of the draw. If they are fairly new and haven't be over heated you're in luck. You are ALLWAYS better with new sodium valves ($50-$60 a pop), IMHO good used sodium is next, then stainless steel. It all depends on how long you want the engine to last.

The valves being "sunk" like you describe is probably from a past valve job where the old seats were used, or it is valve recession from overheating is my best guess. Or it may just be normal, if they are all the same I wouldn't worry. Next thing is to clean the combustion chambers REALLY good and look for cracks. They usally form in the small area between valve seats or between the Exh valve seat and the spark plug hole. You can run an aircooled motor with cracks, but they will just get worse, and then the seats will drop.

Look at the tops of the pistons, should be dark (depending on mixture) and smooth. If it resembles a sponge, or there are little balls of aluminium on it you had a detonation problem. While the motors out you might consider seeing if any of the rings are broken. You will need a ring compressor and some assembly lube.

Can't remeber about the oil cooler coming off first or not. But it's so easy to do with the motor out (and fan housing off) why not do it now? When I take it off I soak it in a gallon of carb cleaner overnite to clean out all the fins. Don't submerge it though, DO NOT let the carb cleaner get INSIDE the cooler. The nuts on the cooler are a low torque (aren't all the 914 nuts ) so be careful.

Buy Tom Wilson's book on aircooled VW engines. It has all kinds of goodies to look for while the motor's apart.

[Pritchard]

Thanks! Great information.

I was only going to put off the oil cooler thing a couple of days until my parts get here from PP.

PRITCHARD

[Dave at Pelican Parts]

The piece of sheetmetal between the cooler and the cylinders should just slide out upwards, without pulling the cooler.

There's a piece down underneath the cylinders and head, and you need to at least remove the three screws that hold it on. One out on the head, and two into the case.

Hold the head up to the light and try to see if you can see any light leaking around the valves. If you can, then you've found a problem. The pushrod wear is definitely bothersome! Have you figured out exactly what they wore on?

Remember that the pushrods are hollow, and carry oil out to the rockers. All the oil that lubes the rocker arms comes through the pushrods. An extra hole will let the oil out and your rockers will suffer.

Look for small divots or other damage around the valves. That is the sign of a valve seat that came out and slipped back in.

The sodium-filled valves have a dimple in the middle of the valve face (the big end inside the combustion chamber). Regular valves don't. They may or may not be able to be re-used, depending on the wear. Have a machinist check them. Find one that knows 914s, or Type IVs, or 911s, or aircooled Volksies. (Preference in that order.)

Good luck!

--DD

[Pritchard]

Thanks for the input. I haven't figured out yet what could have worn the pushrods in that manner. The worn area is too far away for the pushrods to have been rubbing on the head. I haven't noticed any metal in my oil changes. This is the first time that I have pulled the pushrods out of the engine. Maybe the damage occurred with a PO. I have noticed that the PO had some engine work done. I have found that the valve seats for the "bad" cylinder look to have been ground down already, heli-coil insert to rethread spark plug hole, and several sheet metal screws used where the cheese head screws are supposed to be.

I read something on this site somewhere, some time ago about adjusting the proportioning valve for the rear brakes. If you know which way to turn the screw to give rear brakes a little more stopping power, I would love to know.

Thanks for your help!

PRITCHARD

[Jim Branch]

Years ago while I was having a tune up done on my 914 2.0 Ltr. The mechanic was adjusting the valves, he noticed one of the pushrods was rubbing against the wire that holds the pushrod tubes in place. He took it out and replaced it. He gave the damaged one to me. The cut is about 3/8 long and the cut is deeper near the end than further down the pushrod. I still have it to remind me of what could have happen.
Jim Branch
smijobs@gte.net