Intake/exhaust valve question

[chrisreale]

I took the carbs off of my 2.0 to do some cleaning and poking around. I put my fingers into The two holes that the carb body covers up, and I think I can feel either an intake valve or an exhaust valve. My question, is which ones are insynch? 1 and three, 2 and four, 1 and two...???? When the car gets stuck while I am pushing it backwards, I reach into these holes and feel all valves blocking any attempt to go deeper. Is this a familiar problem? I am trying to figure out why the engine is still freezing whenever I push it past a certain point. It's like this: If you were to look at a tire and mark the top as 12 o'clock, whenever I push the car backwards in gear, it always catches when the tire mark reaches 12 o'clock. Make sense? I will try to think up abetter way to explain if the need be... Thanks

[DDS]

Hi Chris:

Fun isn't it?

The 914 engine is simple as engines go, there are really only a few moving parts, though the valves themselves (if whole)are unlikely to be blocking anything.
Did your engine experince a catastrophic failure before it was laid up?
Does the problem occur once per ENGINE revolution, or once per two engine revolutions? (use the fan as a reference, or calculate from the reverse gear ratio)

Dave

[jabb]

The 2.0 is famous for dropping valve seats.
This is a possibilty why the engine will only turn so far then stop. If the valve seat drops this prevents the valve from fully retracting into the head. When the piston come up it makes contact with the valve and stops the engine from completing a full revolution.

Good luck

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• Joe A.
• 84 911 Targa
• 75 914/6 3.0

[Dave at Pelican Parts]

Chris, I can't quite tell your level of expertiese from your note, so I'm going back to A-B-Cs. Forgive me if this is too simple.

When you look in the holes in the top of the head (these are the "ports"), you see the back side of the intake valves. The valves open by being pushed a little ways (it isn't very much, something like 1/20th of an inch!) into the combustion chamber. This lets air flow around the edges, but the opening is far too small for you to push your fingers through.

If you have dropped a valve seat to the extent where it prevents the piston from moving up all the way, it should be pretty obvious if you take the valve covers off and look. When the valves are closed, and the rocker arms are not pushing on them, you'll have one valve that is a good bit (~1/4") closer to the head than the rest. That is because the valve seat has come out of the head, and has gotten stuck between the valve and the head, preventing the valve from moving back to sit flush with the wall of the combustion chamber.

If none of the valves is like this, then it is unlikely that a piston is hitting a valve. With something between 1/8" and 1/4" of difference in mine, my engine would still turn over. And it was quite obvious once I looked at it.

The question as to which valves are in synch is a little more complicated... The firing order is 1-4-3-2, and each cylinder goes through four strokes: Intake, Compression, Power, Exhaust. So when #1 is on Intake, #4 is on Exhaust, #3 is on Power, and #2 is on Compression. So you could say that the #1 intake and #4 exhaust valves are in synch, but that's not really accurate.

I'm also not sure what it has to do with your stuck engine.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

[chrisreale]

Dave- ABC's are good for me! My knowledge about 914's is boderline nil, but I am slowly learning. Basically, what are the causes of a frozen engine? This car was running well, then a FI problem caused a conversion to carbs. Hasn't ran in eight years. I got it to turn over the other day, but there was so much Marvel oil in the plug holes, a spark was probably impossible. I am now letting it dry out a bit, and then I will try again.

[Dave at Pelican Parts]

Could be anything from a big lump of rust in one area of one cylinder, to a chunk of "something" in one combustion chamber, to a dropped valve seat, to problems with the gears on the crank...

It's really tough to say. If it is still getting stuck, even after the MMO treatment and taking the plugs out, I'd guess that it's a motor that you don't really want to be driving. But that's just a guess. The only way to know for sure is to tear it apart.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling