Porsche Valve Adjustment, 1974 2.0 Options

[NJTom]

While the 914 motor is out of the car to repair the rear main leak, I decided to recheck the valve adjustments because there seemed to be at least one making quite a bit of noise. When each cylinder wast brought up to TDC, I found the valve adjustments to be way too tight — all of them. Can’t quite figure that out as I checked, double checked, and triple checked the adjustments when the engine was on the stand. Who knows why that happened, but frankly, that’s not my concern. So I went through the motions of bringing each piston up to TDC and readjusted the valves. During the process, I just happened to pull on another rocker to see if there was any play — and there was — a lot. As a matter of fact, when #1 piston was @ TDC, there were other pistons at such a stage where at least one valve was closed. In measuring the lash of that closed valve, the gap was greater than when @ TDC in most cases. For example, when piston #1 was at TDC, the respective exhaust is @ .008 and the intake .006 — as they should be. However, when piston 1 is @ TDC, cylinder #2’s intake is closed — reading = .06 (as it should be) and Cylinder 4’s exhaust is closed with a reading of .12 — way too much. I checked and rechecked my findings.

Below is a little summary for all cylinders.

When 1=TDC, #2 intake = .06 & #4 exhaust = .12
When 2=TDC, #1 exhaust = .11 & #3 intake = .13
When 3=TDC, #2 exhaust = .12 & #4 intake = .06
When 4=TDC, #1 intake = .13 & #3 exhaust = .11

All valves of all four cylinders are in spec when @ their respective TDC.

I highly doubt this is normal. Logic says none of the gaps shouldn't be any greater than the TDC readings.

[MartyYeoman]

How are you establishing TDC?

[stugray]

You are not at TDC when you think you are.
Do you have a mark on the flywheel?
If so, this should indicate TDC cyl #1.
Rotate engine (CCW from FW side) and watch the valves operate.
When cyl #1 has just closed the intake valve keep rotating until the mark on the FW is at the top of the case aligned with the case halves split.
This is TDC cyl#1
From there go 180 degrees for each cyl in firing order.
I make a second mark 180 degees from the first so you can see them from underneath the car

[r_towle]

I can make this easier for you.
When cylinder number XXX has its valve all the way OPEN, the valve on the other side it closed and can be adjusted.

Stop worrying about marks, TDC or anything else.
Just watch the valve that is open, you can see when it goes over the top of the lobe and starts to close...roll it back a bit so its on the top of the lobe, all the way open, and adjust the valve on the other side of the motor.

Simple to see, and because the cam lobes are shared for the valves on each side of the motor, its not possible to screw up using this method.
Remember, the camshaft has four lobes, not eight.
Picture how it works...it will make sense.

Rich

[jeffdon]

I can make this easier for you.
When cylinder number XXX has its valve all the way OPEN, the valve on the other side it closed and can be adjusted.

Stop worrying about marks, TDC or anything else.
Just watch the valve that is open, you can see when it goes over the top of the lobe and starts to close...roll it back a bit so its on the top of the lobe, all the way open, and adjust the valve on the other side of the motor.

Simple to see, and because the cam lobes are shared for the valves on each side of the motor, its not possible to screw up using this method.
Remember, the camshaft has four lobes, not eight.
Picture how it works...it will make sense.

Rich

(IMG:style_emoticons/default/agree.gif)

[NJTom]

TDC of cylinder #1 is established using fan timing marks, distributor notch, and visually looking down the spark plug hole to see when the piston's upward travel stops. Then, using the firing order, I just rotate the engine by hand and work my way around the four cylinders. Believe this is a correct procedure

[NJTom]

How are you establishing TDC?

TDC of cylinder #1 is established using fan timing marks, distributor notch, and visually looking down the spark plug hole to see when the piston's upward travel stops. Then, using the firing order, I just rotate the engine by hand and work my way around the four cylinders. Believe this is a correct procedure

[Dave_Darling]

My engine is the same way. I was never able to get a good answer about why it happens.

--DD

[NJTom]

My engine is the same way. I was never able to get a good answer about why it happens.

--DD

So if I understand correctly (and I'm adjusting them now and would only like to do once). You agree with what Rich said and suggested? And THANKS!

[sfrenck]

Read this thread.... then read it again.... then read it again. Took me that many times to figure out the method - but it works


Cap'n Krusty valve adjustment thread

[Dave_Darling]

What I know is that I use the 'book method" to set my valves. I set each cylinder up to TDC (verified by the flywheel notch and checking that both rocker arms are slack) and then I check the clearances. Then, if I rotate the engine to where one valve on a particular cylinder is open, the other valve on that cylinder will have a much larger clearance.

The only things I can think of are that either the rocker stands move around (even with proper torque on the retaining nuts, torqued when both rocker arms have slack on them) or that there is something in the geometry of the cam/lifter/pushrod/rocker/valve that causes this.

That is one of the main reasons I am uncomfortable with the Krusty method of adjusting valves.

--DD

[rjames]

What I know is that I use the 'book method" to set my valves. I set each cylinder up to TDC (verified by the flywheel notch and checking that both rocker arms are slack) and then I check the clearances. Then, if I rotate the engine to where one valve on a particular cylinder is open, the other valve on that cylinder will have a much larger clearance.

The only things I can think of are that either the rocker stands move around (even with proper torque on the retaining nuts, torqued when both rocker arms have slack on them) or that there is something in the geometry of the cam/lifter/pushrod/rocker/valve that causes this.

That is one of the main reasons I am uncomfortable with the Krusty method of adjusting valves.

--DD

I stumbled on what I believe was an explanation for this on the internet a couple of years ago and it made me question the 'easy' way of adjusting the valves. I'll see if I can find it again and post it here.