What Am I Doing Wrong? Valve Adj.

pryord · pryord's Garage

Last week, I tried my first valve adjustment. After adjusting all valves, the car ran poorly; exhaust popping and misfiring on acceleration. I figured I left the valves too loose, so I went back and tightened them up. Car ran just the same. I've now tightened them all little more and the car still isn't running as well as before I started the adjustment. I tightened all the valves to a point where it was a little difficult getting the tool out. I can't imagine getting them tighter.

After the last adjustment, I warmed the car up and accelerated fairly hard through the gears, thinking maybe I had loosened some carbon (I pulled the spark plugs on cylinders 1-3 during the first adjustment, but left them in after the first test drive). This seemed to help a little, but there are still noticeable problems.

On acceleration up to 4k rpm, the car skips with occasional exhaust pops. Above 4k, it runs great. I can hear the valves when the car warms up. Not sure how loud they are supposed to be.

Are these symptoms of poorly adjusted valves? Could I have done something else wrong? The plugs and plug wires have less than 2000 miles on them.

I can't bear the thought of draining oil from the crankcase one more time.

Noel · 03-20-2005, 02:26 PM

Was the car running well just before the valve adjustment? Was any other work done to the car? Usually mis-adjusted valves will simply be noisy if too loose and you'll notice a lack of power (Valves not opening all the way). If they are adjusted too tight you could have running issues from the valves is not closing all of the way (Thus loosing compression).

BTW, you don't need to drain the oil if you jack up one side of the car at a time and let the oil in the sump drain to the opposite side of the engine.

ruf-porsche · ruf-porsche's Garage

Are you adjusting the valves in the order that the cylinders are firing, or are you adjusting one bank of cylinders at a time? Valves should be adjusted in the order that the cylinders are firing.

Do a compression test on all the cylinders to see what the compressions are. Like Noel stated, if the valves are to tight, you won't have the required compression in the cylinder to produce the power.

Remove all the spark plugs so you can spin the engine faster and test each cyulinder. They should be pretty close to one another. If you find a cylinder(s) that is lower than the rest you might want to redo the valve adjustment.

How does the engine idle? If it sound as though it is missing you can isolate the problem by removing each spark plug wire from the distributor and noting any change in engine speed. I use an insulatede spark plug wire plier to remove the wire because after 30 year of tinkering with cars I can't take the high voltage shock any more.

TerryH · TerryH's Garage

I would triple check the firing order and check for broken plug wires before removing the valve covers again.

pryord · pryord's Garage

The car ran perfectly before I started messing with it. No other work was done on the car.

I'll double check the plug wires again. What should I look for?

So how complicated is a compression test? Is there a link you can point me to for the procedure?

Thanks for the quick response!

David

jester911 · jester911's Garage

Make sure your distributor cap is on properly and securely.
Also what reference did you use for your adjustment.
101 projects is very good for this procedure.

Por_sha911 · Por_sha911's Garage

This may be elementary but a good friend of mine had serious problems with rough running after changing his plug wires until he found out that they snap into place on the plugs. A few clicks later the car ran like a champ.

yelcab1 · 03-20-2005, 03:14 PM

Since this is your first time, did you make sure that you started on the right cylinder? Right now, I would suggest manually turning the pulley to Z1-TDC, and open up the disty cap to find out which cylinder the rotor is pointing to, 1 or 4, and then start the adjustment (check it) at that cylinder, then move it all the way around.

If that was it, don't feel too bad. It is truly hard to find that 0.1mm gap for a first timer.

MobileWrks · 03-20-2005, 03:21 PM

Hey pryord,i did the same exact thing when i first started my first valve adjustment. Did it maybe 4 times before i realized i bumped something that i wasnt supposed too. spark plug tapped the side wall and went out of adjustment,also pulled a vaccum line out. Also you may want to ohm your wires,maybe you pulled one slightly out of place. Do a visual,minor inspection of what you pulled off(wires to cap,spark plug adj.,wires end caps tight etc...)

makaio · 03-20-2005, 03:33 PM

I had the same problem when I did my first adjuctment. It turned out I was using the wrong mark on the crank pulley. I used the 5 degrees BTDC mark instead of the Z1 mark, and that boogered up my adjustment on cylinders 1 and 4.

Oh yeah, that was on my 78 SC about 5 years ago.

pryord · pryord's Garage

Ok, you got got me thinking I should check some basics. I just ran out and pulled all the spark plugs. Lo and behold, one had a gap of 0.00000000! It wasn't until I looked at it that I remembered dropping it days ago. It must had landed directly on the electrode.

I regapped it and everything now runs great. What an idiot!

At the very least, it's good to know I was doing the valve adjustment correctly. After going through this 3 times, I'm now an expert at sliding the feeler gauge in blindly.

Thanks again everyone,
David

MobileWrks · 03-20-2005, 04:01 PM

glad to hear.........Remember always start at the basics,and everything works out easy!!!!!! Good Job....

Jimmy

TerryH · TerryH's Garage

Glad you found the problem. Spark plugs are like buttered bread, they almost always land bad.

Make it a habit to always check the plug gap just before installation. But you probably know that now.

Noel · 03-21-2005, 05:04 AM

Glad you figured it out and it was something simple...it usually always is. Thanks for posting the result.

Look on the bright side, with one valve adjustment procedure you got the experience of doing it three times.

Thomas Owen · 03-21-2005, 07:01 AM

Don't forget that you concluded your first post by saying 'I adjusted the gap so tight I had trouble getting the tool out'. If you have not done so, go back and adjust everything properly. Before you burn a valve!
Good luck -

hoff944 · 03-21-2005, 07:56 AM

I've had a similar problem after doing a complete tune up on my car. I adjusted the gap to .31 just before installing. My Clewett plug wires aren't sealing over the valve covers either. I seriously doubt it was my valve adjustment because I double checked it myself and had my dad come and check it since he's done some P-car valve adjustments. He said they felt good. I'm going to maybe call Clewett and see if they can help me with the sealing problem.