Eric Kessel

My 90 C2 had a valve adjustment done 10k miles ago (it has 100k now).

It has had a loud valve ticking for a while (it didn't right after it was adjusted last year, i'm not sure when it started). I just finished adjusting them myself, and both intake and exhaust valves for cylinders 5 and 6 were very loose. The locknuts were tight, but the valves were way out of adjustment.

All other valves were pretty good. Any ideas what could cause only two, next to each other to be real loose? ( put the feeler gauge in, and could still cause at lot of travel while wiggling the rocker arm)

After the adjustment today, the car sounds much better. I can still hear the valve train, but there isn't a loud ticking anymore.

I also found a bit of water at the start of draining the thermostat housing, so it looks like i'll have to find a longer way to work........(30 miles each way, and the thermostat always opens, but not long enough I guess)

Thanks,
-Eric
90 C2
NER/PCA
Rennlist Member

Arjan B.

I did the adjustment once on the wrong way, may be you did that too.......... Adjustment needs to be done between the screw and the valve......

You need the right tool for that, Porsche sells is for a reasonable price.

springer3

I have always found valves to be spot-on, or very slightly too close. Only two things can cause clearance to increase: mushrooming of the valve stem, or build-up of deposits between the valve and its seat. Neither is a good answer.

Are you sure it was done correctly last time? Have you checked compression? A big change in valve clearance is a warning sign, but in your case you can hope the job was botched last time. If you read Arjan's excellent thread on his service, he made a mistake, and the valves were way too loose. Perhaps that is what happened on yours?

garrett376

All too often they are not set correctly for one of MANY reasons.

As Springer says, you probably had a bad previous adjustment. Unless you don't tighten down the locknut, it won't get super loose on its own, unless you break something...

...but if you set it wrong to start with, it will not tighten up on its own!

Michael Gibney

Eric,
Wear on the valve seat - either on the seat itself or on the valve face - causes the clearance to reduce.
Wear on the valve stem causes the clearance to increase.
Wear on the cam lobe - at the high point - will cause a tappetty noise even though you have correct clearance on the back of the lobe where the adjustement is done.
You can see from the above that your symptoms don't quite fit the usual so the usual suspects would be:
1. Spark plugs were changed before the valve clearances were checked - causing carbon from the end of the plug threads to fall onto the valve seat and give a "loose" reading". Later when the carbon gets "blown" away the valve sounds "tappetty".
2. Either you or the previous fellow got the adjustement wrong - and be assured Porsche valve clearences are not easy to do.
3. You have another problem - and one possability was mentioned above - being loose carbon flying around - but this is unlikely unless engine has been extra hot when it is usually cold and never given a good run - the carbon builds up over time in a cold slowly driven engine and then gets burnt and flies araoud and out the exhaust with a good hot run. If you have anothe problem it will show up and aside from taking it to a good Porsche shop and giving them an open cheque all you can do is look and listen.

FWIW I would put a dollar on - if you have done the clearances correctly - you may not have another problem because the only cause that "fits" is carbon bits on the valves that took a while to get blown away - and it can take a while in the car is not driven hard - because some "ninny" loosened the plugs on 5 and 6 before they did the valve adjustements.

Regards,

Michael Gibney

Eric Kessel

Thanks for the advice. I had the valves adjusted when I first bought the car by a professional mechanic I trust (did great work on my previous two 944's) I did the spark plugs a few months after that, since I pulled the engine myself to change the flywheel (a whole different story....).

I'm intrigued, since the previous owner did not drive too hard, and I had done a few autox's last year, probably when the tappety sounds started happening....... and a nice hard day of drivers ed.

The cam lobes seemed nice and smooth (I read about loud valves causing cam wear, and was anxious to check, but it seemed smooth to the touch), so hopefully it was just some carbon. It was definitely quiet when I first bought the car.

I'm going to hope for the best. The car ran great today at our local autox!

-Eric
90 C2
NER/PCA

JasonAndreas

How difficult is raising the car and lowering the engine? Did you use the 1, 2 or 3 jack method? What did you rest the engine on? Did you remove the rear bumper to reduce the height you needed to raise the car? I'm about to drop the motor to replace the clutch so if you have anything you would like to share about your experience, I'm all ears (i.e. any Kahdmus moments you'd like to share... that I need to look out for)

Eric Kessel

It wasn't particularly hard. I used one floor jack with two jack stands to get the car up (probably would have been better with two floor jacks, I had to run from one side to the other, bumping up the jackstands one click at a time......)

I bought the $120 Sears ATV jack, which was great for raising/lowering the engine/transmission with the muffler removed. It was balanced just right without the muffler.

I did remove the rear bumper, it wasn't too bad.

Pay attention to the orientation of the clutch. That was my biggest failing. I have the LWF, and wasn't paying attention to the clutch disk when I removed it....... I ended up putting it on backwards, and had to redo the whole thing...... lots of sparks from the guide tube being ground down by the clutch center.......

The accelerator cable was a pain to detach, and drop the rear mounts a bit before trying to remove the top starter nut.

With the write up on Pelican's site, and the advice on this board, it is suprisingly straight forward. Any other questions, just write.
-Eric

(If you want to borrow the ATV jack, it's out in Sterling, Mass.......... )

JasonAndreas

I would definitely be interested in borrowing the ATV jack, I'll be in Worcester sometime soon to borrow a low-profile high-lift jack from my sister. I can leave a hammer as a security deposit if you'd like.

964porschedude

I have used a dial indicator with a "Z" bracket and measure .004" within .0002" or so for 15 years on 911's and 964's. It is the only way to do it in my opinion. It doesn't lie and there is nothing to feel like a feeler gage.

springer3

A feeler gage does not lie, and "feel" is not rocket science. You want a little friction, but not enough to require any real muscle to move the blade. Get about an ounce of friction on the blade, and you are better than +/- 0.0002". The Z-bracket and dial indicator are expensive, the dial is delicate and frankly a chore to maneuver into a position where you can see it and still get to the adjustment stud. I have both tools, and use the dial only to check the valve timing. For routine valve adjustment, the feeler gage is easier, faster, and just as accurate, in my opinion.