911SC valve adjustment remarks

[Jail1980]

Hi all! Writing here the first time although not being new to the forum as I've been learning a lot of stuff for different projects for my '78 911SC.

Last weekend I did my very first valve adjustment on the car, and ever. Then did it again. And then did it yet again. Did the adjustment three times (maybe 8 - 9 adjustment rounds in total) over as between the adjustments the car felt down on power, hesitated on low revs and started to backfire. I suspect the backfires are intake backfires as they feel quite subtle, and not seeing any flames. Cold and at idle the car idles, sounds and hums nicely! Warm and on the move I can hear some valve noise reflecting from road side fences and other cars when driving window down.

Did the adjustment according to the procedure and in correct firing order (1-6-2-4-3-5) and did check that the rotor pointed to #1 and cranck TDC when I started.

Annoyingly, after the third adjustment and the symptoms are still there! Did my third round adjustment with extra-extra care to feel the drag with feeler gauge. And then checked for correctness once more. Actually I think going any more tighter the feeler gauge actually gets stuck under the elephants foot which is not correct. Did replace the distributor cap and rotor, which made things even worse - so I "backdated" to original rotor and cap. Also the car now seems stall when ever I drop into neutral (e.g. coming to red lights).

So, car feels down on power, hesitates on low revs, backfires (intake, mostly on low revs) and stalls. Car run great before my adjustment efforts. From everything I saw I suspect the valve covers haven't been off for some time.

Does my adjustment simply suck (too tight/ loose) or can this be e.g. CIS or timing issue? I didn't check the timing. Now I'm thinking it's probably best to get the car somewhere properly done before I damage something.

Setback for the DIY-man in me.

[john walker's workshop]

recheck the order of the plug wires on the cap and at the plugs.

[DRACO A5OG]

Make certain all plugs are fully seated, you should feel clicks

[Targalid]

You should post your location. If you are in Porsche country there are probably ten guys within a half hour who can walk you through the procedure and any trouble shooting you need to do.

[timmy2]

When installing wires they go in a counter clockwise rotation on the distributor.

[Guardsred911]

My experience was that after my first valve adjustment with engine out, I still needed to readjust as it ran a little choppy.... I was pleased to find good results the second time and only needed to re adjust 1 2 3 intake based on my ear..... My other thought is that I find I have good luck doing one fix at a time, not more, as it gives me a baseline for success of each discrete fix. Thus, you might think of valves, see how that works, then rotor cap.... Just a thought...

[NoYouRelax]

I found my wires off by 180 degrees from the previous owner's work. Also, It is possible to install the distributor 1 gear tooth of mechanical timing and still start the car. Don't ask me how I know this. Verify that TDC is trued up at the pully and distributor.

When adjusting the valves it is alway good to verify that you can move the rocker arm to verify slack before adjustment. If it does not move, you are probably not at TDC for that cylinder.....

It will all come together and make sense soon.

[newms]

If you can get the gauge out its not too tight. it's not a friction like sensation. It's a tight slide. And yes after pushing the rocker to open. If plugs and wires and cap an rotor are good. For sure. Valves too loose. Good luck.

[tazzieman]

Originally Posted by Jail1980

Last weekend I did my very first valve adjustment on the car, and ever. Then did it again. And then did it yet again. Did the adjustment three times (maybe 8 - 9 adjustment rounds in total) over as between the adjustments the car felt down on power, hesitated on low revs and started to backfire.

Each time you adjusted , the engine was "stone cold" , right?

[kodioneill]

You may have bad spark plug wire ends. When you pull the wires off the plugs sometimes they'll separate and cause a misfire situation.

[scotricker]

Clicky valves are ok. Too quiet would be too tight. Like above comments, your situation sounds like you should be checking ignition. stick with it. this will be fun. don't bail. we've all been here, too. When you get it right, you'll feel like a super hero mechanic!

[awhnry]

Without a doubt, getting the car to TDC is the hardest part of the valve adjustment. The first time I tried, I couldnt move the exhaust rocker and declared that I had a seized rocker. After multiple consultations and ordering parts(luckily fairly cheap), I realized one day that I was not at TDC while reading the manual. It helps to be a gymnast since you have to rotate the pulley, confirm distributor position, confirm intake position and then roll under the car and confirm exhaust position. Now you can begin to adjust #1. You have to play that same game with each cylinder until completed. I could justify paying someone to do it but hate the idea of not being able to work on my own car. You will learn a whole lot about your 911 very quickly doing the valve adjustment dance And to think that I sold my Elise for the 911 because I didnt like being a gymnast for ingress/egress purposes. YMMV

[Jail1980]

Ok, took my car to a specialist and asked them to figure out what's the problem. Also asked them to check the valve as I didn't trust myself anymore. Turns out my valve adjustment wasn't bad after all! The problem was with plug wires and with too big resistance. That's now been sorted and I'm happy to report the car has been running great for couple of weeks now.

Tazzieman, yes the engine was dead stone cold each time.