tinkering w/ new SC....think I goofed.

[gldnedge]

I've had this '78 SC for a few weeks now, however this morning was the first chance I've had to spend a lot of time to get to know my car. I was checking out a few basic items and making minor adjustments when during a test drive things went south on me. Here's what happened....

Started with ignition timing. I overshot the mark and noticed pinging.....simply throttled back the distributor until the pinging went away under WOT.

Then I set the air/fuel mix so it was richer than it was, but not so rich that the engine bogs down when I come off the throttle. This I feel as if I adjusted to just the right setting.

Feeling pretty good now about the way the car was running....so I decided to jack the car up and have a look at the clutch cable. The clutch feels like it's slightly out of adjustment....with the clutch engaged, there's too much "free pedal" before the friction point grabs.

I loosened those two retaining nuts and came to find that the threads under the nut closest to the helper spring were almost completely gone. I adjusted a little to give the nut more "bite" and snugged it back down. No question that I'll have to buy a new cable assembly

So I take the car out for a quick "spirited" drive to see if what I did was helpful. The car felt great, no issues at all. I was running hard, but not anything crazy at all. I Could hear the slightest pinging around 5500 rpm. No biggie, I can fix the ping.

Then......all of a sudden the car felt as if it had lost power....almost like a clutch slip was going on. The engine felt almost rough. The car simply would not pull at all.....even under WOT. The panic set in quickly.

Limped the car home and gave her a few minutes to cool down (backed off the distributor just a hair too) and decided to try a leisurely drive down the street....no leadfooting, just see if anything was odd. Believe it or not, no problems at all.

Well, it's time to pick the kid up from pre-school......'ll be back in 30 minutes and let you guys know if anything happens.....good or bad.

Hope someone can help me here......I'm totally confused.

Aaron

[tsuter]

Originally posted by gldnedge
Believe it or not, no problems at all.

So what again was the question/problem????

[bigchillcar]

aaron,
if it was running at least 'decently' before your adjustments, it's probably related to the changes you made in timing and/or mixture. does the 78 use ignition points? when these get old and begin to 'close up', you'll notice a very definite loss of power, even minor backfiring often begins. do you have a timing light? you need to check your total advance..your manual or a placard should spell out the details for what rpm, total advance and whether or not you unplug your vacuum retard (or advance depending upon which distributor you have). i imagine your dwell angle changed when you adjusted your timing..you always have to go back and forth to get both of these two parameters optimized. remember that 'small changes' go a long way with mixture adjustments on these cars, too. finally, don't hesitate..order a new cable. it's a good idea to always have a spare on hand anyway..and sounds like yours is running out of adjustment? don't let it stretch until it breaks and strands you (ask me how i know).
ryan

[Superman]

Sounds like you understand how cars work. Advance ignition until pinging happens, then back off a degree or two. If your engine has a performance problem, I'd probably suspect mixture. It's pretty hard to set mixture properly by ear.

[cowtown]

I loosened those two retaining nuts and came to find that the threads under the nut closest to the helper spring were almost completely gone. I adjusted a little to give the nut more "bite" and snugged it back down. No question that I'll have to buy a new cable assembly

There's an adjustable clevis at the pedal-cluster end too.

On the timing and mixture, I wouldn't use the "advance until pinging then retard" method. You're not covering your bases if temperature goes up, octane down, etc, especially if you're just trying to get it running right. Try setting timing to factory spec as a baseline first.

Can you borrow or buy a Gunson CO meter? Try setting CO to spec as well before changing anything else.

[gldnedge]

Everyone-

Okay, I'm back from preschool.....no apparent issues while on the road. BTW, my 4 year old LOVES the car

Thanks for the quick advice! This site rocks!

So I got back home and thought I'd better do what Colin suggested, set ignition timing to factory spec. While turning the pulley with ye ole 24mm socket to find my TDC indicator, I couldn't help but notice I had a loose belt. Hmmmmm. It's the inner vertical belt, NOT the outer that drives the smog pump. Looks like I'll be chaning or tensioning a belt before I do anything else.

I haven't done belts on this car yet...do I simply add or delete spacers for tension? I have a replacement belt and might just slap it on for piece of mind. Could this belt issue have something to do with my running problem?

With all that said, I'm going to lean out the air/fuel mix since this has been the most substantial change I've made of all the little tweaks. I get some light backfiring/crackling when slowing the car down while still in gear. I'll bet that's a mixture thing.

Again, you guys are simply a wonderful resource!

Aaron

[carreraplanes]

Aaron,

If your early SC is anything like the late one I had you will have breakerless ignition. When I bought mine the advance and retard mechanism had stuck at near max advance. If I it were me I would check that out then set the timing up with a light as per the book (or best recomendations from this site if the octane of your gas is different to that in the manual). Then pop the car down to a fairly well equiped garage so they can set the CO on their analyzer. They should also be able to give you an idea of the condition of the top end. 15 - 30 minutes work. IMO the rough and ready method of advancing it until it pinks then backing off a tad works well on water pumpers but is not accurate enough for air cooled stuff. From my experience with air cooled engines it seems that they are less tolerant of over advance than their water cooled relatives. A small amount often causes transient pinking that you will not feel and will not harm the motor all the time you are running it down the shops. Open it up for an extended amount of time on the freeway and that transient pinking will cause the cylinder head temps to rise and top end meltdown looms. You will probably not feel it pinking though. If anything it might seem even more powerfull.

I would be interested to hear what other Pelicans have to say on the subject of over advance and over leaning.

Keith

'70 T

'73 RS

[gldnedge]

Kieth-

Funny you should mention that the car will feel even more powerful. That is exactly the feeling I had while on my fun run. It felt strong and then suddenly got weak.

The timing is back to where it was when I started (very near factory spec) and will stay there until I process all this info. As much as I hate to, I may ask the local Porsche guy for some help. I'll take care of the belts and possibly the clutch cable before then, but I know when to call for reenforcements.

Aaron

[Jamie79SC]

I got a batch of bad gas recently. I can tell you that when serious pinging starts, power is GONE. I would suspect your timing advance too.

IMO, there is too much at stake to set timing by guess and by golly.