930 overheating at idle

[Browzer52]

Subject....1986 930.Did a city Canada Day parade with my PCA group, very warm day, watched the oil temp climb to 275+ F as we sat idling for almost 45 minutes.
Once on the highway temp dropped back under 200.Have changed both thermostats, now new, flushed lines and both coolers and installed an aux return cooler @ the tank. Also installed an aftermarket fan in front of the front cooler which I run off a toggle switch. Have heard that the aftermarket headers(boxed for cab heat)that are in place may be a source for this problem.....any thoughts?

[jwasbury]

Sounds normal to me. Even with a front mount oil cooler in addition to the fender cooler, mine will get hot stuck in traffic. There's just not enough airflow when you're sitting still to carry the heat away. Fans will help, but eventually the oil will get too hot.

[Robbbyg]

hows your tinware and aprons around engine?
they all must be sealed and well
They make a big difference in cooling

[Browzer52]

Originally Posted by Robbbyg

hows your tinware and aprons around engine?
they all must be sealed and well
They make a big difference in cooling

Removed engine a few years ago. All tinwork was powdercoated and installed with stainless hardware. Any rubber in need of attention was replaced. Foam around front cooler was also redone.

[unclebilly]

Yup my 86 also got pretty hot in the Canada Day Parade with 2 4 year old huligans yelling 'Happy Canada Day' and waving flags out he sun roof. It wasn't in the red but it was up there.

These cars are not made to idle in traffic.

Mine has the oil cooler in the right rear fender and no fan.

[Bucketlist]

Originally Posted by unclebilly

Yup my 86 also got pretty hot in the Canada Day Parade with 2 4 year old huligans yelling 'Happy Canada Day' and waving flags out he sun roof. It wasn't in the red but it was up there.

These cars are not made to idle in traffic.

Mine has the oil cooler in the right rear fender and no fan.

I was wondering about the cooler in your right rear fender, is it a radiator type cooler? I have been thinking about adding one inside the fender vent. Do you have a picture? Has anyone else done this?

I know this is the left fender but you get the idea.

[mooney265]

When I first purchased my car in 2009, it could get pretty hot in traffic. Then, i did the following:

1. Only run Mobil 1 Air Cooled
2. Ducted the Front Oil Cooler [located behind spoiler] and added 2 T-stat relayed fans.

Now, in traffic [or simply at stop for 30-minutes], in Louisiana Summer, the car never sees above 215F. It usually cruises at 170F in the Heat.

Took some work, but no more worries...

[ficke]

Adding oil coolers will not help sitting in traffic heat dissipation, because to get air flow over those coolers you need to be moving. You have to add fans on oil coolers to help sitting in traffic temps.
Adding an electric fan on your fender cooler will help.
I did that and added another fender oil coo0ler with fan on the right side, now i have no more heat climb sitting in traffic.

[Miguel Antonett]

Air cooled cars don't like idling, and 45'... you're lucky that nothing else happened.

[T77911S]

how is the timing? too much retard(not enough advance) will make it get hot idling.

mine got up to 210 the other day idling for a while. (working on it). found my timing was not set properly. (i do run with the retard connected and all is fine when set properly). i think i hit 185 one day. yea, its hot here.

[dos531]

Originally Posted by T77911S

how is the timing? too much retard(not enough advance) will make it get hot idling.

mine got up to 210 the other day idling for a while. (working on it). found my timing was not set properly. (i do run with the retard connected and all is fine when set properly). i think i hit 185 one day. yea, its hot here.

Is advancing the timing at idle as simple as disconnecting the vacuum retard? Heat and traffic are inevitable here, and my fan helps, but still doesn't cut it. I need all the help I can get.

[jeos]

we just have to realize that 930 is a race car that can not tolerate muck round idling

[mark houghton]

Originally Posted by dos531

Is advancing the timing at idle as simple as disconnecting the vacuum retard? Heat and traffic are inevitable here, and my fan helps, but still doesn't cut it. I need all the help I can get.

Not that simple. Need to keep both vacuum lines connected to the pot. Loosen the distributor clamp and rotate to the timing you desire. Then, adjust your idle speed to drop it back down to spec. Finally, if you have on-board AFR measuring capability, check your idle AFR and adjust if needed.

This is a well covered topic....distributors, vacuum lines, retard and advance, mechanical advance, boost ignition retard, adding ignition advance, yada yada yada. Can quickly become confusing. Don't go crazy and dial in too much advance...it can be detrimental to your health when on boost.

I was running 12 degrees advance at idle with all the lines connected; others have run even more advance. This all assumes you're running with an MSD or similar programmable ignition to allow bleeding off the excess timing as the boost builds.

[dos531]

Originally Posted by mark houghton

Not that simple. Need to keep both vacuum lines connected to the pot. Loosen the distributor clamp and rotate to the timing you desire. Then, adjust your idle speed to drop it back down to spec. Finally, if you have on-board AFR measuring capability, check your idle AFR and adjust if needed.

This is a well covered topic....distributors, vacuum lines, retard and advance, mechanical advance, boost ignition retard, adding ignition advance, yada yada yada. Can quickly become confusing. Don't go crazy and dial in too much advance...it can be detrimental to your health when on boost.

I was running 12 degrees advance at idle with all the lines connected; others have run even more advance. This all assumes you're running with an MSD or similar programmable ignition to allow bleeding off the excess timing as the boost builds.

So there's no way to get rid of the idle retard while maintaining the vacuum advance and boost retard?

[T77911S]

you can pull the idle retard. i dont think there is a need to. personally i think mine idles better and sounds better with the small amount of retard it adds. you dont jsut want to advance the timing without checking it.

what i would do is check the ignition timing to make sure it is correct. if your timing is not advanced enough, just pulling the retard is covering up the problem, plus you are losing performance.

now, you CAN just pull it and see if it helps the hot idling. if it does, check your timing and set it correctly.

[dos531]

Originally Posted by T77911S

you can pull the idle retard. i dont think there is a need to. personally i think mine idles better and sounds better with the small amount of retard it adds. you dont jsut want to advance the timing without checking it.

what i would do is check the ignition timing to make sure it is correct. if your timing is not advanced enough, just pulling the retard is covering up the problem, plus you are losing performance.

now, you CAN just pull it and see if it helps the hot idling. if it does, check your timing and set it correctly.

I pulled the vacuum retard and let the car idle and it made a big difference in terms of overheating. So the question is, if I simply plug the line and port will I still retain the vacuum advance/boost retard on the other side of the pot? Are they independent of each other? I dont want to change the timing except getting rid of that idle retard.

[JFairman]

The 1986 vacuum retard pot has nothing to do with vacuum advance or boost retard and when the motor is above 1500 rpms the outer edge of the throttle butterfly has gone past the little hole in the throttle body wall for it and there is no vacuum retard anymore.
The purpose of vacuum retard was to retard timing at idle, very low speeds, and deceleration to raise exhaust temperature which heats up the catalytic converter faster so the car will pass emissions.

You can leave the retard hose off it and plug the end with a bolt or something or cap where the other end connects to the throttle body. You might have to hook it up when doing California emission testing if they do exhaust sniffer tests.
I would put a little curved hose that points down and is vented to atmosphere on the vacuum retard pot nipple. I never tried capping it so maybe you can do that instead. You just don't want water getting into it and ruining the insides if it rains.

My '87 has the same distributor I think and the vacuum retard pot decided to stop working on it's own and the car ran better and idled stronger. My idle timing is around 15-20 degress BTC and it idles smoother there than at 0. I shortened total centrifical advance to compensate. Thats easy to do.

The 1986 and '87 stock idle timing was retarded so much it was a little after TDC to pass emissions which also makes them get hot and they were so sluggish and lazy off the line it's ridiculous. Most people could get out and run faster than these things could get moving off the line if you left it stock.

[mark houghton]

Originally Posted by JFairman

The 1986 and '87 stock idle timing was retarded so much it was a little after TDC to pass emissions which also makes them get hot and they were so sluggish and lazy off the line it's ridiculous. Most people could get out and run faster than these things could get moving off the line if you left it stock.

No kidding, and man am I finding that out with my "new" ride. Need to buy a boat load of replacement tools, the first of which will be a timing light and the second of which will be an AFR gauge before I start tweaking.
Getting closer to having my shop put back together and really itching to waken up the 930.

[Robbbyg]

I dropped my temps down using my front cooling mod using ---Silicone at speed it works exceptionally well but at idle it makes no difference,,

[dos531]

Hey guys I just wanted to give my experience with removing the vacuum retard. It idles fine, but on boost it falls flat on its face, then pulls fine once fully spooled. It seems to me that it is pulling the vac advance timing sooner without the pressure on the opposite side of the diaphragm to even it out. I have done back to back tests and it is noticeably down on power during spool with the vac retard disconnected. To remedy the problem, I installed a vacuum check valve between the throttle body and the vac retard port that allows boost to reach the diaphragm, but vacuum is blocked. Runs perfect now!