Will Any 12v Coil Work?

[gungadin]

I'm having a misfire problem and since I'm no genius I'm using the "just throw money at it a little bit at a time" approach.

I'd like to try a different coil before I buy a new one.
Would any 12V coil work temporarily?

'76S w/ '79 3.OL eng.
points ignition.

[mb911]

You have an sc engine with points? not possible.. I doubt that a quick coil change will be terrible but I would worry a bit about the cdi box getting fried

[cashflyer]

Originally Posted by mb911

You have an sc engine with points? not possible...

Why not?

[gungadin]

Originally Posted by mb911

You have an sc engine with points? not possible..

I've asked here about that before and I thought I got a definitive answer.

On the clamp holding the fan housing it's decal says "911 SC"
On the engine case right side below the fan are these numbers
6392956 and below that 930/03

Can someone positively ID this engine from these numbers?

It does have points. CCW rotation.

[3.2 CAB]

The 930/03 engine number shows to be used in a ROW-1979 911SC with that engine number range. It also states that it did not have points from 1978 on. Apparently someone changed it to a point type ignition at some time in the past. The engine serial numbers started at 6390001-on. The 1978 serial number range started at 6380001 - on. Hope this info helps. Good luck!!

[cashflyer]

I think any coil with the correct resistance should work. Many of us have replaced our original coils with the MSD high vibration coil. About $50.

[tcar]

Gungadin,
Are you sure you have points? That engine did not have them from the factory.

Regardless, any 12V coil should be fine.

[emac]

I cannot see any reason why a 12v coil would not work with or without points.

[David E. Clark]

If this were my car I’d start by trying to determine what was causing the misfire.

Normally, it's one of three things: (1) bad or no spark; (2) improper air/fuel mixture that is not igniting properly; or (3) loss of compression. I’d start my diagnosis in that order.

(1) Bad spark is most commonly caused by worn, fouled or damaged spark plugs, bad plug wires, or a cracked distributor cap. A bad coil could also lead to poor spark but I seriously doubt that a bad coil is the cause of your misfire. While a weak coil can cause bad spark, it would affect all cylinders and not just one. Start by looking at the free stuff. Are all your plug wires properly seated on the plugs? Are any of the plugs fouled? Should you change the plugs? Is the cap cracked? Does it need replacement? How old are the plug wires? Should they be replaced? Are your points pitted or worn? Is the gap correct? There are lots of good threads about replacing and testing plug wires. Plugs and wires is one. If you want a quick, but not definative, test, run your car in complete darkness, open the hood and look for electrical arching or a blue auroa around any of the plug wires. If you see this, you've got a bad wire(s) (not seeing it does not mean your wires are good they still should be tested).


(2) Improper air/fuel mixture can cause “lean misfire” when there is not enough gasoline in the mixture to burn. This can be caused by a clogged or bad fuel injector(s); air leaks; or a defective fuel pump causing low fuel pressure. Like a bad coil, low fuel pressure would affect all cylinders rather than an individual cylinder so I doubt that a bad fuel pump is your problem either. If everything in (1) fails to resolve your problem, you may want to have your injectors checked and/or cleaned. Sometimes an injector "leaks" and causes misfire. This is not uncommon in Porsches. Many owners have had good luck with Chevron Techron Fuel System Cleaner (It's Porsche approved). Just make sure you change the oil after you run it through the tank.


(3) Loss of compression can be caused by a bad exhaust valve or blown head gasket(s) (can you say expensive!). Blown gaskets normally affect more than one cylinder so that is unlikely to be your problem. A bad exhaust valve, on the other hand, could likely cause these results but it’s the last place I’d look given the cost involved. Let’s hope it’s not this!

Hopefully some of this will help. Merry Christmas!!

[RWebb]

After that, check the coil or replace it. msd is fine. The newer Bosch ones are notious for QC problems. IIRC, they are silver and are made in S. America.

[cashflyer]

It didn't really sound that odd to me that somebody put a late engine into an early car and opted to use the chassis' original electrical and ignition system.

[Paulporsche]

I have points w/ my engine.

[mb911]

Originally Posted by Paulporsche

I have points w/ my engine.

Wow guess I never saw one that way.. Most (99%) sc engines run a trigger/magnetic pickup..

[cmonref]

Points on an SC I gotta see! CCW rotation would require mirror-image points -- do they make those? Maybe the distributor is a non-SC adapted to turn CW by a new gear at the bottom? Who would take the time (and spend the money) to go backwards to points?

Paulporsche -- can you fill in the blanks?

Brian

[mb911]

Originally Posted by Brian K. Haggard

Points on an SC I gotta see! CCW rotation would require mirror-image points -- do they make those? Maybe the distributor is a non-SC adapted to turn CW by a new gear at the bottom? Who would take the time (and spend the money) to go backwards to points?

Paulporsche -- can you fill in the blanks?

Brian

my thoughts exactly

[Paulporsche]

Brian and Ben,

About 20 yrs ago one way to get more hp from the SC engine was to enlarge it to 3.2L, using (I think) a larger bore and creating what was known as a 3.2 Long Stroke. Typically this would have about a 10 to 1 to 10.5 to 1 CR and would be twin plugged. Obviously this would require something different in the dizzy department.

When my original 2.7 packed in, I located this engine, which had just been built and installed in a car, which was then promptly stolen. It was recovered, but the car was parted out.

Since my budget was stretched to the limit, my mech installed the engine w/ a single plug dizzy c 1974 w/ points. To prevent detonation, I run it retarded about 2 or 3 degrees from stock. I have put about 65000 mi on it over the last 17 years or so and it still runs great. In the lighter S chassis (2500 lb), it has very nice acceleration, especially coupled w/ my new, smaller dia tires (205/50/16). According to unconfirmed reports, I have about 220 hp w/ the Dansk exhaust and SSIs. which is fine for this nearly 60 YO guy.

As Brian suggests, the rotation is opposite to the standard SC and is handled by a different gear. The points are as used in pre SC engines.

[gungadin]

Thanks for reading my post and for the suggestions... And the holiday wishes-- back atcha!!
OK lets update.
Car originally has "bonanza syndrome" so two months ago I take it to a reputable mechanic. Motorsports International in Portland OR.....THEY:
-check wires and plugs cap and rotor....OK
-say it was running rich....adjusted
-replace the points....set timing and dwell
-They say it's running OK and I thot so too. I drove it several hundred miles.
On Thanksgiving eve I encounter some stop and go driving on the freeway and as the temp goes up it begins to run not so great. Seems the Bonanza thing is back with a vengance.

Foul weather season begins in Oregon with considerable rains.

Progressively the car develops a strange misfire. It starts cold and runs smooth but as the temp goes up it gets worse and the hotter the worser...
When it misfires I see RPMs drop off the tachometer. the worse the misfire the more RPMs drop off. If I stick my foot in it it goes strong with no misfire.
The misfire is not steady but random....

Two days ago I replace the plugs and wires with new. Didn't help

Yesterday I replaced the coil with a new coil. Didn't help

There is no change except it might be getting progressively worse.

A little over a year ago I had a similar incident. It was poring rain and it started the same (I think) misfire... only so bad that I had to get towed.

I replaced the cap and rotor then. It seemed OK at that point but still had it's regular Bonanza syndrome. No misfire.

I'm going to check for water in the distributor I guess. I'm going to check to see if the points have closed or have insufficient gap. I may change the cap and rotor again.

Who can tell me where the primary ground for the ignition system is located?? Since the engine has been replaced at least once I suspect that the ground may need to be re established.


My dad is the origional owner of this car. Be for he had a '72T. I got to drive the '76 home from the dealership. I remember thinking "OMG!!! like a little 'vette that goes where you point it!!!"
He had the 2.7 fixed once and it failed again. I remember big oil on the garage floor. His mech puts the 3.0L in it. Some parts stirring happened as it still has a 5 blade fan and the points ign. And no forward oil cooler.
As he got older and couldn't get in/out he turns the car over to me. Blessing or curse???
It's an Irish green cream puff that's been garaged it's whole life and not driven much.
I don't see any SMILEYs that are crying. (maybe you guys wore that one out)
I'm getting a lump of coal in my stocking.

[gungadin]

PS:
I have a Pertronix ingition but haven't installed it yet.
Do we see any problem with the counter rotation?
I really do hate points which means I'm not good at adjusting them.

[HarryD]

What is your CDI Box? Bosch, Permatune, MSD?

Maybe a bad ground there.

Grounds. How does the grounding strap look between the engine and the body?

[HarryD]

Originally Posted by gungadin

PS:
I have a Pertronix ingition but haven't installed it yet.
Do we see any problem with the counter rotation?
I really do hate points which means I'm not good at adjusting them.

Gap is not that significant on a CDI System as the points only turn the unit on and off.

While I do not want to throw stones at Wayne's Shop (he seems like a square guy), have you considered getting a second opinion at one of the other reputable shops here (if you are on the west side, maybe Marque Motors or Stuttgart)?