I don't get it!

[MikeP]

Heres the story. Bought a 67 912. One of the valve keepers was broke! So I pulled the engine first thing. Replaced, the rings, rebuilt the heads, and rebuilt the carbs.
Today after getting the engine back in, had a difficult time starting it. I had to use starting fluid!. So it finally started. sputtered a little, but the carbs aren't adjusted, yet. The oil pressure comes up as it should (thank god)! I ran it for 5 minutes. Shut it off. And now the damn thing won't start. She turns over really really slow, and is very difficult to turn over by hand. any ideas??? the oil pressure was good the whole time. what would cause this? lack of lubrication, over heating, or is this standard when seating the rings?
mike

[Efrain68912]

You say it is difficult to turn over by hand; are you turning from the crank pulley, or the generator nut? How much resistance are you getting? With my engine out of the car, I can turn the engine over from the generator nut with a large wrench with minimal effort.

Efrain
68 912 Coupe

[WFBowen]

Efrain: To be safe, I'd start by pulling the plugs & the valve covers to make sure everything's working on the top end. Was there any difference with clutch engaged/disengaged? Is the resistance you feel constant or do you hit "hard spots"? Any unusual sounds, etc? Starter motor disengaging? As for the resistance, if you put a 12" crescent wrench on the crank pulley nut, can you turn it with one hand?

[Ads912]

Any chance your battery lost its charge while the car was out of use? It would explain a slow crank and lack of starting.
I rebuilt my top end in the spring and noticed no difference in trying to start the car with the new rings and honed cylinders.
Double check that all of your spark plug wires are connected and on the correct cylinders.
I know these are simple ideas, but hopefully helpful.
The last thing that you want to do now is pull the motor again.
One last thought, you did adjust the valves?

[C. Clark]

Hello,

Since the engine did start and there where no unusual happenings during the initial startup, I would say it's electrical. I assume everything went back together easy when you put the engine back in? If it were a overheat it should spin once it cooled down. The engine being hard to turn over manually I think should be expected with a upper rebuild, tighter specs, more compression etc. Porsche electrical is weird, everything must be very clean with the connections. Ground wires can do strange things if there dirty or loose. Like the other guy said is the battery good / starter? If it had not started and ran ok initially I would be suspect for the re-build, another Porsche mystery. Good luck I hope it's something basic.

Chas.

[MikeP]

Thanks for the good ideas guys.

The battery is good. It has sat on the charger. Its good!

The starter it is brand new and functioning properly.

After I put it all back together the engine was easily turned over using the alternator pulley. Now it is soo tight that the belt slips and i must use the crank pulley nut to turn it over. It turns, but it very tight.
And yes, it does have some spots that are stiffer than others. But it was that way prior to this "stiffness" problem. I assume these areas are the compression strokes.

I suspected that somehow the clutch was adding resistance, but after fiddling with it, i was able to 99.9% reject that suspetion..

Today after the engine sat over night and cooled, it is a tad easier to turn but is still stiff. The Starter does turn it over, slowly. Not enough to start it, though. And after several brief tries the battery is next to dead.

I am stumped. Bearing? Rings? top end lower end?

I wonder how long a 67 912 would float?

Thanks again for the ideas, anymore???
mike

[ClayMcguill]

Ummmmm....sounds bad.

If it's still hard to turn over by hand, pull the plugs and try to spin it-it should spin over easily. If it doesn't, then you've got something mechanical binding-my guess either a spun rod or main bearing. Not good. Time to pull it, dissect it, and find the problem.

Sorry.

[josh912]

I would try another battery. I've had new batteries check out fine on the charger and be bad.

[MikeP]

Yeah thats what i've been thinking...Bearings! Oh well!
I don't think its the battery, because the engine is hard to turn over by hand and with the starter. I think that elimates a battery problem. I wish it was a battery problem. Thats easy to fix!
Is it possible to determine if a bearing is bad without opening the case? What about an oil test?
So does anyone know a good mechanic in the San francisco bayarea???
I think i might let someone else done a complete rebuild. What do you guys think? How many of you have done a rebuild yourself? And how involved was it?

MIKE

[C. Clark]

Hello,

Pull the plugs, I know it can be a hassle, the rear ones for me anyway. but that will tell the tale. With plugs out it should spin easily. I have a hard time believing that a top end rebuild would trash the lower end that quickly.

In high performance Chevys I always will rebuild both ends, generally the rods could knock, oil pressure problems, leaky gaskets and seals etc. with the improved compression, but even with a blown or spun rod bearing engines will generally turn over freely. But I am new to Porsche. Let us know what it turns out to be. I had a pressure plate bolt lock up an engine once, fell between the flywheel gear and the bell housing that was an old Chevy though.
Good luck,
Chas.

[Roland Kunz]

Hello

Check your spark plugs gap maybe your piston runs against the tip of them. if yes you didnīt CC ed the heads and have a to high compression as well.

Grüsse

[MikeP]

No, the pistons aren't hitting the plugs. And she still is tight with the plugs out. I am going to pull her today. I'm hoping theres a problem with the clutch binding up somehow.
Keeping my fingers crossed!
mike

[MikeP]

Haven't pulled it yet, but i determined that there is a definate tight spot near #3 TDC. Doesn't seem like this could be a bearing problem. More like a crank shaft or piston binding up somewhere. Any ideas???
mike

[pokemon]

Some more tests:
1. do a compression test. This might give an idea about the mechanical condition of the upper parts of the engine. (carbs must be held open + remove all spark plugs for compression test)
2. if you pull the engine, take first the third piece off. Thats the easiest and if the binding is in there its easier rectified.
3. after that if # 3 has a tougher spot then take # 3 off first. Remove the piston and try rotating it again.
4. check the end-play. Pull and push on the flywheel. You must feel it "clicking" in and out.
5. take off other loads like distributor, generator. Maybe they are binding.
6. add some two-stroke oil to the fuel.(mix with some fuel before pouring it in the tank) If this loosens up the engine then the binding is in the upper areas of the engine.

Still tight? Open the engine I'm afraid. Have you done this before? You'll need some special tools and buy the Maestro book Secrets of the inner circle. The technical advice given is worth every dollar you pay for the book + the rebuild of the 912 engine is explained step by step.
I had never opened an 912 engine before but with that book at hand the work was done without mistakes and believe me, there are many ways to rebuilt a 912 engine wrongly.

Good luck,
Patrick

[Roland Kunz]

Hello

First is to remove the valve train ( Rocker arm carrier ) and turn the engine without valve action.

If you still have a bad spot the heads are down some minutes later .

If you used aftermarked P&C then check if they didnīt need a big shim on the case side. I think cheap NPR copys can run against the head if build straight in and not shimed. Donīt ask me how I found out, car came from the US and still today I canīt beleive it runed.

Grüsse

[MikeP]

Thanks for the ideas. I'll let you know what happens!
mike

[MikeP]

Ok so i spent the afternoon pulling her apart.
Compression is fine.
Pulled the plugs. tight spot and noise near #3 TDC still!
Pulled the valve train. Tight spot and noise still.
The spot and noise seem to occur at or near#3 TDC, thus i believe it must be a cam or distributor problem. Right? If it was a crank problem it would occur twice per cycle.

This brings me to another question. I've got a Bosch 031! Anyone ever heard of a 031 in a porsche?
I'll probably switch distributors, because there is a broken spring in the existing one.

Also when i removed the heads i found that the #3 cylinder was heavily covered in carbon compared to the others. And #4 was completely clean. Sounds like an ignition problem too.

I don't see any alternative to a rebuild. Any ideas what i should do?
mike

[C. Clark]

Mike P,
Did you pull the distributor out and try turning over the engine? What did 1 and 2 look like? I assume you pulled them too. With all that carbon on 3 how did the engine sound when it was running?, 3 cylinders firing or 4? Check the sump for engine debris / particles in the oil, though I doubt you find any.
Good luck,
Chas

[MikeP]

Yes i pulled the distributor and turned the engine over. It didn't make a difference.

1 and 2 were lightly covered with carbon, so they were firing ok.
It sounded ok when it ran, but this was the first time i've heard it run before. it wouldn't idle below 1200 rpm, I assumed the carbs had to be fine tuned. But i'm sure it was only running on 3 cylinders, now though.

I did notice the clutch fork pulsing in and out as the engine turned, it this normal???

[C. Clark]

Mike P,

So you never heard this car run before, I take it you bought it as is and rebuilt the upper end. The 1200 idle is semi normal for a Porsche with older carbs, which I assume they are... Mine has new Webers and idles best around 900 to 1100. The clutch fork movement is interesting, I've never noticed any pulsating in mine. Did it work normally when it ran? did it engage and dis-engage? The mystery thickens...... Go 9ers!

Good luck,

Chas