Need Help Fast!

Efrain68912 · 02-04-2002, 02:41 PM

Have a major misfire in my 912. I replaced the points, cap, rotor, condensor, and plugs (009). Did an oil change, timed the car to 3 degrees advanced at idle (1100 rpms). Car ran fine that night. The next day, on the freeway, the car developed a major misfire above 4000. I noticed an intermittent trail of smoke behind the car. I pulled over and found that oil was leaking from the oil pressure sending unit. It had been moved, I assume at some point when the distributor was out. I moved it back and the oil leak was gone. I haven't rechecked the timing, but I did spray the carbs with carb cleaner, and noticed this; when sprayed into the carbs on drivers right, the car does not bog down (I use Weber 40s). When sprayed onto the drivers left carb, the car bogs and almost dies. I sprayed it in short bursts for 15 minutes while the car ran, and the bogging down never got better. Driving it afterwards, the misfire had become much worse.

Any ideas? Dunkel's is in six days!

josh912 · 02-04-2002, 04:08 PM

Sounds like a intake manifold leak. Check to make sure all of the bolts are tight, and if that doesn't work replace the gaskets or use gasket sealer for the time being.

Efrain68912 · 02-06-2002, 07:38 PM

Update: The carbs have been running rich for so long we think they may have killed my rings. Compression test showed:

125 100

125 90

We're going to lean out the mixture and hope that the rings re-seat themselves. If they don't - anyone in need of some 912 motor parts?

wastintime · 02-06-2002, 07:54 PM

I don't think that's a very likely answer to your problem. Even if it is the rings, I don't think your carbs did that. Running them rich isn't half as bad for the engine as running it lean. I think runnig it lean would be more likely to fry piston rings. Granted, I know a lot more about aircraft engines than car engines, but you always run aircraft engines rich to make them last longer even if it uses a little more gas.
Also if you have webers there are two seperate mixtures, one for idle, and one when you're out of idle. It's possible to idle rich and run lean and vice versa.

josh912 · 02-06-2002, 08:03 PM

Efrain, don't give up now. Those compression test results may not be perfect, but they aren't that bad. Like wastintime said, don't lean it out. #3 will burn up in a heartbeat, trust me (the whole reason behind my last rebuild). Check the gaskets (bad gaskets will cause fluctuating air-fuel mixtures), readjust the carbs, make sure the valves are adjusted, a little on the loose side, and check the timing. Its all a mater of getting everything to sync together. Until then you will havesome headaches, but in the end its all worth it. And no matter what happens, keep the motor. See you at Dunkel's! Maybe we could look at it then? Give me an email.

Josh

Duke · 11:10 AM

If your compression figures are correct, your engine needs an overhaul. The limits for the 912 engine are 170-140psi. Anything lower than this and you are on borrowed time. Also the difference between the highest & lowest cylinders should not be more than 25psi. I just went thru this two years ago. Good luck. Duke, 69 912

Efrain68912 · 02-07-2002, 11:18 AM

I e-mailed the Maestro, he told me that the car should run fine with those numbers. I drove the car yesterday and it sounded and felt terrible. We'll do one last check of the ignition, lean the mixture down to something that won't foul the plugs, and see if it gets any better.

If not, its a good excuse to hurry up and build my 1911 T4.

josh912 · 02-07-2002, 12:07 PM

What plugs did you put in? I have a strange suspicion that the pistons might have hit a plug or two.

Efrain68912 · 02-07-2002, 03:33 PM

The Bosch plugs that Performance Products gave me. Hmmm....I'm going down there to check it out. I'll be checking for stuck floats as well.

wastintime · 02-07-2002, 03:49 PM

I'm sure there are worse places to get parts from than Performance Products... I just haven't found them yet. Maybe Josh is right about the plugs?

josh912 · 02-07-2002, 04:52 PM

Efrain, Performance sells 2 different Bosch plugs. The W5AC and the W6BC. If you have higher compression and/or a big bore, there is a good chance you need the W5AC, which is a shorter plug, to prevent the pistons from becomng too friendly with the plugs.

Geez Efrain, your bringing back memories! Good or bad, well thats another story.

Efrain68912 · 02-07-2002, 05:27 PM

Just back from Eurosport:

No plug to piston contact
Floats were fine

Retimed the car to 4 degrees, got the car running as best we could. I can drive it to Dunkels, but afterwards I park it and yank the engine. I'm pretty sure that a T4 is going in in place of the 912 engine. (So then I will have two 912 longblocks).

So see you all bright and early on Sunday!

Efrain68912 · 02-08-2002, 07:42 PM

Pleasant update:

Leaning out the mixture seems to have worked. Before, when the plug wires (for nos. 1 and 2) were pulled off of the engine, there was no noticable change in the running of the engine. Now when they are pulled they engine noticably bogs. The carbs are horribly out of balance but we did that to see if we could wake up the right side, it seems to be working. Still has a ton of vacuum leaks. The car is down on power bellow 3 thousand, but feels normal above it. I will do the Marvel Mystery Oil Trick tomorrow, then the wash/detail. Then its the 45 minute drive to Anaheim at 5 am Sunday.