Houston, we have a problem.

Check your plug wires. On a VW dune buggy we had one wire would get too hot and the spark would jump. The wire had high resistance. The engine at cruise speed was fine unit you accelerated. The engine loaded up and miss fired. It's a simple check before tearing the carbs apart.

Ben: See if you can find your problem and solution mentioned in one of the stories in this website. It's great and informative reading. Good luck! www.hcpresearch.com/index.html

Pull out all four plugs and report back what each one looks like in detail (color, amount of carbonization, etc.) Keep them them separate so you'll know which cylinder each came from so we'll also know. Also tell us exactly what the plugs are (make and model so we'll know the heat range) Don't buy a new set of plugs until you report.

Throw away your old plug wires and install a new set, along with disti cap, points and condensor.

cheers, Gordon

Ben, check your idle jets. I was having a similar problem and have dual weber 44's. Once I got up to around 2500 rpms it went like hell, but lower than that and it missed. Turned out one of the idle jets had a piece of dirt in it and once I blew that out it was fine. It happened again and it turned out to be another idle jet on a different cylinder. Haven't had the problem now for a while.

Recardo, That is a great site.

Gordon, the plugs,cap, rotor, points and wires are new. The plugs are Bosch supers. I the heat range is R0 285. When I pulled the plug on #1 (the mis firing cyl) it was black (rich) but not wet. I was missing on that cyl all the time. I put in a hotter plug (491) and it now is in the fire under load mode. I also tried another plug wire, but had the same result. I set the timing as well, but really need a better timing light as the site Recardo sent me to says to set the timing to 33 degrees advance at 3000 rpm. I do not have a degree wheel and my timing light it a simple static one. It is entirely possible that my jets are too big but that should just show up as black smoke out the exaust right? By the way, does anyone have a process for getting the correct jets?

One other thing worth metioning is that you can smell gas. I have ran all the lines except under the tank and have not found a leak. I am going to take a wheel off tonight and check the tank.

Chris,
I rebuilt the carbs, I might have ended up with a plugged jet. This sounds stupid, but where on the 44's is the idle jet? ( I borrowed Instructions and have since returned them)

Thanks,
Ben

I have a problem which I think is carb related. When under power my engine runs like a scalded dog. Hits on all four, if you know what I mean. When not under power, that place where you are just maintaining speed, it misses. As soon as I give it some gas, Wham! and off we go.

Now I have a 69 912 1600 cc engine. Stock, as far as I can tell. The reason I think it is a carb problem is that I have Weber 44's. On a VW 1600 I would be way over carbureted, I am assuming the same for the Porsche motor. I suspect that one cylinder is loading up (#1). I have set the carbs up using a syncronometer. I set the flow across the barrels of each carb then to each other. Purrs like a kitten, sounds good as well. Reminds me that I didn

Ben
The idle jets are located on the side of the carbs with the mixture screws. Brass screws high and toward the center of the carbs. The jets are located in the inside end on these screws. If your are running rich on just #1, check and make sure the idle jet screw is tight and that there is an "O" ring on the screw. If the screw is not tight it will allow fuel to go around rather than through the jet and it will run rreeaall rich. Ask me how I know
Bill

I just chased away the same symptoms. It was the idle jet that was blocked. Pull plug wires at idle and confirm which cylinder you pull the wire on has the least impact on idle speed and roughness. That will usually be the one to check the idle jet on.

Sorry I haven't posted sooner but out driving the speedster. Took out #1 Idle jet and it was plugged. Cleaned it out and it helped but it looks like I have another one plugged as well. (#3 best I can tell.)

I took the car out Friday and it still smelled gassy. I looked all over for leaks but didn't find any. I put it in the garage and decided to have one more look. Light was just right to catch the drips off the fuel pump. The 912 has a piece of sheet metal under the fuel pump that allows the fuel to pool and pretty much hide the bottom of the pump. Difficult to find small leaks there. Lesson #212 about 912 engines.

I had rebuilt the pump and checked it by manually pumping gas though it, but I never blocked off the outlet (carbs full). The in and out are pressed in fittings about twice the size of a VW pump. The outlet was seeping where it was pressed in. Ran down to the VW shop and sure enough, they can get a pump next Tuesday for $230 (lesson #1 about Porsche 912 engines: Parts aren't cheap) We have the spring hotrod nats in town (2200 cars '49 or older) so I want to drive it today, or Saturday at least. JB Weld is amazing stuff. Just wish it cured faster than 16 hours.

Anyway, I took it over to a get together with some of those Samba.com guys and then cruised it Saturday night. What fun! Like hanging on to a tiger. Can't wait to change out the wheels and tires. More pics to come.

Ben; I'm glad everything worked out; I can't stress enough the virtues of JB Weld. The Maestro's website is cool too; it's sad that he's no longer with us; he was such a colorful and knowledgeable character. Those DVD's on 356/912 repair would be a great addition to any of our libraries; you can't never learn enough and judging by the Maestro's writing style they should be fascinating.

Ben:

Trash-can that 912 fuel pump and install a decent rotary pump and filter up front under the tank. It'll give you more constant fuel pressure and costs about 1/4'th that of the 912 number.

gn

Gordon,
Thought seriously about it. Would have but I had already had $40 bucks into the pump for a rebuild kit. Then theres that stock look thing.

Finally got all the jets cleaned out. Can you say silky smooth?


Thanks Guys!

Great!

Isn't it amazing how they get crudded up?? Try to seal better around the top and bottom of your air cleaners and it might prevent this. Several folks have offered different sealing solutions on here.....I use a bead of Permatex Blue on both the base and the cover, but I let it cure for an hour so it becomes like an "O" ring for the element. Had one partial clog in three years now (running Dells) and it eventually sucked out on acceleration.

gn

Gord; what about the K&N sealing grease for the elements? It sounds like a good idea too.

Yup, that works well, too. I just didn't happen to have any when I last cleaned them so did the Permatex "O" ring trick. I was also wondering if the grease thins out when it gets hot. {8>)

Letting it cure before you put everything together makes it seal well AND you can easily get the elements out later and then just peel the "O" ring out and make another.

Never thought about that but it's a great idea. Did you use the regular or high heat variety?

Reg'ly old Blue stuff.

Just make a 1/8" wide bead around the base plate and cover where the element contacts, and let it cure as a bead. When you put everything together, it'll squish the bead and seal really well without adhering.