Loss of power (above idle)

[lep]

My engine performance seems like it has been gradually decreasing over the last few months. A couple months ago, after noticing that the engine "seemed" to be running on 3 cylinders, I pulled the number 1 cylinder plug wire at run-time and indeed nothing changed. I then cleaned out the carb jets (essentially new IDF44 webers) and it ran better.

Overall, however, I think I am losing a cylinder that is firing intermittently, and I can't chase down which one it is. What is also happening is that when I increase the throttles into the mid range, the RPM drops as if it is not getting any fuel. After cleaning the plugs today, it wouldn't start.

The weber instructions don't offer any recommendations for setting adjustments in the mid-range (are there any adjustments above idle?). In addition, this is an engine that 2 years ago received a new big bore kit, new cam, new Pertronix, new spark plug wires, Denso iridium plugs (gap = 0.024in), and new Weber IDF44's -- and had tremendous power. The car itself has not been driven a lot since the engine work, because of a needed brake caliper rebuild, and other restoration work.

Regarding the current engine performance I think it may be a carb issue, or a bad distributor.

Can anyone recommend a priorities for rapidly decreasing engine performance?

[maybe368]

Did you check to see that you have spark? I know it is a basic response, but it is very easy to tell if it is a fuel problem or a spark problem. You can of course pull a plug wire and stick a screwdriver into the end a hold it close to ground, but one thing you might try is to put an inductive type timing light on each plug wire to see what is happenning at each cylinder through the rpm range, as well as if there is spark at all. If it turns out to be a fuel problem. I do not know much about Webers, but I would check to see if your gas is bad, if it has been sitting a while. Good luck

[cgarr]

Pull your high speed jets (tubes) and check them for flakes of dirt. Those are good size carbs for that engine.

The only adjustment for mid and high range is to change your e-tubes and jet sizes.

[lep]

Thanks for the tips on (a) pulling the high speed jets and inspecting them for flakes/dirt, and use of an inductive timing light to observe spark intensity as a function of RPM. I'll look into those.

lep

[Jaems]

First of all the 44's are too big for a stock 912. You should have purchased 40's with 30 ventures and the jets, air and etc. depends on where you live mountains or sea level.

If you can fine someone with a Sun. Have them check the spark to all the cylinders. You also could be loading up with those 44's. Or if they were adjusted too lean then you could have a burnt valve or two. You can check the burnt valve by doing a compression test and a leak down.

My motor was built over five years ago. When I said built I meant that I started with a new case and heads. I used a forged crank, pistons, and rods. I also did have the heads polished and ported to match the intake and 40 IDF Webers. I also use a 031 with pertronix's.
The motor in fifth will pull from about 2500 to 5800 rpms with out lugging. I wanted the car to be streetable not a race car. I do not get to drive the car much. So it does sit a lot. However, it always start right up and drive perfect. About a year ago I put the car on the dyno and the motor produces a 103 hp and a 101 # of torque at 5800 rpms wheels to the ground.

[lep]

Thanks for the suggestions.

I learned that the spark plug gap was too small, and since I use Denso Iridium plugs, the gap has to be about 0.8 mm, which is actually huge. Therefore, I opened up the gap. I also installed a new high torque starter, and it fired right up.

I will never go back to any other plug besides Denso Iridium. I also use a Pertronix magnetic distributor breaker system (type 009 Bosch).

[Scott Douglas]

If you're using a 009 distributor you have much better choices available now. I'd look into getting an RS0012 distributor if I were you.

[lep]

I looked at the CSP web site but no RS0012 distributor could be found. Can you provide a link(?), thanks.

[C. Clark]

For some reason it's not listed on the web pages of CSP, you can call and order one though. I've heard good things about the CSP unit.
Chas.
356912911

[BryanM]

Harry is selling his unused unit. can't beat the price
http://www.912bbs.org/index.php?a=thread&p=190111

[Scott Douglas]

Bryan beat me to it.

Help Harry out by buying his.