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Posted by: derekdenman Nov 12 2007, 06:09 PM

I am hearing a pop sporadically while driving at a constant RPM. Whenever it pops you can feel the engine miss as well. The engine is a very fresh 2056 with dual Dellorto 40’s, mild carb web cam, and a stock 050 distributer. Also it runs strong from idle to about mid throttle but after mid throttle it has no power and goes from a smooth sound to a very low throaty sound. It seems like it is rich due to the lack of power after half throttle but it the pop seems like a lean miss. Any suggestions? Maybe multiple problems?

Posted by: degreeoff Nov 12 2007, 06:12 PM

Hmm sounds almost like a ignition issue....

Posted by: cobra94563 Nov 12 2007, 06:20 PM

I'm experiencing something similar (on a different engine).
I have an O2 sensor on the exhaust and my mixture is fine thru the range, so I'm thinking something in the ignition.

Posted by: derekdenman Nov 12 2007, 06:28 PM

I am running a Crane XR3000 ignition with the LS91 coil. The wires plugs, boots, and cap are all new. One the vacuum advance there are two nipples. One nipple is pulling a vacuum from the manifold. The other (closest to distributer) is not connected to anything.

Posted by: Headrage Nov 12 2007, 06:50 PM

Clogged idle jets.

Posted by: 9146986 Nov 12 2007, 07:00 PM

Ed Mayo once told me that half of carburator problems are ignition.

Check to make sure your distributor is getting full advance, and also check your timing at full advance.

If that checks out OK, then I'd suspect you might need to go up a size on the main jet. I don't know how much trouble it is to change jets on Dels.

Posted by: thomasotten Nov 12 2007, 07:16 PM

Sounds a lot like the same problem I ham having. I'm running Dells too. What are your jet sizes?

Posted by: So.Cal.914 Nov 12 2007, 07:59 PM

Posted by: degreeoff Nov 12 2007, 09:12 PM

QUOTE(derekdenman @ Nov 12 2007, 04:28 PM)

Posted by: Twystd1 Nov 12 2007, 09:28 PM

If ya plug the other nipple. The advance plate won't move... ya leave it open

Clayton

Posted by: Joe Ricard Nov 12 2007, 09:31 PM

These threads are sooooo funny.
What RPM cruising up to 3500 RPM Throttle slightly open. you are on the idle jets feeding though the progression ports.
As the throttle opens up and RPM increases the mains start flowing so if you put your foot down and it runs good then it isn't the mains.

I bet one partially clogged idle jet. which causes you to run lean.

Posted by: thomasotten Nov 13 2007, 06:16 AM

I have heard bad things about that distributer, 050.

Posted by: Thack Nov 13 2007, 09:47 AM

Sounds like it's lean before you get into the mains. That low/mid throttle transition is tricky with carbs. Does it get better once warmed up?

Posted by: Borderline Nov 13 2007, 10:49 AM

Look for a vacuum leak. spray some carb cleaner around the intake manifold and head while the engine is idling & listen for a change in idle speed. I was so sure my new thick universal gaskets couldn't be leaking...........wrong. Also, if the carbs are older, they may be leaking around the throttle shaft.