CARB. PROBLEMS?

[Fred Gruendig]

HELLO ALL,
LAST YEAR I HAD MY CARBS REBUILT BY BIEKER ENG. (SOLEX 40PII-4) FOR MY 65'SC (NEW REBUILD).
I INSTALLED THEM, ADJUSTED VALVES, NEW PLUGS, POINTS ECT. THE ENGINE RAN PRETTY GOOD. I COULD GET THE CARBS ADJUSTED QUITE NICELY FOR A FIRST TIMER.
THE ONLY PROBLEM I HAD WAS AN ANNOYING OCCASIONAL FLAT SPOT @ 2500-3000RPM.
AND I COULD NOT GET THE IDLE TO STAY @800 RPM. IT WAS EITHER AT 500 OR 1200.

I THOUGHT THIS MIGHT BE STICKING WEIGHTS ON THE DISTRIBUTOR. SO I TOOK IT APART AND CLEANED BUT IT MADE NO DIFFERENCE.
(THE ENGINE RAN GOOD ALL LAST YEAR AND THE BEGINNING OF THIS.)

SO, A NEW 022 FROM GEARHEAD. NO DIFFERENCE.

NOW SOMETHING HAS HAPPENED. THE CAR IS DIFFICULT TO START COLD. IT WILL SPUTTER LIKE NO GAS OR PLUGS MISSING. AFTER ABOUT 1 MIN. IT RUNS ON ALL 4.

IDLE IS OK AND I CAN ADJUST TO RUN @ ABOUT 700-800 RPM. ALL PULLING THE SAME AMOUNT OF AIR.
WITHIN ABOUT 5 MIN. THE IDLE WILL RUN UP TO 3000 RPM AND STAY THERE.
IF I ADJUST THE IDLE BACK DOWN AND BALANCE THE CARBS I'M BACK TO SQUARE ONE WHEN THE ENGINE IS COLD.

THE IDLE JETS ARE CLEAR, THE INJECTION NOZZLE PUTS OUT .65CC/2 SQUIRTS AND THE MIXTURE SCREWS RESPOND TO ADJUSTMENT. NEW BASE GASKETS WERE USE AND THE CARBS ARE TIGHT ON THE MANIFOLD.
DO I HAVE A VACUUM LEAK SOMEWHERE? MANIFOLD TO HEAD?

THANKS,
FRED
#3877

[Guest]

Sounds like you covered most everything. I had an issue like this years ago and it was timing/advance related.

One of the carbs could be messing with you. I replaced a piece of gasline last year, very carefully, but I still ended up with a small piece of rubber in one of the jets. I had to pull the carb to find and fix.

It sure seems like a fuel or timing issue.

Make sure the condenser on the points is wired and grounded too.

[Martin Minnich]

What you are experiencing is consistent with a vacuum leak. You might have a warped carb base or intake manifold flange that gradually creates the leak condition as the engne comes to temp. As the mixture leans out, the idle runs up. The old school troubleshooting method is to spray carburetor cleaner all around the mating joints. The idle will alter when you hit the area where the leak is occurring.

Best of luck,
Marty

[Al Zim]

We use distributors and carburetors by Don and Harry. These are carefully done and should cause no problme. Check the advance to make sure that you have 30 degrees or so at 3000. The check the fuel pressure. is should be below 2 PSI. Finally with a flashlight look down the carburetors as the throttle opens. the accelerator squirt shoul be at the edge of the throttle plate if not nogas is getting in the engine. Also check the brass plates on the side of the carburetor venturi. If one is loose, this could cause you flate spot.
Finally: you cannot syncronize carburetors at an idle. Sycronize them at 2000 or slightly above. This will even out the air flow. Then reduce the idle speed to a lower RPM.
Don can help you if you give him a call 503-835-8410 al zim

[Ron LaDow]

"We use distributors and carburetors by Don and Harry. These are
carefully done and should cause no problme. .....
al zim"

Regardless of who does the carbs (and I like to think Pre Mat does a good job), it is almost impossible for carbs to cause this problem. You'd need 'way too-big jets, 'way too-high a float level or some other obvious carb problem. Check the plugs for 'wetness'; it's an oiling problem.
Thanks,
Ron LaDow

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