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914World.com _ 914World Garage _ Dellorto's revisited- HELP!

Posted by: 914ghost Jan 27 2004, 09:05 PM

Back to recurring carb problem I've traced the problem to one carb and a very specific problem:
Background: 1.8 L in my 70'
Swapped my 36 dell's for 40's, rebuilt , rejetted, clean solid carbs.
Dizz: 050, pointless ign, timing ON, valves ON, compresion 160 on all 4.
PROBLeMO: <_<
EVERY TIME I hit 5400 RPM or a little above while car is running smooth great power no glitches,
when RPM's come back down and I'm driving just normally AFTER hitting mentioned engine speed (5400) I lose 1 cylinder and another runs badly.
Previously thought it could be dist and timing/dwell, switched distributors, same problem.
Traced it to #1/2 carb.
Pulled out the plugs that cover the air correction screws and adjusted- FIXED! BUT! it still does it, every time I hit 5400 I have to slow back down pull over and turn the air correction screw out 1-1/2 turns and drive for a while, then I can turn them back in and its fine.
Also, seems like a BUNCH more fuel being delivered from the 1/2 carb than 3/4. Plugs read the same but I can see a spray of fuel (not from injector nozzle!) out of the auxilliary venturi on 1/2 but not 3/4.

Anyone.. ..? J-Raby? Speek up or send me a 4900 rev limiter for an 050!!

TIA
Robert O

Posted by: philinjax Jan 28 2004, 12:17 AM

Perhaps the float in carb 1/2 sticks open or the needle valve doesn't sufficiently close down when backing off the high rpm operation, thus flooding the float chamber and forcing fuel at pump pressure to the main jet.
Opening the air correction screws leans out the rich mixture and the needle valve resets.
I recommend removing the carb., carb cover, and checking the float adjustment. Replacing the needle valves with Gross Jets would certainly be an important upgrade too.

Phil

Posted by: ChrisReale Jan 28 2004, 12:21 AM

I recommend Fuel Injection
sorry