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Carburetor sucks, literally
https://slantsix.org/forum/viewtopic.php?t=4880		 Page 1 of 1
Author:  tglander [ Mon Jan 27, 2003 5:33 pm ]
Post subject:  Carburetor sucks, literally
Yep, on the '66 225 I've got the original 1920 type Holley. Now get this. If I put a couple of fingers across the intake throat (after removing air cleaner housing) and hit the throttle, the engine guns readily. Remove my fingers, leaving a fully unrestricted open throat, gun the throttle, and the thing acts like it's getting too much air and bogs down. Have to ease the gas on or it bogs.

Is this normal? I know nothing about carburetors, but it seems something's up when I restrict airflow and the engine likes it.

Carb needs rebuild? Also, why does engine die when I pull the PCV valve hose off the carb's crankcase vent tube fitting?

Head's been rebuilt with all new exhaust valves and two new intakes, new seats, guides. Engine runs fine otherwise. Haven't adjusted the timing yet. Still checking on the PCV valve and yes, the accelerator pump is shooting raw fuel down the carb throat when pumped.

Engine was warm when I did the finger thing, but not hot. Will fiddle some more and learn some new stuff, plus keep reading the manual, but it's definitely not as good as you guys are.

Any ideas or thoughts on the finger thing? There is a little air room around my fingers, as their not real big or anything.

Thanks,

Tom
Author:  Justin [ Mon Jan 27, 2003 7:18 pm ]
Post subject: 
well this is a 1bbl carb and they are not the greatest for performance or anything bug it should go right on up if you hit the gas, about the onlything that i can think of is the accelerator pump isnt set right. cutting off the air supply like this gives it WAY more fuel than it needs and should cause the engine to bog down (i suggest not doing this too often cuz if she backfires u got one blown up or fried hand). what is your idle set at and what about idle mixture? but the pump shot is my #1 awnser

Justin
Author:  tglander [ Mon Jan 27, 2003 7:24 pm ]
Post subject: 
Thanks, Justin. I just checked the acc. pump and NO fuel is being pumped in. Seems it may be messed up. Will a kit of some kind fix this?
Author:  Super6 [ Mon Jan 27, 2003 8:11 pm ]
Post subject: 
If you restrict the air flow and the idle picks up--you have a vacuum leak somewhere. Id start with the usual suspects..make sure the carb is bolted down tightly, gasket is in good shape, possibly a worn throttle shaft, and of course every rubber vacuum line.

As Justin said, the mis-adjusted accel pump is the reason for the off-idle stumble.

-Aaron
Author:  tglander [ Mon Jan 27, 2003 8:34 pm ]
Post subject: 
Quote:
If you restrict the air flow and the idle picks up--you have a vacuum leak somewhere. Id start with the usual suspects..make sure the carb is bolted down tightly, gasket is in good shape, possibly a worn throttle shaft, and of course every rubber vacuum line.

As Justin said, the mis-adjusted accel pump is the reason for the off-idle stumble.

-Aaron
So, how does one adjust the accel pump? Are there parts to buy? :?:
Author:  Guest [ Mon Jan 27, 2003 11:57 pm ]
Post subject: 
Ifr I am reading your post correctly, you have a lean, not rich condition. this is why when you restrict the air flow, the carb runs correctly. It would also explain why it dies when you pull the PCV hose, it is receiving additional air. I would look to a vacuum leak first. then move on to fine tuning the carb.
Author:  d150ram [ Tue Jan 28, 2003 6:12 am ]
Post subject: 
Your carburetor sounds like its plugged up from stale gas and/or you have a vacuum leak. Good luck
D150
Author:  rustycowl [ Tue Jan 28, 2003 8:10 am ]
Post subject:  check ball
most accel pump systems have a check valve in them. Sometimes it's a flapper valve, or a little ball bearing, or brass 'needle' , or occasionally both. When you open it up, look for it, it may have been left out by the previous rebuilder.
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