# Carb Dead Spot?



## Wob (Dec 2, 2010)

Hi All:

The other day sitting in horrible traffic I was getting hotter than I usually like. I run 180 all day in nearly stopped traffic for 30 minutes or so maybe 210-220? This was a particularly bad night and spent almost an entire hour stopped and was in the 230-235 range. 

Since then I have noticed two problems that seemed small and are starting to appear to get worse.
-1) There is a dead spot in the gas pedal just a hair off of throttle to get a slow roll going from a stop and there is a hesistation like it is struggling to rev and then catches. When its cold now it will just sputter a little and stall if try to slowly get on the gas. Makes me believe that I am going lean, but what would be the cause of this randomly? It could be connected to the hotter night or maybe not. 
2) When I go around a right hand corner I get a hesistaion now too like when you are low on gas and it comes back after a 1 second of straightening out. 

The car revs smoothly and cleanly in park and neutral and once its past the hestistation point in the gas its fine 

Its a 65 326 2bbl Rochester. Now i know its likely only one a few things, but wanted to get advice before hunting around. Was thinking it could be the accelator pump?

Any advice? thanks guys.


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## BearGFR (Aug 25, 2008)

For symptoms you describe the accelerator pump is usually a prime suspect. When you first open the throttle plates coming off idle, there's a short period of time when the plates open but the air flow velocity isn't high enough yet to make the main circuit in the carb start feeding fuel, so you get a momentary lean condition. The "shot" from the accelerator pump is supposed to add just enough fuel to get you through this transition period. There are other things that can cause similar symptoms (fuel mixture being too rich or too lean, for example).

Check your carb over, look for linkages that appear to be disconnected... look for obvious signs of leaks...

Could just be a coinsidence of timing with your 'getting too hot' episode. You say it seems to be getting worse - that would be consistent with a pump that is gradually failing (diaphragm/pump seal is deterioriating/leaking - not "pumping" and getting worse)

Bear


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## Wob (Dec 2, 2010)

Thanks Bear, great stuff. I took a look the other day and didnt notice any immediate leaks. I will check to make sure the linkages are good etc. I have never rebuilt a carb / installed a new accelator pump (grew up in the EFI generation). Is it somethign that you might as well do a total refesh on the carb or something you can pull and reinstall simply? Have you seen any rebuild articles? I have a Chilton from 1967 which discusses the Rochester, but I have to double check if it explains a rebuild/acel pump.


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## geeteeohguy (Feb 2, 2008)

Wob, I think it's the accelerator pump as well. If the car otherwise runs well, I wouldn't personally do a complete carb overhaul unless you are comfortable with it. I would get a rebuild kit, and replace the pump and upper air horn gasket. While at it, I would set/check the float level and replace the needle/seat assembly, or maybe just the needle if the seat is frozen. Very low tech and reliable carb, and not hard to service at all.


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## Instg8ter (Sep 28, 2010)

:agree stall on turn sounds like vapor lock or float bowls, you also may want to check/replace the rubber sections of fuel line as they will get very small cracks (not enough to leak) and suck in air causing a lean condition under load. Check filter(s). A lot of people install the cheap clear canister style filters before the pump and then another good filter before the carb log. that way when the lower one gets fouled its a 5.00 swap and easy to see when dirty...demons are often in the details


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## Wob (Dec 2, 2010)

Jeff @ OPGI recommended a guy local to us in OC - spoke with him - he will do a full rebuild for $120. I may just go that route and know I have a fresh setup. That seems like a good price given the rebuild kits cost about 50% of that.


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