I just installed a new 3124 carb on my 65 BB. seems to run fine until the engine heats up abit. When I step on the brake I loose rpm's. Almost wants to stall. Any thoughts???????
thanks / Fred
thanks / Fred
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Re: low idle
The idea of stepping on the brake affecting engine rpm and idle sounds very strange, all I can think of is since the pedal bracket is connected to the firewall, as is the accelerator pedal and linkage, there is some flexing going on that affects the idle, but this would also imply that the throttle stop screw is not bottoming on the carb to control the idle speed, and the linkage is somehow limiting the minimum throttle position. Since you mention it is a new installation, it makes me wonder if there is a linkage adjustement issue going on. Another out there thought is if the car has power brakes, when you apply the brakes if there is some type of diaphram leak and you are loosing vacuum through the booster somehow, it could affect the idle with a leak....Craig -
Re: low idle
Check your fuel filter and line also check your float levels. I had a 56 and everytime you stood on the brake it would nearly die, turned out to be a bad fuel filter. Good luck!Comment
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Re: low idle
Boy, the logic in that completely escapes me!Comment
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Re: low idle
Lemme get this straight. You step on the brake with the car not moving and idling. Is that correct? Does it have power brakes?
A little more information on the actual conditions present when the problem occurs would be helpful.
DukeComment
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Re: low idle
sorry I failed to say the car has power brakes.
I did think it could be a vacccum leak, but was not sure.
Would it be normal to get any type of drop in RPM with power brakes?
also It is a new fuel filter
FredComment
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Re: low idle
In my situation the car would be moving and when you applied the brakes fairly hard the engine would nearly die. It was a clogged fuel filter. It did not have power brakes.Comment
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Re: low idle
I would think a vacuum leak would cause an increase in rpm, due to extra air.Comment
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Re: low idle
I still do not understand the conditions when the problem occurs. Is the car idling in neutral, you step on the brake and then the engine nearly stalls?
A small vacuum leak vacuum leak will cause an increase in revs. A big leak will lean out the mixture so much, the engine might stall.
Pinch off the vacuum hose to the booster then step on the brake and see if the same problem occurs.
DukeComment
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Re: low idle
Duke,
The conditions are as follows:
Start the car cold. All is normal. High idle works fine. engine warms up.choke opens, idle drops down to normal idle, around 800-1000rpm. I drive the car down the road, maybe 5-10 miles. apply the brakes at a stop sigh and the car wants to die. this is with my foot on the brake.
thanks FredComment
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Re: low idle
Sounds to me that you have an electrical draw on the alternator, causing a load on it which would lower the RPM.Comment
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Re: low idle
It's still not clear to me. Are you declutching from speed as you approach the stop sign, then apply the brakes and the engine almost stalls?
Try this - car fully warmed up at a standstill, idling in neutral, service brakes not engaged. Now step on the brake pedal. What happens?
DukeComment
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Re: low idle
Duke
That is correct. I am decellerating and apply the brakes approaching the stop sign. It wants to stall
Thanks/ FredComment
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Re: low idle
This sounds like a fuel float problem. On braking the fuel levels in front and rear bowls change and if they're not "spot on" the engine might bog. Holley's invented all sorts of fixes for the level control problem including: center hung floats, "vent whistles" and main jet extenders. The other cause could be a damaged booster diaphragm causing a massive loss of manifold vacuum and hence signal to the carb. You might also check the power valve for damage or mis-speced opening range. Good luck!Comment
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Re: low idle
I wonder if this could be a float level problem causing fuel starvation during slosh when braking??? CraigComment
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