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Holley Bog - Accelerator Pump Cam

4K views 6 replies 6 participants last post by  lluciano77 
#1 ·
I've been playing around with different accelerator pump cams for my Holley 4150 and finally found one that eliminated my off-idle bog and gave a good crisp acceleration. However, when accelerating from a dead stop I've now got a bad bog between shifts (TH350). I'm not really sure why this is happening - possibly not enough fuel at that point? Any ideas/help would be greatly appreciated.
 
#4 ·
I agree the problem is not an acc. pump or cam problem if it is happening up in the RPM range. You are not lifting for the tranny to shift, right? If you are accelerating smoothly and when it shifts the engine bogs you have some other issue. You said it is a 4150 but, you didn't say if it is a vacuum secondary or not? If it is a vacuum secondary that would explain the bog in the upper RPM range during shifts. When the tranny shifts that put a higher load on the engine and that could cause your vac. secondaries to open. If the secondaries are opening to fast you will get a bog. You will need to tune your secondaries, this is done by finding the spring that will give you the opning point and rate that your engine needs. It is a trial and error situation. The spring kit is cheap (if it didn't come with the carb). If your carb is a mechanical secondary model (I don't see how it could be) then you have another issue.

Royce
 
#6 ·
skizot
If you are making a lot of power or your fuel supply is plugged or isn't up to snuff you could be running out of fuel at the top of the gear. I dont know your setup but I had that problem with a 750 vacuum sec and 350 in my camaro. I installed jet extentions and readjusted the float levels on mine. I always adjust mine with the bowls off the carb. I turn the bowl upside down and adjust it to 3/8" clearance between the top of bowl and the float. I run two 850's on my blower motor and the carb shop man that built them had the level high like that. I have the clear sight glasses and the levels are high. I asked about the high levels when I saw where they were set and he said they set them dry and not to change it. The problem could be any of the previous things mentioned on the post to.
Kevin
 
#7 ·
When you run lean on your jetting with a vacuum sec. carb, the secondaries will open earlier. That could cause a bog. I'm not saying that you are running lean for sure, but it is worth checking into.

The best way to jet your carb is to jet it for cruising. Cruise at various speeds in 20 mph increments. Jet down until you feel a lean surge, and then jet up a couple sizes. Don't go on a full throttle run while doing this!
 
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