Gene Fiore
Famous Member
I'm re-posting an original thread from the aluminum head section that I posted a few weeks ago. I recently switched from my 2bbl conversion log head to the aluminum head and intake using the same carb.
I have an update on how my setup is performing...and it's not all good. Here is the baseline for my Holly 500 2bbl which ran great btw on my log head.
Main jets: 73
Acc pump squirter: .031
Acc pump cam: brown on #1 hole
50cc pump( stock with the 500 Holley )
PVCR: .055 (I have the QF billet metering block which allows you to adjust the power valve channel restrictions).
Power valve: 65
Initial timing: 10 deg
Float level is good...right at the bottom of the threads while the engine is running
Car runs greats under light to medium acceleration both from a standing start and while cruising...very responsive and nice power. I put about 200 miles on it and when I checked the plugs they all looked like the day I installed them...white porcelain...no coloring. So I figured it's running a bit lean...no biggy. The real problem is at WOT acceleration...it falls flat on it's face and stalls! Here is what I have done so far with not much success.
All of the following tests are from a standing start. First thing I did was change main jets to 75 since I feel it is a bit lean...I also installed a new 65 powervalve just in case the old one was bad. WOT still stalls out but really didn't think that would have any affect. Next was to tackle the pvcr. Thinking it might be lean I installed .057 restrictor but was at least as bad as before...maybe worse. So I drastically went the other direction and installed .049 restrictor...better under 3/4 throttle acceleration...now it lays rubber and feels stronger but not great...WOT start the same...stalls out. Next I tried leaner yet on the pvcr to .047. No noticeable difference really...WOT start still stalls. Next I changed the acc pump squirter to .028. Seemed a bit better under 3/4 throttle start but WOT start the same.
UPDATE AS OF 1/20/2018:
So I thought now that I might just be getting too much pump shot so I purchased an accelerator pump cam assortment. Based on an article I had saved from fordsix I started changing the pump cams and making test runs.
The article said that the volume delivered for 10 strokes of the pump with a 50cc pump with the cam in the #1 position are:
white 17cc
blue 18cc
red 18.5cc
orange 19cc
black 19cc
green 24cc
pink 30cc
brown 36cc
So I started at the bottom and worked up. Since I already have the brown cam I started with pink and went up the list. I stopped at orange (only reason I tried this one is it had a wider cam surface very similar to the brown one that came on the carb). Each cam I tried had the same results...instant stall going to WOT from a standing start.
I'm questioning my technique for adjusting the acc pump since you need to do that each time you switch out the pump cam. Hold the throttle wide open and attempt to put a 15 thousands feeler guage between the pump lever and pump arm...adjust if necessary.
WHAT AM I MISSING OR OVERLOOKING??? I would really like to be able to use this carb as I have alot of money into it.
I have an update on how my setup is performing...and it's not all good. Here is the baseline for my Holly 500 2bbl which ran great btw on my log head.
Main jets: 73
Acc pump squirter: .031
Acc pump cam: brown on #1 hole
50cc pump( stock with the 500 Holley )
PVCR: .055 (I have the QF billet metering block which allows you to adjust the power valve channel restrictions).
Power valve: 65
Initial timing: 10 deg
Float level is good...right at the bottom of the threads while the engine is running
Car runs greats under light to medium acceleration both from a standing start and while cruising...very responsive and nice power. I put about 200 miles on it and when I checked the plugs they all looked like the day I installed them...white porcelain...no coloring. So I figured it's running a bit lean...no biggy. The real problem is at WOT acceleration...it falls flat on it's face and stalls! Here is what I have done so far with not much success.
All of the following tests are from a standing start. First thing I did was change main jets to 75 since I feel it is a bit lean...I also installed a new 65 powervalve just in case the old one was bad. WOT still stalls out but really didn't think that would have any affect. Next was to tackle the pvcr. Thinking it might be lean I installed .057 restrictor but was at least as bad as before...maybe worse. So I drastically went the other direction and installed .049 restrictor...better under 3/4 throttle acceleration...now it lays rubber and feels stronger but not great...WOT start the same...stalls out. Next I tried leaner yet on the pvcr to .047. No noticeable difference really...WOT start still stalls. Next I changed the acc pump squirter to .028. Seemed a bit better under 3/4 throttle start but WOT start the same.
UPDATE AS OF 1/20/2018:
So I thought now that I might just be getting too much pump shot so I purchased an accelerator pump cam assortment. Based on an article I had saved from fordsix I started changing the pump cams and making test runs.
The article said that the volume delivered for 10 strokes of the pump with a 50cc pump with the cam in the #1 position are:
white 17cc
blue 18cc
red 18.5cc
orange 19cc
black 19cc
green 24cc
pink 30cc
brown 36cc
So I started at the bottom and worked up. Since I already have the brown cam I started with pink and went up the list. I stopped at orange (only reason I tried this one is it had a wider cam surface very similar to the brown one that came on the carb). Each cam I tried had the same results...instant stall going to WOT from a standing start.
I'm questioning my technique for adjusting the acc pump since you need to do that each time you switch out the pump cam. Hold the throttle wide open and attempt to put a 15 thousands feeler guage between the pump lever and pump arm...adjust if necessary.
WHAT AM I MISSING OR OVERLOOKING??? I would really like to be able to use this carb as I have alot of money into it.