Holley accelerator pump tuning kit-Tampa?

[john.thompson068]

Does anyone in the Tampa area have a Holley accelerator pump tuning kit laying around? I have been struggling with a stumble off idle and a hesitation when going from part throttle cruise to instant full throttle. I already went from a #31 on the front squirter to a #35 for a slight improvement when revving up from idle, but not while driving. I also tried hole two and three on the stock pump cam which only made the situation worse just as I expected. I am not going to buy the tuning kit because I am on a very limited and negative income, so this is about my only hope to getting the carb tuned. I can buy squirters from United Speed World in Tampa for only 8$ compared to the $20 Jegs wants for a single squirter, but I don't know if United will sell me the cams or not and how much. Plus I would waste a lot of money I am afraid on things I don't need and I don't know yet if United would let me return stuff or not. So I will contact them next week and see if I can try out some different size squirters and cams and returns the ones I don't need.

 

[john.thompson068]

It looks like this belongs in the wanted section after just happening to read that one sticky post. Okay no problem, if I can't find it anymore I will look for it in the wanted area. I'm new. :sign12:

 

[coloradodave]

John, Have you adjusted the pump arm so that any movement of the throttle moves the pump arm? This is very important. Also try adjusting the cam position so that it gives a big squirt at the RPM you're having a problem with. Make sure the float levels are set correctly (low float level will cause the problem you're having). Have you tried advancing the timing a couple of degrees at a time to see if that helps?

 

[Homstead]

If you really cant afford to buy new squirters you could always drill them out. It would get you in the ball park for now.

 

[john.thompson068]

John, Have you adjusted the pump arm so that any movement of the throttle moves the pump arm? This is very important. Also try adjusting the cam position so that it gives a big squirt at the RPM you're having a problem with. Make sure the float levels are set correctly (low float level will cause the problem you're having). Have you tried advancing the timing a couple of degrees at a time to see if that helps?

Yes the pump arm is adjusted as you mention. Also, I tried hole two and three on the stock cam and it only worsened the stumble. Float level has been fine tuned so that the car will no longer stall when braking, turning, or panick stopping. Timing is also set at optimal degrees, but I have had the timing all over the place and this never neutralized the stumble. It does not take long at all to replace squirters and cams and readjust the pump arm. If I had parts to test and tune I bet I could have this thing tuned up in a few hours.

 

[coloradodave]

I understand that you adjusted the float level down to aleviate the stalling problem. When you remove the site plug is the level right at the bottom of the opening? When did this hesitation problem start? I've never had to increase the squirter size beyond a #35 in a street car. With the motor off and air cleaner removed, does movement of the throttle produce a good stream from each tube on the squirter? Is this a vacuum secondary carb (didn't see carb number here)? Is the secondary staying shut when you blip the throttle? Answers will help to narrow down the possibilities. Hang in there.

 

[PoppaSmurf]

first thing that comes to my mind is a Power valve issue.... has this carb backfired lately what rpm range are we talking here????

 

[john.thompson068]

I understand that you adjusted the float level down to aleviate the stalling problem. When you remove the site plug is the level right at the bottom of the opening? When did this hesitation problem start? I've never had to increase the squirter size beyond a #35 in a street car. With the motor off and air cleaner removed, does movement of the throttle produce a good stream from each tube on the squirter? Is this a vacuum secondary carb (didn't see carb number here)? Is the secondary staying shut when you blip the throttle? Answers will help to narrow down the possibilities. Hang in there.

The hesitation has always been there. It hesitated even when the float level was mistakenly adjusted too high. By too high I mean that fuel would come out of the sight plug and the car would stall when turning and braking. Then I adjusted the floats until fuel was just below the level of the sight plug. The stalling became less often. I then lowered the level of the float 1/16" at a time until I could test the car and it would not stall. But the car would still stall when doing a panick stop. So I lowered the rear float 1/16 an inch and the car does not stall at all. Now the level of the fuel will be 2/16 of an inch below the front sight plug and 3/16 of an inch below the rear sight plug, but this is where it needs to be set at. Fuel starvation is not a problem with the fuel pump set at 6 psi.


Again, the car still had the stumble when the floats where adjusted too high, and also when they were adjusted at the manufacturers recommended level which caused my car to stall. I keep the accelerator pump adjusted so that the instant the throttle moves, the squirter begins to pump a stream of fuel into the motor from both nozzles while still having the .015 gap to prevent the diaphragm from being over extended at WOT. This is a mechanical secondary 4150 double pumper with 850cfm so the secondaries only open when operated by the throttle linkage.


I think part of the problem is the carburetor is too large for the motor. The motor is a 446ci motor that produces over 540 hp and I shift at around 6000 rpm. The motor has an Edelbrock Performer RPM manifold which does have larger and longer than stock runners which can cause fuel to get stuck to the sides of the runners. This requires using a larger squirter. Also, I think one of Holley's tech pages said if you have really long or really big runners like a tunnel ram you may have to use the #40 or even larger size. If I had to guess, I would say the motor would like me to install a #37 or #40 accelerator pump on the front and go up to a #35, #37, or #40 on the rear as well. The #40 squirters require the 50 cc accelerator pump diaphragm as well as the hollowed out screws. Unfortunately, I think the only way to know which way to go or by how much is to test and tune.

 

[john.thompson068]

first thing that comes to my mind is a Power valve issue.... has this carb backfired lately what rpm range are we talking here????

I have installed brand new 3.5 power valves which I already had and also 2.5 power valves. The car has not backfired since having either of those in there and has blow out protection factory installed on the carb because it is a newer model 4150. The rpm range is immediately off idle when revving up in park or rolling it on in drive. The larger squirter has almost completely eliminated the stumble when just revving up the motor in park or neutral, but it still remains when driving. The full throttle hesitation happens whenever going from part throttle to instant full throttle. I did a slow roll WOT in second, and also a 45 mph cruise to WOT in both second and third and it sort of bogs for a split second and then accelerates.

 

[john.thompson068]

• 66 Satellite
• Full weight street machine
• 446ci 440
• Eddy RPM heads/intake
• Holley 850 double pumper with mechanical secondaries
• Comp 305H cam (.525/.525) 305 Duration (253 @.50) 110 lobe separation
• 1 7/8 headers 3" exhaust
• 10.5:1 forged pistons
• 13* timing
• Electronic ignition/good plug wires/etc.
• 727
• 4000 rpm stall torque converter
• 3.91 gears
• 29" tall tires

This is the relevant information on the car.

 

[john.thompson068]

I don't know if this thread will get any attention on the second page so here it is again.