When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Happy Tuesday! As some of you might recall, my truck ('56 F-500 w/272 2 barrel Holley) is a bear to start after it's been sitting for a few weeks. I disconnected the accelerator from the carb and gave the throttle arm a few pumps and watched the jets. Nothing. It seems there is no fuel in the bowl. I've done extensive research on this problem and found a thread elsewhere about a similar problem another Y-Block owner was having. It mentioned that there might be a problem with the accelerator pump diaphragm. Can anyone indicate which part that actually is on my carburetor so I know what I'm looking for?
Your carb doesn't use a diaphragm in a manner like newer 4160 Holley's. The acc. pump is the plunger part in the center of the picture, 9B544. There are seals and check ***** in the bottom (all those little pieces below the plunger in the pic) that can gum up, too. The 9531 rod is the part on the outside you see that connects to the linkage, which pushes down on the plunger.
Thanks. So basically inspect the plunger and compare the parts to the drawing...and look for anything gummied up. Parts missing, or any degradation could lead to the bowl emptying?
Pretty much. Make sure the passageway beneath the check ball at the bottom of the chamber is clear and the ball works. Check the plunger seal and make sure it's pliable and not broken, and the bore is clean and smooth. Spring tension should be good. Just the basic look for something wrong and clean/repair as necessary.
Even a totally shot accel pump on these carbs will squirt some gas out the jets, I think your problem is simply that there is no gas in the carb. Could be it simply evaporated since the last time you ran it, or the fuel pump is weak and not refilling the carb quickly, lots of things.
The piston seal on the accel pump can be leather (old style), black rubber (generally not suitable for gasohol), or blue rubber (usually good for gasohol). Leather is good for any fuel, but only a couple vendors sell them. The whole pump rod/piston (part #6 below) is replaced, not just the seal.
I'm having some issues with my Holley 94 as well. A bit hard to start after it's been running a while. I think the bowl empties quickly as well.
I'm looking at the power valve. On one ebay page selling the power valves he says this: "These power valves are machined flat up next to the threads for the early carbs. The later style valves with the radius around the threads will not seal on the early 3 bolt carbs. WARNING---Most of the carb kits sold today for the 94-2100 Holley carbs come with the later style power valve. These will not work in the early 3 bolt carbs and will leak fuel into your intake and cause the carb to run very rich."
That would cause my drop in mpg, but it could also drain the bowl as well (I think) That may or may not be related, but I thought I would share. I'm tempted to purchase a new one built by professionals. I tend to balk at that price tag along with the desire to do things myself.
As usual, good info here. And I thank you all! One of the very first things I did when I got the truck was rebuild the carburetor. I *recall" getting the rebuild kit from Macs. I took every piece apart and cataloged it, then made sure to put the new parts back on...then removed the old piece from the cataloged spot to make sure I had not left any parts behind. I wonder what the Macs parts were. I can't really remember the rubber being a color other than black. But the carb is so easy to remove and take apart. I'll do that tonight and report back.
EDIT: I just went through my rebuild pictures and found the rebuild kit. That plunger is blue! So I'll take it apart and take a closer look but I'll still get the leather part.
That pump leather looks like something out of a Coleman stove. In fact if they are the same size it would work fine lol.
The only difference really in the power valve is the later Holley valves have a rounded radius at the 90° part, so they bottom out before being tightened. Chuck it up in a lathe and remove that. The original style are still available if you dig around.
As far as # selection start with the factory spec in the shop manual for your engine and local elevation. It helps quite a bit to plumb a vacuum gauge into the cabin and see for sure what your particular engine pulls in terms of vacuum at different speeds and particularly steady, level ground highway cruise and on slight inclines. The goal here is that the power valve (economiser) remains solidly closed at medium and high manifold engine vacuum levels at all times. If it does not correct jetting selection is impossible and of course fuel economy or range will drop off a cliff, for example travelling in a stiff headwind on the highway. PV should only open when needed for acceleration or under low manifold (high load) vacuum conditions.
Get you a ethanol resistant pump from charlie price at vintage speed in Florida. My 272 would not crank after sitting over a month without pouring a little gas in the carb, the pump rubber will draw up and not seal off in the cylinder. Got a full kit from them and now she runs fine.
The ebay seller realrodder is Charlie Price ,He was a big help on the phone ,a nice older fella, he has you tube video's showing how to rebuild all the old style carbs.
Happy Tuesday! As some of you might recall, my truck ('56 F-500 w/272 2 barrel Holley) is a bear to start after it's been sitting for a few weeks. I disconnected the accelerator from the carb and gave the throttle arm a few pumps and watched the jets. Nothing. It seems there is no fuel in the bowl.
I've done extensive research on this problem and found a thread elsewhere about a similar problem another Y-Block owner was having. It mentioned that there might be a problem with the accelerator pump diaphragm(parts catalog calls it a cup).
Can anyone indicate which part that actually is on my carburetor so I know what I'm looking for?
9B544 is the accelerator pump piston, 9572 is its cup.
B5A-9572-A .. Accelerator Pump Piston Cup / Obsolete
NOS PARTS LTD in Waxahachie TX has 3 = 972-937-2201.
CARPENTER NOS OBSOLETE PARTS in Concord NC has 9 = 800-476-9653.
GREEN SALES CO. in Cincinnati OH has 11 = 800-543-4959.
The flathead carbs (7RT-9510-A, for example) use the same "cup" as the typical Y-block carb (B6Y-9510-C, for example). Parts lists #T3 and T36, both list B5A-9572-A for the cup. That's because the Y-block Holley 2110 was an evolution of the flatheads' Model 94. The bowl components, including accel pump, were not changed. The 2110's have larger venturi's and throttle bores and a different design for the venturis. The MAC's leather cup will work.
Look at this leather clad accelorator pump from my 54 carb that was rebuilt in 1999. I can't believe this still worked. I was amazed so much that I've kept it hanging on a shelf in my garage ever since.
WRONG part! This is for a flathead. Mac's application chart does not show 1956.
