Man, I really should have started watching those Holley TV videos earlier. I just ordered that book from Amazon, as well as a set of pump cams.

So it looks like I currently have a #31 pump jet and an orange #466 pump cam. The cam was mounted on the #2 hole, so I switched it the #1 hole and went for a test drive. It didn't seem to make much difference, if any. Still sputtering to the point of dying when full throttle is applied at idle, along with occasional light backfires. Sounds healthy when you gas it from part throttle. According to the video I watched, this suggests that I need a larger pump jet, but considering that the jet kit is $125 and the cam kit is $20, I'll start playing with different cams first. I can always drill the jet myself.

I found this graph on the Holley website, but there are similar graphs on other sites that show things differently. Looks like some experimentation is in order. I should probably see if I can get my wideband sensor to work.
http://www.holley.com/data/Products/Tec ... mGraph.pdf

Thanks for the help, guys.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Don’t buy a jet selection kit, most if not all of the jets will be way too big for our application; instead get a few a la carte. Same with power valves; PV has to activate as soon as the A/F mix goes lean and vacuum falls off along with the accelerator pump shot. Accelerator pump shot can be tuned for quantity and delivery speed… long and light or short and heavy, or somewhere in between. This is where were good note keeping will make your Holley cohabitation less of a hair pulling experience. There are so many variables to contend with when tuning a Holley from engine build, timing, rear gear, to all the different adjustments one can make on the carburetor its self; kind of like Domino’s 10,000 pizza combos… Sometimes the settings on your Holley will end-up back to just a plain old out of the box 10 inch peperoni pie…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Long day of wrenching and drinking yesterday. I couldn't find individual pump jets until I refined my search terms this morning. Apparently you can only see them on Amazon or Summit using the proper terminology "accelerator pump discharge nozzle." I ordered a #35. We'll see if I can get it smoothed out with these parts. If I have to use a larger jet size than that, I apparently also have to step up to a larger diaphragm assembly as well.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

That's crap. I've used a #37 shooter with the pink cam and standard diaphragm when I needed a short fat shot of fuel (you will need the special drilled screw for the shooter to get the amount of fuel it will flow)....I choose the pink cam as it keeps pumping through the whole throttle plate movement, unlike the orange cam that stops after 60 degrees...

You can only use the brown and yellow cams with the 50cc "REO" pump conversion, but that is a lots of shot...I have yet to see a slant six need it and I'm running more engine than you are tuning on.

The key here is to get the right amount of gas without flooding the engine or without running out of fuel in the pump...if the cam remains the same...a larger shooter will dump a lot of fuel quickly and run out sooner on the throttle opening...a smaller shooter will restrict the flow a bit and allow the shot to take a little longer to dispense the fuel...The cam adjusts how large of a shot is available (volume), and at what throttle position it's available....

If buying a "shooter", the preference for performance is to get the one that has two little copper nozzles sticking out the body...these are more positive at directing fuel to the center of the venturi bore and hitting the side of the booster for better atomization.

2 cents,

-D.Idiot

Okay, good to know I won't need the larger pump. I'm pretty sure I bought a #35 jet without the two little nozzles, but the #31 in there right now doesn't have them either. We'll see how it goes. All the stuff I ordered should be here by Thursday, and the jets are available from Amazon Prime, if I need another by this weekend.

I'd been considering some other stuff, like blocking off the exhaust heat riser. The diverter plate (not sure what it's called) in the exhaust manifold still works properly, though, so I'm not sure this is worth the hassle. I may just put together a Home Depot-quality cold air intake and call it good.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

That heat riser aids drivability after a cold start by quickly warming the intake manifold, and as the engine warms to full operating temperature heat, or exhaust flow is redirected directly down the exhaust system. This device helps improve fuel economy while engine reaches operating temperature by aiding A/F mixture to stay in suspension, or in other words prevents fuel from condensing on cold inner manifold surfaces. When this happens engine sees lean condition, cylinder bores see liquid fuel that washes oil from the cylinder walls & rings accelerating their wear, and can dilute oil in sump; not good.

Being in Texas you may not often encounter temperature and humidity conditions that contribute to carburetor icing, but when those conditions are present drivability and fuel economy become dreadful. I recommend to keep the factory manifold heat intact.


Jegs, has Holley parts as well, and as you discovered these small parts are sometimes hard to locate on these various websites.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Alright, parts came in yesterday and I got a chance to play with it tonight. Comparing my old pump jet to the #35 that I ordered, I'm thinking that the old one had already been modified by someone. The #35 may actually have smaller holes than the supposedly #31 jet that I had. Still, I used the new #35 just so I know where I'm at. Changing the jet alone didn't make much of a difference, anyway.

For the cams, I started with the pink cam on the #1 hole, but that seemed to make the idle transition noticeably worse. The engine would die without fail when giving it full throttle from idle, and at less aggressive throttle application it would sputter and backfire worse than before. Judging by the cam graph on the Holley website, this seemed to make sense. I needed more gas sooner, and the pink curve started out shallower than the curve for the orange cam I started with. It did get noticeably better after I re-adjusted the lever screw at WOT according to the HolleyTV instructions, but it was still pretty bad.

Unfortunately, that Holley chart doesn't specify different holes for each cam. I did a little digging and dredged up this graph, which some guy made using a dial indicator in his garage. I'm not sure if the guy readjusted the lever screw with each cam test, though, so I'm not sure how useful this is.

Anyway, I went ahead and tried the blue cam with the #2 mounting hole, since this looked like the most aggressive initial pump rate. That seemed to work much better at acceleration from idle, both at full and partial throttle application. It seemed to be happy at acceleration from higher cruise as well. I still need to play around with it some more, but I ran out of daylight.

This weekend I'll also have access to my friend's vacuum gauge, so I should be able to figure out if I need a different power valve. The HolleyTV video on power valves seems to suggest that I might need one with a lower number if I have a cam that's more aggressive than stock. I really need to get my O2 sensor working again as well.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

When I run a long vacuum tube connected to a vacuum gage from carburetor to dash and drive the car I can see and feel when the power valve kicks in. As video implies the engine calls for a PV tip-in low enough to stay closed until engine load requires additional enrichment and high enough to keep mixture from going lean as engine load increasses.

By driving a week or so with vacuum gage placed on top of dash one can get a real world feel of what vacuum readings are for your engine under most driving conditions. If you see that vacuum tends to be close to or below PV rating at level ground crushing under constant throttle you can better pick a more suitable rating.

The Holley tuning book outlines tuning methods to dial in each of the four stages of the carburetor's functions; idle, transition, main jet, and power valve. I had to read and reread tuning section and other related chapters several times before it started to sunk in.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Okay, I have a question about the vacuum reading. Do you hook up the vacuum gauge to the port on the base of the carburetor, or directly to the manifold runner? Teeing off from the line on the carb port (which goes to my PCV valve), I'm only seeing something like 8 inHg of vacuum at idle while in gear. I have a mild cam, but I didn't expect the vacuum reading to be that low. My valve lash was recently set to be slightly looser than stock, FYI.

Does it make a difference to measure directly from the intake manifold port? Is this low reading indicative of a bad vacuum leak somewhere?

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Hook the vacuum gauge to the manifold.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Okay, thanks. From the #6 intake runner, I'm seeing just a hair over 15 inHg. That sounds a lot more like it. I'm going to order a 7.5 PV, per the Holley instructions.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing