Has anyone ever used a 50cc accelerator pump on their Holley 4-barrel? I'm using the 30cc pump and the pink 330 cam on the 4180 on my 460 and the throttle response is awesome everywhere over 1500rpm but in the lower rpm-range, the throttle response is pretty rough. I've tried an assortment of different cams but none seem to cut it. I was thinking about a 50cc pump but I'm not sure as to whether or not it will be too much for a stock 460. Does anyone have some input to lend?

 

I always switch to 50cc. Even on 302 or 351's. I would also recomend going to a bigger squirter. Makes all the difference in the world.

 

Right now I have the .37-size tube-nozzle squirter which is pretty large already - still a bigger one, say a .40 or so would be better?

I looked on Holley's website at what you get with the 50cc pump and it comes with a yellow and a brown cam. Their line-graph showed the yellow cam as the one with the biggest lift and longest duration and the brown cam was a little lower. The total output with either of the cams is almost triple what I'm getting out of the pink 330 cam. It wouldn't be too much for a stocker 460

 

The 50 cc pump is a larger capacity pump that will provide a greater amount of total volume. I highly doubt that you are running out of fuel with a 30 cc pump.
Changing cams is an art in itself, but can be done with success.
There are two and some have three screw holes in the cams, and these are there for adjustment as well.
Your symptoms of a hesitation or a bog is also indicative of too much fuel.
The accelartor pump is just there to add fuel to an engnine when the throttle is stabbed and the vacuum goes to zero. Since there is little vacuum, the booster does not recieve the correct signal, and fuel is not being drawn out of the carb.
Booster signal is the key here, and booster design can play a role in this hesistation.

OK, so getting too aggressive can also lead to problems. Watch for signs of toomuch fuel in the exhaust. Black smoke under acceleration can indicate a condition where too much fuel is being added, and your problem will be compounded.
Usually, the engine will try to run up, or increase in rpm with reasonable response and then fall off and run terrible, until it slowly reaches rpm. This is different than when it just hesitates right from the time the throttle is stabbed. Usually if you "blip" the throttle and you get a slight hesitation then you size up the squirter, but if it has a hesitation a little later in the throttle, then you could have too much 'shot" and have to back up. Easy to start going too far with this and the problem gets worse.
Long recovery times could idicate a shot that is too large, or a duration that is too long.

How does the throttle react in high gear? Off idle respons is only one area where the accelarator pump us active. Smash the gas under load in high gear to tune further.

 

Sounds like your nozzle is too big causing a over-rich bog off idle.
Does it stumble when pushing the throttle slowly or quickly.
Also recheck the initial timing. If too low, it can act the same way. Should be at least 10* BTDC.

 

I have annular discharge boosters on the primary side and standard passenger-car type secondary boosters. Annular boosters provide a good signal without being restrictive (says Holley) so I don't think the boosters are at fault.

Since I don't have the kickdown linkage adapter yet, I can put the motor under a good load by hammering it in high gear. When I stab it doing, say 55mph, it hesitates for a split second until the secondaries open up. I've played around with different secondary diaphragm springs and found the lightest spring (white) to be the best.

I have my timing advanced 12deg. and the motor idles around 750-850rpm. If you crack the throttle from idle it sort of "deisels" or misses as it builds rpm until it reaches about 3-grand where it starts running strong. It doesn't blow any black smoke out of the exhaust when I goose it so it's hard to say whether it's getting too much gas or too little, or simply delivering it at the wrong time.

I can try swapping the .37 for a .25 shooter and see if it makes a difference in the right direction. Though when you use an agressive pump cam with a smaller nozzle, the initial shot will be smaller but continue to spray longer, correct? Perhaps the .37 nozzle and 330 cam combination dispenses too much fuel at one time?

So many combinations and possibilities Guess I'll spend a few more hours tinkering with it tomorrow.

 

You know this carb's on a 460, right?

 

I spent a few hours today playing with the accelerator pump. I tried a .25 squirter and throttle response was much worse. I also tried a few other cams and nothing changed for the best so I put the .37 squirter and the pink cam back on.

I got into my Holley book and discovered I had my vacuum lines ran wrong. When I put the carb on, I capped all the vacuum ports and kept the original vacuum line configuration. Well the "original configuration" was messed with by someone else that had the vac. advance hooked up to the bottom port on the PVS, which is a "filtered air inlet" that only draws 5" of vacuum at all RPM - not enough to advance the timing. I got out my vacuum tester and found the "timed spark signal" port on the carb - it draws 0" of vac. at idle, and tops out at 25" at 3000rpm - more than enough to make the vac. advance work!

I took it out on the road and it made a HUGE difference. The throttle response is perfect through the whole rpm range. I can't believe it was just a simple vacuum/timing issue the whole time

Thanks for your help and suggestions guys. That's $50 you saved me from spending on a 50cc pump I don't need. I'm sure that once I go through the motor and give it a little more heave-ho I'll get one - but at least the motor will be needing it then.
I think I'll find an excuse to go for a drive now

 

I was going to ask about that next. Ported vacuum is your friend on the vacuum advance.
Glad you got it figured out.

 

Indeed it is your friend! I also screwed around with the vac-advance diaphragm on the distributor. I didn't know it was adjustable. Some clown had the screw backed out almost all the way so it didn't advance much. I screwed it all the way in and backed it out four turns and that livened up the motor some more!

 

Yeah, some are and some aren't. You've got a good one

 

Anyone can upgrade their advance diaphragm without swapping distributors though, right?

 

Wow I'm a dummy I completely overlooked my throttle response problem. I started noticing a hesitation when accelerating from a dead stop in drive and reverse and wondered if maybe there wasn't enough fuel in the float bowls and the little that was in there was sloshing away from the jets or acc. pump pickup. I pulled my bowl plugs and there wasn't fuel anywhere near them. It took six turns out on the float adjustments on the primary and secondary bowls to get fuel to start bleeding from the holes. I guess my bench settings were a little (ok, a lot) off

Problem solved (I say again, hopefully for the last time). The cam and squirter combo I'm using is right on and throttle response is absolutely beautiful. It's gotta be love

 

I always run mine just below the site plug. This gives the fuel room to expand when it gets hot. Glad you got it figured out.
I guess you ain't as crazy as your screen name says

 

Oh I is crazy... I is

I'm more worried about fuel sloshing out my vent tubes - haven't had any problems with it yet, but a little extra insurance never hurts. I might install a set of vent flutes when I pop in a bigger set of jets. Just have to machine my metering block because the 4180's have a hump in the vent passage.

Maybe when I'm done I can submit an article to Hot-Rod or Fast Fords... call it "Crazy Eddie's Crazy-'80"!