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I am used to Rochesters but now have a Holley 4150

Moparfiend

Moparfiend

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Working on my tune of the car currently. Just added a Lokar throttle cable as the original was just too short. Needs more advance and will get my wideband O2 on there but have a question about the Holly. This is a mechanical secondary with no choke by the way.
I am able to get the full throttle set with the new cable and confirm that the mechanical secondaries is getting “opened” at WOT. I however expect more acceleration when this happens as compared to all my Rochesters of the past. Again I know I am running very retarded right now as I wait for my dizzy Advance Limiter and I have not looked at the AF mix live yet so this all may be tune related. I am just curious what the difference might be of the 4150 compared to the Rochester at WOT with respect to performance acceleration.
 
What is your combo? Is it the sport Satty with a 340? What 4150 650 750 850? IMO use a vaccum secondary on the street. The rochestor was a vacc secondary carb. With a heavy car the double pumper is not optimal unless it is strip only.
 
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Everyone always says put vacuum secondaries on them, I've ran both on my car and won't be putting another vacuum secondary on it. What it comes down to is heavy cars with street gears don't accelerate fast enough to burn all of the fuel being dumped in so often times you make the car slower. My argument is if your any kind of driver you should know when to floor it and when not to? You learn your car and you learn where the engine comes on strong... that's when you put it to the floor. Keep in mind I'm running 3:55's, have a standard and a pretty healthy running engine which makes a difference. If mine were stockish, I'd put vacuum secondaries on it.

Going back to your question we'll need to know a lot more than posted, are you floor boarding it right off the bat? What gears are you running? Engine specs? Carb size?
 
i ran a 3310-3 which is a vacuum secondary carb with a little tunning you can leave the line quicker and save a little fuel on a vacuum carb. my car 3400 lbs and ran 11:40 117 mph .i ran that until i put a 451 stroker then i ran a 950 hp holly double pumper.
 
747mopar said:
Everyone always says put vacuum secondaries on them, I've ran both on my car and won't be putting another vacuum secondary on it. What it comes down to is heavy cars with street gears don't accelerate fast enough to burn all of the fuel being dumped in so often times you make the car slower. My argument is if your any kind of driver you should know when to floor it and when not to? You learn your car and you learn where the engine comes on strong... that's when you put it to the floor. Keep in mind I'm running 3:55's, have a standard and a pretty healthy running engine which makes a difference. If mine were stockish, I'd put vacuum secondaries on it.

Going back to your question we'll need to know a lot more than posted, are you floor boarding it right off the bat? What gears are you running? Engine specs? Carb size?
Click to expand...
I have also run both style carbs and really have felt no difference on the street except for fuel mileage. Heavy 68 R/R 440 auto 323s. Nice thing with a vacc carb like a 3310 is you can easy change the secondary spring to get like near DP performance in a minute or 2. And yes it is all about driving style. Heavy foot both about the same, drive like an old fart then the vacc carb hands down.
 
wagonman said:
I have also run both style carbs and really have felt no difference on the street except for fuel mileage. Heavy 68 R/R 440 auto 323s. Nice thing with a vacc carb like a 3310 is you can easy change the secondary spring to get like near DP performance in a minute or 2. And yes it is all about driving style. Heavy foot both about the same, drive like an old fart then the vacc carb hands down.
Click to expand...
THIS IS CORRECT READ A HOLLY PERFORMANCE BOOK AND IT TELLS YOU HOW AND WHY. THERE IS A CHECK BALL IN THE VACUUM CARB THAT NEEDS TO BE REMOVED IF IT CAME WITH ONE.
 
also what power valve is in the carb ? this needs to be done with a vacuum gage 1/2 of vacuum is what your power valve needs to be set to.
 
vance.dykes said:
also what power valve is in the carb ? this needs to be done with a vacuum gage 1/2 of vacuum is what your power valve needs to be set to.
Click to expand...
I ran a 870 Avenger for a while, biggest improvement made on that carb was the power valve, way to lean from the factory.
 
My inquiry is based on the lack of secondary acceleration. It feels very linear as opposed to my GM Rochesters of the past. When those vacuum secondaries opened you knew it. I am not aware of the check ball.

Peg leg 271 waiting to get the funds to add something like a 373 to 391 sure grip

1973 340 30 over guessing
10.5:1 estimated min
Very Aggressive cam unknown specifications
Mopar High Rise Manifold
CFM 650
Power valve is 125-65 stock

88F68AA9-DA68-4138-A98F-5C8EC1470D27.jpeg
 
Did you already look in the Ventura to confirm your getting a healthy squirt when the secondaries open? Yes those gears are going to kill any seat of the pants acceleration, I'd get it moving good up around 3,000 rpm before kicking them in. Not sure about your setup but I can feel the secondaries in the pedal?
 
747mopar said:
Did you already look in the Ventura to confirm your getting a healthy squirt when the secondaries open? Yes those gears are going to kill any seat of the pants acceleration, I'd get it moving good up around 3,000 rpm before kicking them in. Not sure about your setup but I can feel the secondaries in the pedal?
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No I don’t feel the secondaries kick in at WOT at 3000 RPM or so. This why I am asking. This is my first Holley and first mechanical secondary. It has a linear acceleration like the secondary not coming in. I will check the squirt to confirm fuel delivery.
 
hook a vacuum gage to a manifold port in drive what is vacuum ? i.e 10.5 in vac then put a 5.5 power valve in. what rear jets are in the rear metering block ? some say square all jets i have found 2 to 5 above front.
 
FWIW I ran Rochestor carbs for years o my Wagon. The secondarys are tunable just like the Holleys. Went with a Street Avenger 670 because o more tuning ability with a more radical cam.
 
If you had no fuel or it was lean when the secondary's open on your holly you would know...the car would fall flat on its face or worse back fire thru the carb. your holly has front and rear throttle plates that are the same size. the rocherter quadra bog has massive secondarys that you cant help but feel when they open as the primarys are very small. also with your rear gears if you open your carb at a low rpm the motor will rev slow till it comes on the cam. My old 340 did not come on till 3000 rpm. I ram a 6 pac, when it was open on all 6 everyone around knew it....
 
No doubt the rear gears are dogs and I am planning on changing them as soon as I can afford it. I am definitely get fuel in the secondaries.
It sounds like the linear acceleration is because thats the way a double pumper works as compared to my Rochesters.
 
If the car runs good and doesn't bog or pop back your on the right track . a 650 is also a small carb. Also make sure your kick down is adjusted right.
 
vance.dykes said:
THIS IS CORRECT READ A HOLLY PERFORMANCE BOOK AND IT TELLS YOU HOW AND WHY. THERE IS A CHECK BALL IN THE VACUUM CARB THAT NEEDS TO BE REMOVED IF IT CAME WITH ONE.
Click to expand...

The reason Holley uses the check ball is so the secondaries close fast enough. They could just have the vacuum hole to the vacuum secondaries the size they want but it would not release the vacuum in the diaphragm fast enough and can cause the secondaries to hang open to long when off the gas. So they made the hole the size they felt best with a check ball in the vacuum hole to the secondary diaphragm. And then when you let off the gas the check ball lifts off its seat and makes the vacuum hole larger so it lets the vacuum out faster.
Mow many gearheads remove the check ball to get the secondaries to open faster and of course they will now close fast enough since it has a larger vacuum hole to release the vacuum fast enough. Holley feels that removing the check ball can make them open to fast and could bog at times so that's why they engineer the vacuum hole to be the size it is when the check ball is in there. That way they open at the rate Holley feels they should and they close fast because the check ball lifts off its seat and makes the vacuum hole larger to release the vacuum faster. Holley says to just change the spring tension to make them open faster. But if you remove the check ball and the car does not bog and still works ago then you can get away with it. As for the 6 pk carbs I have not seen them use the check ball but I am not sure if any 6 pks ever did. It may be when feeding two carbs the vacuum hole is large enough to release the vacuum fast enough so no check ball is needed. Ron
 
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