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Re: 3310 vac.sec to 750 d.p.
[Re: mcmopars]
#834844
10/20/10 09:23 PM
10/20/10 09:23 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Street car or strip car?
Any steet driving at all and I'd go with the vacuum secondary.
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Re: 3310 vac.sec to 750 d.p.
[Re: Mr.Yuck]
#834846
10/20/10 10:20 PM
10/20/10 10:20 PM
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Joined: Oct 2003
Posts: 1,371
Costa Mesa, CA
chache876
pro stock
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pro stock
Joined: Oct 2003
Posts: 1,371
Costa Mesa, CA
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Quote:
I don't know why DPs get a bad rap on the street. They can be just as effective as a vacuum carb. It's all in the tune.
I'm not a carb expert by any means but whether they're just as effective or not as a vac sec carb is debatable. If it were all in the tune, your average hobbyist doing his own work probably wouldn't be able to do it himself and thats probably why vac secondary carbs are preferred for street use.
Just my 2 cents anyways
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Re: 3310 vac.sec to 750 d.p.
[Re: chache876]
#834847
10/21/10 12:15 AM
10/21/10 12:15 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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V sec. are more "streetable" because of there metering plain & simple, they "can" be tuned for performance if you understand how metering works, most people don't even though they claim too, A DPer is more responsive/aggressive because of its metering along with haveing the Mech. sec., but its not just that, its still in its metering, i've seen guys that know how to tune VS carbs metering to perform like terrors at the track.
Now as for going with a DPer, i say "do it", you'll most likely run faster with your gears & cam, especially if your running at least a 3000 stall.
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Re: 3310 vac.sec to 750 d.p.
[Re: chache876]
#834848
10/21/10 08:24 AM
10/21/10 08:24 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
I don't know why DPs get a bad rap on the street. They can be just as effective as a vacuum carb. It's all in the tune.
I'm not a carb expert by any means but whether they're just as effective or not as a vac sec carb is debatable. If it were all in the tune, your average hobbyist doing his own work probably wouldn't be able to do it himself and thats probably why vac secondary carbs are preferred for street use.
Just my 2 cents anyways
I guess I got lucky because I dropped a 750HP on my old 340 swinger (very mild set up) and avg'd 17mpg hwy at 70mph w/ 3.55 gears (auto) The car never smelled like gas, did not run rich or have any ill driving habbits. It did however take the car form 14.02 w/ the carter 625 to 13.80.
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Re: 3310 vac.sec to 750 d.p.
[Re: Evil Spirit]
#834852
10/21/10 12:41 PM
10/21/10 12:41 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either. 
That is curable 'problem' that can be taken care of and no worse than the kick down transition. 
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Re: 3310 vac.sec to 750 d.p.
[Re: MoparforLife]
#834855
10/22/10 02:36 AM
10/22/10 02:36 AM
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Joined: Jan 2005
Posts: 3,699
Newport, Mi
Evil Spirit
master
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master
Joined: Jan 2005
Posts: 3,699
Newport, Mi
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Quote:
Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either.
That is curable 'problem' that can be taken care of and no worse than the kick down transition.
I've tried every trick I've heard of; from lightest springs, ball/no ball, opening up the feed holes to the diaphram, modified return linkage - to the point it would backfire from no accelerator pump shot. Right now I have the lightest spring and no ball; I can stage at 3000, and the backs come in about 20-30 feet out and stay open all the way down the track. If you have any other tips, I'm not too old to learn.
Free advice and worth every penny...
Factory trained Slinky rewinder.........
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Re: 3310 vac.sec to 750 d.p.
[Re: Evil Spirit]
#834857
10/22/10 03:50 AM
10/22/10 03:50 AM
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Joined: Jun 2006
Posts: 5,167
CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,167
CT
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Quote:
Quote:
Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either.
That is curable 'problem' that can be taken care of and no worse than the kick down transition.
I've tried every trick I've heard of; from lightest springs, ball/no ball, opening up the feed holes to the diaphram, modified return linkage - to the point it would backfire from no accelerator pump shot. Right now I have the lightest spring and no ball; I can stage at 3000, and the backs come in about 20-30 feet out and stay open all the way down the track. If you have any other tips, I'm not too old to learn.
Is the car bogging when the secondaries come in? In that case you need a heavier secondary spring (I believe black is the heaviest). Try the black, if the problem goes away work your way lighter until it comes back, then go back to the lightest one that causes no bog. In my experience a quicker advance curve will also allow you to run a lighter spring and get the secondaries open sooner. I really got my car to respond much better by recurving the dizzy and opening the secondaries quicker.
Last edited by GTX MATT; 10/22/10 03:54 AM.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: 3310 vac.sec to 750 d.p.
[Re: Evil Spirit]
#834858
10/22/10 07:41 AM
10/22/10 07:41 AM
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Joined: Feb 2005
Posts: 4,321
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,321
Prospect, PA
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Quote:
Quote:
Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either.
That is curable 'problem' that can be taken care of and no worse than the kick down transition.
I've tried every trick I've heard of; from lightest springs, ball/no ball, opening up the feed holes to the diaphram, modified return linkage - to the point it would backfire from no accelerator pump shot. Right now I have the lightest spring and no ball; I can stage at 3000, and the backs come in about 20-30 feet out and stay open all the way down the track. If you have any other tips, I'm not too old to learn.
Wow. Evil Spirit - I have to hand it to you, you're the first person on here that seems to have my exact experiance, which I've proven to myself time and time again. Simply said - If you tune your Holley vacuum carb street car for the lowest possible et at the track, it will likely bog under heavy acceleration, especially in a 3-2 kick down. Generally, the tighter the converter and taller the gear, the more the bog will be pronounced. Also, if you tune on the street for no bog, or tune for the "perfect" A/F by slowing down the secondaries - you will have probably slowed the car down....probably by .3 or .4.
Certainly every car is different. But this has been my experiance on several street cars in the 12, 13 and 14 second et.s with different carbs, including the six pac.
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Re: 3310 vac.sec to 750 d.p.
[Re: GTX MATT]
#834859
10/22/10 09:23 AM
10/22/10 09:23 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
I dont think double pumpers are good for the average street car. The idle circuit is intentionally extremely rich to satisfy cars with very big cams. Other than the fact that you need to change plugs more often, I think they are overall a more responsive carb. Im considering ditching this thing for a double pumper since a cam swap is in my future along with a third pedal.
Never had that problem and I've used 750Dp's on any motor, 340, 383, and a few 440's. plugs look fine no gas smell, runs good all the way thru the power band. You can adjust the rear doors ya know.
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Re: 3310 vac.sec to 750 d.p.
[Re: BSB67]
#834860
10/22/10 12:14 PM
10/22/10 12:14 PM
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Joined: Jan 2005
Posts: 3,699
Newport, Mi
Evil Spirit
master
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master
Joined: Jan 2005
Posts: 3,699
Newport, Mi
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Quote:
Quote:
Quote:
Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either.
That is curable 'problem' that can be taken care of and no worse than the kick down transition.
I've tried every trick I've heard of; from lightest springs, ball/no ball, opening up the feed holes to the diaphram, modified return linkage - to the point it would backfire from no accelerator pump shot. Right now I have the lightest spring and no ball; I can stage at 3000, and the backs come in about 20-30 feet out and stay open all the way down the track. If you have any other tips, I'm not too old to learn.
Wow. Evil Spirit - I have to hand it to you, you're the first person on here that seems to have my exact experiance, which I've proven to myself time and time again. Simply said - If you tune your Holley vacuum carb street car for the lowest possible et at the track, it will likely bog under heavy acceleration, especially in a 3-2 kick down. Generally, the tighter the converter and taller the gear, the more the bog will be pronounced. Also, if you tune on the street for no bog, or tune for the "perfect" A/F by slowing down the secondaries - you will have probably slowed the car down....probably by .3 or .4.
Certainly every car is different. But this has been my experiance on several street cars in the 12, 13 and 14 second et.s with different carbs, including the six pac.
My issue - 45-50MPH in high gear (2500RPM) drop into 2nd (which is now 5500) while matting pedal. A mech carb will pull instantly due to open back barrels and pump shot. A vacuum gauge in the intake will instantly drop to about 2-3" of vac. The vacuum carb will spike vac gauge high, then quickly drop down to the 2-3" range. The high vac spike is from the high RPM and the back barrels not open yet, which is the "nose over" I described. You can only bring the back barrels in so fast, because there is no rear pump shot, and you are past the front shot. This is why the "fix" for the 6bbls is to convert the ends for an accel pump.
Free advice and worth every penny...
Factory trained Slinky rewinder.........
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Re: 3310 vac.sec to 750 d.p.
[Re: Evil Spirit]
#834861
10/22/10 10:14 PM
10/22/10 10:14 PM
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Joined: Feb 2005
Posts: 4,321
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,321
Prospect, PA
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Quote:
Quote:
Quote:
Quote:
Quote:
Only thing I don't like about vacuum secondaries is the delay when you are driving and go down a gear to "pass". My car noses over a lot that brief time before the back barrels can come in. Other than that, I love the response of the vacuum carb, and I don't seem to lose any E.T. either.
That is curable 'problem' that can be taken care of and no worse than the kick down transition.
I've tried every trick I've heard of; from lightest springs, ball/no ball, opening up the feed holes to the diaphram, modified return linkage - to the point it would backfire from no accelerator pump shot. Right now I have the lightest spring and no ball; I can stage at 3000, and the backs come in about 20-30 feet out and stay open all the way down the track. If you have any other tips, I'm not too old to learn.
Wow. Evil Spirit - I have to hand it to you, you're the first person on here that seems to have my exact experiance, which I've proven to myself time and time again. Simply said - If you tune your Holley vacuum carb street car for the lowest possible et at the track, it will likely bog under heavy acceleration, especially in a 3-2 kick down. Generally, the tighter the converter and taller the gear, the more the bog will be pronounced. Also, if you tune on the street for no bog, or tune for the "perfect" A/F by slowing down the secondaries - you will have probably slowed the car down....probably by .3 or .4.
Certainly every car is different. But this has been my experiance on several street cars in the 12, 13 and 14 second et.s with different carbs, including the six pac.
My issue - 45-50MPH in high gear (2500RPM) drop into 2nd (which is now 5500) while matting pedal. A mech carb will pull instantly due to open back barrels and pump shot. A vacuum gauge in the intake will instantly drop to about 2-3" of vac. The vacuum carb will spike vac gauge high, then quickly drop down to the 2-3" range. The high vac spike is from the high RPM and the back barrels not open yet, which is the "nose over" I described. You can only bring the back barrels in so fast, because there is no rear pump shot, and you are past the front shot. This is why the "fix" for the 6bbls is to convert the ends for an accel pump.
Exactly
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Re: 3310 vac.sec to 750 d.p.
[Re: GTX MATT]
#834862
10/22/10 11:43 PM
10/22/10 11:43 PM
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Joined: Feb 2004
Posts: 1,012
indiana
mcmopars
OP
super stock
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OP
super stock
Joined: Feb 2004
Posts: 1,012
indiana
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Quote:
Quote:
I have used vac sec carbs with reasonable success but I always end up running the dbl pumper at the track the vac carb looses too much over allpower and generally goes up to .25 sec slower. I was lawys told never run a dbl pumper on a heavy auto car wrong! I tune mine to get throttle response from a very heavy car, Don't over jet and if I had the option I would use the 650 dbl pumper for real fast low speed response. I use the 750 on my stick car but a 650 has almost run the same time as the 750 off by.08 in qtr Going to try a 750 street avenger against a 650dbl hopefully this weekend. I want see all the hoopla over this carb
I assume you mean 770 Street Avenger. If there is hoopla there shouldn't be, its like any other carb. And the calibrations out of the box suck, on my stock 440 with headers the plugs were ghost white with the stock calibrations. Opening the secondaries provided no extra charge either.
I dont think double pumpers are good for the average street car. The idle circuit is intentionally extremely rich to satisfy cars with very big cams. Other than the fact that you need to change plugs more often, I think they are overall a more responsive carb. Im considering ditching this thing for a double pumper since a cam swap is in my future along with a third pedal.
your chirping 3rd with a 273?wish i could do it with my 727,must need more h.p.
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