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Which carb?
#834778
10/20/10 05:59 PM
10/20/10 05:59 PM
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Joined: Apr 2008
Posts: 90
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Frederick
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Hi, I'm looking for advice on which carb to get for my engine. Specs: 383 +0.030 Lunati 60302 flat tappet hydraulic cam (220/226 @0.050 duration 0.475/0.494" lift) Edelbrock performer RPM heads 9.7 compression Edelbrock performer intake 600cfm 1405 Edelbrock carb 1-3/4" headers 2-1/4" dual exhaust 3.3:1 diff 4 speed manual 4000lbs 13deg advance at idle, 34deg max No racing, street only. I'm thinking of buying one of these Quickfuel carbs: SS 650 or 750 mechanical secondaries SS 735 or 780 vacuum secondaries I keep getting different advice about whether to run mechanical or vacuum secondaries with my heavy 4speed car.  The 600 eddy carbs isn't performing to bad, but it does have a slight off-idle stumble and is holding back higher up in the rpm range(measured 2.2" of vacuum at 4.5k rpm WOT). Thanks
Last edited by Frederick; 10/21/10 06:34 PM.
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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Re: Which carb?
[Re: ireland383]
#834780
10/20/10 06:33 PM
10/20/10 06:33 PM
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Joined: Apr 2008
Posts: 90
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Frederick
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I know Holley states that if your car is more than 3100 to run a vac secondary. But my friends keep telling to forget the weight, I've got a manual and should run a mechanical secondary carb. Myself I'm not too sure about this.  The car won't ever see a strip and I've heard mileage is better too with a Vac/Sec. I know I don't want to get a 750 edelbrock, I have read too many stories on that. 
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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Re: Which carb?
[Re: ireland383]
#834781
10/20/10 06:37 PM
10/20/10 06:37 PM
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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:
I have similar set up to yours with a bit more cam, rear gear and run a Holley 750 w/vac secondaries, good response. It is an automatic, they say not to run mech. secondaries on a car above 3200 lbs. 
what kind of logic is that? Mech carbs are way more responsive and easier to tune. Doesn't really matter the cars weight. Almost every racer uses a mech carb. not sure what happend to my 1st post but I'd slap a 750DP on it and roll. That 600 is for a 318
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Re: Which carb?
[Re: Mr.Yuck]
#834782
10/20/10 06:43 PM
10/20/10 06:43 PM
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Joined: Apr 2008
Posts: 90
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Frederick
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Quote:
Almost every racer uses a mech carb. not sure what happend to my 1st post but I'd slap a 750DP on it and roll.
This isn't a race car and it will never ever see a strip, street driven only.
Would you still recommend a mechanical carb for this?
edit: max rpm is about 5500 rpm.
Last edited by Frederick; 10/20/10 06:44 PM.
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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Re: Which carb?
[Re: Frederick]
#834784
10/20/10 06:58 PM
10/20/10 06:58 PM
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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:
Almost every racer uses a mech carb. not sure what happend to my 1st post but I'd slap a 750DP on it and roll.
This isn't a race car and it will never ever see a strip, street driven only.
Would you still recommend a mechanical carb for this?
edit: max rpm is about 5500 rpm.
yes, no reason against it. But a Vacuum would work just as well.
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Re: Which carb?
[Re: Mr.Yuck]
#834785
10/20/10 07:07 PM
10/20/10 07:07 PM
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Joined: Apr 2008
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Frederick
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OK, at least we got it down to 2.
Sounds like it's either the 735vs or the 750dp.
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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Re: Which carb?
[Re: Mr.Yuck]
#834786
10/20/10 07:59 PM
10/20/10 07:59 PM
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Joined: Nov 2004
Posts: 843
Suffolk,VA
ireland383
super stock
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super stock
Joined: Nov 2004
Posts: 843
Suffolk,VA
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Quote:
Quote:
I have similar set up to yours with a bit more cam, rear gear and run a Holley 750 w/vac secondaries, good response. It is an automatic, they say not to run mech. secondaries on a car above 3200 lbs.
what kind of logic is that? Mech carbs are way more responsive and easier to tune. Doesn't really matter the cars weight. Almost every racer uses a mech carb. not sure what happend to my 1st post but I'd slap a 750DP on it and roll. That 600 is for a 318
I just stated that mine has good response and yes a mechanical is easier to tune for a novice (not saying the OP is a novice). And as stated he is not racing.
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Re: Which carb?
[Re: ireland383]
#834787
10/20/10 08:26 PM
10/20/10 08:26 PM
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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:
Quote:
I have similar set up to yours with a bit more cam, rear gear and run a Holley 750 w/vac secondaries, good response. It is an automatic, they say not to run mech. secondaries on a car above 3200 lbs.
what kind of logic is that? Mech carbs are way more responsive and easier to tune. Doesn't really matter the cars weight. Almost every racer uses a mech carb. not sure what happend to my 1st post but I'd slap a 750DP on it and roll. That 600 is for a 318
I just stated that mine has good response and yes a mechanical is easier to tune for a novice (not saying the OP is a novice). And as stated he is not racing.
no I mean who made that up about heavy cars and vacuum advance? I've never heard of that.
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Re: Which carb?
[Re: Mr.Yuck]
#834788
10/20/10 08:41 PM
10/20/10 08:41 PM
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Joined: Apr 2008
Posts: 90
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Frederick
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Quote:
no I mean who made that up about heavy cars and vacuum advance? I've never heard of that.
I think you misread the vacuum advance bit.
However Holley themselves have this on their site:
"For street cars the vacuum secondary carburetor works best on midweight or heavyweight cars with an automatic transmission. They are more forgiving than a Double Pumper is because they work by sensing engine load. The mechanical secondary carburetor is best on a lighter car with radical camshaft and a lower gear and manual transmission or on a car that is going to be used for racing purposes."
And if you use their "interactive carb selector":
"Use of a mechanical secondary carburetor should be limited to use on a lighter vehicle.
The vehicle weight should be less than 3100 lbs., full weight,
Full weight includes fuel, water and the driver.
If the vehicle meets the above weight requirement and has a manual transmission with a low first gear plus 3:73 or lower rear end ratio, you can use a mechanical secondary carburetor. If the manual transmission has a high low gear, such as 2:20, you should hav e a rear end ratio of 4:46 or lower to use a mechanical secondary carburetor.
If the vehicle has an automatic transmission and meets the 3100lbs weight requirements it should have a true minimum stall of 4000rpm, a minimum 4:56 rear end ratio for two speed transmissions or a minimum 3:73 rear end ratio for 3 or 4 speed automatics before you should use a mechanical secondary carburetor."
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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Re: Which carb?
[Re: Mr.Yuck]
#834789
10/20/10 08:47 PM
10/20/10 08:47 PM
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Joined: Mar 2008
Posts: 390
kentucky
superbyrd
enthusiast
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kentucky
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alot of people claim that the heavier car,with a mechanical secondary carb tends to bog because the fast dump of fuel. i have heard that for years,but,have never had that experience my self. for your set-up,another good choice would be the 670 street-avenger holley. it is actually a 750 vac-sec,with quick change secondary pod,electric choke,chromie finish,etc. they are a very street/tuning friendly carb that is virtually ready to go out of the box. so many people tend to "over carb" with their thinking of "max power" or power and use of RPM at 20 feet before the finishline at the strip. where a street car is not going to see that much use upstairs.
i mean,really,a 500 holley 2 bbl. would feed your car,and drive around with no problems. but,a 1050 dominator would feed it too. but neither are optimal. to me a 750 mechanical is not a neccesity for your very mild 383. but what do i know.....lol.
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Re: Which carb?
[Re: ireland383]
#834790
10/20/10 08:53 PM
10/20/10 08:53 PM
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Joined: Jul 2006
Posts: 4,319
Puyallup, WA
StealthWedge67
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Posts: 4,319
Puyallup, WA
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Best thing to do is to go to Holleys website and use their carb selector tool. I tend to theink they know Holley carbs better than the average Moparts poster. Not saying a 750DP won't work, but IMHO, its not the right carb for your application.
I'm going to suggest you consider a 670 street avenger series. I ran a 750 v.s, on my 383, It was very similar, but ran an RPM manifold and 3.91's out back. I raced the car and wanted max upper RPM HP. The smaller venturi 670 carb will be more responsive at off-idle, cruise, and midrange, however. The 750 will make more top end HP, but will be little tougher get tuned for crisp street use on a low compression 383.
Mathematical figures say that a 388" motor @ 6000 RPM will use 673 cfm @ 100% V,E. A good street motor will be lucky to operate at 90% V.E. So anything over 670 isn't offering much to a street car
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: Which carb?
[Re: Frederick]
#834792
10/20/10 10:00 PM
10/20/10 10:00 PM
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Joined: Jan 2003
Posts: 5,449
So Cal
Sinitro
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So Cal
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I have a very similar setup to yours.. And settled on a Holley 770 Avenger, but I added a Quick Technology adjustable secondary component. Now you can dial in exactly when you want the secondaries to kick in... Just my $0.02.. 
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Re: Which carb?
[Re: Frederick]
#834793
10/20/10 10:00 PM
10/20/10 10:00 PM
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Joined: Jan 2003
Posts: 8,943
Holly/MI
Dean_Kuzluzski
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Holly/MI
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Let's see here...........
4000+ lbs
mildish cam at [Email]220@..050[/Email]
small runner dual-plane
mildish axle ratio
5500 rpm limit
smallish exhaust- 2&1/4"
4 speed- no stall or/like such torque multiplication (wide or close ratio????)
I'd be thinking a 625-670 cfm vac. sec. carb myself.
AND, the current problem you have with that stumble can be cured by putting in lighter/thinner metering rod springs, fatter metering rods, more pump shot, different nozzles (a few are available last I checked) and..............the much overlooked mech. ignition advance (13 is good, you may need more).
You get all that tweaked & tuned and it will snap your neck like a PEZ dispenser.
You should also get 15-17 mpg minimum.
Also, you need to check your WOT fuel pressure to see if you're overrunning your fuel supply or jetted too lean in the secondaries.
Last edited by Dean_Kuzluzski; 10/20/10 10:03 PM.
R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04
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Re: Which carb?
[Re: Frederick]
#834795
10/20/10 10:04 PM
10/20/10 10:04 PM
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Joined: Jan 2003
Posts: 5,444
Indiana
YO7_A66
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Indiana
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Frederick, ""OK, at least we got it down to 2. Sounds like it's either the 735vs or the 750dp."" Have you checked out the Quick Fuel Super Street Carbs? http://www.quickfueltechnology.com/carburetors-ss-series/They have both vacuum and secondary carbs with electric chokes and plenty of tuning gadjets. The mechanical carbs have adjustable secondary linkage which I like to play with. You can select 1:1, 40% and 60% delay on the secondaries. I run the SS750-AN on my car (listed below) and I do agree with you can run DPs on the street. It is all in the way that you tune them. 
Last edited by YO7_A66; 10/21/10 08:46 AM.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
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) & alot more cfm than you have now but not too large. Should be a good improvment
