Hello, I am currently running a Holley 650 DP carb (that was a friends and rebuilt), and it's currently way too rich--even after dropping the jets, etc. I guess what I am looking for is advice on a new carb to bolt on and be reliable and streetable. I know carb preference is mostly perspective....people like different carbs for different reasons. I have heard that the holleys can be tough to tune. I'd also like to keep the expensive stainless double feed line I already have. Thanks for any help!!!!
383 Carb Situation
NRMEDIC984
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Hello, I am currently running a Holley 650 DP carb (that was a friends and rebuilt), and it's currently way too rich--even after dropping the jets, etc. I guess what I am looking for is advice on a new carb to bolt on and be reliable and streetable. I know carb preference is mostly perspective....people like different carbs for different reasons. I have heard that the holleys can be tough to tune. I'd also like to keep the expensive stainless double feed line I already have. Thanks for any help!!!!
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Holley 9381...830 annular, excellent carb for that motor. Less than $400 new.
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I had a 750DP and was not impressed with it on my 383. I swapped out the intake for a spreadbore and went with a Sean Murphy Inductions custom built 750 Quadrajet Stage 2 for $325. Awesome carb, bolted right up and my engine has never felt stronger or more responsive, plus I get better mileage as well since the engine draws what it needs rather than having gas pushed down its throat for no reason.
www.smicarburetor.com
Holly 830 is going to flow way too much for that size engine.
Running:
Edelbrock Performer 2101 Aluminum Intake
Edelbrock 7201 Intake Manifold Gaskets
Sean Murphy Induction Custom Built Stage 2 750 cfm Quadrajet Main Jet .075, Metering Rods 42K Primary, DA Secondary
Mr Gasket Model 86 Heat Dissipater, Quadrajet, 4-Hole, 1/ 4 in. Thick
www.smicarburetor.com
Holly 830 is going to flow way too much for that size engine.
Running:
Edelbrock Performer 2101 Aluminum Intake
Edelbrock 7201 Intake Manifold Gaskets
Sean Murphy Induction Custom Built Stage 2 750 cfm Quadrajet Main Jet .075, Metering Rods 42K Primary, DA Secondary
Mr Gasket Model 86 Heat Dissipater, Quadrajet, 4-Hole, 1/ 4 in. Thick
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477 Posts
Thats interesting DP Holleys are actually the easiest to tune in my opinion.
AFB / Edelbrock is probably the second easiest
Quadrajets pull 3rd place
They are all reliable to an extent. Streetable depends on if your asking about milage or if it will run without being way to rich. Yes they can all run without being way rich in street trim.
Milage wise a Quadrajet probably takes 1st
AFB / Edelbrock is probably the second easiest
DP Holleys most likely the worst unless you have a very light foot.
Flat out drag racing DP Holleys are best
AFB / Edelbrock and Quadrajet are all a tossup pretty much depending on a million variables.
Just my experience and opinion
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Not true. Here`s an example:Brian Lewis said:
Local guy here wanted to just get into the 12`s. When asked would make him happy he said 12.80`s would do it.
I built a 385 for his 70 Chevelle. Using 9.5-1 compression, Hyd F/T cam, Air Gap w/830 (9381) annular carb.
3.55 gears and drag radials.
Very 1st pass he ran 12.10 ET @ 112 mph
He was floored!
That carb works and it works very well in those 383/406 motors.
Steve
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I agree but since the NRMEDIC984 said "streetable" and I wasnt sure if he was going for the Maximum ET or for milage/throttle response with some good performance I didnt want to say 800+cfm Holley. Holley carbs are not the best milage carbs. Also Dragracing is the one case you can "over size" your carb and still gain performance. Im not saying 830 is too big. Im just saying he said streetable and throttle response will perk up with some with a smaller carb and fuel milage should also.BigRed-L72 said:
With the information NRMEDIC984 provided JimM was probably the safest all around response. Ok thats my .02
I say get the 650 DP right first -- if you can't get this one tuned you won't get a new carb tuned either.
I would suggest starting with the jets recommended by Holley for your model carb first (by memory I think you need 67F/73R). Then set the idle mix screws with a vacuum gauge for best vacuum. Then put in the correct power valve. That should get you pretty close without too much effort.
And if your plugs are too cold they will look rich and foul easily. Same with timing, not enough advance and it will act rich.
I would suggest starting with the jets recommended by Holley for your model carb first (by memory I think you need 67F/73R). Then set the idle mix screws with a vacuum gauge for best vacuum. Then put in the correct power valve. That should get you pretty close without too much effort.
And if your plugs are too cold they will look rich and foul easily. Same with timing, not enough advance and it will act rich.
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What I've done to tune a DP for the street is basically do everything (Except idle)backwards!
Do the Idle mix first, for best vacaum at idle,
Then the primaries, for best lean cruise (I've dropped 8 or more sizes from factory to achieve this.)
Then the power valve, both the valve itself and the channel restrictions, which may need to be enlarged to compensate for the lean primaries. Tune for throttle response. Drive the car, with a vacaum guage you can see. That way you'll know at what throttle opening/speed/load the power valve opens. You get a bog before, it needs to open sooner. you get a bog after, you need to drill the restrictor.
Then the primary pump, to eliminate any boggyness that's still there.
I would do all this with the secondaries disconnected.
Finally hook the secondaries back up and tune them for WOT. They will need to go richer, again to compensate for the lean primaries.
When it's done right, they run GREAT! But, a DP will not tolerate a "dumb foot" Unlike an air valve or vac sec carb, airflow is directly connected to your left foot. If you give the engine more air than it can take, velocity will drop, fuel flow will lag, and it will bog.
Example would be "mashing the throttle from a slow roll." A Q-jet, with it's tiny primaries and air valve controlled seconaday's, will not have a problem. The secondaries won't open until the engine can "USE" them.
With a DP, that kind of behavior will inevitably make it bog. The engine simply cannot use that much airflow that quickly. The solution, of course, is to take a second, or a second and a half, to get the throttle wide open.
Do the Idle mix first, for best vacaum at idle,
Then the primaries, for best lean cruise (I've dropped 8 or more sizes from factory to achieve this.)
Then the power valve, both the valve itself and the channel restrictions, which may need to be enlarged to compensate for the lean primaries. Tune for throttle response. Drive the car, with a vacaum guage you can see. That way you'll know at what throttle opening/speed/load the power valve opens. You get a bog before, it needs to open sooner. you get a bog after, you need to drill the restrictor.
Then the primary pump, to eliminate any boggyness that's still there.
I would do all this with the secondaries disconnected.
Finally hook the secondaries back up and tune them for WOT. They will need to go richer, again to compensate for the lean primaries.
When it's done right, they run GREAT! But, a DP will not tolerate a "dumb foot" Unlike an air valve or vac sec carb, airflow is directly connected to your left foot. If you give the engine more air than it can take, velocity will drop, fuel flow will lag, and it will bog.
Example would be "mashing the throttle from a slow roll." A Q-jet, with it's tiny primaries and air valve controlled seconaday's, will not have a problem. The secondaries won't open until the engine can "USE" them.
With a DP, that kind of behavior will inevitably make it bog. The engine simply cannot use that much airflow that quickly. The solution, of course, is to take a second, or a second and a half, to get the throttle wide open.
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Again the 830 is way too much carb, especially for a streetable application.
Take it from Holley, not my mouth if you don't believe me
http://www.holley.com/data/TechService/Technical/Selecting A Carburetor.pdf
A High Performance Engine's maximum torque is achieved at a volumetric efficiency of 85%. All out racing engines achieve maximum torque at a volumetric efficiency of 95%
A 383's maximum rpms is 5500-6000 rpms. Using Holley's graph at 100% volumetric efficiency, that engine at 6000 rpms can only pull in 690cfm!!! And thats at 100% which the engine isn't at maximum torque. At maximum torque for that motor, 6000rpms, 586cfm is all that is required.
So there is no way if you take a 650cfm, 750cfm, or 830cfm carb will you obtain any more maximum torque or horsepower out of that engine.
An engine is a pump, it can only pump as much air as its displacement + rpms can pump, no matter what carb is on it.
Take it from Holley, not my mouth if you don't believe me
http://www.holley.com/data/TechService/Technical/Selecting A Carburetor.pdf
A High Performance Engine's maximum torque is achieved at a volumetric efficiency of 85%. All out racing engines achieve maximum torque at a volumetric efficiency of 95%
A 383's maximum rpms is 5500-6000 rpms. Using Holley's graph at 100% volumetric efficiency, that engine at 6000 rpms can only pull in 690cfm!!! And thats at 100% which the engine isn't at maximum torque. At maximum torque for that motor, 6000rpms, 586cfm is all that is required.
So there is no way if you take a 650cfm, 750cfm, or 830cfm carb will you obtain any more maximum torque or horsepower out of that engine.
An engine is a pump, it can only pump as much air as its displacement + rpms can pump, no matter what carb is on it.
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Im not trying to be difficult but that is not entirely true. If it was the case use your math and take a Pro Stock engine for example. 500 inch motors some are less if you know your PS engines. Now Brian use your math and tell us what is the MAX carb a 500 inch V8 should never exceed. Now whats the smallest Dominator carb multiply it times 2. I think you will find you have a error in your calculations in the prior post. Holley uses this to help as a guidline. Im not saying it wont work but its not a set in stone rule.Brian Lewis said:
Just trying to clarify a little.
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a ProStock engine runs at 9000+ rpms, producing over 2.5hp per cu inch, its a completely different beast over a streetable 383 stroker. Not to mention the $75,000 difference in price. Because of the higher rpms its able to pump more thru itself per minute. Unless you have a supercharger/turbocharger, the engine is only going to pull as much cfm as it can pump. Air/fuel isn't going to move any faster into that engine than it can physically pump into itself.
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Well from looking at the combo in his signature (3000 stall, 3.73's, 200cc heads, etc...) I don;t think the engine/car was built for commuting. The 650 is on the small side, but should be able to run decent.
I agree 100% with the recommendation Big Red (Steve) offered. I ran that exact same carb on my 385 and the throttle response and performance were un matched by any other carb I tried (which included a 750DP HP Series and a 750 vac secondary). The 830 will work perfect on your combo. If not, just cut it up in small enough pieces for me to swallow it and I will eat it. That's how confident I am about it.
No carb will be perfect out of the box, all carbs need tuning. I don't care if you have a carb custom built for your application, you will still have to do some tuning.
What are you after? Mileage, performance, etc... Any carb once tuned right should keep it's tune and give you trouble free operation. The biggest mis-conception about Holleys are that they always need tuning. This is not true. They are also very easy to tune. They are almost to tune-able and that's what gets people into trouble.
If you just want something out of the box that will be "close enough" and not have much tinkering to do, try an Edelbrock. You can set this carb up "decent" by only adjusting the mixture screws. You will not get all the performance potential of your engine, but it will start and run decent. You won't even have to touch it.
Brian, That calculator should be done away with. I guess it helps someone that has no clue at all, but it is almost always on the small side and doesn't take things into consideration. I am not a big fan of "formulas" anyway, just for that reason. You also said it yourself "Air/fuel isn't going to move any faster into that engine than it can physically pump into itself." The 830 is not too big for a 383+ cube engine. You also have to remember this is an annular booster carb, makes quite a difference.
I usually stay away from cam and carb posts because very rarely to they stay civil. People have their opinions and experiences and tend not to want to hear out the other side. Take my opinion for what it's worth.
I agree 100% with the recommendation Big Red (Steve) offered. I ran that exact same carb on my 385 and the throttle response and performance were un matched by any other carb I tried (which included a 750DP HP Series and a 750 vac secondary). The 830 will work perfect on your combo. If not, just cut it up in small enough pieces for me to swallow it and I will eat it. That's how confident I am about it.
No carb will be perfect out of the box, all carbs need tuning. I don't care if you have a carb custom built for your application, you will still have to do some tuning.
What are you after? Mileage, performance, etc... Any carb once tuned right should keep it's tune and give you trouble free operation. The biggest mis-conception about Holleys are that they always need tuning. This is not true. They are also very easy to tune. They are almost to tune-able and that's what gets people into trouble.
If you just want something out of the box that will be "close enough" and not have much tinkering to do, try an Edelbrock. You can set this carb up "decent" by only adjusting the mixture screws. You will not get all the performance potential of your engine, but it will start and run decent. You won't even have to touch it.
Brian, That calculator should be done away with. I guess it helps someone that has no clue at all, but it is almost always on the small side and doesn't take things into consideration. I am not a big fan of "formulas" anyway, just for that reason. You also said it yourself "Air/fuel isn't going to move any faster into that engine than it can physically pump into itself." The 830 is not too big for a 383+ cube engine. You also have to remember this is an annular booster carb, makes quite a difference.
I usually stay away from cam and carb posts because very rarely to they stay civil. People have their opinions and experiences and tend not to want to hear out the other side. Take my opinion for what it's worth.
One thing about DP's is that they have richer idle mixtures, so GENERALLY you will get a stinky idle/cruise. My 750 DP runs superb, but I couldn't tune out my stinky idle no matter what I did. However, I was able to greatly reduce the stink by closing the primaries which closed up more of the transfer slot. Running manifold vac will allow you to close the throttle more. You can also open the rear blades a bit if needed (if you dont have vac advance). The transfer slot adjust is probably one of the most misadjusted things on a Holley. Despite all this, DP are still just rich.
Now, I just got a 770 Avenger new from ebay (only 300.00), and I must say I love this carb! Just as much power as the DP, but no stinky idle/cruise at all - and I haven't even tinkered with it yet!
Now, I just got a 770 Avenger new from ebay (only 300.00), and I must say I love this carb! Just as much power as the DP, but no stinky idle/cruise at all - and I haven't even tinkered with it yet!
No and 830 is not too big for the application, many people run them on 383s.Brian Lewis said:
Max VE is usually just past peak tq, meaning an engine which has 105% VE
will have about 100% VE at peak tq, which doesnt really matter, because the
carb needs to feed the engine past peak hp, at a higher rpm. Also many street
engines make 100+% VE, which can be measured on a dyno with a hat.
A 383s max rpm is not 5500-6000, that depends totally on the way its built - cam, heads,
induction, exhaust... Also the cfm and vacuum can be measured on the dyno, and
will tell you exactly how much air the engine is using and needs. If 585cfm is all that
is needed then just stick a 2-barrel on it and see how much power it makes.
If what youre saying is true, a tunnel ram would never work, because how would
a sbc run with a tunnel and 2 - 750s on it? Its all about having enough signal
to pull thru the boosters - 8 boosters work better then 4, so the 1500cfm can
be used effectively.
A 650, 750, 850, and 950 will each make more tq and hp on a decent street 383,
around 450hp or so. Do some testing on a dyno 1st, before makin such statements.
The thing that matters - is that booster signal good enough for the engine to perform well.
My Luv has a HP950 on a smooth idle 383, gets 22-23mpg, streetability and mileage
are possible. So please speak from experience, (yours and others) not just from what
some tech guy at Holley told you.
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Pro Stock engines, and any N/A engine that is over 100% VE is doing something called "Inertia supercharging".Brian Lewis said:
This is the effect of raising the intake port velocity to the point that inertia of the incoming charge over-fills the cylinder.
I agree that an 830 with anular boosters is not too big. It may even make more power than the 650. While the 650 is on the small side, I personally usually recommend using what you have unless its broke. Carbs often get blamed for a bad tuneup and prematurely replaced.
Another option would be to put a ProForm main body on it and convert it to a 750 HP style carb. That will definately take some tuning to get nailed down though.
Another option would be to put a ProForm main body on it and convert it to a 750 HP style carb. That will definately take some tuning to get nailed down though.
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Sideways, Yes, we are talking the 830 DP anuular booster carb. Definetly worth trying if you have access to one.
With the annular boosters, they are VERY sensitive and create awesome throttle response.
Eric, I agree the 650 can be made to work if he isn't looking for every bit of HP available. There should be no problem tuning it to work well on the street. The problem I see is that it is "rebuilt" and who knows if it was done correctly. It might need to be rebuilt again and then tuned. From the sounds of it he is not very comfortable with Holleys.
With the annular boosters, they are VERY sensitive and create awesome throttle response.
Eric, I agree the 650 can be made to work if he isn't looking for every bit of HP available. There should be no problem tuning it to work well on the street. The problem I see is that it is "rebuilt" and who knows if it was done correctly. It might need to be rebuilt again and then tuned. From the sounds of it he is not very comfortable with Holleys.
Since the 830 annular is a DP, can you guys tune out the rich idle/cruise or do you just live with it?
830 might work good in place of a 750DP b/c annulars are a little more restrictive up top from what I understand.
This also begs the question: If annulars are so great, why doesn't everybody run one?
830 might work good in place of a 750DP b/c annulars are a little more restrictive up top from what I understand.
This also begs the question: If annulars are so great, why doesn't everybody run one?
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