Carb question

[dwbiggs]

I'm new to forum...been lurking for a few years.  I don't have a Charger but do have a Challenger and wanted to get some expert opinion on a carb choice I feel I need to make.  Below is my combo:

440 +0.040
Ross forged pistons
10.5:1
Hughes 3844 hyd. 238/244 .536/.549 108
Eddy out of box 84cc heads
Eddy RPM manifold
35 deg TT, 15 init/20 mech, no VA
TTI 1 7/8" headers
T/A 10" tight converter
3.55 gears

Right now I am running an out of box Holley 80508 I believe (basically a 3310 with bells and whistles).

Is this carb too small for rest of combo?  If so, what would you recommend that would give me no loss in throttle response but would give a more tunable idle?

Thanks!

[Ghoste]

It wouldn't hurt you to move up a little in size to something more like an 850.  As for tuning, if you want something that offers more tuning than what you have, our resident experts have been touting the ProForm carbs lately with the four corner idle.  I have no experience with them personally but I definitely trust the judgement of the guys endorsing them.  It sound like they are a kind of super Holley.

[firefighter3931]

For that combo i would run the Proform 750 dp'er.....it flows 830 cfm and will move more than enough air for your build. 

Welcome to the site Dan 



Ron

[dwbiggs]

For that combo i would run the Proform 750 dp'er.....it flows 830 cfm and will move more than enough air for your build. 

Would there be a noticable difference?  Don't want to shell out $500+ if there isn't an obvious improvement. 

[Ghoste]

An obvious difference at the drag strip or just driving around town?  If you want the maximum performance you can get from the car then you will find it with the upgrade.  If you're just driving the car around town and all you want is a strong street runner that isn't going to see any actual timed acceleration trials then you are probably fine with what you have.

[dwbiggs]

An obvious difference at the drag strip or just driving around town?

Well, I was looking for an overall improvement.  True, I won't be taking it to the drag strip but I do make mad dashes to 100mph every now and then.  I am also wondering whether the 4 corner idle and downleg boosters on the Proform would improve response and/or idle.

[Ghoste]

There will be improvements but I think you're the only one who can answer if they are 500 dollars worth for your driving.  You will notice the difference but it isn't going to be like an "OHMIGAWD!!! THISCARISSOMUCHFASTERITHINKIJUSTCRAPPEDMYPANTS!!" sort of difference.  I don't think thats what you are expecting either but I do think the improvements we are talking about here are less dramatic unless its something you are seeking.  (does that last part even make sense?)

[firefighter3931]

I've yet to see anyone NOT experience a dramatic difference going from a vacuum secondary to a double pumper. 

Brian sure was happy with his Proform carb : http://www.dodgecharger.com/forum/index.php/topic,35989.0.html

Chris likes his PF mainbody : http://www.dodgecharger.com/forum/index.php/topic,12376.0.html


The PF carbs/main bodies are built with a more agressive fuel curve. That helps with cam profiles that produce low manifold vacuum and have lots of overlap. The Cam in Chris's engine is 2 steps down from yours and he noticed a significant improvement in both idle quality and performance.



Ron

[Ghoste]

Well Brian was going from a Carter to the PF on a 505 so he should have seen a huge difference.  I can't argue with Chris' driveability results though.

[firefighter3931]

Well Brian was going from a Carter to the PF on a 505 so he should have seen a huge difference.  I can't argue with Chris' driveability results though.

Brian was running the super duper 800cfm "Thunder" carb....guess it wwasn't so super compared to the Proform. 

Point well taken Ghoste. 

Inmo, it's not allways just about the max cfm rating. Fuel metering, atomization and tunability (adjustable bleeds, accelerator pump, metering blocks, pvcr, emulsion tubes etc...) has a huge impact on performance.

The #80508 Holley that Dan is using would be more at home on a stock 440 or mild 383 build. 



Ron

[dwbiggs]

The PF carbs/main bodies are built with a more agressive fuel curve. That helps with cam profiles that produce low manifold vacuum and have lots of overlap. The Cam in Chris's engine is 2 steps down from yours and he noticed a significant improvement in both idle quality and performance.

Now thats the kind of evidence I was looking for. 

The #80508 Holley that Dan is using would be more at home on a stock 440 or mild 383 build. 

So I am wayyyy off then.  Funny because the car runs great...not flat spots anywhere, great response.  I was afraid to change it.  Guess its like having a restrictor plate...car may run fine, it just isn't flowing as much fuel/air that it can handle.

BTW,  is there any difference between the Quickfuel and Proform?  I just can't stomach that purple. 

[firefighter3931]

BTW,  is there any difference between the Quickfuel and Proform?  I just can't stomach that purple. 

Don't like the purple huh ?  The QF & PF carbs are basicly the same thing except the billet baseplate/metering blocks are anodized different colors. The QF carbs use Proform main bodies in their assemblies so that should tell you something.  I bet the baseplates and metering blocks are identical other than the color. 

So I am wayyyy off then.  Funny because the car runs great...not flat spots anywhere, great response.  I was afraid to change it.  Guess its like having a restrictor plate...car may run fine, it just isn't flowing as much fuel/air that it can handle.

The car may run fine but unless you compare to something else you don't know how much you've left on the table. 

Someone on Moparts recently dynoed a BB and compared a vac secondary carb and double pumper....there was 20 ftlb and 15hp difference and the torque peak came on earlier with the DP'er. Those are differences you would feel in the car and at the track. I've allways preferred the sharp throttle response you get with a DP carb. The key is not going too big on the venturies to maintain strong signal to the boosters at low engine speeds.



Ron

[dwbiggs]

Thanks...I'll be shopping around for a PF or QF carb then.  How about Carb shops...any value in buying one from them and having it tuned for my car?  I am just lazy and don't want to fool with it.  Recommend any?

[firefighter3931]

Thanks...I'll be shopping around for a PF or QF carb then.  How about Carb shops...any value in buying one from them and having it tuned for my car?  I am just lazy and don't want to fool with it.  Recommend any?

Dan,

I would just purchase from Summit or whoever has the best price and bolt it on. The PF or QF should be pretty close if not dead on with your combo which is not too radical. You might need to jet up slightly but i would start with the stock jetting as a baseline and tune from there. 

Check the floats, adjust the 4 corner idle, set the idle speed and go for a drive. 



Ron

[dwbiggs]

Thanks Ron, I appreciate your help immensely...I'm looking forward to seeing an improvement...and getting even less traction off the line.    

Oh...heres my car.

[firefighter3931]

Hot Damm, that is a sweet Challenger !  I'm pretty sure i drooled over your car at Carlisle in 2007   

Let us know how you like the carb...i'm confident your report will be positive. 

I also have a PF 750 on my 446 that made 540hp so I know it moves plenty of air. A friend dynoed a customers race engine with a QF 750 and it made 660hp. The guy allready had the carb and when they tried a 950hp it made less than 5hp difference. Needless to say he kept his 750 and is running low 10's with a big ole b-body. Those carbs just plain work ! 


Ron

[MSRacing89]

Thanks...I'll be shopping around for a PF or QF carb then.  How about Carb shops...any value in buying one from them and having it tuned for my car?  I am just lazy and don't want to fool with it.  Recommend any?

Dan,

I would just purchase from Summit or whoever has the best price and bolt it on. The PF or QF should be pretty close if not dead on with your combo which is not too radical. You might need to jet up slightly but i would start with the stock jetting as a baseline and tune from there. 

Check the floats, adjust the 4 corner idle, set the idle speed and go for a drive. 



Ron

Proform will do the trick but the jetting is 74p and 84s stock, so you should not have to jet up too much.  I have a BIGS 750 which is a similar carb and I am at 74p 82s. 

I run a AFR gauge in my car and have been able to witness first hand what this carb can do.  Very nice.  The only thing I am working on now is trying to figure how to get the rich "light throttle cruise" out of it.  Everywhere else the carb does great. 

[dwbiggs]

Guess a Proform would be OK...I do have a drop base air cleaner do I wouldn't see that Barney purple anyway.   

That would be a race series, not street series correct?  Proform 67200?

[firefighter3931]

Guess a Proform would be OK...I do have a drop base air cleaner do I wouldn't see that Barney purple anyway.   

That would be a race series, not street series correct?  Proform 67200?

Yep, go for the race series with no choke horn. 

http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRO%2D67200&N=700+4294925239+4294839063+4294919007+400405+115&autoview=sku



Ron

[69chargerboy]

Ron, Is it a big deal not to have a choke horn on the carb for a stock to mildly build engine?

[MSRacing89]

Ron, Is it a big deal not to have a choke horn on the carb for a stock to mildly build engine?

I personally don't think that its an issue, I never run chokes.  The only issue with getting an HP/Proform/Quickfuel type racing carb for a mild street application is that is tends to be a great all around carb but it likes to run a little rich a light cruise applications.  Ron can back me up on this, but we believe the carbs are built for weak vacuum, big cam set-ups.  So when the vacuum signal gets strong i.e. light throttle cruise, it wants to pull a lot of fuel.

I am trying to get it worked out right now.

[greenpigs]

Ron,      you run 82 jets on your secondaires? So what would be a good startin jet for my mild 440? I got the MP jet kit and will be getting a secondary metering plate soon. I plan on getting the Proform converson kit front and rear. 

[speedfreak68]

Without the choke do you have problems starting when its cold?

[firefighter3931]

Ron,      you run 82 jets on your secondaires? So what would be a good startin jet for my mild 440? I got the MP jet kit and will be getting a secondary metering plate soon. I plan on getting the Proform converson kit front and rear. 

GP, start with 74/80 on the jetting and see how it runs....that should be a good starting point for a mild 440 


Ron

Without the choke do you have problems starting when its cold?

Nope...you just have to coax it for a few seconds and once it warms up it'll settle into a nice idle. 



Ron

[speedfreak68]

Without the choke do you have problems starting when its cold?

Nope...you just have to coax it for a few seconds and once it warms up it'll settle into a nice idle. 



Ron
[/quote]
I gotcha Ron, Thanks for the answer!