440 with a 595 CFM carb....?

[John_Kunkel]

The stock AFB & AVS carbs were rated @ 625 CFM (340-383) & 750 CFM (413-440). I have re-built a few Holley 4160 carbs for early C bodies running a low performance 440 that were rated @ 575 CFM.

The factory Performance Clinic literature (which I've long since lost) disagrees. For the AVS they said more like 635 and 685 respectively.

I have never found creditable CFM numbers for OEM Carter or Holley carbs, most numbers quoted as fact are just guesses based on butterfly/venturi size.

[Cooter]

Personally i dont think the words fuel economy and carburetor should be in the same sentence, not to mention really anything about our cars in general (unless were talking SB that is taken out for parades or something). If you want better economy go with some kind of computer controlled injection that you can monitor and tune, could go from economic to performance with some software changes. But in the end is the few MPG really worth it? Probably not.

I tend to disagree here. We have a 355 C.I. Chevy with a metric 2004R and 3.08:1 gears. This thing with a Quadrabog and manifolds is getting 25 MPG on the highway. Has excellent throttle response as well as drivibility... I just saw this posted on another board and thought you guys might try and "Debunk" the 595 CFM 4BBL on a 440 a little bit better than many on the other board. The 440 i'm referring to will run a 650 DP holley that has had it's choke air horn milled off, consequently making it a 700 or so CFM DP carb. The engine has Six Pack pistons with .040 Quench with .020 compressed steel shim head gaskets. Not really looking for balls out performance as much as good throttle response and fuel mileage. (As good as a 440 will ever get.)...I will be running a 4 speed with 3.54:1 Dana 60 trac-lok rear.

I figure this might put this 440 into the upper teens if I stay out of it on the highway. But was wondering as according to this formula, I'm over carb'd at 700 CFM, how you guys would see it.

BTW: We also have a 331 C.I. Stroker in a street Mercury Cougar(Fox body) with an AOD and it gets horrible mileage with Fuel injection. Of course, the big 'ol cam ain't helpin', but my point is, Fuel injection doesn't nessesarily mean good mileage.

[Scaregrabber]

I built a strong 440 in the mid 70's and bolted on what i was told was a 750 double pumper. That car ran like a bat outta hell, eventually I checked the # and it was a 700DP, it was on a single plane torker manifold though (which probably saved the combo) but it ran very well. I'm sure the topend was down a bit but that car ran quite a bit slower when I bolted a new six pack on. After I tweaked the Six Pack it started to run as good as that 700 did. That build had ported heads Forged Six Pack pistons and a 510 lift hydraulic cam with headers.
Going for fuel mileage? TQ is your best friend.

Sheldon

[flyinlow]

About the intake style discussion.

I have a SD intake (one large plenum) . My Performer RPM intake is not totally separated. There is an area in the dividing wall that is left out apparently letting gas/air dump into the other side. For more single plane like performance?      

[myk]

The stock AFB & AVS carbs were rated @ 625 CFM (340-383) & 750 CFM (413-440). I have re-built a few Holley 4160 carbs for early C bodies running a low performance 440 that were rated @ 575 CFM.

The factory Performance Clinic literature (which I've long since lost) disagrees. For the AVS they said more like 635 and 685 respectively.

I have never found creditable CFM numbers for OEM Carter or Holley carbs, most numbers quoted as fact are just guesses based on butterfly/venturi size.

Hm.   Guess we'll never know...

[firefighter3931]

About the intake style discussion.

I have a SD intake (one large plenum) . My Performer RPM intake is not totally separated. There is an area in the dividing wall that is left out apparently letting gas/air dump into the other side. For more single plane like performance?      

The hole in the divider is there to help with fuel distribution and allows all 8 cylinders to see all 4 venturies. Not as evenly as with a single plane but it does help. 


Ron

[firefighter3931]

Cooter, the 650dp will run fine and the throttle response will be very sharp. Smaller venturies means higher velocity as well as improved economy. 

The dyno is a pretty good indicator of how efficient an engine is and you need to pay attention to the cfm numbers. Most mild 440's that i've seen won't pull over 700cfm at WOT. Remember that a 6-pack uses vacuum secondaries (out board carbs) so the engine is only pulling what it needs. There's no way in hell that a stock 440 or even one mildly modified is using anywhere near 950cfm 

As long as the cam profile isn't too racey it should work great. Hotter cam profiles with lots of overlap and low vacuum require a more agressive fuel curve.


Ron

[Cooter]

Ron, Remember me asking you a while back about my 650 DP that is modded? Well, I'm about finally ready to dump the engine in a fire it up. All I hear ALL DAY LONG from EVERYBODY when they see that there is no choke and assume that Holley MUST BE a 800 DP or something, is "Damn! That 700 Is WAAAYYY too small for that 440!"

I don't seem to think so since talking to you. I know the throttle response will be better, just wondering if the performance will be satisfactory in the upper RPM.

I remember you telling me as I was wondering if milling off the choke Air horn would increase the CFM, as I thought CFM rating was only due to the venturi/BBLs of carb. However, you stated that you actually had one go up around 50 CFM just by milling that off. I just got this one at a deal and thought, Why not go outside of what I've always done(Bigger like 750-850) and actually go smaller and see what happens.

I guess my build would help more here huh?

Stock 440 block, Six Pack pistons, Lunati "Voo Doo" Cam .513 .533 and like 225 and 230 @ .050 I think, can't remember right now Straight up, Ported "915" heads with 2.14 in. 1.81 Ex. Steel shim gaskets with .020 in the hole and .020 Compressed for total of .040 Quench. Should be around 10.5:1....
Single plane Torker intake gasket matched, 700 Holley DP, Headers 1 7/8" primary, 2 1/2" Exhaust with "X" pipe and Dynomax mufflers. Oh and good 'ol 4-speed, with Dana 60 and 3.54:1 gear and Trac-Lok.

[firefighter3931]

Sounds like a nice build....well balanced and thought out 

With the single plane torker that carb will be fine. The choke horn surgery is worth around 50cfm so that carb should be in the 700 range give or take a few cfm. If i had that carb....i'd certainly be trying it before bolting something else on.    With the sum of parts listed it's probably a 450hp build depending on how well the heads flow but it should have a nice fat torque curve and pull real well to 5800 rpm or so. 


Here are some engine combos with dyno numbers/CFM @ peak HP to illustrate ;

(1) 446 E-head > 535hp/540tq with 830cfm dp'er = 760cfm
(2) 493 E-head > 563hp/592tq with 850cfm dp'er = 785cfm
(3) 572 Indy head > 715hp/720tq with Quickfuel1050 (4150) dp'er = 930cfm
(4) 572 Indy head > 722hp/725tq with Holley 1150 Dominator = 960cfm

The comparison between number 3 & 4 are interesting ; this is my 572 and we tried to see if the engine really wanted more carb. Despite a 100cfm increase in carb sizing, going from a 1050 (4150) to an 1150 Dominator it only made an additional 7hp even though the engine was ingesting 30cfm more air. What i learned from this was throwing more carb at it doesn't allways translate into bigger numbers....and lots of air equals a small amount of power if the engine doesn't need it. In most cases if the carb is sized appropriately going bigger will just soften up the throttle response and make the driving experience less enjoyable. 

I can say that the smaller 4150 Quickfuel 1050 was waaaay more responsive than the Dominator. Smaller venturies mean increased airspeed and sharper throttle respone.....allways has, allways will ! 

I'm not even sure that 7hp would even show up on the timeslip at 4100lb raceweight and there was no way i was going to trade off a razor sharp throttle to find out. 



Ron

[Cooter]

Got me curious now....I think I will Dyno this thing just to see how far off my "Home porting" was from 450 HP....Was hoping for around 500 HP/500 torque, but alas, I am running A/C on this thing.

I haven't paid for Dyno time in over 15 years. I think I will shoot the moon on this one and see what happens. Again, Thanks Ron for helpin' an 'ol redneck try and get his Challenger running.

[firefighter3931]

You're welcome Cooter. 

That 450hp number was just a ballpark without knowing the actual flow numbers on your heads. If they flow really good that combo could make 500hp....it has all the required parts in place. The only "unknown" is the cylinder head flow at this point. 


Ron