Carb decision: airhorn or no airhorn?

[jgkurz]

I need to make a decision on my carbs for my new stroker 427. I was planning to use a set of Holley BC/BD carbs but for a several reasons I may change direction. The aircleaner I need to run for hood clearance is the 2x4 Cobra style with a KnN 1.8" oval element. It looks great but the element size is horsepower limiting to say the least. I wanted to use my BC/BD carbs so I had a choke and because they run well if setup properly. My car will be used for street driving mostly. I will drag race a few times a year but not with the Cobra air cleaner. That is just for the steet and car shows. 

1) Considering my limited air cleaner, would carbs with no airhorns help? I know I'd lose the choke capability but would there also be a noticeable horsepower benefit? It seems logical that I would get more power by using carbs with no airhorns but my aircleaner may null the potential gain. The vent on the BC/BD carbs is very close to the top of the aircleaner assembly which is also an issue. I'm concerned it may create a vacuum across the vents. I believe newer Quick Fuel carbs won't have this issue.

2) How painful is it to NOT have a choke? I know that building a big power engine with a choke somewhat defeats the purpose. Am I over thinking this and it's really not that big of a deal to warm up the engine without a choke?

[Drew Pojedinec]

I don't use a choke on anything.  When possible the air horn is milled off as well.

Can't say I miss them.  Seems like my vehicle runs rough and I need to fire it up at 1200 rpms for 30 seconds once a day, after that they start and idle just fine.

[Lenz]

X2 on the no choke, I just fire up and feather it for a minute or so, just like living in the late 60's when everything you started needed a minute or two of attention immediately after cold fire up.

[jgkurz]

Thanks guys. That's the perspective I needed.

[plovett]

x3 on no choke.  I have a Holley 850 with no choke on my 428 and it'll start in single digit temps.  I have to tap the gas pedal for a bit and then hold it down to keep the revs up for couple of minutes before it will idle on it's own.  No big deal.  With limited air cleaner height I think taking the choke horn off makes sense.

JMO,

paulie

[cammerfe]

I gave up on using carbs more than 20 years ago---right after my first experiences with Holley EFI on my own 390 in my '63 F-100 ICB and a pair of much the same units on Brother Lon's 427 '67 Mustang. There is no comparison between the street manners and general driveability. With that said, I believe that there is no advantage to the removal of chokes/chokehorns in regard to flow UNTIL one gets to the far outer reaches of demand. For your purposes, I agree with the comments above. Air cleaner obstruction is all you need to pay attention to. JMO

KS

[jgkurz]

I gave up on using carbs more than 20 years ago---right after my first experiences with Holley EFI on my own 390 in my '63 F-100 ICB and a pair of much the same units on Brother Lon's 427 '67 Mustang. There is no comparison between the street manners and general driveability. With that said, I believe that there is no advantage to the removal of chokes/chokehorns in regard to flow UNTIL one gets to the far outer reaches of demand. For your purposes, I agree with the comments above. Air cleaner obstruction is all you need to pay attention to. JMO

KS

KS, I'm a  EFI guy too but I wanted old school carbs for this project. I have a 2x4 setup so I think that means I'd need a custom programmable EFI vs a bolt on Holley EFI or FAST.

[My427stang]

I don't think the choke issue, if compared to a manual choke will be too bad, just need to let it warm up before you go.

As far as the horn, if the horn is too close to the lid it will help airflow, but having air turn a corner right over the booster isn't the greatest for metering either.

The oval air cleaners with a stock height filter are pretty bad, its a 90 degree turn right at the carb.  Any way you can give that air time to turn, the better.  Another option may be to cut the choke horn, but not all the way to the base, or if there is a way to make room, run a taller filter element

Also make sure there is room for the bowl vents, some Holleys have some pretty tall vent tubes an they need some airflow too, although not a lot.  It's also best to keep them up above the entrance to stop pullover/slosh, especially during launch and braking

[GJCAT427]

Last spring at Beaver Springs I ran my stock 63 427 galaxie  a bunch of times. We noticed a bog at the lites at 5500, checked it out and found the air element sucking in. Quick fix was to run with out the air cleaner after talking to Larry (Battlestar Glactic) made a big difference on the takeoff but we still had problems (tires and a slipping clutch). Next yr I hope to resolve the tires and freshen the clutch. On the street the motor never sees WOT more than a few seconds and I don`t fell the bogging effect that dragging does. As far as startup I have yet to use the choke but it does run rough for a few minutes do to the blocked crossovers. About 5 minutes it levels off and runs just fine.

[Falcon67]

Don't have a choke on anything here.  Not a problem with occasional use cars IMHO.  On the tunnel ram project for the 302, I wired the choke plates on the Edelbrocks open to make sure there was no interference.  Good size cam and cold motor means you'll have to nurse it a few minutes, it's a personal thing IMHO whether it's a problem for you or not. 

[cammerfe]

I gave up on using carbs more than 20 years ago---right after my first experiences with Holley EFI on my own 390 in my '63 F-100 ICB and a pair of much the same units on Brother Lon's 427 '67 Mustang. There is no comparison between the street manners and general driveability. With that said, I believe that there is no advantage to the removal of chokes/chokehorns in regard to flow UNTIL one gets to the far outer reaches of demand. For your purposes, I agree with the comments above. Air cleaner obstruction is all you need to pay attention to. JMO

KS

KS, I'm a  EFI guy too but I wanted old school carbs for this project. I have a 2x4 setup so I think that means I'd need a custom programmable EFI vs a bolt on Holley EFI or FAST.

We did a bunch of CNC-ing to create a custom oval aircleaner and so-on for the dual set-up on Brother Lon's Mustang. But we were trying to subtly call attention to what was, at that time, the only Holley EFI/dual installation in existence. But unless you were looking for it the throttle bodies hide under the aircleaner and aren't at all obtrusive. Drivability is VERY MUCH better with the EFI. We used a pair of the 900 CFM units but to have things work seamlessly we swapped to a set of smaller injectors, since the ones that came with the kits were, in dual use, outside of the adjustment range of the controllers.

KS

[Falcon67]

I would add that - just for me - I'm not going to mill the airhorn off the two 1850s I plan to test on the 351C tunnel ram until I'm satisfied with the performance.  If it turns out I don't like how they work, I can put the choke plate back in and re-sell at least one.  If I like 'em, they will lose the air horns.  Having said that, it's not like 1850s aren't a dime a dozen and I haven't actually looked at how they will affect air flowing into the Hilborn-lookalike scoop.