Carb Choice - Help wanted

[mikey]

Awaiting shipment of my Mowtown 415 and need to choose a carb. Many are advising of the Edelbrock over here, but I am a great lover of the Holley.

I am interested in the Barry Grant Speed Demon - anybody got any experience of this unit - is it better than the standard Holley.

Also I had assumed with the 415 cu in block and Edelbrock Victor Junior Heads/Performer RPM Hydraulic Roller cam I would have needed around an 800cfm carb - not so according to the Barry Grant Web site. Any opinion on this as they advise that a 750cfm should suffice. I would prefer higher intake flow if delivery is sufficient.

The other thing is they only do mechanical secondaries without the electri choke and I believe the vac secondaries set up is better for the road due to wash down etc - am I right in thinking this. I dont want to run a choke set up so does anybody know if its an easy job or not to simply take the electric choke off the unit.

I always find your help invaluable and I would be grateful if you could once again help me with my queries.

Hope you are all well out there - hope to come over in the near future to meet up with some of you.
Mike.

[MidOHasp]

I'm currently running the BG Speed Demon 750 (double pumper) on my 408.

I'm running a decently stout cam (.576/.580 I/E lift), 10.25:1 compression, AFR 185cc heads, and an RPM Air-Gap intake (built this one for torque. Would've used Vic Jr, 205AFR's and a little bigger cam for HP).

The BG S/D 750 D/P is just enough carb. We went up a couple jet sizes and put in a bigger power valve on the dyno...not a ton of difference. 508HP, 544TQ at flywheel.

Tony, the guy who dyno'd my motor, hates the BG carbs. Said he'd put a Holley 750DP up against it ANY day and gain 40HP. But he also expected us to come in about 40HP shy of where we did. He said that every now and then you'll get a good BG carb, but they are inconsistent and he would never use one on an engine he personally built. FWIW.

I like it, it runs well, and it looks good, too. You should be fine with the Holley or BG 750. That's most likely enough CFM unless you are going to run 7000RPM, which I would NOT recommend with your setup. Your engine will likely make less HP at 6K than it will at 5500, but will still make good HP to 6000-6300 probably.

Just my $.02

[mikey]

A good $.02 worth - thanks for that. One of the things I like about the Barry grant is the ability to fine tune the idle metering. I had to mess about with drilling holes in my last set up - trial and error you know.

Cheers
Mike.

[Mr.Fixit]

I prefer Holley's over the BG's. Either of them over an Edelbrock.

It is a piece of cake to remove any choke off a Holley. If it has vacuum secondaries there is one screw hole you will need to plug with epoxy however (not necessary on a mechanical secondary Holley)

On the 500+ hp winsors I used to deal with, they got a little more top end out of an 850 holley Dp compared to the 750, but the 750 is better suited to driving the car on the street. The difference between the two wasn't really great either way, just trade a tiny bit on the low end for a tiny bit on the top end.

[Bruce Robles]

mikey-
You've just gotten the straight scoop on the carbs. Forget the Edlebrock. It's nothing but a 1960's Carter AFB with a chrome housing and a different name on it. A real pain to work on, and you can easily drop one of the springloaded screws that hold down the metering neddles, in the carb while your trying to get it apart, or putting it back together after changing jets and metering needles. The plunger in the accelerator pump will shrink and not work if the car isn't used for a while.

[need4speed]

I have the BG Mighty Demon 750 on my ZZ430 and have been extremly pleased with it so far. Very tunable and absolutely no problems since initial startup of the engine. In fact I used it set as-is right out of the box and it fired right away, requiring only minor idle and mixture adjustments. There is no choke to remove and according to Chuck Beck it produces about an additional 30HP on the top end over a similar Holley model. I can't say that this is a definite fact since I have never seen any real data but Chuck does know a thing or three about this topic since he has been building race cars for over 40 years, including one of the GT40's as part of Shelby's team back in the 60's.

That said, I think that either the 750 cfm Demon or Holley will work equally well and they both can be enhanced quite a bit more if necessary. The Vac secondaries are really not necessary in such a light car with that much power. In the case of the Mighty Demon DP, it comes with a progressive secondary linkage to tame it down a bit but this can be changed to a 1:1 linkage to really give it some juice.

[trularin]

Take the the cubic inch of the engine and multiply that times the the maximum RPM you intend to turn. Then, divide that number by 3456. Add 10% and you should have the size of the carb you should be shopping for ( find the model that fits ).

Personally, Holley is a great choice and you can get parts anywhere in the world.

Just my $0.02

[mikey]

Thanks Guys as always you have really helped me.
Mike.

[Spoony]

I have had problems with BG Street Demon carbs. I have only 550 miles on my SPF and I have had "2" defective Carbs. I am trying one more Demon - BG Mighty Demon, so far I like it a lot, much better than the street demons. But lets see if it lasts.