Edelbrock vs Street Demon

[Edward Michael]

Ordering one on Monday.  
Running on the F350.
What have you say folks?

Edelbrock 1406
https://www.summitracing.com/parts/edl-1406

Street Demon 1901
https://www.summitracing.com/parts/dem-1901/overview/

1. Composite bowl option seems the most important difference.  Is it the final straw?

[Gary Lewis]

On a 460 I'd go with the Street Demon.  But, I might go with the 750 CFM version instead.  And the polymer bowl.

The 1406 is a good carb, but it doesn't have all the features of the Street Demon.  I've run one on two different 351's and it was all the carb the engine needed.  But, I don't think it would be enough for the 460.

[PetesPonies]

You certainly can run a 600CFM carburetor on a 460. You will have great atomization and thus, throttle response. Most people over carb an engine anyway. What that does is make it run lean. You may think the reverse . .but not true. When you aren't pulling enough air through the venturi to have a good vacuum signal, not enough fuel escapes from the nozzle. The unknowing think they have too much fuel, so they jet it down .  .which only compounds the problem, makes it even leaner and why they give up on that carb. It truly is an area where false information is passed on and becomes "fact".  LOL  Unless you really need as much power as possible and are building for that in every way you can, I'd stay small. The 625 would make a nice feeling, peppy, and responsive engine.

[Gary Lewis]

I agree that it is better to err on the small side.  But, one thing to check out when selecting a 4bbl carb is the air flow potential of the primaries, and not just the air flow potential of the whole carb.  After all, you'll be running on the primaries the vast majority of the time, so we really ought to compare those specifications from one carb to another.

Unfortunately the vendors don't provide us with the flow specifications on the primaries, just the whole carb.  And while we can try to deduce those specs by taking a ratio of the size of the throttle bores of the primaries vs the secondaries, that is fraught with problems since the primaries usually have better boosters/venturi than the secondaries do, and that makes them flow less percentage-wise.

So, about all that we can do is compare primary throttle bore sizes between carbs.  And the two carbs we are talking about give us an interesting example: The 600 CFM Edelbrock 1406 has larger primary throttle bores (1 7/16") than the 625 CFM Street Demon (1 3/8").  Not only that, but the Eddy has an earlier style of boosters that probably is less restrictive than the "Triple-Stack" boosters on the Street Demon.

Basically, the Street Demon is much closer in design to a Quadrajet than to an AFB/Performer.  The AFB/Performer is a "squarebore" carb, meaning the primaries and secondaries are roughly the same size, while the Q-Jet is a "spreadbore" carb, meaning the primaries are much smaller than the secondaries.  In my opinion, an equally-sized spreadbore carb will give better economy and part-throttle driveability than a squarebore due to the smaller primaries.  And, you can usually get similar economy and part-throttle driveability on a larger spreadbore as compared to a squarebore.

[85lebaront2]

One thing, the Q-jet primaries, other than the SD455 Pontiac ones, flowed roughly 260 cfm, so they are small. Too much cam, or too large an engine, and you were pulling fuel from the main nozzles at or a little off idle, Cadillacs with the 472 and 500 engines were a nightmare to get right, particularly if the engine was a bit weak, they would dribble from the main nozzles and run pig rich.

[Gary Lewis]

I thought that there was a Buick 800 CFM Q-Jet that might have had the larger primaries like the SuperDuty one?

But my ‘72 390 wasn’t too big. That Q-Jet provided more power and economy than the 2100 did.