i am running a edelbrock 600 cfm carb right now. a few of my freinds have some holly 650's and one has a 650 demon.

my quesiton is would going to a demon or holley be better for performance? also what is the difference in performance on a vac secodary vs a mech secondaries carb?

thanks.

 

yes a 650 holley double pumper would be a more ideal choice for performance

 

would a mech secondaires give a better throttle response than a vac secondaries. i was thinking of getting a new carb to work on my 400 but still work ok on my 350 untill the 400 is ready to go. i was thinking a 750 or 650 but don't know.

 

WIth a manual trans, you will feel a big difference w/ a double pumper, vs a vac sec. Go with the DP. A 750 DP would be the cat's ***.

 

Mechanical secondaries is a mechanical linkage that opens the secondaries. As soon as you get in it, the secondaries are opening. With vac secondaries, vacuum pulls the secondaries open. You will get better mpg with vac secondaries. As stated, if you have a manual transmission, you'll probably want to run a mechanical secondary carb. As for Holley vs Demon, it all depends. Some motors will make more power with either or. As for size, you should post up your motor combo.

 

demon = overpriced poor quality control

holley = good quality control, ok price

 

I don't know xpndbl, old Holley stuff was well made. I have heard lots of complaints about their new stuff. I bought one of the "chrome" looking 750 Holley DP's 2 or so years ago and it never ran right. The squirter was so loose out of the box that fuel was squeezing past it and making a mess.

 

Holley's need some tuning but are a very popular choice by racers, or at least that's what I see a lot of at the track. I'd go Holley.

 

Holleys are simple and very durable for lots of tear-downs. They definitely get the worst gas mileage of the bunch.

 

demons come with free aluminum shavings in all the passages that you get to clean out.

 

ok thanks for the info. that is what i wanted to know . i don't drive the car very far distances so mpg is not huge but it is a factor i am getting about 15 or so with the edelbrock 600 on a mild 350.

my motor i am getting ready to put in is a 400 4bolt, balanced, 11:1 forged pistons,, stock heads ported and polished.i have not bought a cam for it yet but i am lookin at voodoo cut cams. torker jr intake. wih a little nos.


so i am figureing on a 750 but don't know.

 

Stock what heads? Stock 400 heads aren't worth painting, let alone porting.

Torker Jr.? Not sure I've heard of that. There is a Torker, Torker II, and Victor Jr. The Torker is okay, but not much of a street intake. The Victor Jr. is a good piece but pretty much race-only. The Torker II is junk.

 

vic jr. sorry

what heads would be good for this motor then. i have most of the short block done but have not done the heads yet. i figured they would have been alright with porting and polishing. maybe 202 160's

 

anything aftermarket, check out the dart iron eagle platinums in the 200-215cc range depending on your cam and how big you want to go.

 

You running flat top pistons?

You should look at a carb between 650 and 750 cfm.

400's are great. On my 400 I'm running dished pistons with untouched vortec heads (it's the build described below, minus the carb and roller rockers). So far I've ran a 13.4 in the quarter but I think this thing will go 12's on the motor (once I get roller rockers and a better carb).

Chevy high performance did a build on 400 with dished pistons, vortec heads, roller rockers, 750 Holley DP, a lunati cam (230 duration .480 lift) and an air gap intake. And you could even run 91 octane. None the less they made 430 hp and 525 ft lbs on the engine dyno. Not bad for stock heads.