Which Carb for my set up

[73Runner4spd]

Hey guys, its getting nicer up here in the northeast so I figured I would put some coin into my old bird. I am in the process of rebuilding a set of 3.91's to replace my 3.55's. I would also like to pick a different carb with the advice of you guys. My set up is a stock bottom end 73 400 with steel crank a set of 915 heads and the 284 484 purple cam. It has a dual plane intake on it currently, however I do have a single plane torquer that I just powder coated for myself. On top currently is an edelbrock 1407 750. I am wondering if switching to a pro form, demon, or holley would benefit me in any way. I was looking at the holley 4150, a speed demon 750, and a proform 67200. All 750s. Im just not sure if any of these would give me better performance over the edelbrock with my current cam and rear end. This is in a 73 b body 4 speed car with soon to be 3.91's. Also once I get the brackets and pulleys to delete my a/c I may decide to put a different cam in it, maybe one of the hughes whiplash cams as I feel that my current cam bleeds off too much cylinder pressure on an already low compression engine. The specs are .229-.242 .518 .518 at 107 lsa.

 

[rumblefish360]

IMO, the draw back of the Edelbrock AFB carb is the weighted air door bog when you wack the go pedal. After that, the other Holley and Holley based carbs redone by companies do have a edge. It is also a disappointment of the AFB's is that there is no models out that can deliver a pump shot to the secondary side. It is possible to add one though.

This is where I like the AVS style carb better. You may even like the 650 AVS better than the AFB 750 on that stock low compression bottom end.

IMO, if top of the line performance and every last bit of HP is wanted or needed, the Holley carb or Holley based carb should be looked into. It's just up to you to decide if that is level of performance you want and you must be able to justify the cost of the swap for what amount to probably just a few HP that you may not ever feel.

On the intake, what dual plane intake so you have now?
Again, IMO, if you have a RPM up top, keep it. The single plane will loose you enough torque to notice and without any real gain of HP over the dual plane RPM.
One more time, IMO, the whiplash cam In The low compression engine and a 650 AVS is a winner. Your not going to need a big carb on top.

I'm also running a low compression 400 in a '79 Dodge Magnum. I've tried a 600 AFB, 750 AFB and I ended up with a large TQ on top of a Holley Street Dominator. (The only intake I have for a big block)

 

[RustyRatRod]

You said wack.

 

[rumblefish360]

LOL, yea, I did because " I wacked it!"

 

[73Runner4spd]

So rumble you would recommend a 650 avs style carb, along with thee whiplash cam? I will be building a more stout variation of a 400 or 383 in the near future. Just want to get the most potential out of what I have right now. Plus its nice being able to pull up to any pump lol. So with the intent of building a stout engine I was thinking a 750 that I can swap when I finish the other motor, will the power gain from the whiplash and an avs style carb even justify the cost?

 

[Budnicks]

cubic inches X peak RPM, divide by 3456 = appr. CFM {400ci x 5500rpm, dived by 3456 = 636.57cfm}... I personally like any Quickfuel, Proform, Pro Maxx, AED, Holley HP or most any 4150-4165 type Carb {even some 4160} over an Edelbrock RPM/AFB "Weber" knock off {Edelbrock does make some great products}, I will choose the Holley type carburetor every-time, unless a rule says differently & mandates a different carburetor, Holley/Quickfuel for all around performance applications... some guys swear by the Edelbrock's, I'm not one of those people, they are fine for mild street performance, or multip[le carburetor application & have their place, in racing or street use... but the Holley based carburetors are far better in my opinion.... There are a bunch of threads all over the www, that are about tuning issues with the Edelbrock's, just do your research, before you buy.... I have a #1411 Edelbrock 750cfm w/electric choke, I'll sell you dirt cheap...LOL... buy a book or CD/DVD on how to tune a Carburetor of choice no matter which style, of your choice... Make sure it's the proper size/style application for the intended usage... opinions will vary vastly I'm sure, "that's mine", track & road tested...LOL...

 

[73Runner4spd]

Thank you very much Budnicks and Rumble, Thats why I love this site. real world experiences none of this well the manufacturer claimed this bullshit. Ill go ahead and do some more research on the avs style carb and call up a few manufacturers to see what they recommend as well. Ill def buy a book and read, god carb tuners are becoming harder to find these days!

 

[Tex013]

best bang for buck is to fit a proform.i have fitted several and always been happy with the result.
your cubic inches in my opinion put you on the tipping point of 750 or 850 but engine build and result will choose which one. low comp small cam,current motor, 750 with either manifold - easy enough to swap out. if going closer to 10:1 comp with a better cam and wanting the most bang go to a 850 with a single plane manifold.

Tex

 

[MikeyT]

750 3310 series Holley vacuum secondary carb would be an awesome carb for that set up.

Mike

 

[73Runner4spd]

Howcome vacuum over mech?

 

[MikeyT]

73runner,

For me it comes down to driveability. I like the vaccuum due to ease of dialing in the 3310 verses a 750 DP. However, if you are looking to do a little track time. i don't think you could go wrong with a 750 DP either.

Mike

 

[rumblefish360]

will the power gain from the whiplash and an avs style carb even justify the cost?

This is up to you to figure out for yourself.
Some people think spending $2000 on a set of heads is a great thing to install on a stock engine.
And that is the only real big deal upgrade.
I've seen this before and it's not a pull on another thread I'm in. Just a FYI so there is no confusion.

Anyway, that was my opinion for the build now considering the low compression engine.
If you feel that getting a 750 now, for a build you'll do later, but can use now is a thing you wanna do, go for it.

I, myself, did not like the 750 on top of my '78-400 with a Holley Street Dominator and the 727 & 3.55 gears on a 245/60/15 tire.
I did like the 600 better and love the TQ and still run it.

 

[oldbee]

MikeyT has it right. Double-pumpers are great for the track, but too much for the average street motor. 750-780 cfm should be just about right. I love AVS's & Holley's.. In my experience the Carter's are a little more dirt tolerant. Street motor---vacuum secondaries......

 

[73Runner4spd]

Thank you guys a lot. I just found a demon 750 with vacuum sec. 2500 miles for 175$ worth it?

 

[67steve]

toilet bowl an alky

 

[73Runner4spd]

67 For me, the sequence is usually alcohol then toilet bowl...wait we're talking about carbs, nevermind... heh heh

 

[747mopar]

I had a 750 Demon on my last car and loved it "great carb", they are basically a Holley with billet aluminum instead of cast lessoning the chances of casting flaws. I did a lot of research when purchasing my carb and found that a vac sec is recommended for heavier car 3,200lb+ if I remember correctly, reason being when you mash the gas in a heavy car the motor can't accelerate quick enough to use all of the fuel being dumped in by the double pumpers. I'm sure you could dial it in to make it work but that's what they recommend. I used the same formula as Bud posted and like the Demon's and Holleys, never used a Proform and never had much luck with the Edelbrocks. Also I just wanted to mention that I just read a intake dyno shutout (mopar muscle) where the torker really supprised me, it beat out the others finishing a close second in hp and dominated in torque. Good luck

 

[73Runner4spd]

Actually just found a 750 speed demon electric stroke, vacuum secondaries for 200 bucks. I think I'm going to go check it out tomorrow!

 

[747mopar]

Actually just found a 750 speed demon electric stroke, vacuum secondaries for 200 bucks. I think I'm going to go check it out tomorrow!

That's what I had, a Speed Demon. 0 problems, the only thing I didn't like was no choke so it took two people to start the car when cold (one to start and the other holding their hand over the carb). They sell choke kits for them.

 

[73Runner4spd]

Yeah the guy said he added the choke kit. What is your engine set up? I think it may be a little too much for my current set up. Im running an edelbrock 1407 It isn't to snappy though