750 cfm for 340?

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69 Valiant Kid

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as ive been reading other threads, im wondering about my choice in carb. im thinking holy 750 double pumper jetted down for my 340-350 hp 340. any comments or thoughts?
 
Yes, it can be set up to work quite well. Especially with tall gears, and good heads,cam,and headers. I used one with a single plane intake, and had good luck. My current engine(340) uses a 670 Street Avenger, and it works even better than the 750. The old spreadbore Carters were rated at, what, 850 or thereabouts? I think being a double pumper should help you out.
 
750 is ok especially if your running 3.91s or lower or a 4 speed. For auto cars with 323s or 355s and an auto I would stay with a 650 Vac secondary.
 
Any engine performance parts added on?
 
mild cam and head work done. little bit bigger valves and ports opened up a little. bought the motor and trans for $1200. only has 3-3500 miles on it but its been sitting for 3 years. im a chrysler mechanic, so i just dumped 1 grand at the parts counter today. good thing is a i can put like 5 gran on my account there! the guy i bought it from was thinking 340-350 hp. ill take some pics of this trans. the case looks brand new. scary.
 
today i ordered, kickdown cable, black wrinkle cast aluminum valve covers and gaskets, intake manifold and gaskets, blue engine paint, intake bolts, bolts for water pump, thermostat housing, thermostat and gasket, mechanical high flow fuel pump, cast iron cleaner system, electronic igniton system including distributor, reistor, ecu and wiring, high performance street ignition coil and lightweight starter.
 
Get a Holley Street Avenger 670 cfm. From the description of your engine mods, a 750 double pumper will be overkill.
 
I recently had some head work done and got the compression on my 273 that has been bored over .060 up to 9:1 compression. BJR racing did the math and came up with CFM that I need and it was 622 CFM. The formula is what NHRA uses. Now considering you have a bigger motor (more air) I would go with the 750 flat out and see how it does.
 
right on, thanks guys...any of you used the /6 to v8 motor mounts from schum? im hearing no fabrication and then hearing some fabrication. seems that in rumblefishes thread he had some fab work...?
 
69 Valiant Kid said:
right on, thanks guys...any of you used the /6 to v8 motor mounts from schum? im hearing no fabrication and then hearing some fabrication. seems that in rumblefishes thread he had some fab work...?
Click to expand...

Get the Trans Dapt mount from Summit Racing. Sam e as the Schumacher but half the price. Used them in my Scamp.
 
My Duster needed a minor amount of fab because it has the spool mounts. If your car does not have the spool mounts but the sandwich type buscuits, do what Adam told you and save big.

Other than that, the drive shaft needed to be shortened.
cast iron cleaner system,
Click to expand...
Whats that?
Other than a very general description of the engine works, I'd have to error on the side of caution.
Knowing the intent of the engine/cars build or some of the more important specs, I'd go 650 vacuum secondary carb.

The problem is the discription is soooo general, it still could be any thing or nothing.

What size is the cam, the compresion ratio, kind of intake, headers, exhaust size, stall converter? and speed of stall, rear gears, and intent of useage of the car.
 
I have a 340 with a 650 Mighty Demon and it works awesome. FBO worked some magic on it too. 750 would work but would be overkill with your mild setup. Don't make the mistake of going too big. You'll be happier with something smaller.
 
Rob, Its the cast aluminum air cleaner that matches the valve covers. That thing is heavy, LOL
 
Agreed with all above

FYI I have a 360 that had a 830 Annular (got Free) 13.2 went and got a 750DP and dropped to 12.7 @ 109mph thinking might go to a 650 now

Too big is no good

Cheers
 
I just when through this last summer and the 750cfm just seems to be a little to much carb for a 340 or 360 street engine. I ended up with a 650 and it works great!
 
69 Valiant Kid said:
jetted down tho?
Click to expand...

Jetting doesn't have that much to do with the horsepower level of an engine. In other words, a lower HP engine won't necessarily need smaller jets than a higher HP engine. It boils down to a combination of overall efficiency - cam, airflow, intake, etc. A single plane intake will likely need more jet than a dual plane and a big cam will likely need more jet than a small one. But every combo is different and will likely need more changes in the accellerator pump squirters and pump cams.

A 750 double pumper will be harder to tune than a 750 vacuum carb, especially the pump cam & squirters. But a DP can be faster, "IF" you get it right, by as much as a tenth. The milder the combo, the harder to tune. But either way, jet for mph and tune squirters and pump cams for 60' times. Of course, the vacuum secondaries can affect both.

I think a 750 vacuum or smaller will work best for your combo and provide the least amount of headaches, as well as a good dual plane intake, like an Eddie RPM, LD 340 or Weiand Stealth. A 4-hole spacer would also be worthwhile to try.

If your budget will allow it, consider TTI headers. Best fit, easiest installation and great performance.

www.ttiexhaust

http://www.moparmusclemagazine.com/techarticles/155_0307_mopar_crate_engine_exhaust/index.html
 
AdamR said:
Rob, Its the cast aluminum air cleaner that matches the valve covers. That thing is heavy, LOL
Click to expand...

LOL, He said cast iron though.

I looked into his profile and clicked the garage. He has a street master on top of the engine. Still need some info. Good lookin car for a starter Mopar. And being a Chrysler Mech. with a book of goodies to put on a account. Sweeeeeeeeeet
 
the intake manifold sitting on my eng right now is THE COMPLETELY WRONG intake manifold for it. it came with it. was not used on it. i was just taking pictures for the id for my heads. anywho, the old car situation is a little different than working on new, injected cars, as most of you i assume know. with that being said, thanks for the comments. and im still not sure what im going to do. it has a 2200 stall converter. and i didnt say jetting had to do with hp's...what i was getting at was too much fuel and obviously it will burn too rich, and run like poo....what i heard for the 340 hp on my eng was that he used a 750 jetted low. the guy that told me this has a 62 dart wagon with 1000hp. id like to think he knows what hes talking about.
 
CAST AIR CLEANER SYSTEM, im reading it right from the list dude, grab your parts catalog pn 00pm4633 if you need help.
 
FWIW, I have had Holley 600, 670 and 750 plus a BG 725 on my 360. The 600 had awesome low mid rpm throttle response but gave up some power above 4500 rpm to the 725 or 750. The 670 Street Avenger has the same throttle response as the 600 but my butt dyno does not feel any difference on the top end compared to the 725 or 750. The Holley 750 worked ok but it gave up 5mpg on fuel efficiency to the 670. The BG 725 just plane didn't work well at all below 2000 rpm. I spent a whole summer trying to sort it out. Also, BG's tech line was useless.

IMHO, the 670 Street Avenger would be a perfect choice. Also, you can't compare the cfm rating of the TQ that came on the engine, the primaries of that spreadbore are tiny which gave it it's great throttle response and the air door on the secondaries would never fully open on a stock engine so it was really acting like a much smaller carb.
 
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