Hot 318, carb choices.

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frosty_the_punk

frosty_the_punk

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Need some advice on which VAC SEC carburetor to run on my stout little 318.

specs are as follows

1967 Aussie VC valiant. (same as USA's 1966 valiant)
318 + 0.030" (323ci)
10.39:1 CR (KB399 pistons)
915 "J" Heads with minor bowl work
2.02/1.6 Valves
Comp Hyd Thumpr cam (227/241 @ .050")
Cast exh manifolds. Twin 2" pipes for the time being.
Edelbrock Performer RPM Dual plane.

Standard factory rods
340 steel crankshaft, full blueprint and balance on rotating assembly.

904TF with 3000-3500 Stall
3.7:1 final drive gears. 25 inch tires.

It's a street car 95% of the time, but I'm taking it drag racing in December and I believe the car should be cabable of mid-low 13's if I get the tune right. (I'm guessing)

It currently runs a 500cfm Edelbrock thunder AVS and seems to be rich all the time. I had this leftover from a previous 318 which was a standard high mileage engine.

With the 500 AVS it falls flat on it's face from idle til about 2000 rpm and probably isn't performing to it's potential up high in the RPM either.

If I'm going to spend time tuning a carburetor, I want it to be the right size for the application

I've been recommended the 750 Holley as well as the 650 Speed Demon.

There seem to be countless options out there.

I'd like to get some recommendations based on personal experience with a similar engine. no brand name fanboys please.

Thanks in advance, Frosty.
 
95% street?!?! 650 CFM

A speed demon is a copy of the Holley design. Unless it is that brand spanking new one. That is like a AVS/TQ hybred. IDK how that one is.

IMO, be it a Edelbrock or Holley, you have to be OK with the manufacturer/style of carb. But a 650cfm is what would work best for the street.

Just a side note, the exhaust is to small.
 
I have to ask why you think his exhaust is too small? the rule of thumb is 1 in per 100 horsepower. So with two 2 in exhaust pipes he should be good to about 400 HP. I have 2 in exhaust on my dart with a 340 in it and it works just fine.
 
Rumblefish, This is the link to the Demon carb i have just recently been looking at. http://www.demoncarbs.com/1282010VE.asp

I have access to an experienced tuner who prefers holley carbs. would that most likely mean a Demon is fine for his expertise?



1968dartman, That theory of 100hp per inch is interesting but seems inherently flawed in that a single 3" diameter circle has more area than a pair of 2" diameter circles combined.

I plan to put extractors (or headers) early next year. I may go for 2-1/4 inch pipes at that stage. but fitting them on a 1966 is a fair PITA job and I want to spend a little time enjoying my new motor first lol.
 
just food for thought i have a 625 demon on my 273...bought it in 07 runs good but the adjustment screw's for some reason just "free float"no resistance ...its hard to dail in...

anyhow not to steal you thread but i also have a "hot" 318 going...so im interested to see which one you choose..im leaning towards a holly myself...318 .40 over zero decked,eddy heads,eddy air gap,prw adjustable rockers,lunati cam 243/251 @50 might go with a 235/243 @50 because my piston to valve clearance might not work
 
If your 500 is rich,your not going to like a 750.
Sounds like someone has the 500 way out of wack.
Your car should run good with a 600-650 cfm carb.
You just need to decide which brand to go with.
I've had good luck with Ede carbs. My choice would be a Ede 600
for that hot little teen.
 
IMO, this is one of the best bang for the buck carbs out there. All screw-in air bleeds, screw-in idle feeds and pvcr's, secondary metering plate with changeable jets, and the vacuum canister is adjustable to tailor the opening of the secondaries. If your buddy is a Holley guy he'll have no problem with this one. You can use Holley jets, air bleeds, power valves, etc. The only difference are the block and bowl gaskets. I've used standard Holley gaskets on mine with no problem (gotta stretch it a bit), so they can be used in a pinch. I just put one of these on a car my buddy owns and it's a dang nice carb for 300 bucks.

http://www.summitracing.com/parts/QFT-SL-750-VS/

http://www.quickfueltechnology.com/carburetors-slayer-series


Also, vacuum secondary carbs tend to "size" themselves to the motor, so I don't think it's too big.
 
I've been waiting for one of these threads to come up as well. For a hot street 318 like was mentioned, what do you guys think of the new Holley Ultra HP carbs? I have my eye on this one...The vacuum secondary electric choke unit is 670 CFM not the recommended 650...

http://www.summitracing.com/parts/HLY-0-86670HB/

And how would this carb perform on the OP's hot 318?
 
Anyone had experience with the Edelbrock's 650 thunder AVS on a 318/340?
 
mopardude318 said:
I've been waiting for one of these threads to come up as well. For a hot street 318 like was mentioned, what do you guys think of the new Holley Ultra HP carbs? I have my eye on this one...The vacuum secondary electric choke unit is 670 CFM not the recommended 650...

http://www.summitracing.com/parts/HLY-0-86670HB/

And how would this carb perform on the OP's hot 318?
Click to expand...
$548 is a bit pricey IMO. I'd run the AVS style Edlbrock. It'll perform just like the AFB except the secondary is tuneable which gets rid of the dead spot on sudden W.O.T. Application.

Frosty, I have yet to own the Edelbrock AVS style carb. I have always has a good AVS on hand to run and there WAY better than a AFB, IMO.
 
The best carb on my 318 was a 9379 750. Put it on, turn a few screws.
 
Your likely going to get a lot of opinions here, but for what it's worth though... I have run quite a few hollies in the past and I've always had great luck out of them. East to work on and adjust. They hold a tune quite well. Aesthetically they just look better to me.

My buddy prefers edelbrock for some reason and he seems to have more issues out of them more often than I do. Could be him though. He's not a patient enough guy to stick with it and get it right lol
 
Thanks guys, I have decided on an AVS 650 because I believe they might be the least complicated to tune myself.

Time will tell how it goes on my combo.
 
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