What cfm carb and gears should I use?

[unapez]

I have a 72 Dodge Dart Swinger... I just dropped in a freshly rebuilt 360, bored .040" over, lunati bracket racing cam and matched lifters, edelbrock ld4b intake manifold, Hedman Long Tube Headers, Electronic Ignition, etc. Stock valves 1.88"/1.60". Also installed a 2800 stall converter, I have 3.23 gears and suregrip 8 3/4" rear. I have a 600 cfm edelbrock #1405, but this engine seems to feel like it does not give it full gusto WOT from the line, no squealing tires except from 1-2 gear and 2-3. I plan to change the rear end gear, so I get the tires going, but it seems I would have more power from this engine... Should I be using a 750 cfm carb? Also I want to drive this to cruise-ins and yet still kick some tail at the dragstrip, what gear do you all recommend? I was thinking 3.73... Thanks guys!

 

[rumblefish360]

I have a 72 Dodge Dart Swinger... I just dropped in a freshly rebuilt 360, bored .040" over, lunati bracket racing cam and matched lifters, edelbrock ld4b intake manifold, Hedman Long Tube Headers, Electronic Ignition, etc. Stock valves 1.88"/1.60". Also installed a 2800 stall converter, I have 3.23 gears and suregrip 8 3/4" rear. I have a 600 cfm edelbrock #1405, but this engine seems to feel like it does not give it full gusto WOT from the line, no squealing tires except from 1-2 gear and 2-3. I plan to change the rear end gear, so I get the tires going, but it seems I would have more power from this engine... Should I be using a 750 cfm carb? Also I want to drive this to cruise-ins and yet still kick some tail at the dragstrip, what gear do you all recommend? I was thinking 3.73... Thanks guys!

Your combo is out of balance and a bigger carb will hurt it in it's current state. A smaller carb lacks top end but helps low end. With the current gear ratio and intake, hold onto the 600 for now.

Your cam specs are witheld and are a vital part of whats going on. Theres also no mention of compresion ratio.
You should change out the intake since it is a 318 intake and look at a RPM/Stealth or like intake.

A 3.73 is a good gear and compromise for your description.
A 750 will more likely be fine for the engine.

 

[Johnny Dart]

Sell the ld4b and install a Edelbrock RPM or RPM Air Gap.
Go to a 750 cfm carb.
Lights Out !!!!!!!!!!!

 

[unapez]

I'm running speed pro hypers at 9.5:1.

 

[dgc333]

I have a stout 360 ~370 HP based on 1/4 trap speeds.

Anyway I have had 600, 670, 725 and 750 carbs on it. The 600 has awesome off idle and throttle response. It has a noticeable less power above 4000 rpm then the bigger carbs. The 725 and 750 had more top end than the 600 but they also had less low rpm throttle response. The 670 has all the throttle response of the 600 and all the top end of either the 725 and 750 according to my butt dyno.

If I had to chose between the 600 and 750 I would go with the 600. The 600 is so much better in the low rpms where a street car lives. If you can't burn rubber off the line with the 600 the 750 will be worse.

BTW, the only 1/4 mile times I have on my car are with the 600 where it has run a best of 13.7 @ 102 mph with a very traction limited 2.2 60' time. With a 102 mph trap speed dialing in the chassis so it will hook off the line will give me low 13's maybe a high 12.

 

[2 Darts]

That's a huge cam you're running on the street. Big cams like big compression and big gears in the back. A cam like the Bracketmaster is going to want a 10.75:1 -12.5:1 compression ratio and 4.10:1 gears or higher. Best power is going to start at 3500 rpm. Unfortunately, the stock 360 heads are going to stall out around 5500 rpm. You can get more than 5500 rpm out of the engine, but you won't be flowing more air. If you can get the air to it, the cam is probably good for up to 7000 rpm.

Without popping the heads off for a full-fledged race prep, a better combination would be a 215-224 deg duration @ .050 cam. Couple this with a 3.55 - 3.73:1 rear. Power band will be from 2000 - 4800 rpm. The 750 cfm carb with an air valve secondary would work well. Definitely put an intake on that will take advantage of the bigger ports on the heads you have.