Too much carb?

-
71Duster

71Duster

Well-Known Member
Joined
May 22, 2004
Messages
915
Reaction score
14
Location
Alberta Canada
I've fought with the same issues from day one with my 650 speed demon mech secondary carb. Great mid and high rpm throttle respone and power and poor bottom end.

This car most days wont even do a brake stand. The carb has even been tuned on a gas analyzer and otherwise runs great. I am thinking I should go with vacuum secondaries but the engine shop insits the mechanicals are the way to go.

Am I missing somthing obvious here? Below are the car's specs.

Specs: 1971 Plymouth Duster 340

650 Speed Demon mechanical secondaries, on an edelbrock rpm intake

Stock J Heads 2.02 intake 1.60 exhaust and Crane Gold 1.5 ratio rocker arms.

3.55 gears and a 727 with 3000 stall from SMR, stage 2 shift kit from transgo.

It runs a Hughes cam #heh2328al

111deg lobe seperation/installed centerline 108deg
intake lift .506/ exhaust .524
[email protected] Intake223deg/ Exhaust 228deg

Engine is .060 over with Keith Black Hypereutectic pistons on stock rods and a stock forged crank.

Ignition is an FBO box
 
No, not to much carb. 1 of 2 things come to mind right away.

Not enuff/incorrect timing

Carb opens up to much to quick.

if your tires are large, this can be an issue as well.
 
Swap out to a stock 3310 750 and that sumbitch will run like a ****.
 
Tires are just BFG Radial T/A's 255/60/15 big but not massive.

Distributor was curved by a good mopar tuner with 18deg initial and all in @ 34deg by 2500rpm I think.

The engine shop wants to check the distributor as well so I'm gonna let them sync it up.

I've never played with the factory pump cam on the demon not sure how to go about it.

The other odd and recently noticed issue is going from light throttle cruise to an emergency brake apply the car will stall.
 
Timing needs to be all in by 2000.
 
71Duster said:
The other odd and recently noticed issue is going from light throttle cruise to an emergency brake apply the car will stall.
Click to expand...

Say what now? Float level is low.
 
mullinax95 said:
automatic trans = vacuum secondaries

manual trans = mechanical secondaries
Click to expand...


i don't know about that. the mechanical secondary proform 750 Dp that was on my dart ran awesome.. car did anything i wanted it to. cruise around real slow in stop and go traffic, cruise the highway, or race at the track. that carb never had a bog, hick-up or anything. ya hit the pedal and the car just went.. :)
 
Well that's what Holley recommends but I guess they could be wrong. They seem to recommend to small of carb for engine applications.

If DP are so highly recommended then what is the best application for the vacuum secondaries?
 
i guess its personal preference.

i think they recommend so small of carbs because they assume 100% efficiently in their formula. a street car will never see that.
 
I'll re-check the floats, they where 3/4 on the front and half on the rear as suggested but I havent looked in awhile.
 
You must log in or register to reply here.
-

Back
Top