Carb and/or ignition problems, which carb/ignition do u suggest?

[streetstang67]

Finally got my car out of the shop after adding A/C and having a few misc. things fixed. As long as I've had this car, the engine stutters and stubles sometimes, especially when the throttle is pushed quickly. After getting rid of the points system and changing to electronic (crane-xr i), the problem didn't change. Well when I got the car back the mechanics were discussing this problem, especially since they had to set the idle especially high after the A/C installation...One mechanic has been tellin me for months that my holley 600 is too big and its crappy (b/c he hates Holley's). Another mechanic agrees the carb is a problem, but also thinks the bigger problem is not enough spark, he suggested a bigger coil. What do you think?

Basically, in general, with my setup, what ignition and carb would be adequate?

Thanks

 

[thehueypilot]

It sounds like you need a new mechanic (s)? If the car stumbles during intial acceleration I would check the accel. pump diaphram for holes and if it is good I would increase the pump squirter nozzle by two numbers and recheck.

 

[grego37]

ditto.
find a mechanic that knows fords and holleys.
carb doesnt sound too big.

 

[LMan]

whats the history of your carb? Huey Pilot is on the right track.

Its not too big, btw. Id say you were talking to a GM mechanic, but they always think Ford carbs are too small....and advocate a 850DP on a 283

Ive never heard the coil excuse before ..but I would recheck your XR-1 installation

(sidebar: I tried one of those, threw it into a dumpster after one-too-many heat-soak episodes )

RE: ignition, Im a strong MSD advocate. I run a 6AL spark box and Blaster coil with a Duraspark distributor..... rock solid, idle to redline

 

[krash kendall]

Buy a new car.




Just kidding! The carb isn't to big, but sounds like it needs work. You may not be developing enough vacuum, running to rich, accelerator pump, and so on. Go to a mechanic that was born back in the time before all cars came fuel injected.

 

[streetstang67]

Well I have had back-firing problems recently, I had the plug wires incorrect, as well as a few other little things...therefore, could the 'power valve' be screwed up? I've heard that backfiring will ruin the power valve on a holley, and also the mechanic mentioned power vavle problems. what do you think?

BTW, what is a power valve?

 

[mustangman70]

I am also a very partial to MSD.....Also i had a stumble problem with my old edelbrock.then i bought an old ass holly rebuilt it and it runs PERFACT, how ever i have a little too much carb as its a 650, but i dont have a cam or head work.i say your carb is PERFACT when was the last time it was rebuilt????

 

[pabear89]

The power valve is on the metering plate inside the carb,
if its leaking you will have hard starts after sitting over night.
The gas drips down the intake and you crank the engine more one
first starting.

your idle setting is to compensate for the Ac compressor when its turned on.

Your stumble problem is from the accel pump improperly set.
try loosening the screw on the pump lever till it just Barely touches the arm,and test for the stumble.

PB

 

[streetstang67]

Well after talking to another mechanic, (the one that will be machining my heads for screw-in studs); He says the carb is okay, but could use a little jetting changes. So while he has the heads, I want to work on the carb. What size jets should I install? Also, while it's off, what else should I do?

 

[10secgoal]

I wouldn't mess with the jets quite yet. That has to be tested while on the car, cruising around, and at WOT. Trying to guess now, would just be shooting in the dark. Then it sits until your heads are done, not knowing whether you are even close, or even went the right direction.

 

[Spicoly]

Hey Guys,

I have a 66 GT with a similar issue and stumbled across this thread. I dont have the electronic points but it seems like a lot of people suggest me to start there. This is a great thread. Love the comments about getting a new mechanic.

Any suggestions on Pertronix II vs Crane Cam XR-i electronic points.

 

[krash kendall]

I have a Pertronix II. I bought it a year ago and the car hasn't stumbled once. I also put in an MSD Blaster coil. The pertronix needs full 12V so you have to run a new wire from the ignition but the Blaster can use the stock resistor wire.

 

[streetstang67]

I'm still using the factory 12V ignition source to the coil, and I have Crane XR-i electronic box (just like pertronix)...I tested the wire with the key turned on, and it read 11.98 volts. You said you had to run a new wire to get 12 volts?

 

[streetstang67]

Is this electrical system ok?

 

[thehueypilot]

Is this electrical system ok?

I know on a 68 the resistance wire is located at the ignition switch. It limits the voltage to 12 volts max so you don't burn up the old type points. Since you upgraded your ignition system you do not need this resistance wire and you could increase the output of your coil by using alternator voltage (14.8), but this has nothing to do with your stumbling problem.

 

[broncobear]

600cfm is TOO BIG for a 302

Do the math you guys, before trying to guess some help for someone.

http://www.classictruckshop.com/garage/shopmathcfm2.php

The formula is as follows: ci x 2 - 15% or ci x 2 x .85
4.125" Bore: 302 x 2 = 604____604 x .85 = 513.4cfm
4.155" Bore: 306 x 2 = 612____612 x .85 = 520.0cfm

Unless this guy has a huge cam, 600 is too big for a 302.
A stock 302 reguires 513.4cfm___If it's bored .040 over, it is a 306.

 

[PUNISHER RACING]

you can use that formula till you run outta calculator batteries its dumb! A 302 will run fine with a 750dp if its set up right. The extra cfm's of air it puls through the throttle bore is not gonna kill it. For gods sake the same 585cfm carb they put on 80's 302's is the same one that was on the 460's. its all in how you set the carb up. Thats my 2 cents and thats enough to cover that 1 cent equation!

 

[D.Hearne]

you can use that formula till you run outta calculator batteries its dumb! A 302 will run fine with a 750dp if its set up right. The extra cfm's of air it puls through the throttle bore is not gonna kill it. For gods sake the same 585cfm carb they put on 80's 302's is the same one that was on the 460's. its all in how you set the carb up. Thats my 2 cents and thats enough to cover that 1 cent equation!

I agree with you here, except for the 750 Dp carb. It IS too big for a mild 302. Nail the pedal from a dead stop and you see that it's too big.

 

[D.Hearne]

The 600 Holley is perfectly sized for a 302, it just needs to be tuned better, as in accellerator pump arm clearance, secondary spring changes, and maybe check the powervalve to see if it's not ruptured, I doubt it would be, i've never had one let go from a backfire. And as 10secgoal suggested, wait til it's fully drivable before doing any jet changes.The XR-1 is also fine, I have the same thing on my 89 V8 Ranger and it'll start and idle with no choke or pump shot in 25* weather. Coil is Mallory Promaster points coil. Plugs are Autolites, Wires are Ford Racing 9mm's.

 

[68stang351]

I'm partial to Crane Hi-6 Fireball ignition. Do some research comparison between it and the MSD 6AL and I think you will be suprised. I don't have to spend money on stupid pill kits either, I just turn two dials with a small flathead screwdriver.

My ignition consists of Crane Hi-6 Fireball box, Mallory Unilite dist., MSD Blaster Coil (I'll buy a Crane when I need a new one though), Ford Motorsport 9mm wires, and Autolite plugs. I'm happy with it.