59A Breaks up around 1/2 throttle

C

Chappy

Member
Being new to flatheads, and starting off with one that wouldn't run, I'm happy to say I've put around 1500 miles on it this summer with the help of you guys. My only issue that I need to resolve now is even warmed up to operating temperature (at the 1/2 mark) the engine starts breaking up at around 1/2 throttle. For instance when I'm cruising and I give it about 2/3 throttle or I'm trying to climb a hill the engine runs extremely rough, to me it seems like an ignition issue, my guess would be the vacuum advance or lack there of is my problem. It runs good up to that point. I'm running a 59A, 6V + ground, single Holley 94, petronix pointless module and petronix coil, stock trans and rear end in a 48 2dr sedan. I think my timing is about maxed out, as the screw is just about at the bottom of the opening, it seemed to run best at that setting, and doesn't ping. I'll also say I can cruise at 45mph for about a long time and my temperature stays at about 5/8 on the temp gauge, but if I go up to 50mph the temp goes to 3/4, not sure if that's a completely different cooling issue or timing related.
 
Chap,
Root around and find a crab dist with points and a condenser, all in decent
condition then install a Car Quest 52-1902 coil ( internal resistor ) or equiv. Be sure
the pos terminal of the coil is attached to the dist.
Charlie ny
 
Charlie, I still have the original coil off of the car, which I think is in good shape, will that work or should I go with the new coil?
 
Could it be the power valve in the carb? I just rebuilt two of them and noticed there are two different valves in the kit and two different gaskets for them. It was confusing. From what I glean, these add extra fuel under the conditions you mentioned. No carb expert, just a thought from my recent experience.
 
The coil I suggested , which I have had excellent results with , has the benefit of
an internal resister, you jump out your present resister. The stock dist and this coil
is where I'd start.
Charlie ny
 
Charlie ny said:
The coil I suggested , which I have had excellent results with , has the benefit of
an internal resister, you jump out your present resister. The stock dist and this coil
is where I'd start.
Charlie ny
Click to expand...

I must add that on my very first venture into 'town', 12 miles away, I was running on an original ford coil because I liked what it looked like. I broke down twice and had to be pushed off the road by good samaritans, I got a ride to our only auto parts store, a napa and bought a 6v coil with internal resistor (because that's all they had.) I bypassed the resistor by stacking the wire on top of the other one and boom, she fired right up and I never looked back. Drove home on my own four wheels.
 
I have had a problem like this a few times and it has been problems with the HT side of the ignition. I run the crab caps and they can and do fail. I also had a rotor arm that failed.

Your description of being able to run at light throttle and things go wrong when warmed up and applying more pedal sounds very much like my problems. I would get a new crab cap and rotor, and the clip kit to fit them (if you have the rabbits ears type cap) and a new set of leads and try that.

You might be able to detect marks inside the cap caused by stray sparks.

Mart.
 
Bad fuel pump could act like that too. Years ago an International pickup had similar symptoms. A new fuel pump fixed it.
 
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