Thought maybe someone out there would have idea about a problem a friend of mine is having with his 41 Chevy. We built this car about 2 years ago, it had 350/350 eng/trans, he burned the engine up then changed it out with a 283. It was running a HEI distributor which went bad and we installed old OEM points distributor with Pertronix upgrade. Are running resistor type coil as suggested. The engine starts great, idles really good, but when you put in gear and try to accelerate it pops and falls on it's face, if you feather the throttle it will go but as soon as you get into it, it pops and goes dead. I suggested to him that vacuum advance could be the problem what do you all think. Plan on checking all the grounds to the chassis and engine. Engine timing has been checked and re-checked. Carb is new and I don't really think it is a fuel problem. Any suggestion is appreciated.
Check it to see that the vacuum advance is working like you said to begin with.
BTW, do all the initial and mechanical advance tuning w/the vacuum advance disconnected and the line to the carb plugged. Once you're done tuning, hook the vacuum advance to manifold vacuum (aka full time vacuum).
Verify the timing marks are showing TDC.
Most vacuum advance cans give too much advance; you really only want about 12-14 degrees w/a mild cam and "normal" compression ratio. To limit the total amount of vacuum advance you will need to physically limit the vacuum advance can's travel w/a vacuum advance limiter plate like the Crane p/n 99619-1. This part also fits the points-type distributor. Or you can make one.
Then use a timing light to see that the mechanical advance is working as it should. If you don't have a dial back light, you can make a timing tape to see what the total timing is.
I would give it more timing if you're at or below 6-8 degrees BTDC (like has been mentioned already). You use more timing for a bigger than stock cam.
Be sure the total (mech. plus initial timing, no vacuum advance included) isn't higher than about 36 degrees BTDC (stock heads), and that the mechanical advance is all in by 3000 rpm or less.
More info on setting up a performance timing curve is here. Balance the initial plus mechanical advance figures as needed. As an example, if you use 10 degrees initial, you'd use 26 degrees mechanical (36 total is the target, minus 10 degrees coming from initial = 26 degrees mechanical). 15 initial gets 21 mechanical, et cetera.
As stated previously; verify the timing marks are correct.
- Is the vacuum advance can particularly ancient? I've never seen one go bad, but I have used the adjustable can before.
- Can you give us some specs on the motor? Does it have Vortec-style 305 heads on it per chance? Vortec heads have slightly different timing requirements. While this wouldn't be the entirety of the problem, it may not be helping.
- Forgive me for asking a simple question, but where is the vacuum line from the distributor connected on the other end? Is the vacuum line new?
- What carb is on this 283? Has the carb been rebuilt recently? Was it rebuilt back to a baseline tune? You really only need a 600cfm carb on a 283.
- Are you guys using an MSD type ignition box?
BTW 1st Pertronix conversion I did sitting on my couch watching a basketball game. In theory it could be a bad module but I HIGHLY doubt it. Was this the old, original Ignitor? Or the later Ignitor II or Ignitor III? The first generation had a design flaw; I seem to remember if you left the power on to the ignition too long, it would fry the electronics.
I'm a little lost who suggested a resistor coil and how did you wire it?
The Pertronix unit should see a full 12 volts. If you wire in a resistor it should be between the 12 volt source and the coil, the 12 volt source should contine on to the Pertronix module inside the distributor.
I've included a SnapShot of the Pertronix wiring link for space to add some comments. Check out your wiring compared to my comments and their instructions.
Well to answer somewhat, we were in a pickle of a rush to get this done when we installed the distributor with Pertronix trigger, didn't read the instructions in detail, ran a regular coil and it got so hot it almost blew the end off. Went back to the instructions which said use a ballast resistor or use a resistor type coil which we used the coil. Problem is still there though. We will give out but won't give up. Appreciate the link to Pertronix will revisit the wiring!
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