HEI question
 

hi guys, this looks like a great forum. I have been searching old threads looking for an answer ,but couldn't find it. I have a 72 lemans with a 400 in it and the previous owner put a hei dist. in it , I have been trying to fix spark knocking issues since I got the car . I've adjusted the timing up and down and adjusted the vaccum adv.and it seems to go away for a while and then starts again.

After reading through some threads I see that I need to verify that I have a 12 volt power source to the dist., also they have the electric choke tied in at the dist. , could this be an issue? Anything else I need to look at? one thing I'm not sure about is I think the dist. is in backwards , the vaccum advance is on the drivers side, I am not as experienced with pontiacs ,but I know that this would be wrong on a chevy, so is it backwards? and could this be part of the issue?

The vaccum advance on my 68 Firebird is to the drivers side. As far as your HEI powersource when I installed mine I went right to the fuse block. I'm no electircal guru, but that's what the instructions said to do. HEI's are apparenlty finicky with their power requirements so I'd start by putting a voltmeter on the BAT terminal and see what it's being provided. Also, how's the gas in your area? Mine's expensive crap.

Normally a dist would cause spark knock by having the timing advanced too far or the mech/vac advance curve too high or the wrong curve. Make sure you have at least 12V to the dist BAT terminal and you have no loose connections.

Other possibilities are perhaps your compression is too high, or the timing ring on the crankshaft damper has slipped, and your timing is not what you think it is.

George

thanks for the reply, I hooked it straight to the ign. prong on the fuse block yesterday and it wasn't spark knocking last night when I took it for a ride. It was hooked to the old coil wire and was only getting 9 volts so this could have been the issue. As far as our gas it's about $3.70 a gallon here.


I tried retarding the timing and tuning in the vaccum adv., I think I need to change the springs ,it seems to be fully advancing when you start off so I think it needs heavier springs or wieghts. I hope I got the 12v issue resolved. Other than the way it seems to adv. at take off it seems to be running pretty good right now. Unfortunately I don't know the compression on the motor , but I also considered this as a possibility. The guy told me it was a 72 block with 67 gto heads and intake.
I hope the damper has not slipped. thanks for the help.

With 67 heads the compression is most likely on the high side. What are the numbers cast on the center exhaust port? Remember the Pontiac distributor rotates counter clock wise.
Find another electrical connection for the choke.