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RD
RD, ASE Certified Technician
Category: Car
Satisfied Customers: 1942
Experience:  Ase Master 35 years
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350 pontiac: I replaced the coil, cap, rotor, and module

Resolved Question:

I have a 69 350 pontiac motor with an aftermarket HEI system. It started to break down under full load and one day it just would not start. I replaced the coil, cap, rotor, and module. Now it runs better, but at 3500 to 4000 rpm is starts to break down and once you get past 4000 rpms, the problem clears up. Can you please give me some insite on what to check next. I already put new wires on also and the plugs are fairly new.
Submitted: 8 years ago.
Category: Car
Expert:  RD replied 8 years ago.

Hello

I cant get live chat to work sorry.

Do you have a electronic tach hooked to the HEI?

Thanks Hart

Customer: replied 8 years ago.
Reply to HART's Post: Hart,

Yes I do. It is connected on the tach side of the coil. Let me give you some more insite. I am using the standard plugs for a 350 pont. 69 motor. I just opened the gap to .045. The timing seems to be on target, but I can't be positive. The motor has modified cam and I don't know what size. Not anything wild, I would say its just over the standard stock type. I have timing set to 13 degress BTDC. Stock calls for 9 degress,

Thanks
Expert:  RD replied 8 years ago.

Ok

 

Here is what id look at i have run into a break up on the HEI with a few different causes,

Remove the wire from the HEI for the tack,, then test for the break up,

I have seen a electronic tack do some weard stuff to the HEI

If were ok there, pull the cap, remove the rotor,,, check the counter weights

should move freely and snap shut with ease..

if were ok there don't put the cap on yet remove the distributer from the motor

check for end play on the distributer shaft not up and down but back and forth,If you can move it around its doing that spinning in the cap,,,,, will cause a miss and fluber

If were ok there check the other end see if it is spinning freely from by the end that goes into the motor, there is a brass bushing there can be bad

and last thing to look at have seen but not very much

check the power at the distributer at 3500, 4000 rpms should be at 12 volts

if under 11.5 the HEI is nor getting enough voltage,, could be ignition or regulator

 

 

One of these will get ya going

Hart

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