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2nd gen HEI question???

T

tat2

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new guy here but i have been reading alot on here since i got my 86 k5.
my blazer has the stock set up, rebuilt 305/700r4. my question is that i am having problems with getting the timing right, i have issues when i set the timing to specs on the sticker under the hood my truck will diesel when i cut it off and it also will sparkknock some. after reading a thread on here a guy here talks about a GM bulletin on a mod that you cut the black and blue wires at the computer box behind the glove box and splice them together to basicly to make the 5 pin module like the older 4 pin version. what i want to know is the whole instruction,process on doing this mod, also i got one of those carbs with a electric mixture things on top of the carb that has no harness for it so i am going to get a older version. any help on these would be great. awsome site thanks tat2
 
Do you have a plug on the drivers side front of the carb as well?

Need to figure out if you have ESC or the CCC system. Only ones to get CCC were CA trucks, however vehicles move.
 
no i dont have the plug on the drivers side of the carb. i belive i have the ESC system, i have a knock sensor and a vacuum sensor thing on the fire wall that works with the computer box in the dash. thanks
 
tat2 said:
no i dont have the plug on the drivers side of the carb. i belive i have the ESC system, i have a knock sensor and a vacuum sensor thing on the fire wall that works with the computer box in the dash. thanks
Click to expand...

You may have read about me doing that with the ESC. The knock sensor and 5-pin HEI module just induce a delay that effectively retards the ignition. By jumping the wires together, you just complete the loop and remove the knock sensor from the equation. I believe it's the green and black wires. You also need to unplug the ESC computer at that point, as it's no longer needed.

The reason that GM issued a service bulletin and approves of this mod is that the ESC system was apparently known to be troublesome. If you have a 305, you'll need to retard the ignition timing from the factory setting to avoid spark knock. Mine has a 350 now, so the ESC and the baseline timing that go with it went out the window along with the old 305.
 
jonrpick, yep your the guy that i read this info from. which really got me thinking about my problem. so i splice the black and green wires unplug the esc computer and retard my timing. so the spark knock sensor and vacuum sensor becomes trash. cool i will try it and hope it helps. as soon as i get the cash a 350 crate going in with headers. thanks
 
tat2 said:
jonrpick, yep your the guy that i read this info from. which really got me thinking about my problem. so i splice the black and green wires unplug the esc computer and retard my timing. so the spark knock sensor and vacuum sensor becomes trash. cool i will try it and hope it helps. as soon as i get the cash a 350 crate going in with headers. thanks
Click to expand...

I did my mod internally in the distributor. That particular distributor has a notch in the metal base for that connector. I didn't use the factory connector that comes out the of the distributor base though. In hindsight, I should have. It keeps dirt and moisture out.

Still, I like the cleanliness of not having that harness coming off the distributor. Eventually I'll just replace it with a standard 4-pin HEI.

I never bothered researching, but I'm not sure if the weights and springs are the same as on a 4-pin HEI. So, basically I don't know if the curve is exactly correct for a 350 or not. Mine runs like crap, but I think timing is the least of its problems... :doah:
 
jonrpick, could i just swap in a 4-pin hel in my truck? would i have to mod the harness connector? thanks for the help
 
Like dyeager said(who is really sharp with emissions) you probably dont have a CCC carb. If it only has the dual capacity pump, that could be easily modified and tuned like any other quadrajet. Good luck
 
tat2 said:
jonrpick, could i just swap in a 4-pin hel in my truck? would i have to mod the harness connector? thanks for the help
Click to expand...

The 4-pin HEI module could probably be made to work in your distributor, but it'd probably be more trouble than it was worth.
 
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