HEI help

[Cody Garcia]

Morning everyone I am new to this forum and recently became the new owner of a 1986 GMC Sierra Classic 3500 Dually. The guy I bought this from had started a rebuild on it and never completely finished it the truck starts and runs but alot of electrical things seem to be unfinished/or improperly installed. When I got this home I started really going through the engine and noticed the negative and ground wires seem to be reversed the yellow wire is in the center location and the black is set to the location closest to the front of the truck. The question is would this still allow the truck to run. It starts and idles great at cool temp, seems to drive fine but after warmup when stopped it idles rough and when starting back up it can die when placed in gear. I will be tuning the carb a bit today since I bought it out of Denver Co and brought out here to Nebraska I figure the elevation change will affect this a bit. I will finally be able to actually work on it today so any advice will be greatly appreciated. Thanks

 

[Overland Suburban]

Morning everyone I am new to this forum and recently became the new owner of a 1986 GMC Sierra Classic 3500 Dually. The guy I bought this from had started a rebuild on it and never completely finished it the truck starts and runs but alot of electrical things seem to be unfinished/or improperly installed. When I got this home I started really going through the engine and noticed the negative and ground wires seem to be reversed the yellow wire is in the center location and the black is set to the location closest to the front of the truck. The question is would this still allow the truck to run. It starts and idles great at cool temp, seems to drive fine but after warmup when stopped it idles rough and when starting back up it can die when placed in gear. I will be tuning the carb a bit today since I bought it out of Denver Co and brought out here to Nebraska I figure the elevation change will affect this a bit. I will finally be able to actually work on it today so any advice will be greatly appreciated. Thanks

It should work but only if you drive in reverse! JK

Hopefully someone will be along soon who can help


Tracy

 

[Overland Suburban]

It should work but only if you drive in reverse! JK

Hopefully someone will be along soon who can help

Tracy

 

[Snoots]

If the negative and ground wires SEEM to be reversed, you do not have a problem.
FIRST, Start at the battery negative and clean all ground connections.
Those under the hood should be easy to spot.
Then you have a ground connector under the dash on the upper left kickpanel.
There is also one at the rear of the truck, drivers' side, just near the bumper.

When you have them all cleaned, remove the + wire from the dizzy, turn on the ignition and check for +12.

You're right about the altitude adjustment. It could be timing (which I would check first) a choke adjustment (2nd) or vacuum leak. Check all of the vacuum lines.

Get a can of carb cleaner and check for leaks around the intake.

Keep us posted and put up some pix!

 

[Cody Garcia]

Thank you for your help. I spent all day working on the blue beast. It's been quite the little project replacing vaccum lines and wires that had been ran next to the exhaust . Hopefully I found everything gonna check the timing and replace plug wires and plugs today. Hopefully that gets her running smooth. I will snap some pics for ya today.

 

[Cody Garcia]

Snoot I am getting some conflicting results online for timing. I am seeing everything from 4° btdc - 12° btdc what would be recommended for my truck?

 

[Snoots]

Your correct timing should be on a label on the top of the radiator cover with the engine size, code and vacuum hose layout.
I'm GUESSING that initial timing should be 8 BTDC for a 454.

You need to disconnect the vacuum hose from the distributor vacuum advance, plug that hose, then set your initial timing.

If it's jumping around at that point, pull the dizzy cap and check the advance springs and weights; free movement, springs (2) are there and, if you have a vacuum pump check the diaphram.