Opinions please

[IROCmenace]

Hello, this is my first post on here. I have wrenched for years on F bodies but never really tore into one of these trucks. I have researched a lot since I got my 86 GMC and now I have questions. I am trying to get this into daily driver shape. It is an 86 GMC C2500 5.7 Vin M, TH400, 4:10 3/4 ton
It only has 107K miles. But the maintenance has been lacking. I have put about 1K miles on it.

It was completely stock with all the heavy emissions stuff still on it. I have removed and plugged most of that now as both air pumps were locked up and I only need to pass a sniffer test.

I have put new plugs, wires, coil, cap, rotor and module in.

I have picked up a high idle and dieseling issue that is pissing me off right now. I did my plugs with AC 45's for a more complete burn but then the dieseling started so I dropped the heat range back down to the 44's. Still doing it. Seafoamed it. Still doing it. I still need to check the timing and replace all the vacuum lines and carb gasket but I am not impressed with carbs at the moment.

Now my questions

It has a Quadrajet on it and I can't decide if I want to rebuild it, get an Edelbrock 1406, or convert it TBI


Quadrajet seems overly complicated to me when an Edelbrock is so much less hassle.

I am leaning toward TBI but the fuel lines with sending units and tank valve that have return lines will be the most expensive part. I can get all the TBI parts from local u pull yards cheap.

What are your opinions on each of those options and some tips you may have that may lean me one way or the other. TIA

 

[Jims86]

Hello, this is my first post on here. I have wrenched for years on F bodies but never really tore into one of these trucks. I have researched a lot since I got my 86 GMC and now I have questions. I am trying to get this into daily driver shape. It is an 86 GMC C2500 5.7 Vin M, TH400, 4:10 3/4 ton
It only has 107K miles. But the maintenance has been lacking. I have put about 1K miles on it.

It was completely stock with all the heavy emissions stuff still on it. I have removed and plugged most of that now as both air pumps were locked up and I only need to pass a sniffer test.

I have put new plugs, wires, coil, cap, rotor and module in.

Now my questions

It has a Quadrajet on it and I can't decide if I want to rebuild it, get an Edelbrock 1406, or convert it TBI

Quadrajet seems overly complicated to me when an Edelbrock is so much less hassle.

I am leaning toward TBI but the fuel lines with sending units and tank valve that have return lines will be the most expensive part. I can get all the TBI parts from local u pull yards cheap.

What are your opinions on each of those options. TIA

The Q jet is the best carb you can get, dont ruin the truck with an Edelbrock. TBI is good too, Just a bit of work.

 

[animal]

Hello Shawn and welcome to the site . I personally always liked my q-jets once I found someone local that could properly tune them. I think for everyday drivability and fuel millage the TBI may be your best option. Some of the TBI guru's like Jims86 or Retro will chime in shortly with some additional info. Again welcome.



Jims86 beat me to the punch

 

[IROCmenace]

Thanks for the fast replies.

 

[animal]

Thanks for the fast replies.

I do fast... Jim does good and informative

 

[IROCmenace]

Jim86, have you tried rebuilding the Quad yourself?

 

[bucket]

So I'm guessing by your screen name you like third gens?

 

[Boone83K10]

Check timing then carb.

 

[IROCmenace]

So I'm guessing by your screen name you like third gens?

Yeah. Been my favorite since I was a kid. Product of being raised in the 80's I guess.

 

[89Suburban]

Yah, definitely check the timing and go from there. I do love my TBI. Welcome aboard.

 

[Stroked]

Like Jim said, don't ruin it by throwing an Edelbrock on it. My 3rd gen had one, my '72 C10 had one, and my K10 has one. All from previous owners. I'm far from impressed. A quadrajet is the best carb ever made for streetability in my opinion. Find someone to tune it properly and you'll love it.

Just my 2 cents.

As for your high idle and dieseling issue, I would check your timing as others have said.

 

[da_raabi]

I just fixed the exact same problem, and discovered it was the oil pressure sender that controls the choke, led to a VERY rich mixture, dieseling, and a stupid high idle. All I had to do was change out that little sensor and now it runs smooth as silk, I mean it really purrs. If your 86 is anything like mine (although you have a 350 vs my 454) then that could also be your issue. That's just my 2 cents.

This is what I replaced (from RockAuto):

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[bucket]

Yeah. Been my favorite since I was a kid. Product of being raised in the 80's I guess.

I'm a big fan too, had 10 or so of them. Currently only have three.

 

[Driver4r]

Stick with a Q-jet, but one thing to think about. Your Q-jet is computer controlled, you should convert to non-computer controlled. That involves, dist, and carb.
And i dont know why everyone says their SOO confusing??????? I find them simple.

 

[SlickGTP]

I'd say stick with the Q-Jet as well... Love 'em, but then again I grew up on them too. lol

I found this book to be invaluable for understanding, rebuilding, and modifying them:
http://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189