86 GMC Short Box Engine Swap To TBI

[Creedux]

Hey everyone

I'm new to this site and I was really hoping you guys would be able to give me a hand in this project of mine that im going to start very soon.
Like the title says I just picked up a 1986 GMC short box and i want to swap out the stock / weak carb 305 and drop in a strong 350 4-bolt main TBI. So heres my question. the truck is a 86 2 wheel drive and the engine i want to use is a 350 4-bolt main from a 92 3500 1-ton 2 wheel drive. If i drop the 350 in the 86 will i have to order headers for an 86 - 350 or a 92 - 350 ? The reason why im asking this long question is because I dont know if there will be clearance issues to worry about with the 350 TBI with If there is then i guess i'd have no choice to use stock exhaust manifolds I dont want to have to go down that road because i want to get as much noise out of the engine as i can.

Any help or advice will be greatly appreciated !

 

[Jims86]

Hey everyone

I'm new to this site and I was really hoping you guys would be able to give me a hand in this project of mine that im going to start very soon.
Like the title says I just picked up a 1986 GMC short box and i want to swap out the stock / weak carb 305 and drop in a strong 350 4-bolt main TBI. So heres my question. the truck is a 86 2 wheel drive and the engine i want to use is a 350 4-bolt main from a 92 3500 1-ton 2 wheel drive. If i drop the 350 in the 86 will i have to order headers for an 86 - 350 or a 92 - 350 ? The reason why im asking this long question is because I dont know if there will be clearance issues to worry about with the 350 TBI with If there is then i guess i'd have no choice to use stock exhaust manifolds I dont want to have to go down that road because i want to get as much noise out of the engine as i can.

Any help or advice will be greatly appreciated !

It will swap right in. Just retain the starter and flywheel from the 350.
One thing you should know about that particular engine...It is not the 210 HP engine that was used in the 1/2 ton trucks, it is the lower compression 190hp heavy duty engine, but still has the 300ft lb torque rating.
Use an 87 throttle cable.
If you are pulling all the TBI stuff from an existing truck, you need to grab all of the engine, And harness related stuff, the harness in that truck will be longer than what the 87s used....dont forget the computer, and the charcoal canister, and all the relays that may be on the firewall...may be only one.
Grab the Park/neutral-reverse light switch at the bottom of the column.
Grab the fuel Tank and internal pump, I am not 100% sure the tank will bolt in, but grab it anyways.
The exhaust manifolds from the 92 will not clear your more narow frame rails, but your 86 manifolds will bolt right up to the 92 heads.
Take note of where the o2 sensor is on the 92, some were in the Y pipe, some were in the drivers side manifold.
Your 86 drivers side manifold should already have a sensor, or a tap for one at least. If not, an exhaust shop can tap into the pipe under the manifold.
From there on, we can get you some digrams and walk you through the wiring.
and it will be plenty loud with stock manifolds if you use a short body muffler...the longer, the quieter.

 

[Creedux]

Hey Jim, thanks for all of your advice. So what about headers ? the frames for a 92 3500 are different then a 1500. the headers that are on the 350 right now are basic long tubes and they wont clear on either side. So does that mean i could cheat and just order headers from a store and tell them i need headers for a 92 1500 instead of a 92 3500 ?

 

[Creedux]

Or do I need to try to order headers for an 86 350 ? thats my main concern before i start this project

 

[Jims86]

You need to get headers for your 86. The frames on the squarebodies is narrower than the GMT400 series, which is what the light duty pickups from 1988 are designated. Try to order them for an 87 if you can, that will give youthe O2 sensor spot in them, unles you are going mid length or long tube, which will require you to upgrade to the 3 wire heated o2 sensor from a 94-95 truck.

 

[bucket]

It's very easy to add in an O2 sensor bung. Or you can buy header reducers with a bung already in them.

BTW, I love Ren and Stimpy!!

 

[Creedux]

Hey guys, I know someone that has headers for 63 to 82 Corvette. Whats your thoughts ?





http://www.summitracing.com/parts/big-11106flt/applications/?prefilter=1

 

[Jims86]

Hey guys, I know someone that has headers for 63 to 82 Corvette. Whats your thoughts ?





http://www.summitracing.com/parts/big-11106flt/applications/?prefilter=1

They are not for a truck.

 

[Creedux]

No your right they are not for a truck, but do you think they would fit ?

 

[bucket]

They might very well fit. They look like one of the Hedman versions for these trucks. Plan on removing the starter to get the right side in (plus the plugs/wires like any other install).

 

[Creedux]

Ive sent the guy an e-mail asking him why they didnt work for his truck. Also i think im going to have to try to talk him down on his price lol

 

[Jims86]

Ive sent the guy an e-mail asking him why they didnt work for his truck. Also i think im going to have to try to talk him down on his price lol

I personally wouldnt buy them, because I dont know exectly how or if they would clear the crossmember or the steering shaft for that matter....and that drivers side one looks like it drops a little too much straight down...right towards the motor mount/crossmember

 

[Creedux]

yeah thats a good point. who knows if i can get him down to a price that i feel is reasonable i might just keep them for a later project

 

[Jims86]

yeah thats a good point. who knows if i can get him down to a price that i feel is reasonable i might just keep them for a later project

If you dont mind the experienced suggestion, do the swap and make sure everything is right, and then add the hi po parts.

 

[Creedux]

I agree 100%