deisel to gas swap ???

[chevman-67]

Has anyone put a 350 gas into a 6.2 deisel 86 3/4 ton 4x4.What I need to know is when I put in the 350 can I change the whole underhood wiring harness and leave the in cab harness.I have the underhood harness with my 350 if it will just plug into the origanal at the firwall and still have all the gauges ect work.It will save me a lot of cutting and trying to figure out all the wiring if you know what I meen.any help would be great thanx.

[ltitsnw]

I did that swap about 8-10 yrs ago on a 84 2by sub, I'll try to remember best as possible. I know that I just broke out the engine harness part of the plug and replaced it with the gas harness. I did have problems with the fuel gage working properly. The diesel trucks have 2 wires, yellew and a pink, one is for gage and the other is for the water in fuel light, don't remember for sure which one is sending unit. And it seems like I had to hook a hot feed in to the engine harness that fed power to the headlights, this part is a little foggy to me, could've been my donor harness was incomplete, just don't remember to well about that one. But the fuel gage I'm pretty certain about. I have most of all the wiring diagrams for the mid 80 trucks, so if you need any help with wire colors and thier purpose, just post and I'll try to help. Then after switching everything over to gas, a guy I work with pointed out that if I had put in an Olds motor I could've used the original trans and front brackets, oh well, had chevy stuff laying around anyway. Good luck it's not that bad if you have all the brackets and a little patients. Troy

[chevman-67]

It sure would be nice if everything hooked up nice.I had a 350 deisel conversion and put in a 350 ods engine YES it was nice but this 1 is a 6.2 L
and I thoght if the wiring harness from the donor truck under the hood would maybe plug right into the deisel 1 at the fire wall id be laghing I would still have the deisel dash w/glow plug light and water in fuel light as long as everything else worked.If not ill hack up the deisel wiring but thought of saving that 1 in case i ever go back to the 6.2L.Yes a wiring diagram for my 86 3/4 ton standard cab 4x4 would be nice.Any other info appreceated.

[SSC's76]

Alot of over thinking being done here. What is the end goal of this swap? Is it to save money or is the end goal some thing that looks factory and operates to meet certain emmision criteria.

If you just wanted to slap a cabred 350 in no biggie just use the existing harness for accesories/guages. Now if it were a TBI/MPFI swap yes then you would have to convert the full harness.

[86swb]

Well, you would save money I think. I know deisel fuel in higher but do you get more mpg with that deisel? I do not think you have as much get up and go with a deisel. If I am right, these engines are gas engines that GM changed over to a deisel. Let me know if I am wrong. But that is what I have been told over the years. Those are not true deisel engins.

[SSC's76]

Originally Posted by 86swb

Well, you would save money I think. I know deisel fuel in higher but do you get more mpg with that deisel? I do not think you have as much get up and go with a deisel. If I am right, these engines are gas engines that GM changed over to a deisel. Let me know if I am wrong. But that is what I have been told over the years. Those are not true deisel engins.

Ive driven a 6.2L with a full Banks turbo conversion. OMG that sucker would go.

Thats a good question, I honeslty dont know 350 diesels are before my time. I was talking to a guy that use to work for my parents, he said they use to convert some diesel engines to gasoline back in the early 80's. I should have gotten a little more info about what they were doing but I think it was a BOP engine.

[86swb]

Originally Posted by SSC's76

Thats a good question, I honeslty dont know 350 diesels are before my time. I was talking to a guy that use to work for my parents, he said they use to convert some diesel engines to gasoline back in the early 80's. I should have gotten a little more info about what they were doing but I think it was a BOP engine.

I have heard of changing the diesel engines to gas but never a 350 gas to a diesel. That is a new one on me. I am not saying it did not happen, just never heard of it.

[SSC's76]

Originally Posted by 86swb

I have heard of changing the diesel engines to gas but never a 350 gas to a diesel. That is a new one on me. I am not saying it did not happen, just never heard of it.

I did a little diging on the web last night. Apperently it was the Olds 350 rocket. From what I read the engine could go either way since the diesel engine was based off the gasoline design. I couldent find information on the heads since I would asuume they are where the difference is, super high compression for the diesel process but there was mention of different acc holes in the heads.

It's got me interested.

[chevman-67]

Sorry guys mine has the 6.2L deisel in it now and the compression is shot and the head gasket or head is done now so I want to take it out and put in a gas 350 5.7L the deisel dont have a distributor ect.So to hook up a gas engine like my spare 350 I have the whole truck for parts as well can I just unplug my wiring at the firwall and plug in the gas harness. PS.I have had nothing but probs with the 6.2 and they are noisy motors that sound like a rod is coming out of the block.They are no cummings anyway.And the price of feul isnt a concern its just that I have a gas motor on hand.

[Beefcake]

ok. I have some experience w/ this stuff.


1. the 6.2l has the same footprint as a small block chevy. what I mean by that is it bolts up to any small block trans. everything else, especially the weight of the motor is diffrent.

2. Sounds to me like you just want a quick fix, then you can button things up later. Im not sure, but you probley need small block engine mounts. You will need to change your torque converter to a gasser tc. As for the wiring, dont swet it- just hook up your 12v feed to your dizzy, your alt/starter should be the same. Later when you have some time you can remove all the extra crap thats for diesels. Then after that, you will notice a diffrence in your handling. You should swap your springs to small block springs... I believe the 6.2 is more heavy than a 454....

3. the 6.2 was never a small block. It was designed by detroit diesel as a diesel. They've got a lot of bad wrap because of lack of power and poor durability. The later is because of operator error. If you treat them right with the proper care, I've seen 400k mile 6.2s....

[chevman-67]

Thanx for all the info thats what I needed to know. The springs are not that much of an issue as I am going to be using a plow for the winter and heavy is going to be nice . Can anyone send me a complete wiring diagram of the deisel harness so I can figure out what they are all for and hook them up to the gas.Thanx again.