79 C10 2wd SWB. 6.2L in place of original l6 cylinder

[HondaCowboy82]

Hey guys. Looking to take on a new project. The truck I am looking to end up with is a 79 SWB 2wd Chevy. it has a inline 6 cylinder with an automatic. The donor truck is an 85 Chevy with 6.2L with Automatic (TH400?). Donor truck belonged to an elderly man who died and has 79000 miles on it. What kind of problems can i expect making the diesel fall in the place of the 6 cylinder. I plan to do a single 3" straight pipe as well as a ram-air system with KN filter and electric fuel pump. I may also install an electric fan to eliminate the drag of the stock fan and delete the nonworking A/C. Can anything else be done to these to increase mileage and dependability? Planning to immediately install a water temp gauge and make sure the radiator is cleaned and flowing. With these mods, would 30 mpg be achievable highway?

 

[towcat]

....... With these mods, would 30 mpg be achievable highway?

realistically?
nope....
mid 20's is somewhat realistic.

 

[HondaCowboy82]

Would 3.08 gears be the best for this little combo or would the 6.2L not even make the Torque to pull itself with gearing that high? What year did they start putting the 700R4 behind these motors?

 

[tanman_2006]

My 82 GMC has a 700R4 and 3.08 gearing. It got 28mpg last time I drove it. I started parting it out a few yrs ago when I needed some money so it isn't on the road anymore (missing seat and some engine parts). I have a decent front clip for it but it needs a new cab (or the current one patched up) and bed replaced.

I will likely change the gearing to 3.42's or if there is a gear set between 3.08 and 3.42 i might try it. I got around fine on 3.08's as long as I didnt hurry and the lightest load meant dropping to 3rd, the tire size on these stock is only a 28" tire so thats where it gains some RPM's. I'm thinking a cruising speed of 1600 @ 60-65 would be good.

 

[opusd2]

Those 3.08s came in the stock form of the military Blazer, and they are holding up just fine in mine. And I have the 6.2/400/208 combo pushing 37" Goodyears around, or rather the HMMV tires. It's not ******* the engine at all, maybe the axles, but so far no issues since I run in high range unless I am in some deep stuff then the transfer case goes low and I walk right out of whatever the situation might be.