350 to 6.5 swap

[Chris Guthro]

hey, i was just wondering whats involved to put a 6.5 turbo diesel into a 1976 GMC 3/4 4x4? It did have a 350 auto, would the tranny and everything be useable? whats all needed to do this swap?

[gofastbobby]

FWIW, I think it'd be easier and more beneficial to swap in a 4bt.

[kwin]

4 bt's are very hard to find up here north of the border, nothing wrong with a 6.5 as long as you have realistic expectations.

Keith

[Chris Guthro]

Yea just want a diesel, maybe something biggger injectors, intake and nice exhaust. Cummins is out of the question, its either gonna be a 6.2 or 6.5, just wondering how hard the swap is

[89 crewcab]

I am interested in this swap too. I have heard it is fairly simple. I have an 89 3500 cc 4x4 with 350/turbo 400. I would like to have a diesel/manual tranny in it as I pull a stock trailer up and down forest roads a lot. I have thought of just putting a manual in with the 350. I have in my shop a getrag 290. Anyone know how difficult it would be to install it in this truck?

[odee]

the stock turbo won't clear the a/c box. If you can find a front mount banks manifold it will work. I redone my ac box with half of an s10's it will turn the evap the other direction. Other than that it is a bolt in swap.

[Chris Guthro]

Do we even need to run a/c? i dont need it down here, robs power anyway hahah

[Edahall]

Originally Posted by Chris Guthro

hey, i was just wondering whats involved to put a 6.5 turbo diesel into a 1976 GMC 3/4 4x4? It did have a 350 auto, would the tranny and everything be useable? whats all needed to do this swap?

350 auto tranny would bolt up but likely would not last long. The best option for a tranny is the NV4500 5 speed manual. You could also use a 700R4 4 speed automatic but make sure you get an 87 or newer. If the 700R4 is not from a diesel, the valve body will have to be modified to lower the shift points. It'll also need a lower stall diesel torque converter.

You'll also need a hydroboost system since the diesel doesn't produce enough vacuum for a vacuum booster. In addition, you'll need a 4 core radiator. These engines produce a lot of heat when pulling. If you've got 4.11's, you'll want to change them out for 3.42's or 3.73's to get good fuel economy. I'm using 3.08's and get 30 mpg with my 1982 Suburban.

[hatzie]

Be sure to get a complete donor truck or price a complete drop-in engine. You need all the "extra" bolt on engine parts... air cleaner, AC Compressor, Alternator, PS pump, vacuum pump, and the starter. Most salvage yards strip some or all of these off for separate sale. If they are not bolted on to your potential engine the yard goons have dropped pieces of the brackets and bolts in the mud under the donor truck.

The 6.x engines run hotter than the gasoline engines. A four row copper/brass or a quality aluminum radiator is a must. The 90s 6.5L has an external oil cooler. I recommend an external transmission cooler as well.

You'll need to replace the vacuum brake booster with a Hydroboost unit. All diesel trucks and some gas engine C30-C80 had hydroboost. Make sure you get the pushrod, master cylinder, all hoses, and the firewall bracket.

A diesel TH700R4 is a much better choice than hacking together a "diesel compatible" TH350. A Gas TH700R4 isn't hard to convert to diesel operation and they're cheap used even with an attached transfer case. The TV cable and governor controls your shift points. You'll need the 6.2 TV cable bracket, 700R4 diesel governor, and 6.2L flexplate. You'll also want the torque bar that bolts between the transfer case and the bellhousing.

I thought it was worth noting that increasing your tire size by one inch will drop your effective axle ratio by @ .13 . Example: changing tires from 245 75 16 (29.3") to 265 75 16 (30.5") will effectively change 4.11 gears to 3.95 gears without opening the axles.

[Chris Guthro]

Well im pretty sure a 76 3/4 ton 4x4 comes with a turbo400 dont they? that should be able to handle a 6.5, there not power houses. I am only doing the 6.5 for mileage and turning it up a little bit for the smoke and nice sounding exhaust.

[Chris Guthro]

Im wondering if anyone here has done this swap? as anyone put a 6.5 turbo into your square body?

[Edahall]

Originally Posted by Chris Guthro

Im wondering if anyone here has done this swap? as anyone put a 6.5 turbo into your square body?

Well, it's not a popular swap because you can already buy it this way. The 6.2 was offered in square bodied trucks from 1982 to 1988. The 6.2 is identical to the 6.5 other than the 6.5 being a bored out 6.2 with slightly larger pistons. You can slap a Banks Turbo on a 6.2 and get the power that the 6.5 turbo has. On top of that, the 6.2 has been known to be longer lived than the 6.5 for various reasons.

[hatzie]

Originally Posted by Chris Guthro

Im wondering if anyone here has done this swap? as anyone put a 6.5 turbo into your square body?

Yes. Voice of experience on the missing external parts.