6.5 diesel to 350 Gas Swap - Your thoughts?

[JScott23]

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Okay, so i have a rust free, crew cab long bed 94 C3500 with a brand new 4L80E and a worn out 6.5. The 6.5 has all kinds of problems and i really like the reliability of a 350. My other truck has a 454 so i don't need a "towing rig."

Problems with the 6.5

Failing Injection Pump - New PMD.
Erratic Throttle - Probably a bad TPS Sensor.
Leaks Oil - Valve cover / rear main seal.
Leaks Coolant - radiator and hosesare good.
Starter problems - yes it has the brace, re drilled the bolts after breaking them.
Lacks Power - this thing barley makes it up a hill empty.


What i want to do is put a small block Chevy in it.. i will never tow with this truck so power isn't the issue. Obviously i'll need a mechanical gas pedal, and i'll need to wash out the tank real thoroughly. Now, it has a brand new 4L80E so I'll need something to control that..

Here are the options I've thought about.

1. Carb 350 / 700R4 OR TH400
2. Carb 350 / 4L80E with transgo shift kit
3. Carb 350 / 4L80E with TCI computer
4. Use Mechanical Injection Pump, keep 6.5.
5. Rebuild 6.5 - $$$$$$


Don't get me wrong i love our 93 mech 6.5, but this electronic 6.5 has given me nothing but problems, and i really just want this to be a reliable truck, with plenty of cab room, a nice classy rust free look, and the ability to tow a small trailer if needed. For the most part i see this truck being used for weekend trips, and camping. I can't have a unreliable 6.5, and the 350 is the best gas motor period.

Any thoughts, concerns? What do you guys think? Anyone done something like this?

 

[TylerZ281500]

cough..... cummins.....cough cough.

honestly you already have a diesel i say stick with a diesel and 6.5td;s are great but honestly your gonna be spending possibly the same amount no matter which swap you go unless you stick with the 6.5L rebuild. cummins are reliable as hell, like their mods, and youll love the power even if you are towing a small trailer.

 

[Darkrider]

I vote for 4 followed by 5 when funds allow. Im at the point im seriously considering going to a mechanical ip on my 6.5

Sent from a 6.5 Detroit Diesel powered smartphone

 

[96-1500]

Keep the 6.5. I'm with Chris.
I'd consider the mechanical injection swap, I've seen it done to a truck locally that turned out well. Honestly with the work you listed that you need to do to the 6.5, it doesn't sound that bad when compared to swapping engines. That's your call of course, if you want a project that would be cool, but a lot of work.
Same way with the Cummins: cool, and for an engine that was never designed to go in these trucks it isn't (comparatively) that bad of a job, but it's still a huge amount of work, and a lot of money.

I like my 350 in my 3/4 ton (it's a vortec, yes), and it pretty much does what I need it to, but it does leave something to be desired in a heavy truck like this. The truck is geared low and it chugs along under a load or not, but that's about it. If you expect to see huge performance gains, yeah, well, they have more in the push you back in your seat department, but it's still a big, slow old 3/4 ton truck. I'd rather have a slow old 3/4 ton that gets 20 mpg instead of a slow old 3/4 ton that gets 12 mpg...

I dunno what kind of mileage you 6.5 gets but the one I use for work (a '98 in a C3500HD, which is a big frickin truck) gets better mileage than my K2500 gasser...

 

[BHBurban]

If you were to go the 350 route, find a donor truck around the same year. That way you'd have everything you need (like the engine compartment wiring) to convert over cleanly. You could probably pick up the same year 2wd suburban for pennies...

 

[JScott23]

The ******'s adaptor plate and motor mount's are more than the truck is worth... i love cummins but that wouldn't be a good investment.. i'd be looking at $2k for the mounts and plate and then another 2-3k for the 5.9 motor...way too much


And the only problem with the mechanical IP swap is controlling the tranny and it doesnt solve my oil, coolant leaks