I know this motor has its short comings however some of the claims I have read here make me think I should be getting a little more out of it.

I have a 93 P3500 chassis with a school bus body on it. It weighs about 11,000 pounds with nothing in it. I have converted it to an RV so with load and people probably another 2500 lbs. It has a Dana 80 rear (not sure of ratio) and a rebuilt 4L80E in it, 19.5 tires.

Motor runs fine, starts easy, no smoke, recent PM, 260,000 on the odometer but not sure if that is the engine mileage or not. Since it was a fleet vehicle for many years I suspect it may have been swapped or rebuilt. It is on its 3rd transmission now. One odd thing I have found is that the engine uses a serpentine belt yet when I search for 93 parts all belts come up as v-belts.

On a flat I am lucky if I can get it to 60MPH, 55-57 is about it, downhill 70 no problem, up hill is a joke. We went through a mountain pass and were reduced to 35mph in 3rd gear. Transmission drives fine, engages, but perhaps I am missing something? Or maybe this is what I should expect? Being it was a district school bus I am sure it never had to go over 45MPH, most likely 30-35 its whole life.

Any tips would be appreciated.

 

You have a lot of vehicle to move without a turbo,Horsepower / Torque (at start): 130 hp (97 kW) @ 3,600 rpm / 240 lb·ft (325 N·m) @ 2,000 rpm.

Compare to a volkswagen golf 2.0 L,138 bhp @ 3,750-4,150 rpm; 320 newton metres (236 lbf·ft) @ 1,750-2,800 rpm

I would say they are apples and oranges apart but make the same power?

 

It would be interesting to know the weight difference between them too.

I agree which is why I am thinking this is about all I am going to get. I would like to swap in a 6.5 Turbo if/when the price is right. I know there are better motors but I am also looking for something that will bolt in easily. If I could get ahold of a 6.5 cheap enough, overhaul it and do upgrades to prevent known issues I think I would be in decent shape. I don't need to exceed 70 or tow anything. Right now even the rolling hills cause speed drop.

 

An easier solution would be to get 6.5 exhasut manifolds,turbo and intake(both halves) and put them on your 6.2.

Have the injectors rebuilt to turbo specs(2200-2300 psi pop pressure) with bosch nozzles.

And run it like that-turning up the fuel on the 6.2 IP should be adequate.

An EGT gauge would also be madatory-the 6.5 rh manifold has a built in boss for drilling and tapping for the EGT probe.Limit EGT to 1150F.

Your exhaust would likely need modification to account for the crossover pipe and downpipe.

 

your problem is probably the diff on your truck its geared towards towing not speed,

Its a lot of weight to carry, hence the speeds you will get up too. Its all in the diffs on these trucks.