Motorhome diesel upgrade questions

Greetings,

In my opinion, if you're not getting the power you want/need for your MH out of a 400 cid motor, then I don't think you're going to be much better off with either of the diesels that would be able to fit into your chassis. The only ones that might do it are either the 6.2L naturally aspirated diesel or the 6.5L. The 6.5L was available both as a turbo charged and naturally aspirated unit that came out in '93 but I'm not too confident that you will be able to get the turbo into the engine bay of a '79 van because it needs a LOT of space on the passenger's side for the turbo and plumbing. You should be able to move up to a 454 (7.4L gasser) without too much trouble however.

If you're going to stick with this vehicle, I think you may want to start looking at non-engine related options such as either swapping the gears in the rear end or even adding an overdrive/underdrive unit to the driveline. Either of these options will get you better performance on the hills but the overdrive/underdrive unit should help you on the flats as well.

You can also post these questions to RV related newsgroups like alt.rv and others like it. Those folks may have some good insight as well.

Cheers - Jonathan

I agree with Jonathan. Swapping in a 6.2 or non-turbo 6.5 will be a giant step backwards. A 454 will up the power a bit and be a heck of a lot easier to swap in. There is a good chance your mileage would go up a tad, as the

400 is a gas sucker, but I would not bank on it. In 79 the 454 and 400 used the same radiator and transmission. While you're at it a good set of RV headers would help too. You're going to need to screw with the exhaust system anyway.

Al

alt.rv

I agree a oil burner that will fit will give it less power yet and then the final drive ratio may be wrong too. As the poster said above I would strongly suggest you determine what rear axle ratio you have now and go at least one step deeper. (if you have a 4.10 got to a

4.56, if it is a 4.56 go to a 5.13) You likely have a 400small block and it is a powerfull engine for its size but if it is not geared correctly it will not properly power the motor home. You need proper gears for good performance in hills. Also I would not recommand a 454 because you could have overheating problems in the chassis and 454?s have exhaust manifold problems in motor homes (cracking from extreme heat from limited ventilation. (GM came out with a SS exhaust manifold in the 90?s to cure this problem) You would not see a big power boost over your 400 and you could get the same or better results by simply regearing your chassis with current motor in it.

On Tue, 19 Jul 2005 08:58:03 -0700, "Big Al" spake thusly:

I have been pondering another approach, namely the tried and true. Your touched on headers. Now how about I add some classic goodies, such as an Edelbrock Performer manifold, updated carburetor and a different cam or change the cam timing.

Is a 700R4 transmission strong enough for this application? If I choose a deeper axle ratio, then overdrive would be desirable.

Gad! You know how many years it's been since I used the words "Edelbrock" and "headers" in a conversation? ;-)

Aftermarket fuel injection anyone?

Snip

For one thing a 79 should have a 400 Turbo transmission, not a 700R4. Lots of 70's small blocks develop flat cams, you may want to check that. Forget the intake and carb. What you have is a Qudrajet, and they are fine for what your using it for. Headers and larger pipes with free flowing mufflers will definitely help. One thing I have found on motorhomes is a stuck heat riser. It's in the passenger side exhaust manifold and had a vacuum diaphragm on it. Make sure it's working. They tend to stick from not using the vehicle for weeks at a time. If it is stuck, it will be stuck closed. This will overheat the carb, and reduce the power quite a bit.

Al

On Thu, 21 Jul 2005 21:46:49 -0700, "Big Al" spake thusly:

Oh I knew that. I was wondering if a higher ratio rear axle with an OD trans would do anything for me.

I heard a lot about that with 305s. Seen it happen in a 1980 Scottsdale. Like the cam was made of wood.

I have used Edelbrock Performer manifolds before on small block Dodges with good success.

I did notice one thing when driving the MH. When climbing a hill, I didn't notice the characteristic roar you usually hear when the secondary barrels open up. Didn't realize it at the time but now I am beginning to wonder.

Never though of that. That would also restrict the exhaust flow on one side, I imagine.

Thanx, I'll check it out.

"" wrote: > On Thu, 21 Jul 2005 21:46:49 -0700, "Big Al" > > spake thusly: > > >

The flat cam lobe problem was not wide spread and I doubt it is a issue here. ALso I WOULD NOT do headers because they raise engine compartment temps big time on long hard pulls and it that small comparyment you have in that chassis, it could really be a problem big time. Do not go there. Chevy small blocks respond really good to cams and intakes. THe cam in the engine is very mild and a warmer RV cam with possible a better intake would make a world of difference in power from that engine and a lot more than headers. I have used a Competion Cam H260 a few times in the past with excellent towing results. On the tranny, I would just stay with a THM 400 as they are very trouble free and strong and a OD would be a waste of money unless you put in a LOT deeper final drive ratio because it would lug badly in OD if you did not (you would need about 2 steps deeper finail drive) You might check linkages on throttle to make sure there are working correctly.