I have a 21' 1991 Class C Motorhome, it is built on an E-350 Chassis including a 5.8L. We love the motorhome, but the stock 5.8 gets bad fuel milage (10 HWY) but more importantly, it just does not seem like enough engine for this rig, on the highway it rolls along if it is flat, but any hills wind it out tight. There are tons of parts and ideas for the 5.8, but I am having trouble figuring out what will work in the van chassis. I would consider a new intake, Injectors, Heads, and a cam, but I cannot figure out what parts will work. I would also like to keep the original computer system if possible but I am open to ideas.

 

Welcome to the forum, and my world of disappointing horsepower and fuel mileage with the 5.8L.


My van is a 95, so I probably have the benefit of the newer fuel management and hydraulic roller camshaft. I see so many of the newer motors with much higher horsepower and torque ratings, that leave me wanting more, but alas...


I too, like my vehicle so much, that I have made some adjustments to performance, and mostly to my expectations. 15 mpg empty, 10-12 towing. I just grit my teeth at the gas pump and consider the joy of no vehicle payments and low repair costs. It really is a benefit to have the van for trips and hauling.


Consider these oldie but goodies: the "6litre" tune up. basically a timing bump, hotter coil, spark plug gap, and in my case running 89 mid-grade octane when towing.
ignition upgrade and timing bump (no 56K) - FSB Forums


Here's another discussion from a noted van owner (carringb) with lots of towing experience using the 5.8L, same applies to motorhome.
RV.Net Open Roads Forum: Tow Vehicles: Optimize Ford E150 For Towing


I've done the timing bump, opened the air intake box, better exhaust. My fuel mileage probably isn't any better when I'm towing, but I feel I'm getting all the power that is available from the 5.8L. I could do the head swap, headers, etc. I did all of that and more in my old drag racing days, but I guess I'm leaning towards reliability and making better use of torque when dealing with heavier rigs. The return on investment with this involved engine work on this motor didn't seem worth it to me.


The best single improvement for me using the factory 3.55 gears was to just lockout overdrive when towing. I also installed a factory tach into my gauge cluster, and run about 2,500 RPM approaching 65 MPH. This is near the torque peak for the 5.8L, and it really pulls well at that RPM (considering). I've been reminded of the "legendary" 5.8L Ford marine engines that sing happily for hours on end at higher rpms, while yielding good service life.


Look here for posts by Conanski, I recall he had really good advice regarding cam changes on earlier 5.8L
https://www.ford-trucks.com/forums/9...rque-rpms.html


Now that I've overdone my response, don't fret too much, it's a good motor, just a little "old school", take your time, enjoy the ride, and time with family.


David

 

I forgot to mention, the Motorhome has 4.10 gears.
I will check over the links when I have a spare minute, I am a diesel guy so I have thought more than once about swapping in a 7.3 or 6bt, but that is a much bigger and expensive project than a higher performance 5.8. we put about 10,000 miles a year on the motorhome, so the fuel milage does not bother me as much as the lack of power. I just feel bad when she has to drop into 2nd gear on the highway.

 

2nd gear on the hills sounds familiar. First trip with my trailer I decided to try to keep the speed limit going over Jellico pass, I-75 in Tennessee. Well, it did it, much of the time with pedal all the way down in 2nd.


I determined it really wasn't worth the bragging points, or the drastic fuel drop, now I just ease over to the right, 45-50 isn't so bad, and the overall trip time is little difference. I once wanted a 7.3L diesel chateau van, but have decided the working space under the hood just wouldn't be as much fun.


4.10 sounds decent for that vehicle, you'll love this application: I still use it when contemplating a gear swap in mine.
Visual RPM, Speed, and Gear Ratio Calculator


Not sure about the electronics configuration/friendliness, maybe a 460 swap would give you the power and torque you want on a budget.

 

If you want low and mid range torque then go for higher compression and/or a custom cam. Call the good folks and Crane, or Edelbrock, or whatever and they'll set you up.

Bigger exhaust and intake will not gain low RPM torque.

 

Yeah the way these old motors are configured they are sucking air through a straw.. the heads are way too small, intake isn't much better, and the cam in the early motors is a joke. You could bolt on an aftermarket HCI combo but that will require larger injectors and a tunable EFI system to make it all cooperate.. or you could do a carb but if you vehicle has the E4OD trans then a carb swap isn't gonna work.

A warmed over 5.8 would be a good half way step, find some GT40 heads and install a good EFI friendly cam like the Crane 444232, and then drop the stock manifolds and Y pipe and install headers(shorties are good, longtubes are better) and a high flow cat if so equipped. That will put some more thunder under you right foot and the gas milage should even improve as this will increase torque output as well.

 

I like the idea of the 7.3 since I had one in a 1997 F-250 and have one now in a 2002 Excursion, I have had nothing but great luck with them. They are very reliable and powerful enough for what I need them for. I agree, the hood space is tight, I have looked at several vans to buy as a donor for a swap, but they do not seem to have the power in the Excursion and F250, I read somewhere that they are de-tuned for the Van, I guess there really is no free lunch.

 

Conanski, have you used the Crane 444232? I have seen that cam crop up in some of my searching, I am seriously considering it, also do you have any experience with Longtube headers that work in a van? Will the Coated headers help with Thermal transfer or is it more for looks? I just did the Exhaust Manifold Gaskets in this beast, What a PITA, I should have bought new heads before tackling that project, it is tight as a drum with the new RemFlex Gaskets, Great Product.

 

Also, I see GT40 P heads, GT40 heads, and Aluminum GT40 heads, also good reviews on the AFR heads although they are twice the price of the Cast GT40 heads and look like a piston change may be in order. What do you recommend?

 

welcome to the forum, what is your budget for your engine modifications?

There is power to be had but no free lunches , horsepower costs.

there are lots of options to increase power in these motors , my recommendation would be first to find a tuner in your area who can reflash your computer to maximize any modifications you will make.

after that its basic motor build time of matching the heads , cam , intake , and exhaust to work together in the rpm band you need most . which should be from idle to 4000 rpms. Torque is what you want !

If real power is what you want swap in a stroker . good luck

 

I think member Baddad modded an engine with the GT40 heads---might do a search under that user name to see if his process was/is useful for this project.

 

I have not really established a budget, I know realistically the BT6 swap will cost me around $10,000++ with everything I want to swap out, trans, add 4x4, etc. I guess I would stick 2-3K into this project and keep my reasonably low but maybe a little better fuel milage but acceptable power.