OEM muffler!!! Id bust that off right away. With that age im sure you could benefit from loosing that anchor. Try running with just the cat and see what you get.

 

I pulled a 8-9000# 5th wheel camper with the truck in my sig a couple of weeks ago. With the 3.55 gears, it does seem a bit doggish in the hills, but I would say it did better than either the Ford non turbo IDI or a Chevy 6.2 non turbo diesel that I drove for an employer a few years ago which both of those trucks had 3.73 gearing. While a diesel is obviously going to get better gas mileage, it's also going to perform better in the lower and midrange RPM's than the a stock 460 any day. While I haven't driven any of the newer diesels with a load, I know they've got more power, but I can't complain about the 460 either.

I've got over 125,000 miles of hard farm work and now recently camper pulling on the motor and other than a single water pump that my dad had replaced years ago, it's only been regular maintenance items as far as the drive train goes. I would agree with you that the diesel/460 comparison is apples to oranges; if you want a braeburn to grannysmith apples comparision (still not a great comparison, but at least in the same family ), I'd say compare the older non turbo diesels to the 460 or find somebody with a supercharged/turbocharged 460 to compare to your turbo diesels.

However, to help solve your problem, I'd recommend an aftermarket muffler and either remove your cat or get a high flow version. I noticed a huge benefit from both on my truck. Cutting out the horns in the intake tubes will make the intake louder, but also helped me with the higher RPM power (no difference I could find in low end power). Lastly, I know that everybody else has good results from headers, but I don't have personal experience with those (yet), but they should help a lot.

Edit: Since you asked about fuel mileage in the title: I get 12-13 average when driving 95% highway miles unloaded, town I get 9-10 unloaded. Pulling my 30' 5th wheel @ ~9000 lbs, I got between 6.2 and 7.5 mpg with the camper and usually average 7-8 with shorter (less surface area) loads like pallets of seed on a car trailer, and I know I've gotten as low as 2-3 mpg when pulling 20,000 lb NH3 doubles from the elevator to the field. If it's one thing any 460 owner can guarantee, it's that you'll never pass up a gas station

 

Hey

The only thing that I have not seen mentioned is the fuel filter. When they plug up it hurts power and mileage. They should be changed once a year. I do half city half highway and have been running about 11.5-12 lately i will try to post my mileage charter later tonight when I get home

 

Yes, the fuel filter is on my list of things to changed. Just went under their yesterday and it looked pretty darn old. Who knows when it was last changed, if ever!

I'll go pick up a new fuel filter today. Not sure if I need any special tools yet. I"ll have to look at it a bit more closely. Sometime the use funny crimps on those things!

By the way, is there only the one filter inside the frame rail on the driver side? Not sure if there is something in the tank I need to deal with as well.

Thanks,

Terry

 

Just on the Rail.

 

Since I live in California and have smog rules, I may be a bit limited to the after market exhaust I can use. I've been looking around and there seem to be a lot of options.

Haven't done any research on this forum yet specifically for exhaust, but does anyone have any recommendations for a good replacement setup that is California legal? Not looking for anything high performance, but simply a good stock replacement that is affordable. Probably want to do the cat as well.

With 155K miles I don't need to be pushing the truck any harder than it was designed. Just want to keep it running efficient.

I do have a small exhaust leak I believe on the passenger side exhaust manifold. Can barely hear it when I first start it up. After a min. or so of running it is gone. So I may be replacing those gaskets as well.

Thanks,

Terry

 

Thanks!

Terry

 

In Cali you will have to retain that ceramic cat. Unless you are going to a high flow metal core cat, you will see no noticeable performance improvement by replacing a "working" cat with a new one. For mufflers, I run a single 3" flowmaster which is about as quiet as stock yet much better flowing. There are louder options, but without headers you wont be able to flow enough to need it for performance.

 

Not sure if I need a new cat or not. Looks like it is the original one still on there. Some people suggested if the cat were bad it could be clogging up the exhaust system. It did pass smog with very clean results.

Just want to make sure my exhaust is working properly. Not looking for any huge increase in performance. Just want to bring it back to the stock performance if possible. The flowmaster 3" sounds good. Wan't to keep it quite. I'll look into that.

Thanks,

Terry

 

Low MPG are usually when I am Towing My 30 Ft %th wheel.

 

Nice collection of data! Good way to check that your truck is running efficiently over the years.

Sounds like we have about the same truck except mine is the SRW. Is yours a 4x4?

I'm getting about 6.5 to 7mpg in town right now with a very light foot. And about 7.5mpg towing just under 5000 lbs on the highway.

Just working on my checklist doing the free / inexpensive things first. Hopefully something will pop up.

Thanks!

 

Glad to see I'm not the only person who tracks every tank of fuel, though my list started much more recently. I restarted my gas mileage tracking for my truck this January after finally putting in the first tank of fuel after the 1 year hiatus of fixing it back up to running condition.

Here's my new tracking list:

 

you can check for exsessive back pressure with a vacume gauge. hook it to a vacume port and slowly rev to 2k rpm. as the engine rpm is increased the back pressure from a clogged cat or muffler will cause the needle to slowly drop to zero. the needle then may slowly rise. ir drop to a low point even at idle.

normal reading should be between 15-22 in-hg and holding steady. subtract 1" for every 1000' above sea level.

 

Thank you! I will try this right away.

Terry