I just recently bought a 1976 ford motorhome class-c with a 460. It runs great but has developed an exhaust leak at the manifold. I am interested in replacing with headers while I have the manifolds off. The exhaust shop recommends nothing smaller than a 1/2 inch flanged header. I cannot find anything available larger than a 3/8 inch flange. does anyone have any insight as to where to find these elusive 1/2 inch or larger headers. Or has anyone run 3/8 flanged headers with success?? your help is greatly appreciated. I have found tons of useful info on this forum keep up the good work

 

Welcome to FTE!!!!

If you run it hard up hills, IE foot to the floor or just lugging the engine up hills in a higher gear than it should be in, in a attempt to maintain speed or keep up with car traffic (but not semi traffic) or just generaly do not understand that you are pushing a fair amount of weight while also having a fair amout of wind drag, and you have to go slower and travel according to truck speeds on hills, you will quickly warp the 3/8" flanges.

It will also take longer, but you can warp the 1/2" flanges as well. If you look at the larger gas motorhomes on a steep hill, pushing hard, the exhaust manifolds can glow a dull red !!!

That said, if you drive reasonably well, and the motorhome is a smaller lighter unit, not say a 26', but something in the 18 - 20' size range then you should be ok with the 3/8" flanges. Especially if you live in the flatlands. Myself, I would either get new Ford cast iron manifolds, not used manifolds from the wecker, as you want the latest and best design, there are several revisions, or find a pair of 1/2" flanged headers. Check RV shops and the like.

Ford and Chevy both had issues with this in motorhomes. The larger the motorhome, the worse the problem is. Both have gone thru several exhaust manifold revisions. Dodge used in most motorhomes what was called there 440-3 engine which had different cylinder heads, with increased cooling around the exhaust valves and ports to reduce exhaust temp. Of course a larger radiator was required to deal with the extra water jacket heat. This is one of the few things Dodge did really well.

 

thanks for the input. I have found banks has a .625 flange for the newer model 460 but dont list anything for mine. I am awaiting an email from them regarding my application but outlook is not so good. I will continue to search and will post my findings. I figured someone has encountered this before. all input is welcome and appreciated.

 

Good luck on your search, hopefully someone else will chime in here with some more ideas. Banks is a pretty good outfit, if you don't hear back from them, try a phone call, if you get the right person, they are a wealth of information.

Another thought - make sure that you run the least restictive exhaust downstream of the headers, especially if you end up with the 3/8" flanges. Every little bit helps.

As a side note, is this a new motorhome to you ? Or have you been running it for a while now ? That might also tell you something, at least as to how you have/it has been operatiing, and what and where the exhaust leak occured on the origional manifold. Obiviously your 460 s not new, but just trying to see if this might have been a on going issue?

Extra air space around the exhaust mainfold / headers probably would not hurt either, a class C gets pretty tight though around the engine box. I know of tricks to do to Class A's, but I don't what to advise in your case.

Last thing, late timing, or a overrich mixture will inject extra heat into the exhaust sytem as well. I am assuming that you have made sure the engine is set up properly?

David

 

absolutely, all is up to par. carb has been dialed in on 5gas at work. The motorhome is 3 weeks new to me also my first 460. I have gone front to back on it and replaced many of parts. It runs and drives strong now. The last trip out it developed the minor leak. We all know you have to fix it immediately. Since I have to remove the manifold and have it resurfaced I figure good time to address headers.

 

Sure sounds like you are approaching it well. Hopefully you will find what you are looking for. The 460 was a good engine, I had one in a 1976 F250. You might not pass many fuel stations, but that is not what taking your house along with you is all about.

I have to add, I have owned every type of RV from a tent trailer to a Rear engine (gas - 4 mpg) bus conversion, with the exception of a Class C, and I liked the motorhome and bus the best, especialy with small kids. When it was raining I could just pull in, the coach was warm and I didn't have to get out and set up in the rain.

Not to hijack, but i have been toying around with looking for / purchasing a older PD4106 or PD 4107 GM Bus conversion. Too rich for my blood to get a newer conversion though. I do have a fondness for the Aluminum bodies

David