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I have recently purchased a 1988 27' Class C with a ford 460. It seems to run good but on my first long trip I had to drop to 1st gear on a few hills and seemed to have no power.I also averaged only 6 mpg. It isnt missing but does make a loud hissing sound when under load. Any ideas? This is my first motorhome so I really don't know what to expect out of the Ford 460.
I have just finished doing a rebuild on my 460 in a class A motorhome ( 1987).I had to completely take out the blocks to replace valve seats, I also had some broken bolts on my exhaust.I had to heat them with a torch after I had the block out on the work bench.I cut the heads of the bolts off and then worked on the bolts with the manifolds off. ( more room to work on the bolts.) NOTE : But this was not the worst -- the 460 exhaust manifolds SHRINK meaning that when you take them off you may have to replace with new ones.When I went to put the old ones back on I found that the manifolds,both, where out a half a bolt hole for them to line up.I was told that this is normal for 460 on a class A motorhome.
The "hissing" could be the result of a restricted exhaust system. Two causes come to mind, 1. the baffles in the muffler(s) may have come loose and are stacked together at the muffler outlet. Check for this by going under rig when system is cold and smacking the bottom of the muffler with the palm of your hand or a rubber mallet. If you hear things rattling around in there, then it's time for a new one. The other cause could be a collaspe of the inner pipe in the exhaust header pipes, all the way back to the muffler. These are pipes within a pipe construction and sometimes the inner pipe will collapse upon itself, narrowing the diameter of the pipe. A check with a vacuum gauge is a good test for exhaust system restrictions. I think your '88 may be still equipped with a carb, is that correct?
Broken exhaust manifold bolts. On the 460 it is very common. I need to remove a couple myself. It now has a burnt valve so I will have the heads off and that will make the broken bolt possible. I was told you have to remove the exhaust manifold to get to the broken off bolts in most cases. Then you will most likely break off more and some are imposible to get to with head on engine. That is what I was told.
Kent
I have 94 F-250 truck. I purchased the vehicle new. It has 80,000 miles on it. No problem so far with wxception of mainfold bolt is broken and leaks exhaust an noise. After warming up sounds go away. I have been told this is a problem with 460. Any one had the sme proble? Any experience extracting the broken bolt. Aprreciate any hint.
Thanks for the reply Sam. I have the EFI on the 460. I did go tap the muffler and it sounds ok. It does seem like a restricted exhaust like you said. The hissing sounds like a open air hose blowing. The motorhome has 60,000 miles on it with no major mechanical work done and I purchased it from the original owner. He did say he replaved the catalytic converter a few years back. Can I de-smog this motor and would that give me more power?
email Doug R
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