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Hey guys, i just bought a Winnebago with a 89 Ford 460 engine, stock as far I can see. I took it for a spin (400 miles) and I'm floored by the mileage. Now I know 460's aren't know for fuel economy and the rig is heavy and built like a square sail but @ 6.5 MPG without a trailer seems there might be an issue. Lots of noise and vibration on acceleration at and around 55 MPH. Once warmed up, there is some knocking coming from the cat. I'm thinking it's a blocked exhaust issue. At idle it runs great so I'm hesitant to start pulling plugs. It only has 50K miles so it's sat most of it's life. Could a cat fall apart under these conditions? I haven't measured the exhaust pressure yet. I was going to buy the OCT back pressure gauge but it's almost 300$ on Amazon! Any advice would be greatly appreciated! I want to put some miles in come the fall. Hope to get the mileage up to 10 but I'll settle for 9!
6.5 mpg your doing good. My '89 E350 460 motorhome got average 5.
Good news is the milage is not going to change by towing. A pig is a pig. Lol On mine I gutted the cat and made a huge difference on power going up hills and mountains.
It's as I suspected. The second cat is all in pieces. I cut into the first one and it was fine, I could even see through all the holes so I was worried I was doing all this for not. But once I got all the first one cleared away I could see and feel the second one was all busted up and sideways (the rattle). A buddy said he could weld my cuts shut so I hope that goes well. I'm using a Milwaukee ion battery powered grinder with a zipcut blade and it's pretty easy going. Once I have it open I use a chisel and a hammer, breaks apart easily. If this gives me some more oomph and maybe an MPG I'll be a happy camper! I'll post my new mileage when it becomes available, next road trip. You can see the second set of converters are not aligned with the exhaust flow which I believe are creating a restriction.
I've got an 87 class C 27' motorhome with the 460, and it only gets 7mph running 60mph. Add a trailer, and I'm down to 5. I've only got 40,000 miles on mine, and had the cats rust out several years ago (probably around 30,000 miles or so). I removed them and run straight duals with Flowmasters. Sounds like a Nascar. lol
Now that i have that cat gutted I've been thinking (obsessing) over that smog pump. Am I right in understanding that it draws air from the intake and pumps it into the exhaust? At the expense of the engine? That would be like someone turning a pump that takes air from their lungs and pumps it up where the sun doesn't shine, two things nobody needs. Anyone have experience removing these pumps? What to do about the slack in the belt if I do? Just adjust the tension?
Now that i have that cat gutted I've been thinking (obsessing) over that smog pump. Am I right in understanding that it draws air from the intake and pumps it into the exhaust? At the expense of the engine? That would be like someone turning a pump that takes air from their lungs and pumps it up where the sun doesn't shine, two things nobody needs. Anyone have experience removing these pumps? What to do about the slack in the belt if I do? Just adjust the tension?
I pulled all the smog control crap off my 87 when I put the headers and dual exhaust on it. Any exposed vacuum port got capped, and I think I had to fabricate a small plate to bolt on somewhere (I forget exactly where, now). As for the belt, I just measured around the alternator, and crank pulley, and went to the auto parts store. I bought several sizes close to what I measured, fit them all, kept the one liked, and returned the rest. If I think about it, I'll try to get a couple of pics sometime this week.
. Am I right in understanding that it draws air from the intake and pumps it into the exhaust?
No, it has it's own intake. If the pump isn't seized it's not a significant drag on the motor but that system accounts for one hell of a plumbing mess under the hood of these trucks, and it serves absolutley no purpose if the cats are gone. But... you might open an ugly can of worms removing it all if the motor uses those friggen spider manifolds that feed into each individual port on the exhaust manifolds, that is 8 connectors that will likely refuse to come apart and even if they do it's 8 holes in the exhaust you have to then plug.
But... you might open an ugly can of worms removing it all if the motor uses those friggen spider manifolds that feed into each individual port on the exhaust manifolds, that is 8 connectors that will likely refuse to come apart and even if they do it's 8 holes in the exhaust you have to then plug.
No, it has it's own intake. If the pump isn't seized it's not a significant drag on the motor but that system accounts for one hell of a plumbing mess under the hood of these trucks, and it serves absolutley no purpose if the cats are gone. But... you might open an ugly can of worms removing it all if the motor uses those friggen spider manifolds that feed into each individual port on the exhaust manifolds, that is 8 connectors that will likely refuse to come apart and even if they do it's 8 holes in the exhaust you have to then plug.
Not saying it applies to everything because my knowledge isn't vast on the topic but my 91 e350 460 smog pump did draw air from the vehicle intake. It did not have any manifold connections or thermactor connections. It was connected to the intake and cat only.
I pulled all the smog control crap off my 87 when I put the headers and dual exhaust on it. Any exposed vacuum port got capped, and I think I had to fabricate a small plate to bolt on somewhere (I forget exactly where, now). As for the belt, I just measured around the alternator, and crank pulley, and went to the auto parts store. I bought several sizes close to what I measured, fit them all, kept the one liked, and returned the rest. If I think about it, I'll try to get a couple of pics sometime this week.
Not sure if these will help, but here's mine after the smog crap deleted and headers added.
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Problem with my 89 460 E350
