460 Ford question

[Dumfast]

Would an emissions device sound like a exhaust leak?...EGR?...I have a 84 460 in a class C motorhome and it sounds like a exhaust leak but seems to be around the carb area..Have checked and tightened all exhaust manifold bolts..Has a smog pump and all that stuff also...Any ideas?

[Ziggy]

The most common exhaust leak on a motorhome is caused by the heat created by the stress pushing such a load.The heat almosy always warps the headers or flanges and tightening them will not fix the leak.The heat is a killer so its important to get a good header with a thick flange so it can be shaved when it warps.

[GAME OVER?]

Im guessing it a bone stock 460? check all the rocker arms! just went through this om a 351w. I was convinced it was an exhaust leak on the left bank. I even had the noise pin pointed to the cylinder. turns out a rocker went bad.

[philofab]

460 engines are known for cracking/leaking passenger exhaust manifolds. Both my E350 and my F250 have a tick from the right side.

[sickrick]

I believe their is a exhaust crossover port in the intake. This lets hot exhaust warm the intake to aid in getting everything up to operating temp quicker. If it is leaking at the intake manifold it may the sound you hear.

[JEFFRPM]

Back in those days the intake manifold had a aluminum plate under the carb. the egr valve bolts to it on the rear of the plate. The plate rots out allowing exaust gas leaks. Grab a 2' piece of small diameter hose stick one end up to our ear and run the other end around the base of the carb/egr plate and if their is a leak you will hear it in the tube.
when you buy a new plate you want the STEEL one not another aluminum one also get the gaskets from the dealer the bottom one is a special pattern that looks like a holly 4 bolt pattern but it's not. Also the top one is 3/8 thick with inserts in the carb stud holes so you can't over tighten it warping the baseplate of the carb it also insulates the carb from the heat from a hot soak [shutting off the motor after pulling baker grade] causing the fuel to percolate.

[Dumfast]

Thanks everyone for the possible problems...Going to pull off the carb and try to get a rebuild kit for it...The motorhome has sat for past 6 years and just doesn't seem to have the power I remember a BB to have...Will check out the EGR/crossover madness also...Just replaced the pass side exhaust manifold gasket (stock manifolds) and tightened everything...The noise is definitely up in and around the carb area

[JEFFRPM]

Don't ever install exaust manifold gaskets on a 460 bolt them up metal to metal they will seal just fine. All the gasket does is allow the bolts to get loose and cause another blown out gasket. PS make sure the manifolds are flat.

[Dumfast]

Pulled off the carb today...Not good...Carb to EGR plate gasket half gone,just charcoal in one corner...EGR to intake mainifold gasket almost burned in half..definitely was sucking air in...EGR actuator to EGR plate gasket bad (plate is the steel one)...Small steel tube going in and out of the manifold gasket half gone..Both bolts for this snapped off, in process of drilling them out now...Would think it will run much better when I'm done!...Ahh the joys of motoring..

[Dumfast]

Ok ...Replaced all the bad gaskets and put in a carb rebuild kit....Night and day difference in noise!..Can't even hear it with the cowl/cover thing on...One last question and thanks for all the previous post's...How can I tell if the vacuum secondaries are opening?....I revved it pretty high with the cover off in park, but they never moved...Not enough vacuum without being under load?

[JEFFRPM]

Leave the doghouse off have someone ride shotgun and let them see if they open.

[bajaruner11]

Don't ever install exaust manifold gaskets on a 460 bolt them up metal to metal they will seal just fine. All the gasket does is allow the bolts to get loose and cause another blown out gasket. PS make sure the manifolds are flat.

I feel this is worth repeating, having the manifolds surfaced and bolted back on flat without a gasket is the only
way to seal these up.

[Baja Fool]

Don't ever install exaust manifold gaskets on a 460 bolt them up metal to metal they will seal just fine. All the gasket does is allow the bolts to get loose and cause another blown out gasket. PS make sure the manifolds are flat.
I put in copper exhaust gaskets in my 460, with headers!,over 10 years ago and sold it like that. They are malleable and don't blow out near as easy as the conventional stuff. Just keep the bolts tight.

My 2 pesos.....

[JEFFRPM]

With headers that's correct cast manifolds=no gasket.

[Baja Fool]

That's why I wrote "with headers".....

[KAILUAZ]

Lots of great 460 information here: 460ford.com (http://460ford.com/forum/index.php)