I must have been due for a little luck. After a week of pounding, pulling and pressing four u-joints and two carrier bearings, replacing a rear trans seal and parking brake parts and well...if you own an AS MH you know what I mean. It was time for the dreaded task that strikes fear in the hearts of the owners of old P30 motorhomes with tired 454's everywhere; REMOVING THE EXHAUST MANIFOLDS.
(insert Psycho sound track here)
I had discovered, while repairing another exhaust problem, that two air injectors on the driver's side and one on the passenger's side had developed some severe cracks at the manifold fittings. These cracks were the cause of a very loud exhaust leak at speed and a lot of exhaust fumes in the cockpit at stop lights. Given the upcoming trip back east with the kids in two weeks and the spring camping season upon us, I figured it was time to deal with the last major mechanical issue on my to do list. Besides, I'm tired of guessing if the people in the car next to me are wondering if I'm restoring it...or it's all I can afford - the exhaust sounds, squeaks and rattles don't help.
So the original plan was to remove the air pumps and hoses, cutoff the injector pipes remove the 7/8" flared fittings and replace them with plug fittings. Removing the pumps and hoses...no problem, cutting off the pipes...no problem, hitting the fittings with the impact wrench...big problem. Rounded off two in a row and didn't even budge the rest. Needless to say this was not a good moment. Packed up the tools and went home to drown my sorrows and search the forum for anything related to exhaust manifolds.
So, this afternoon, after a little meditation ("visualize the manifold bolts coming out"), I decided that the only way out of this was to remove the manifolds themselves. That way I could remove the rest of the fittings, or have them machined out.
I had soaked everything with penetrating oil for the last 48 hours so I tried my trusty 9/16" on a breaker bar on the first bolt. No go...didn't even budge. BTW - those are pretty big fender wells when your working on the brakes but they sure to get cramped when you really need to wrench on something. So I took out the impact wrench again....I know, I know this is a REALLY bad idea. But I had been told that my motor was rebuilt about 3000 miles before I bought the coach. I also noticed that the manifolds were sporting new gaskets and reasonably new bolts. There were other clues as well like the drilled out manifold to downtube pipe flange and new bolts. I figured - what the heck...I'll hit it with 1/4 power and see what happens. (gulp)
2 hours and 16 bolts later the manifolds are off. The bolts all came out clean and with their threads using a "gentle" impact wrench and a lot of loosening…spraying with oil, re-tightening, loosening again, etc. Other than removing the master cylinder to get to access to the left front bolt it all went pretty quickly.
After looking at the other side of the air pipes I can understand why the 454's have manifold over-temp issues. They extend all the way into the exhaust port, right above each exhaust valve, inject air into the exhaust port to re-ignite any unburned fuel as it exits the head. This additional heat and turbulence, not to mention that these tubes are the equivalent of gluing a piece of 1/2 pipe inside each of your exhaust ports, certainly doesn't seem to follow the "ported and polished" school of engine performance. I now see why the installation of headers improves flow, heat reduction, power & mileage in a single bolt on.
So...now I'm thinking headers. Something quick and easy and on a budget. Brett had a combo that I liked on another post. I'm currently thinking about Hedmann's (for a Class A 454) into 3" collectors. Then use a kit into DynoMax RV mufflers. Possibly an H kit. Oh...and chrome tips. I think I can get everything from Jegs for about $600.
As always...suggestions would be appreciated.
Oh yes...special thanks should be given to the mechanic who dealt with these bolts before me. Thank you, thank you, thank you! I'll be replacing them with new bolts, smothered in anti-seize so I can pass the favor onto the next guy. After all, the next guy could be me!