Visit our Popular Forums

ALANSD · 03-01-2002, 09:05 AM

What type exhaust configuration do you have on your motorhome? Mine is dual exhaust, and seems to have a free-flow muffler on each. Just curious, as to what was stock if we can tell at this point.

rdm · 03-01-2002, 10:40 AM

Our 325 has dual exhaust I believe this was standard. The system could likely benifit from a fresh air intake system and K&N air filter plus the addition of high flow mufflers. this likely remove some of the retained heat from the big block 454.
Ray

ALANSD · 03-02-2002, 02:29 PM

Thanks for your info. I just received my "Tornado" from Camping World..I stated my skepticism elsewhere, but having done some research I am going to try it and see if it will aid the engine breathing.
Any ideas on exhaust changes? Banks looks great but is quite expensive. I know there are a lot of options for the 454.

PeterH-350LE · 03-03-2002, 08:13 AM

The stock exhaust manifolds on the 454 are constant source of trouble, especially when they get older. Besides that they restrict the exhaust by design. Eventually, I would like to put some headers on there, any input other than banks would be appreciated.
Right now, I have a leak on the drivers side, which goes away after the engine gets warm. But I have to fix it soon, since it will get worse.
The problem is that one of the bolts is frozen to the head. I guess, I will have to use a blow torch to heat it up. But it's right next to one of the power steering hoses. Any suggestions?

ALANSD · 03-04-2002, 10:17 AM

I used to soak a bolt like that with CRC (similiar to WD40) and let it sit overnight, soak it again sometimes and let it sit again, trying to inch it out a bit at a time. Its painstaking, but might loosen it.

thenewkid64 · 03-04-2002, 07:43 PM

The prior owner of my MH said he replaced the factory exaust manifolds with Headman headers. I cannot be sure as they have no paint or markings left on them. It also looks like he replaced the rest of the exaust system with oversized pipes. Prior owner was a hod rod nut.

I will tell you this, the amount of power I have at my disposal is AMAZING!

When I picked up the rig my wife followed me home in the car and she had problems keeping up with me as I merged onto the tollway from our breaks.

From what I can tell the carb has been rebuilt but not modified and I am running a stock airfilter.

Have only driven it home after purchasing but the 200+ mile trip was great.

Brett

PeterH-350LE · 03-10-2002, 04:26 PM

I finally got the frozen manifold bolt out. Warmed the engine up to operating temperature and use pure force. Must be the first time this manifold came off, since it didn't have a gasket.
Had to pull the plugs and was pleased to see the nice light grey color. Jacobs energy pak is doing its job, no more wet looking plugs.

ALANSD · 03-11-2002, 06:48 AM

I need to take a peek at Brett's setup. My rig has decent power, and I see receipts for redone headers, but I think they are still stock spec. My "tornado" got to me , and was the wrong size...for a later model 454. They are sending me a replacement.
Meanwhile cleaning the carb seems to have made a nice difference in idle, it always seemed to high, I think my choke was sticking.

thenewkid64 · 03-11-2002, 08:03 AM

Peter,

Why did you go with the Jacobs system?

Did it improve your performance? Mileage?

Brett

PeterH-350LE · 03-11-2002, 05:20 PM

The performance increase is remarkable. I am getting 8 plus mpg, mostly city/country road driving. I hoping to see closer to 10 for Interstate driving.
I have known about their RV energy pak for some time and almost put it on my previous RV.
I was looking at their porcelan spark plug boots and decided to give the entire system a try.
No more fouled plugs and entire new sense of power.

PeterH-350LE · 03-12-2002, 06:56 PM

Had to get a new exhaust manifold, the old one was leaking on three cylinders. After resurfacing and putting in new studs, I would have spend half the money for a new one from the dealer. (wholesale)
The big question, should I use a gasket or not?
Dealer says no, book says yes?
The surface of the cylinder head is in good shape.

FrankR · 03-12-2002, 07:34 PM

The motorhome I had before our bus was a GMC front wheel drive. Power was extracted from a 455 Olds. Yum yum, lots of power, but the exhaust manifolds were problematic. After much testing and trying, I made some changes in the factory exhaust. The stock exhaust was replaced with Jardine headers. Very heavy flanges and pipe size. The 2 inch dualls were removed and a single 3 inch pipe installed with Borla turbo muffler. The headers were wrapped with cloth heat material and retained with stainless .062 wire. No catalytic muffler and the exhaust pipe came out side of coach to have very few bends. The pipe between headers was 2.5 with flanges for any repair. The inner fender water splash panels were removed, with scoop fashioned under front sheetmetal. The hood was opened to allow hot air to escape. Transmission did not share radiator for cooling, seperate stacked plate cooler with radiator fans on switch and seperate t-stat control. The timing was adjustable from driver's seat. Frank

FrankR · 03-12-2002, 07:40 PM

The front scoop, inner panel removal, and hood vents are to have lots of outside cool air carry away the engine compartment heat. The air cleaner was also enlarged and connected to the front for a ram effect. Engine compartment air is very poor for combustion, milage and performance. Every little improvement helps. A trans temp gage are very important as well as a trans shift kit. It is of great value to have a tachometer to know when to pick a new gear in high demand situations........Frank

FrankR · 03-12-2002, 10:14 PM

I use gaskets as they help take up some clearance as the manifolds are cycling. The manifolds must be flat and straight. There are very special exhaust and intake manifold bolts. In some applications, as in boats, the block is heli-coiled and studs are used instead of bolts. Most bolts are grade 8 and are colored green. Enough......... Frank

Cars for sale
1969 Camaro
1963 Buick Skylark convert
1983 DeLorean
1972 Corvette t-top
and others

Rik · 03-13-2002, 02:13 AM

Years ago (when we had more discretionary income) we put a Banks Power Pack on
the 454 in our old Winnie Chieftain. The difference was nothing short of amazing! The
coach is literally falling apart around us -- but the always faithful 454 still happily climbs
the grapevine on I-5 in 3rd gear at 45 mph, always horribly over gross, and often with
the gas pedal not even to the floor! I realize that the Banks is WAY overpriced, and I
will consider putting a Doug Thorley or similar header set on the Argosy... but the
overpriced Banks came with a lifetime guarantee. And it works as advertised --
something not always easy to find these days. Also, it completely eliminates the periodic
replacement of the 454 manifolds that would be our lot without the Banks. Not to
mention the 15% increase in our gas mileage. I know, it sounds like I own stock in the
company... but not so... this has been my sole experience with Banks.

thenewkid64 · 03-13-2002, 05:16 AM

Peter,

I went through the file of receipts that the PO gave me with my rig and he did put heddman headers on with Copperseal exhaust gaskets in 1999. Part number 7158, about $35.00 from discount auto. His reason to for doing this was due to a failure of the original exhaust manifolds. It does not look like the manifolds have been touched since.

Frank may know more about it than I do but thinking about expansion and contraction of two different sized pieces of steel (the block and the manifold) I would think a gasket to allow for differing rates of expansion and contraction would extend the life of the new manifold.

Dealers are in business to sell you stuff and may not always lead you down the best path, my advice is to follow the book, or ask a mechanic you can trust.

PeterH-350LE · 03-13-2002, 07:46 PM

Thank you for the replies!
I went ahead and used a gasket, new grade 8 bolts, cleaned out the threads to get a good torque and used brass nuts on the new studs. All went well and I am pleased to finally have taken care of this.
On to the next project.

Larry Brown · 07-07-2002, 06:52 PM

Hi peter ,Me again how hard is it to get to the drivers side manifold bolts? the pass side looks like no big deal.Iwas told if I buy replacement exaust manifolds to buy some from a 90s model 454 as they are made from a different type of cast that is less likely to warp in the p30 chassis.Have you heard such a thing. I bet you would have to plug the smog pump holes.Mr gasket makes some extra thick gaskets that I have used on problem manifolds on big block fords that have worked pretty good.I thought about headers but collector gaskets never seen to hold up good.Also on the pass side there is a vacum operated vaulve in the flange that is a leak.What is this? should I dicth it when I do the mods?

PeterH-350LE · 07-07-2002, 07:43 PM

Larry, if you drive up on 1 or 2 1x6 boards, you get the extra clearance to make the work easy. Turn the wheel all the way to the right and you will have space to comfortably sit down, while working on the manifold. All bolts are accessible,
number one by the power steering is a bit tight.
Not sure about the mid 90's manifolds, they probably fit the head, but do they fit your exhaust pipe? All new manifolds come with the threaded holes. The dealer sells the plugs for the holes as well.
The passenger side has a heat riser, which may have the vaccuum you are referring to. I took mine completely out, since the old heat risers are a constant source of leaks. Living in a warm climate, it's not an issue for me to have a working heat riser.
New exhaust manifolds from the dealer are expensive. If I wouldn't get shop discount, I probably would have gone with headers. Full retail is about 250.- ea.
It's a good idea to retorque the manifold bolts after a while.

ALANSD · 07-12-2002, 06:23 AM

since this thread is on exhausts, I can relate what I discovered after my long (2000 mile) trip recently. In N Carolina there was road construction where the Interstate narrowed considerably to 2 lanes, concrete temporary walls on both sides, making a nice tunnel with no room for errors in steering. Of course the 18 wheelers were flying by me, as I do about 60 mph- and I had no place to move to avoid a nice sized truck tire in the road. I did manage to move enough to almost pass over it cleanly- but later I noticed it had hit my right exhaust pipe or hanger at the side exit area and turned an almost 90 degree
angle into a 130 or more. The pipe at the bend is narrowed, and the hanger is nicely reshaped into a new and useless design.
My rig has the original hangers still underneath which lead the pipes further back and out, as they now exit before the rear wheels. My guess is it will be easy for a local muffler place to bend a pipe to match the current config, and I can easily mount it. Another project, thankfully small, as that tire could have caused real damage to the coach or us.