Flow Thru Exhaust and Muffler

[LKappenman]

We were at the Camping world looking at the Gear Vendors over/under. While there the man we talked to said we should get a Gibson Flow Thru exhaust system or another brand but the system. He said it kept the engine compartment much cooler and and increased his mpg considerably. Has anyone done this? We have a 1983 Isuzu Diesel Turbo. Camping World does not see this unit so it wasn't a sales pitch. We are always interested in improving the preformance of our MH

[Andy R]

I used to have a Suburban with a 454. When I added aftermarket headers and exhaust I saw a huge jump in performance. Basically you are removing one ofthe bottlenecks that hinders your engines performance. Allowing the exhaust to flow as freely as possible allows for a more efficient engine.

Of course there are other bottlenecks that may restrict the air on the intake side. If you are thinking about making some engine changes you may want to see if there are aftermarket intake manifolds available for the Isuzu. Also an aftermarket carborator will help too!

[ALANSD]

Short of buying the Banks Power pack which is supposed to be wonderful, I found the Hedman headers readily available and affordable.they are 300-400.00 and seem to be well recommended for Motorhome use. I found them on the net at a nomber of auto and truck parts sites.
I would be interested in other owners ideas on this as well, as far as brand names and so on.

[FrankR]

Diesel performance is similar but different than gas engines. From the least expensive to the big dollar is.... remove all exhaust restrictions, as muffler and cat, modify air cleaner to have better breathing, turn up injection pump, advance timing, and change exhaust to 5 inch with minimun turns or bends. A turbo on a diesel will silence the exhaust tone or noise. Ask any big rig truck shop. Nothing is free, as everything has a plus and minus, for every gain there is some loss. Headers play no part in diesel performance. Oh yeah, ya can add propane too. This will make about 80 HP with a 7.3l engine. All changes should be done with a pyrometer. Frank

[ALANSD]

An Airstream experienced mechanic recomended the Hedman headers combined with a Flowmaster exhaust sysytem. He said the cost would be reasonable, and the performance would be noticeably better. He also said the Banks system was terrific, as we all have heard, but the cost for a motorhome as old as mine may not be justified.
On the other hand, one of the sales guys said you could recoup
maybe 80% of that cost on resale. That assumes I would sell someday though.

[PeterH-350LE]

I wonder, if they teach them that line (could recoup maybe 80% of that cost on resale) at sales school.
I replaced the V8 with this nice air-cooled 4 cyl and the PO lost the generator, when he made a sharp turn, but look at these nice Banks headers.

My bet is 20 cents on the dollar, if that much.
Sure would be nice, though...

[ALANSD]

I am reviving this thread to ask about cost of exhaust systems, other than the Banks which I have a price on.
I saw the Flowmaster system for 454 is about 750 for all without headers
which are 350 roughly for Gibson or Thorley, plus install, unles i do it myself.
Does this seem accurate? About 1100 for the parts?
Also the other option seems to be keep the manifolds, and go with the cat- back exhaust from Flowmaster . This saves the 350, but would it be worthwhile- they say you decrease underhood temps by quite a bit and still increase performance, while retaining the manifolds.
I am saving my pennies for this changeover this winter.

[74Argosy24MH]

I don't know who told you a vehicle with headers runs cooler, but that has not been my experience. Every vehicle I have had with headers is hotter. Instead of cast iron shooting the heat down into one tube and out, you have 4 tubes snaking their way through the engine compartment. Most were substantially hotter inside. That is one of the reasons I wrapped the headers on the Argosy I have now.

Headers/exhaust

Any good exhaust shop can bend the tube you need. I have Hedman Elite headers, 3" tube with an H pipe, and Gibson mufflers, all for about $850. The tube was bent locally, I welded it, so that might cost a few bucks extra.

John

[uwe]

LKappenmann,

Your Engine has a very specialized Exhaust manifold, to which the turbocharger is mounted close by. The exit to the exhaust from the turbo is where you want to start your free flow exhaust system.
I recommend a low restriction air cleaner, and a large diameter exhaust system with performance mufflers. You will very likely not find headers for your turbodiesel.
If you know a reputable exhaust shop, then the modification from the turbo exhaust port on back will not cost very much. But your existing system might be adequate, just have it looked at.
Check your air filter and see if K&N makes one for this motor. Chances are that you can get away with a few hundred dollars of expense and gain a nice amount of driveability, perhaps even more pulling power and better mileage.
The turbo in itself is a great source of heat, and you should make sure that the ventilation under the bonnett is adequate. More than likely you will not see lower engine compartment temp, or engine running temp by this modification. We would install heat shields on turbo cars, to keep the turbo heat away from the sheetmetal of the vehicle.
Make sure the muffler (s) are not too rowdy, or you end up with unwanted resonances inside the coach.

[uwe]

I just noticed you revived this tread for gas motor exhaust questions. Never mind the Diesel post.

[rdm]

Alan
We installed a complete system from Flowmaster Kit # 17240
This kit includes dual series 70 rv mufflers , all exhaust pipe , heat shields for both mufflers and each exhaust tip plus all clamps and rubber mounting brackets. I think summit racing will supply the kit for under $600 US.
We just got back from a 3800 km run in Eastern Ontario and Quebec the exhaust system performed great and the operating temperature was lower than before as stock.
thanks
Ray

[ALANSD]

rdm- are you still using the stock manifolds with the new Flowmaster parts?
Also if headers are hotter, what about the wrapped ones vs manifolds. Are the headers worth the cost, or should I stick with manifolds and just get the rest upgraded?

[74Argosy24MH]

To me headers are worth the cost. You have to think of the exhaust as a system, make it flow as freely as possible; if headers are properly designed they not only flow freely, but pull exhaust out of the cylinder and the fresh charge in. Cast manifolds are a restriction with their tight bends and nearly instant 4 into 1 design. The stock tube diameter and stock muffler are also restrictions. Changing any part will help, but changing the system makes it all work.

Wrapping headers does help keep the engine compartment cooler, keeps it a little quieter. Header tube is very thin compared to the cast iron in the manifold, passes heat and noise much easier. To me the benefits outweigh the shortcomings, but you should really do it as a system for the full benefit.

That's why Banks are so popular, they are a system. Jam cool air in, suck the exhaust out. You can do the same yourself and save a bunch of money.

John

[rdm]

Allan,
Our manifolds were updated before we purchased the 325.
I elected to add a ram air kit complete with a K&N filter and high capacity air intake along with the flowmaster exhaust system.
Thanks Ray

[74SovereignInt.]

Can anyone help me with suggestions on a complete or cat-back system for my '98 350 Suburban? My options seem limited and I need to do what I can to improve performance. I'm pulling a 74 30' Sovereign. Additional info is that it is a 1/2 ton 4x4 with a 3.42 gear. Improving the engine performance would be a big help. Thanks

[davidz71]

If you are running LT265-75-16 tires, get rid of that 3.42 rear end or go to smaller diameter tires. You will never have any kind of performance with that rear. I had it on my '92 Chevy Z71 K1500 4X4 with 5.7 engine which had a Jacobs Electronic Ignition and Amsoil dual filter bypass filtration system. The truck by itself ran great until it was hooked up to my 31' Excella 500 then it turned into a different animal. Ran fine on straight road but any hill or mountain I went up was a problem.

[Sav'h Steve]

I just picked up your thread.
I have a '01 Expedition w/ 4.6L and 3.31? rear pulling a 25' Excella. I originally bought truck for my smaller A/S and was well within limits. Now I'm on the edge.

Financing $35K for this truck means I can't trade to a 2500 Burb without taking a big hit. So I'm thinking of air flow to help this small 4.6L on any hills for now.

I saw that the exhaust was first on the list - like from the Cat back. How much to have a 4.01 rear put in? Trying to keep investment under $1,000, cause like Peter said, probably won't get but 20% back....

I don't expect to make this into a 454!! What your advice?

Steve Martin, Savannah

[hampstead38]

I just wanted to add a note here. Headers are not a bad improvement, but the horsepower increase generally occurs at above 3000 rpm depending on the engine. Simply expanding the size of the exhaust pipe can have a positive effect on engine efficiency. As for as "cat back" systems, I like Banks.

I'm working on a '66 Dodge so it lacks anything related to the modern catalytic convertor. I'm not sure whether or not I'll add headers (at $800) or simply rework the exhaust with a dual-into-one muffler and bigger pipes.

Rather than drop a grand into the exhaust, I would look into a different gearing for the Expedition. I don't know much, but I think you could get a 3.73 or 4.10 rear. Just know that with the 4.10, you're going to wind the engine up at freeway speeds. It will make a world of difference towing, but there are tradeoffs.