I'm starting to make plans for a complete re-do of the exhaust system (P-30/454/24').....

Seems like this is the right time to commit to headers if I'm gonna do it, and it appears that Thorley is the most cost-effective and will give me the most bang for the buck.....A couple questions:

1. Are "low restriction" mufflers an integral part of any increased-performance goals?....And if so, does "low restriction" automatically translate into "more noise"? Do OEM mufflers compromise any gains from header installation?

2. Does more-efficient exhausting automatically equate to a need for more efficient air intake, i.e.: should I be looking at a K&N intake system, special filters for the OEM air cleaner cannister, home-designed ram-air mods, etc?

ANY feedback on 454 header system installations appreciated, especially thoughts about controlling engine & doghouse temps with headers (IF it's even an issue....)

I use and like Thorleys. Got Them from Summit Racing. If you need to pass smog, buy the Thorley heat riser. Otherwise, skip it and same some money (it is overpriced)and have a slightly balky engine until it warms up in the winter.

Mufflers are personal. Listen to other big blocks. A free-er flowing muffler will make more noise and more power at top end. A bit of restriction will make more mid and low end power. Free flowing mufflers with an H pipe are a good compromise. The H pipe smooths out the pulses and boosts mid range a bit.

I am not a fan of K&N air filters. They do not filter as well as good paper. I have LOTS of desert experience with bikes and buggies. A very simple home made manometer will give the lie to their claim of increased flow claims. Hot Rod magazine did some dyno tests in May of last year that showed no difference between paper and K&N. I like a Baldwin paper filter and the Baldwin foam wrap. A filter minder will tell you when to clean the foam wrap or replace the filter. Dyno testing shows little power drop before 20 inches of water suction.

Ram air is an advertising hype, but cold air induction is good. A flexible metal dryer duct running from the air inlet snout to under the bumper will give you a cold air intake. Dropping the temperature of the inlet air by 10 deg F gives you 1% more power and better mileage. I have verified this on my boat.

I have removed the charcoal filter ring inside my air cleaner housing. I removed it, not for airflow considerations, but because I went to a lower air cleaner to compensate for a high rise intake manifold and the wife's desire for a lower doghouse. I have no figures on the charcoal's inhibition of air flow, but I suspect it is a strangler. I guess a manometer would have told the tale.

Do a search here for Thorley.

Bill, the Thorley list shows a DTE-303Y and a DTE-303Y-S. They both have 3/8 flange material and the "S" version is nickel chrome plated. These are the TriY configuration as opposed to the ???-other configuration. Which do you recommend?

Lee, I believe the "S" is for AIR nipples. They are all nickle plated, and have a lifetime warranty.

The other big brand is Banks. They are expensive, but are good, too. The main advantage of Banks is that they sell a complete package. With Thorley, you are on your own with exhaust pipes and intake cold air. The intake cold air is easily done with a flexible dryer duct. Banks gives you a K&N element, which is not a good filter at all. My Thorleys matched right up to my dual exhausts, and I was able to connect them with a band-type coupler quite easily.

To get the correct part number to order, get a copy of the Thorley catalog and call Thorley if you have any questions.

The Banks are equal-length tubes, while the Thorleys are tri-wye. The equal length design is essentially a Hemholtz (or Helmholtz) resonator--that is, it is tuned for one engine RPM, and is most efficient at that RPM. In real life, however, it is not that simple. But longer tubes and longer collectors are better for low end pulling power. The Tri-wye uses firing order from selected cylinders to help each other extract the gasses. In theory, this should be better, but I suspect that a chassis dyno comparo on a motor home with mufflers would show little real world difference. Mufflers and tailpipes muddy the waters enough for pure science to be much less exact. You get more bragging rights with Banks because of their high price and massive advertising campaign, though. I think they give you a sticker for the back, too.

There are other brands out there, but I can't speak from any experience on motor homes with them. Eddie might be able to tell you something about Hedmans. I believe they have 3 inch diameter collectors, which I would suspect is a little too large for motor homes. Avoid the hot rod type headers with large short tubes. They are not good for heavy loads at 2800 rpm.

Thanks Bill, I have taken the first step (bought a can on liquid wrench) and will call Summit's tech line today. Hope I can do the installation myself. I hate to pay someone else when I can skin my own knuckles!

Summit Racing, Thorley part #DTE-303Y, $348 delivered price. Nice folks to deal with.

[This message has been edited by ron (edited November 13, 2003).]

I turn down free Liquid Wrench and pay good money for PB Blaster.

I bought the Hedman's only because of the jet hot type ceramic coating. We live in a coastal environment where your teeth will rust if you don't watch out. They do have 3" collectors. They are a massive improvement over stock cast iron manifolds. Bill, have you ever used AeroKroil for loosening rusted bolts. A machinist gave me a can and it works great. I'll have to try PB Blaster.

"The equal length design is essentially a Hemholtz (or Helmholtz) resonator"

OK Bill, how are we ever going to know if you are just feeding us a line or not.... is a Hemholtz (or Helmholtz) resonator anything like a "dark sucker"??

------------------
"Work hard and save, so that someday you can support those who didn't"

1985 28 foot Regal
Dave and Deb Bowers

RON:

If your engine has a smog (AIR) pump, you need the headers with the nipples. Perhaps I wasn't clear earlier. AIR is air injection reactor, which is a "smog pump". My suggestion would be to be able to pass a smog test, as laws only get more restrictive, and areas for smog standards are always expanding. Plus, there is always the resale issue. Even if you do not use the smog pump, having the capability to make yourself legal later on is a plus.

Again, check with Thorley to assure the correct part number is ordered from Summit or Jegs.

Buy a US or German-made flare nut wrench and squirt them daily with PB for two weeks. Rap them sharply with a light hammer, too. They can be stinkers.

EDDIE:

I have tried Kroil. It is highly advertised in aviation maintenance publications. Every bolt is different, but I believe PB is a bit better. It would be fun to do a test, but, as I said, every nut is different. I am a mile from the ocean, so rust is a big pain for me, too. I am an avionics tech, so I don't do this daily, but I hang out with hot-rodders, racers and restorers, and am influenced by their experience and opinions. One fellow who used to work in a shipyard loved it.

DAVE:

Sorry if I got a little technical there. I used to hang out with Gordon Jennings, an engineer and tech editor for several motorcycle magazines and a fellow road racer. He salted all of his writing and conversation with obscure technical references and it must have been contagious. And some of this is Kevin Cameron's fault, too.

Anyway, here we go-----a soda bottle can be a Hemholtz resonator when you blow across the top. A larger bottle has a lower resonant frequency, as does a longer one. The amount of liquid will change the frequency, too. Organ pipes exhibit the same characteristic.

Some may remember the Chrysler Ram Port Induction of 1959 and 1960. The Plymouth Golden Commando 395 had very long intake runners. So long that the two four barrel carbs sat out board of the engine. The Police Interceptor engines had shorter intake runners, as they were designed to resonate at a higher rpm. Today we see tunnel ram intakes with long runners. Slightly shorter runners for higher rpms.
I had a lot of fun with a Corvair engine in a dune buggy getting the exhaust and intake runner lengths optimized. WOW!

There is even a formula for optimum exhaust length at any particular rpm, but the speed of sound varies with temperature, so it is not an exact science.

Ron The Rocket Scientist will back me up on this, I believe.

But, getting back to motor homes, longer is better.

Ha Dave, you think Bill is blowin' some smoke? LOL For sound attenuation (or enhancement?) and such this is the industry buzz word. Now taking it one step farther and getting the best scavenge effect from pulses in the exhaust system, I think Bill has topped the tech list with this one. By me, makes my head hurt trying to figger it out. :-)

Ron,

Based on MY techno-knowledge, I tend to agree with you, but that's only 'cause I got a headache over the round vs. square headlight issue on a different thread......

As I understand this so far, if I soak my OEM manifold in PB Blaster, highlight the edges with Kroil and toss-out the Liquid Wrench, all the while blowing across the top of a bottle, THEN, and only then..
I won't even need no steeenkin' headers....

Am I keeping up so far?........

Oh...Ya....Got it, Bill....Where's yo yo?

------------------
"Work hard and save, so that someday you can support those who didn't"

1985 28 foot Regal
Dave and Deb Bowers

Good Grief!

If I didn't have to work this afternoon, I would pop a cap about now.

The headers come with adapter/reducer cones that bolt on to the collectors by way of a three-bolt flange. The aft end of the adapter/reducer is 2 1/2 inches in diameter. Hopefully you have that diameter exhaust pipe. I cut my exhaust pipes off just 1/4 inch behind the reducers and connected them with the band-type clamps, available from Summit or a good mufffler shop, particularly one that caters to hot rodders.

Holy-Moly! Crawled over the front tires last evening with my can of PB Blaster to start the pre-soak/loosen process. This must have been an experimental prototype exhaust for a tubing convention! There are quarter-inch tubes on all four ports and that accursed smog pump is hanging there too. But, each and every fastner is well-PB'ed. The splach-shield on the left side is proving to be a pain, but I will remove it in one piece (unless I decide to apply this new SawzAll to the blasted thing!

Watch this space for future revelations (or just a duuuhhh).

[This message has been edited by ron (edited November 20, 2003).]