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Exhaust questions on an 0-540

marshmaster pat

Well-known member
I don't think this was discussed before, I looked and didn't see it.

I got a set of SS exhaust pipes (straights) that are about 10 inches long for a parallel valve. They sound great on an Lycoming (and look great at night - Blue fire), but we were wondering if this would cause any problems. I was told they could lead to burnt exhaust valves by one fellow and another said it would reduced horsepower when compared to just normal headers.

Does anyone know if they could cause problems with valves or loss of HP due to less back pressure when compared to typical collector headers?

Also, does the flex pipe or even mufflers have that much impact on HP produced.

Thanks Pat
I was told by a few people that no pipe off the head would burn valves. so if there is 10" that should be fine. some back presure is good but not in all cases. I was told by a boat builder that he tryed different lenghts and found that 37" mandrel bent pipes worked and gained 300 more rpm on an aircraft boat
I do know that if you run back to the transom and then add super trapp exhaust you can actually pickup a couple hundred rpm's on the 540's with the right # of discs. ---Yeah, but, I like the flames at night too.
Airboats Unlimited /PaulDixon in Bainbridge Ga. has them and is knowledgable about size and # of discs etc. 229 246 5760

Thanks Harvey - sounds like he might get a call from both woody and I.

Can anyone give a brief explanation how that back pressure allows you to increase rpms. Never have understood that.

Thanks again.

I am going to open a can of worms here. O.K. ON ANY MOTOR THAT BURNS GASOLINE. The lower the rpm you want to make power and torque the longer the header primary tube must be. Anybody who knows exhaust technology laughs their ass off when they see an airboat. No other application could benefit from long headers more than an airboat. I have only meet one airboat header builder that understands the physics of exhaust power pulses and savaging. His name is Norman at Innovative accessories. He has made over a hundred set’s of long headers. They work!!!!!!! he can build try Y’s and merge collector headers. The reason back pressure helps is it causes the next cylinders exhaust gases to pack up causing pressure to increase and gases to accelerate. When the gases accelerate they cause what is known as scavenging. The gases leaving a header actually pull the intake air and fuel charge into next cylinder in the firing order. Because the next cylinder in the firring order is beginning the intake cycle. The cam overlap has the intake valve just opening when the previous cylinders gases are exhausting. Thus accelerating the intake charge that’s how people can get volumetric efficiency over 100% of the cylinders volume. So the longer the primary tube the longer the scavenging acures and the more air and fuel gets pulled in during the next cylinders intake charge.
The blue flame you see is unburned fuel being ignited as it leaves the motor. In a car motor that means you’re way too rich however in an aircraft that’s not the case. Because Aircraft engines don’t utilize an efficient cooling system they must use fuel too cool the cylinders. So they intentionally run rich so the excess fuel cools the combustion chamber and exhaust valves.
In addition the mixture distribution in carburated aircraft engines is so poor that when the leanest cylinder is rich enough the richest one is way rich.
My experience only - I'm not an expert.

Strait valve, narrow deck 0-540 on a fiberglass 13'6" Gilileo.
In trying to reduce overall noise - for many reasons - I installed solid exhaust pipes through a spring tension knuckle joint at the 2 1/2" header collector - then into 3" MagnaFlow SS mufflers - then out under the transom lip.

Running a 72" Terminator carbon fiber set to max at 2,750 rpm - I added a full degree to 13 with this muffler system. Notable increase in push and decrease in overall noise. We can carry on conversations while running dry ground at about 1,900. Never before. Best thing is that game animals and frogs are not as jumpy as before.

Understand the thrill of blue flame out of airboats - but, those days are gone with the invasion of Florida's new state bird - the snowbird. We will all ride longer and easier when we ride quiet.
are they going to make it mandatory to run mufflers. I herd that north fl has to run them.just woundring
FFWCC is preparing noise level standards for all airboats - before more counties regulate us off the water due to noise.
There will be a presentation on the innitial findings of the FFWCC testing at tomorrow's Florida Airboat Association meeting in Melborn.
We don't run cars or trucks or motorcycles without mufflers. If we want our grand children to know the thrill, we'd better all get our boats as quiet as they can be.
Truth is, areas next to our wetlands are becoming overpopulated with travel trailer parks and retirement villages. Full of folks with nothing better to do than attack a common irritant - US.
will you be there. I don't have mufflers have 3" collectors with about 2 ft mandrel pipes and I will be there tomorrow
Yes, I'll be there. Wish I was going to be in the woods, though. Another season is fast slipping away. I'll be with a friend in a 14' Freedomcraft / 350 Chevy rig - blue and white. busted the torque side chine out of my boat for the third time and my fiberglass man could not fix it in time.

Hogman asked about through transom exhaust dumps and they are available at most airbpoat accessory shops. I believe Innovative Technologies in Okeechobee likely makes most of these - I know Floral CityAirboats and Airboat Pros offer them. They are in 352 AC / Inverness, FL.

Also, the buddy's boat that will be there tomorrow is much quieter with MagnaFlos than it was with Airboat Pro's "airboat mufflers". No reduction in performance with the Chevy, in fact it seems to have notably more "ooomph"
transom dumps classic in cocoa makes them or diamond back there both in cocoa and about 15 min away
FFWCC is preparing noise level standards for all airboats - before more counties regulate us off the water due to noise.
There will be a presentation on the innitial findings of the FFWCC testing at tomorrow's Florida Airboat Association meeting in Melborne.

Please keep us informed BigDaddy.

are they going to make it mandatory to run mufflers. I herd that north fl has to run them.just woundring
cchardt - Seminole County, FL will give you a ticket right now for not having mufflers, but most Florida counties are inclined to be more consistent with the way "FFWCC" enforces the statutes.
Yea, I knew someone that lived in the Keys years ago. Said all the Yankees came down and fell in love with the place. They retired moved down then realized that they hadn't seen it all and didn't like alot about it so they made it more like the east coast. Seems everywhere they go, they do that.

So the best thing is to not let them know about nice place.

And with that said, if anyone asks you, Louisiana is like the movie Deliverance and all those movies Hollywood made about the backward Cajuns. The food is terrible, the people are unfriendly, the swamps stink and have horrible sunsets, and the view in the marsh is the worst. And the fishing and hunting is the worst in the lower 48. :lol:

May Louisiana stay Sportsman's Paradise.
Waterthunder - So I guess those short pipes are the last thing to use if someone was looking to increase power out of a parallel valve. About right, since they were a great deal.

I really appreciate people with the knowledge sharing it.