headers for 502's?
 

Looks like i need to replace the Gil's that I have on my 502's.... was considering going to headers... any considerations I need to look into? and how badly will I get raped on headers?
Seems this isnt like throwing headers on an old 350 SB anymore... Thanks.

it looks like you have a Cig Top Gun, so headers do look really nice in there. But plan on replacing them every 5 years or so as the vibration tends to fatigue the joints and can hydrolock the engine. Your results may vary. Stainless Marine manifolds seem to perform nearly as good as headers and last forever.

I'd have to argue with that rooster man. :) Standard stainless marine manifolds, have got their azz handed to them quite a bit on most modern marine N/A BBC builds. Mark from MER Performance had a mild 509 on his dyno this spring, that dropped 40hp and 35ft lbs of torque across the powerband by bolting on stainless marines vs his dyno headers. 40hp is a good amount in my book. Epecially when the power gains are throughout, and not just at peak.

Those GIL/Stainless marine/imco/EMI types of exhaust are more like comparing a shorty header to a long tube in the car world.

If I had to buy new exhaust, and didnt want the problems associated with stainless headers, I'd get these

Thunder-N-Lightning Cast Aluminum Exhaust Headers :: Thunder & Lightning Headers :: Exhaust Systems :: Diamond Performance Parts

Loosing 40hp from dry headers, good to know. Wonder how the Eddie Marine did. Reason to ask is mine was at 530 on dyno but have EM but have the +3 on it now
EMI Thunder Exhaust System-BB Chevy +3" Taller Risers Colored Finish

What kind of life span can one expect from the Cyclones? My motors were built in 2009, at that time the Cyclones were new. Now based on what Rooster said I'm slightly paranoid..

why don't people dyno their engines with the exhaust the engines are going to run with? you see virtually every engine dropping 25 to 40 hp from the dyno headers to the marine exhaust.

Lightning headers!!! Got 14 years out of mine in freshwater.

Here you go -

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I second mild thunder. Diamond Performance- thunder n lightning.

I have,

Set up is a little tough, but not bad.

You have to get a dyno shop interested in doing it and you will have to help with $$$$ and time. So, in general, good luck with that.

BT: Water supply for some places can be tough. Those Bravo sea waters pump move massive amts of water. You would be incredibly surprised watching it in person.

You couldn't run the engine off the dyno cooling system and feed the exhausts with a garden hose? It isn't like it is gonna be a half hour full power run.

Subject of this discussion is You want to run the engine fully dressed for a dyno run right ? For full wet exhaust, water can have impact on power and tune up and you can test for reversion. For dry exhaust with water running thru it for cooling only, I guess you could.

Edit in: Oh, and yeh, you run it for a bit to get coolant and oil temps up to where you would run it in the boat....so having water go thru the exhaust this whole time can add up.

My experience consist of working on one ski boat under a tree behind a trailer park, so argue away, Thunder Man! :)

But we haven't even discussed what cam it has! Lol!

There are a few guys that can accommodate wet exhaust on a eddy current dyno.
At least there used to be .
One had the hot water going out through 2 pipes going through the wall , other , in cali , had a door that opened up to the outside parking lot . (Those were later, after hours pulls)

Well i pan on buying a set of the thunder n lightings manifolds for my 548 that just came off t dyno last week....
They clearly out perform some headers that are out there on the market.
I have heard of boats installing the thunder n lightings with gains of 2-3 mph with no other mod....


Anybody have any Drew Marine Shotgun mufflers for sale ????

Those Thunder and Lightening headers that MT linked to look really slick when painted/powder coated.

MT, where those big HP losses on the original SM manifolds or the Gen3 units? I'll be exhaust shopping next year as I feel my repaired CMIs are on borrowed time.

I would look into the pricing on the CMI Fusion (Unitop) headers. One piece E-Top header with no joint. I had them on my Pantera.
They are made for standard Bravo exhaust exit locations.

one mention of the dyno and thread got derailed. so, eichhoma, you are considering headers. why? you have gils currently. do you anticipate upgrading the engines to where the gils will be too restrictive? or are you happy with power and durability you now have, and intend to keep the engines as-is?

Its been a very informative and helpful thread....I am being told my Gil dry exhaust is on burrowed time... getting lots of steam, am being told that the flanges are not sealing well and that I should consider replacing when I pull it all this winter for some other work.... im not convinced it needs to be replaced yet. No major upgrades planned... in fact considering freshening some things up and selling it next year to move on to something else. I admit I like the look of headers if there is some performance in crease (guessing minimal at best) but it also looks like headers would save me a lot of curse words when I am changing the plugs too. The thunder and Lighting set looks very interesting... if I need to go that route

I love my E-tops. There was a very noticeable difference in the jump from 3000 to 5000 rpm time over iron manifolds and you can easily hold one with one hand.

If it needs new exhaust, it needs new exhaust. No new exhaust will pay for itself in added sale price. On the other hand: "For sale. Good cond. Only needs new exhaust." Everybody is gonna think "What else does it need and where else is he not doing necessary upkeep?"

Those 1000 hour Hardin Seaward exhaust have a few positives. The fact that they are "Ideal for 415 hp and lower stock apps" implies they ain't so "ideal" for anything merc put gils on in the first place. But if that corrosion treatment is that good, it needs to go on EVERY ALUMINUM EXHAUST MADE FROM HERE ON OUT!!!

Sorry about yelling.

Mine are not easier to change plugs. The header bolts can be tough to get a wrench on. You might not gain any speed top end. But I can tell you. You will probably get there quicker if tuned right

I had a 50 gallon reservoir with a hose running full tilt into it and a standard Bravo 1 sea water pump would nearly drain it in a few minutes AT IDLE. Dyno would need either a significant reservoir and or massive supply volume. But I'd like to see more wet exhaust testing and full dress pulls too (alternator, recirc pump, seawater pump, P/S pump etc.). We need an engine masters dyno video series for boats.

Years back, we found a 200+ gallon triple washing station from an old restaurant. Even with hose left on in it, sucker would be drained fast while dynoing. AMAZING !

BTW: nowadays one can find empty used but cleaned out 275 gallon chemical containers for $100-$150 now. I bought a few for storing waste oil for the waste oil furnace. Found a guy thru cragslist locally with a ton of them. They are incredibly light when empty.

They are plastic with light steel supports - made so fork lifts can carry them when full of chemicals. Watch out - first one's I went to look at where used for maple syrup stuff first and wasn't well cleaned out. LOL.

https://sep.yimg.com/ay/baytec/recon...tainers-13.gif

I remember "Moonshiners" being fond of those same tanks. :)

Are those the same as the old Keith Eickert headers?

Yes. Dr Parvey was first, then KE, now Diamond Performance. :)