headers for 502's?
08-29-2017, 09:15 PM
#12
Registered
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.
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.
08-29-2017, 09:20 PM
#13
Registered
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
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
But we haven't even discussed what cam it has! Lol!
08-29-2017, 10:18 PM
#14
Registered
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)
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)
08-29-2017, 10:27 PM
#15
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 ????
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 ????
08-29-2017, 10:49 PM
#16
Registered
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.
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.
08-30-2017, 01:18 AM
#17
Charter Member # 55
Charter Member
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.
They are made for standard Bravo exhaust exit locations.
08-30-2017, 11:03 AM
#18
Registered
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?
08-30-2017, 12:52 PM
#19
Registered
Thread Starter
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
