SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: 5oclocksomewhere on December 04, 2013, 10:01:27 PM

Title: Kickin around the idea of new exhaust BBC
Post by: 5oclocksomewhere on December 04, 2013, 10:01:27 PM
Last summer I pulled out the old worn out 330hp motor and replaced it with a 500hp LS6. I'm running logs and the new motor sounds awesome. Everybody that gets behind me now says It sounds like a big boy boat now. Everyone also tells me that the logs are a huge horse power robber. What exhaust would go guys run if you were going to change. I want something as reliable as the logs and the new exhaust would have to still fit under my engine cover (not a hatch). And of course sound awesome.


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Title: Re: Kickin around the idea of new exhaust BBC
Post by: jyeager on December 04, 2013, 10:06:47 PM
Last summer I pulled out the old worn out 330hp motor and replaced it with a 500hp LS6. I'm running logs and the new motor sounds awesome. Everybody that gets behind me now says It sounds like a big boy boat now. Everyone also tells me that the logs are a huge horse power robber. What exhaust would go guys run if you were going to change. I want something as reliable as the logs and the new exhaust would have to still fit under my engine cover (not a hatch). And of course sound awesome.


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If money wasn't an issue i would put a set of lightning headers on there. They are the best money can buy. my dad has a pair on his 383 and it sounds bitchin!

http://www.lightningheaders.com/ (http://www.lightningheaders.com/)
Title: Re: Kickin around the idea of new exhaust BBC
Post by: ka0tyk on December 04, 2013, 10:25:27 PM
Theres quite a few big hp boats out there still running logs. 

That being said you cant beat a nice set of center rise manifolds... theres a couple sets floating around for 600-900 bucks right now with SS risers.
Title: Re: Kickin around the idea of new exhaust BBC
Post by: Your Mom on December 05, 2013, 11:42:03 AM
Dog house? What type of log do you have? If they are the Harman and you have the step down removed already on the snail making 3 1/2... I'd say your only at a 30ish rob and leave em alone. Logs are pretty bitchn...
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi897.photobucket.com%2Falbums%2Fac178%2F2ndlight%2Fym951_zps1f111498.jpg&hash=23125ddd8039e5b5b753f49f7a43afb3e7e13d95)
Title: Re: Kickin around the idea of new exhaust BBC
Post by: Menace Marine on December 05, 2013, 01:59:05 PM
If you really want to ditch the logs find a set of Imco manifolds. Lightning headers make decent power but they eventually rust and leak. The outer tubes are only mild steel. Imco power flows are good to 600 hp and the power flow pluses are good to a 1000. You will pick up some power with these manifolds but honestly you probably won't notice much in the boat. If it was mine I would keep the logs and spend the extra money fuel and beer.


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Title: Re: Kickin around the idea of new exhaust BBC
Post by: More2LifeThanMPG on December 05, 2013, 10:35:35 PM

Dog house? What type of log do you have? If they are the Harman and you have the step down removed already on the snail making 3 1/2... I'd say your only at a 30ish rob and leave em alone. Logs are pretty bitchn...
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi897.photobucket.com%2Falbums%2Fac178%2F2ndlight%2Fym951_zps1f111498.jpg&hash=23125ddd8039e5b5b753f49f7a43afb3e7e13d95)

Sorry to thread jack, but this step down removal that you speak of... How hard is it to do? I never really paid too much attention to it, but if I can remove it easily and make some more power. That's a win win.


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Title: Re: Kickin around the idea of new exhaust BBC
Post by: Menace Marine on December 06, 2013, 05:03:31 AM

Sorry to thread jack, but this step down removal that you speak of... How hard is it to do? I never really paid too much attention to it, but if I can remove it easily and make some more power. That's a win win.


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Not hard. Remove exhaust cut reducer off change exhaust hose and put on larger exhaust tips. If your lucky you already have the larger hose and tips and the reduced exhaust log end is just stepping down inside the hose.


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Title: Re: Kickin around the idea of new exhaust BBC
Post by: Your Mom on December 06, 2013, 05:55:38 AM
First pic is a set of the step down still on and will be 3". By removing the step with a dia grinder..ect it will make 3 1/2" increasing flow. Depending on the type of tip you have will also help out. I have 3 1/2 angled SS.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi897.photobucket.com%2Falbums%2Fac178%2F2ndlight%2F460logs95.jpg&hash=94c442c3960aedb4610ac2fc9767f28f3b7e62e2)
Step removed
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fi897.photobucket.com%2Falbums%2Fac178%2F2ndlight%2F111l.jpg&hash=05bedc6450728c733494d9760411aae4c3a95ad9)

Title: Re: Kickin around the idea of new exhaust BBC
Post by: Second Chance on December 06, 2013, 08:07:47 AM
Mark, check out HDaves exhaust, I'm pretty sure he went to the Imcos and he's making some horsepower in the Hallett. I believe he had Teague fab the down tubes but they did have to notch the doghouse.
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