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d1mbu1b
10-04-2006, 09:39 AM
Question:
I have seen risers that extend the primary runner length on aftermarket water jacketed tubular manifolds like GIL.
Does anybody know of a manufacturer that makes these or am I imagining things?
Basically, it looks just like a riser but made up of 4 small tubes instead of one big tube. I attempted to draw it...
I feel these may get the runner lengths closer to where they need to be for < 5500 rpm marine engine operation.

Anyway:
I have read that cold exhaust = bad.
why are the manifolds water jacketed?
It seems like this would be the ultimate marine header:
1) primary runner would be greater than 30" long
2) exhaust water joins past the collector
3) posibly heat wrapped up to the collector
benefits:
. no more worries about reversion due to the large runner length; run any cam you want
. hot exhaust easier to push than heavy dense ehaust
. with a true tuned exhaust you can gain the benefits of the 4/7 swap cam that can not be gained with non tuned headers
. propper tuned length allows low end torque w/out backpressure and high end HP due to less restriction of conventional systems
. no need to worry about internal welds breakin and leaking

BigGrizzly
10-04-2006, 10:29 AM
CMI (custom marine inc) and Stainless marine. you drew a stainless marine exhaust. Waterjacketed exhaust is mandated by law in a closed engine compartment. I could answer all your questions but it doesn't matter at this point because only so much fits the application.

d1mbu1b
10-05-2006, 10:01 AM
CMI (custom marine inc) and Stainless marine. you drew a stainless marine exhaust. Waterjacketed exhaust is mandated by law in a closed engine compartment. I could answer all your questions but it doesn't matter at this point because only so much fits the application.
I beleive you misunderstood, or I misrepresented.
The point is to extend the primary runner length of the headers before the collector.
I found that CMI and stainless joined the runners at the riser.
Please let me know if I missed it.

My application needs longer than 33 inch primaries at 5500 rpm and even longer if I tune it for the torque peak.
The drawing sucks, but it is supposed to show the primary runners extending from the manifold, forming a riser, and then joining down at the collector before the tail pipe.
heres another bad drawing of what I am trying to say

Rootsy
10-05-2006, 10:07 AM
other than maybe revolution marine, and i am not sure if they even make sbc exhaust... i don't think there is anyone out there doing what you are asking. if you look inside of a SM or GLM or IMCO manifold the runner seperation is ended short of the manifold / riser flange... GIL does the same thing i believe... basically there is no true seperation all of the way up to the flange... Then there are the risers... short of someone making you custom risers i know of none on the market to do this stock...

by the time you have someone manufacture what you are drawing and modify your manifolds ot work with them, you'd be ahead of the ballgame to just buy the Lightning headers that Doncig has for sale...

Pismo
10-05-2006, 10:14 AM
How about CMI sporttubes?

BigGrizzly
10-05-2006, 10:30 AM
Actully My exhaust is exactually like you pictured. CMI has elbow top with short runners and a long dry collestor. The CMI Sport tube or split top(your drawing) are dry up to the end of the collector. Reversion is vertually non exhistant. Garry Grimes uses elbow top on his 383 SBC with 850+Hp. the water entres the exhaust at the end of the collector. Putting my motor on the dyno says my pipes have the same numbers as the headman race pipes do. Btw my 18 Corsican has a 351 ford Clevland big port head and my cam has 108 lobe centers I use sport tubes on it. No reversion. Stainless also has the generation hedders you mite check out.We have built a ton of SBC and havn't founs a problem with Elbow tops as long as they don't go through the prop!-under water exhaust. We are looking at 450+ hp. hope this helps

d1mbu1b
10-05-2006, 11:53 AM
thanks everybody, lots of good info to think about.

Has anyone ever had any oppinions or experiences with the Indmar Tri-Y aluminum header/manifold for SBC?

http://www.motorboating.com/motorboat/features/article/0,12696,588301,00.html
scroll down to singular sensation...

looks pretty impressive and simple to boot.
The runners look pretty long too.

zimm17
10-05-2006, 11:04 PM
Did you check dana marine? Their exhaust has separate internal runners all the way to where the water comes in.

www.danamarineproducts.com