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Discussion Starter #1
Hey, I picked up a set of Indmar exhausts for my BBC. The type that exit out the top rather than logs and it also eliminates the snails(Ive got Hardin logs with snails now and small hose/tips). The Indmars have 4inch hose and tips.
What I am trying to figure out is if the exhausts are worth installing. Im going to have to redo my engine cover to clear the exhausts and I am going to have to cut some larger holes in the transom.
Right now I am running a basically stock 454. Im running a 21ft jet with Berk JC-A pump. Im WOT in the low [email protected]
What gains can I expect to get?
I remember an article awhile back that compared exhausts. Anyone have that article that can scan it to me?
 

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Do you have some pix. of these posting them will help a lot! The holes are easy with the right hole saws. Iwas told to use the saw the same size as holes in transom and bigger saw around the smaller to cut the bigger hole!

WT
 

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The indmar manifolds are arguably the best aluminum "stock" manifold available. Show a pic to make sure they are the ones I am thinking of. Description sounds like it...
 

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E-7 Sheepdog (ret)
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What is teh rest of the setup?

I went to Lightning headers and saw 50HP/200RPM on a Berk A (aggressor B), BUT, Ihad already moddified the intake and cam away from stock. the '049 heads were still stock.

IMO, in my case, the logs were the biggest choke-point.

If I was still running the .472" lift 260" duration factory cam and the iron dual-plane manifold, may have made FAR LESS diference.
 

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I had the Indmars and saw the gains as Lowrider on my fairly stock 502/502.

I get about 68 mph at about 5100 rpm on an A imp.

Low 60's in a 21 jet with a stock 454 is VERY respectable. Assuming it is on GPS.

The Lightnings are very affordable for marine headers. If you go fresh water only, he has some powder coated headers for around $1800.

If you are doing mods to accomodate the indmars, you may consider taking the jump to headers.

J
 

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Discussion Starter #6
Yeah Im not sure what my internals are. I believe its just a stock Hardin Marine 454. The only thing I added was a mid rise dual plane Performer intake, a Pertronix in my Mallory dizzy and a place diverter. Ive hit 62mph and then slowly climbed from there. That was with a GPS. and with my boat loaded with gas and 4 people and all the kid crap under the bow.
Im using a spreadbore Holley 850 and Hardin logs with snails.
I cant go with headers cause I want to keep the interior as it is with the rear seats and engine cover on.
Ill try to round up a pic. Its basically like the EDDIE or DANA marine exhaust manifolds as far as the routing of the exhaust.
 

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21 Daytona
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If your are like these, I would have to believe they would be better than logs, I have no data to back that statement up. but at least
your not pushing exhaust thru that snail, these are currently
what I'm running

 

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Discussion Starter #8 (Edited)

yep those are the ones. Nice engine. The problem im having is with the elbows on top being too high for my engine lid. I know that alot of peeps would be saying just lose the lid and run open which is fine but I have a boat that I believe to have everything original on it. From the original outside gel and interior to the carpet and the boat is from the 70s. Im not sure if I should be cutting into the transom or not. Ive been doing upgrades to it but only ones that I can undo for the most part and also upgrades that are worth doing. When I first got the boat it did 56mph @4400. Added the intake,pertronix, and diverter, it shot up to over 60. When did the upgrades it was noticeable. Just wondering if adding the Indmars will make a noticeable difference.
 
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