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exhaust to help prevent reversion

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Old 03-31-2009, 10:54 PM
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Default exhaust to help prevent reversion

does this type of exhaust set up help in anyway to prevent reversion?
thanks for your help.
John
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Old 04-01-2009, 12:55 AM
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It depends on where the water mixes in the pipes. If it mixes before the second bend, then NO. If after, the probably. I'm referring to reversion caused by cam overlap.

The low outlets could actually make water come in easier if the exhaust tips are below or at the water line.
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Old 04-01-2009, 02:23 AM
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Doesn't IMCO offer a higher elbow to help prevent reversion??




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Old 04-01-2009, 10:09 AM
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the ones i have coming are gill with the high elbow and exit about even with the manifold. they were for sale a while back. i'll send a pic if i can find one. i have not fotten them via UPS yet.
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Old 04-01-2009, 10:20 AM
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Default reversion

this is the set up
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Old 04-01-2009, 12:32 PM
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Wink

If Those high elbows on the risers have the water entrances down at the outlet, bottom end, then this will possibly help if your engines have a bit of reversion from cam overlap, however it would be better if you list your cam specs and basic engine specs here and we could identify how much your engines would be exposed to reversion.

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Ray @ Raylar
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Old 04-01-2009, 08:50 PM
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Default RE cam

I am undecided on the cam as I am still up in the air as to sticking with the 468's or go to 496's. I also am waiting on the flow results from Valako to get to Bob "rmbuilder".

Before I contacted Bob I was looking very closely at the voodoo #60204. I really like the looks of this however I wish it was on a 112 lobe sep. In the past I have used the Crane #134561 with the same exhaust and never had any issues. That was years ago when you never really heard much about reversion though.

Intake:
opens @10.5
closes @42.5

Exhaust:
opens @54.5
closes @6.5



Advertised Duration (Int/Exh): 276/284
Duration @ .050 (Int/Exh): 233/241
Gross Valve Lift (Int/Exh): .554/.572
LSA/ICL: 110/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2200-6400

Intake:
opens @10.5
closes @42.5

Exhaust:
opens @54.5
closes @6.5


Opinions welcome
John

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Old 04-02-2009, 11:07 AM
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Wink How De Do IT!

Those cam numbers don't look like reversion should be an issue with that exhaust. If Bob is working with you on cam choices you're in great hands and I am sure he will be careful with the reversion issue when it comes to a cam recommendations. From a pretty good head expert, when it comes to cylinder head flow, remember that port velocity is almost as important as overall flow numbers in Marine normally aspirated big cube engines! As for cubic inches, the old saying comes to mind ,especially on marine performance engines,
"There's No Replacement for Displacement"

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Old 04-02-2009, 11:08 PM
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Thanks Ray,
I know there is an art to porting heads. I learned back in the early 90's from Valako. He would always strive for velocity. I remember the look on his face the first few attempts I made after throwing my heads on his flow bench. I learned a great deal from him howerver I will never come close to you experts. In fact the last head I needed porting - there are sitting on his bench right now. Leave it to the Pros...

It is kind of fun though.
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