#1
IP: 96.241.200.157
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Exhaust Flange Thread Size?
A quick question.
I'm about to rebuild my exhaust system. Does anyone know the diameter and thread pitch of the internal threads in the MMI exhaust flange?
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@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#2
IP: 71.118.13.238
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Flange
Ed, I think it is a 1 1/2" NPT.
Dave Neptune |
#3
IP: 206.125.176.3
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Sorry Dave - 1 1/4" NPT. I must have bought every piece & combination of 1.25" pipe from about 3 different stores until I found a good combination for my hot section.
Ed, check out my thread from last year. http://www.moyermarine.com/forums/showthread.php?t=2974
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-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) Last edited by sastanley; 07-28-2010 at 02:50 PM. Reason: add link |
#4
IP: 173.166.26.241
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Ed - 1 1/4" is the correct answer for the stock flange. But if you want to upgrade your system, the flange can easily be opened up to 1 1/2" for a huge gain in performance. Regards, Hanley
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#5
IP: 96.241.200.157
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Quote:
On my existing system, it has a short nipple into a bushing that takes it up to 1 1/2, and the rest of the plumbing up to the muffler is 1 1/2". Another question. Having fought with too many rusted-solid exhaust systems, and broken off many bolts & studs and had to hacksaw things apart, I was planning to do this system in red brass & bronze. But I found that McMasters has the same parts in stainless steel for almost the same price. So my question is: Ignoring price, is there any reason to perfer one material over the other? I'm guessing that stainless is stronger, but brass & bronze are easier to make a tight connection. Is one more corrosion resistant in a hot, salt-water environment?
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@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#6
IP: 173.166.26.241
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Ed - Interesting that your system goes up to 1 1/2" via a nipple and bushing. That is exactly how I did my first upgrade when I started re-engineering exhaust systems. I currently have a flange opened up to 1 1/2", then a close nipple, then a bushing up to 2". It was an evolutionary thing. Your decision to go to bronze or stainless is a new one for me. I know that stainless does not like an anerobic environment so if you are planning to wrap it you might get some corrosion. Bronze on the other hand has a very different rate of expansion from cast iron so you might get some fitting issues there. What ever you decide to use, I would go to studs and nuts on the manifold.
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#7
IP: 24.152.131.220
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Edward,
You might want to review this thread from a few months ago. http://www.moyermarine.com/forums/showthread.php?t=3995
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#8
IP: 64.231.104.251
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The only thing that I would say about stainless is that some grades of the stainless steel stand up to the continual hot/cold expansion/contraction cycle better than others.
I would look through a properties chart and select based on that charachteristic over all else in this application. Cheers! |
#9
IP: 24.61.219.184
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I am chuckling
Quote:
David |
#10
IP: 64.231.104.251
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All 30HP of it!
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#11
IP: 64.203.32.52
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30?
In a direct drive A-4 I doubt you'll ever see 30 HP, maybe a lil over 20. You can't get the RPM's for that much power.
Dave Neptune |
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exhaust, flange |
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