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O.S..18 MACS header 4 Nitro Vee

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O.S..18 MACS header 4 Nitro Vee

Old 03-04-2006, 12:54 PM
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jimbat10
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Default O.S..18 MACS header 4 Nitro Vee

I am installing a O.S. .18 CVR-MX in a Nitro Vee.I'm going to use MACS marine header #2043.My question is -how many pressure fittings should I use?? What does the pressure fitting do?,is it important?. The Nitro Vee TRX PRO .15 stock has 3 fittings on header,can I get good preformance with 1 on flat of header where it bolts on ?? Like image at www.macspro.com .
Old 03-04-2006, 02:28 PM
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Ron Olson
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Default RE: O.S..18 MACS header 4 Nitro Vee

Why not use a Traxxas header? I use them in my mouse motor boats all the time.
You should only need one pressure fitting and it should be mounted on the pipe, not the header for fuel pressure. Why yours has 3 pressure fittings, I don't know.
Old 03-04-2006, 02:59 PM
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Default RE: O.S..18 MACS header 4 Nitro Vee

I don't know alot about it,MACS web site says they don't recommed putting fittings on the pipe. What's a mouse motor boat???
Old 03-04-2006, 03:32 PM
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Default RE: O.S..18 MACS header 4 Nitro Vee

I call them mouse motors because they are the small-blocks of boating, under .21's.
Why they wouldn't put them in the pipe or recommend having them there, I have no idea why they would say that.
You also have to watch how you spell Mac as they get confused with MAC, the engines from Competition Marine Design a.k.a. Andy Brown.
Old 03-04-2006, 03:48 PM
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Default RE: O.S..18 MACS header 4 Nitro Vee

It says it may weaken header pipe,and theres "unusual pressure waves"on muffler part of tuned pipe.It's called MACS products at www.macspro.com , sorry for any confusion.
Old 03-04-2006, 03:52 PM
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Default RE: O.S..18 MACS header 4 Nitro Vee

It says not to put it on the muffled section, check the diagram on the macs web site.

Derek
Old 03-04-2006, 04:08 PM
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Ron Olson
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Default RE: O.S..18 MACS header 4 Nitro Vee

True, you never put the fuel pressure fitting in the muffler but just ahead of the divergent/convergent cone.
Some manufacturers of Ready To Run boats put them wherever they're convenient which is not neccssarily the correct place.
Jim Irwin did a lot of testing years ago on the proper size and position of the fuel pressure fitting. His conclusions were to place it at the divergent/convergent cone are using the smallest pressure fitting available, the Du-Bro with the 4-40 threads for any sized engine. Agree or not, those were his findings.
Old 03-04-2006, 05:03 PM
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jimbat10
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Default RE: O.S..18 MACS header 4 Nitro Vee

O.K. I'm feeling dumb now. What is divergent/convergent cone?? Thanks for your help. I was going to use a big fitting(10-32),thinking bigger is better.The smallest I have is 6-32,I'm thinking of putting it in the fat part of my tuned pipe, will this work?? Thanks again.
Old 03-04-2006, 05:10 PM
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Ron Olson
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Default RE: O.S..18 MACS header 4 Nitro Vee

You have basically 2 cones that make up a tuned pipe as we know it. There are some other styles like the "ringed" and "hot dog" shaped pipes but forget those for now. The cones each are parts of the whole pipe, one being the convergent and the other the divergent cone. This is why I find it easier to say "the fat part orf the pipe" as that is where the two cones meet.
You can use the 6-32 if you don't have the 4-40 handy as yes, it will work.
Old 03-05-2006, 10:46 AM
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Vertical3-D
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Default RE: O.S..18 MACS header 4 Nitro Vee

another thing on the nitro vee, first off yeah the stock header is way restrictive, secondly it has three, 1 for the cooling water exit(which the cooling should be changed anyway). 2nd is on the back and goes to the tank for pressure(so theres one we need), 3rd is on the underside and a line leads from it to a fitting on the driveshaft(exhaust residue gets pushed through here a little at a time and lubes the driveshaft(so I'd put to on there) so I'd say one on the manifold for the lube(bottom of the manifold), and one in the pipe...

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