67 Parobolic

[waltr]

Hello All,

I'm finishing up a Phil Thomas Winston Eagle Scale.

I've got a new stock 67 Mac in it now,and Andy's doing a Mod Mac for the boat also.

I have a new Parabolic pipe for it (welded on 90* alumunum fitting)and it's not drilled.

Seems to be about a .200 center hole in it.I can't actually measure it,just looks about that.

Now,trying for the best of both worlds here,and wanting it to be as quiet as possable with the best performance available.

So,should it be drilled and use an add on muffler,or leave it alone,or open it slightly?

Or will it need an add on muffler anyway?

How about length? 11" good for a scale starting spot too?

Any thoughts and help would be much appreciated.

We're on the edge of getting booted from one really beautiful pond and I'm all with you guys on getting these things quieter.I love our pond and it's really close to home.

Thanks

 

[John Knight]

Walt,

Don't know what scale you have. Two thoughts for you:

1. Scales have a tendency of being louder than other hulls, especially ones with the turbine cowl. With all hubbub of the noise going on may want to leave it as it is and try it. Drilling it will make it louder.

2. Drilling it, even progressively larger many times increases performance. But not always. Depends on the engine, mods to it, pipe length, prop, etc. Summary - entire package. The newer parabolics have larger baffle holes in them than the first ones did.

Suggest that you try it as it now and see if works. About 11" is about right. My 67 rigger is slightly shorter than that but that is a rigger and not a scale. Work with it and try to get the best performance out of it without drilling. If you need to then do it in 1/16" increments.

John

 

[ALLAN YUEN]

Hi Walt Don't drill so just leave on it and If you have long header 3 3/4 inches by CMB so set up 11 3/4 inches from center to pipe point and play adjust +/- 1/4 inches. Sound only 88 to 90 db OR standard header 3 inches by CMDI so may drill on pipe stinger and set up 11 inches because make limit play adjust 1/4 inches so will fell off coupler or leak Sound bit of louder 91 to95db Have a fun run Good Luck!