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Mac boost ports ..............
Posted: Mon Feb 18, 2008 9:07 pm
by mcbob
Well fellas how wide can a fella go on the 91b/1, 92, 93 or 101 boost ports i dont wish to raise them just widen them or is this detrimental to the flow rate ??
The standard spec's as regards width is 0.548 but this is for an open engine.
Mc Bob
Re: Mac boost ports ..............
Posted: Mon Feb 18, 2008 11:59 pm
by Gordon Duax
Until a ring hangs in one, and ruins the cylinder.
Then make the next one about an 1/8" (3mm) less
)
Re: Mac boost ports ..............
Posted: Tue Feb 19, 2008 7:36 pm
by jmendoza
Tyr running 100% methanol. that should wake any Mac up. Steve convinced me to try that this year, and wow, what a differance in power it made.
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 2:57 am
by Tom Smith
Mcbob, take a look, maybe you can see about how wide they can be before bad things happen. This was a brand new motor I tried out at a freshly repaved track and it runied the damn thing. It broke the chain 3 times also. Probably not what you want to have happen on a saw. Tom
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 4:11 am
by steveohara
Looks like a Mac KT100 with those studs sticking out of the top
I wonder... when does a Mac cease to be a Mac? Motoplat ignition, GEM intake, who knows what for a head.... obviously no shroud will fit over the coil hanging on the motor. No put down or criticism intended to Tom or others that like the frankenstein motors but it seems some of these wild "Mac" motors are less Mac than they are other stuff. Makes me think a nice Parilla Leopard with a BDC 16 carb would be about as trick a "Mac" as you could get
Steve O'Hara
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 4:35 am
by mcbob
Mcbob, take a look, maybe you can see about how wide they can be before bad things happen. This was a brand new motor I tried out at a freshly repaved track and it runied the damn thing. It broke the chain 3 times also. Probably not what you want to have happen on a saw. Tom
I cannot see how boost ports can break a drive chain Tom ...........
Not unless your saying that the power increase was so great that .............. Well.
Mc Bob.
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 5:29 am
by Tom Smith
The boost ports don't brake the chains, the friggin' nitro does and without the head studs the head flys off the block. Run a mac with 50 degrees lead and see how long the head stays on.
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 3:09 pm
by ted johnson
Tom: I don't wanna hijack McBob's thread, but are those 1/4-28 studs, and did you thread the cylinder for them? I studded my Bonbright 610, and I like the way it works. I'm building a 101 now, and??? Thank you. Ted
Re: Mac boost ports ..............
Posted: Wed Feb 20, 2008 4:09 pm
by mcbob
Tom Smith wrote:The boost ports don't brake the chains, the friggin' nitro does and without the head studs the head flys off the block. Run a mac with 50 degrees lead and see how long the head stays on.
My mummy told me ,any years ago not to play with Nitro ol mate .... i only run pump gas in my saws so hopefully my head will stay where it is supposed to be !!!!
Mc Bob.
Re: Mac boost ports ..............
Posted: Thu Feb 21, 2008 12:05 am
by Gordon Duax
I like the Parilla with the Mac carb idea.......
Is that legal in vintage karting ?
This is my 91 Reed open, and my 101.
The 91 is very fast on strait Alky.
I run a full circle crank, Pro rod, and very big ports in it.
And with a simple bracket, uses a Yamaha ignition.
The 101 is ungodly fast on a short track, and other than the Yamaha head, cut down inner cover, & saved flywheel, is dead stock.
The 101 is being put back to stock because it is such a low serial number.
I'm with McBob on the Nitro issue, not in any of my 2-strokes.