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Glen,
With 1 1/2s carburettors, I suppose you mean HS4? The SU logic is a little
weird. 1" + 1/2" = 6/8" so you would think it are HS6s, but when talking about
HS carburettors, 1 + 1/2 = 1 + 4/8 and they took the 4 to name these carbs
HS4...
Marcel
Van: "fubog1" <fubog1@aol.com>
Aan: "van mulders marcel" <van.mulders.marcel@telenet.be>, "Mike Harmuth"
<ofracer@gmail.com>
Cc: "fot" <fot@autox.team.net>
Verzonden: Donderdag 18 oktober 2018 22:39:39
Onderwerp: Re: [Fot] Weber vs Mikuni
Well I won't speculate on the cause, but I doubt that it's the SUs.
My small crank 1300 w/1 1/2s on a eurospec manifold w/Stahls header, "big"
valve head, would buzz easily to 9k, still making power, if I let it.
Normal shift point 7800-8000.
FWIW...
Glen
-----Original Message-----
From: van.mulders.marcel--- via Fot <fot@autox.team.net>
To: Mike Harmuth <ofracer@gmail.com>
Cc: fot <fot@autox.team.net>
Sent: Thu, Oct 18, 2018 2:12 pm
Subject: Re: [Fot] Weber vs Mikuni
-"...hitting a wall at that point..." : is it possible this is rather pointing
to the camshaft than to the SU's? If it are the carburettors, maybe the power
would decrease more gradually above 6500 rpm.
-In general one choke per cylinder is better, and 2 Webers 40 DCOE isn't
overkill I think
- what about trying HS6 SU's on your actual manifold?
At what maximum rpm is your engine still reliable?
Marcel
Van: "fot" <fot@autox.team.net>
Aan: "fot" <fot@autox.team.net>
Verzonden: Woensdag 17 oktober 2018 15:49:45
Onderwerp: [Fot] Weber vs Mikuni
I'm looking into switching out my twin HS4s on the 1296 race engine to either
Weber or Mukinis. I know this has been done for years and I'd like to get close
the best set up out of the gate.
I don't think the SUs are up to the task of moving enough air with the new
ported head and Stahl header. I've worked on the SUs and gotten them to finally
deliver a good AFR , 12.6, at 6500 RPM under load but I seem to hit a wall
(figuratively) at that point. I suspect that the openings just aren't big
enough to deliver the mass of air required. (spreadsheet or other flow
calculator link appreciated)
Biggest gate I suspect is the intake valve, 1 3/8" head (~35mm) HS4 is ~38mm at
best.
Recommendations? I've seen all these setups at the track, each with pluses,
minuses and overkill cause it looks cool.
One weber DCOE 40 or 2? what jets, tubes etc for a starting point? Best
manifold?
2 or 4 Mikuni 40? jet size?
thanks
mike
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<html><body><div style=3D"font-family: Verdana, Arial, Helvetica, sans-seri=
f; font-size: 10pt; color: #000000"><div>Glen,</div><div>With 1 1/2s carbur=
ettors, I suppose you mean HS4? The SU logic is a little weird. 1" + 1/2" =
=3D 6/8" so you would think it are HS6s, but when talking about HS carburet=
tors, 1 + 1/2 =3D 1 + 4/8 and they took the 4 to name these carbs HS4...</d=
iv><div>Marcel</div><div><br></div><hr id=3D"zwchr" data-marker=3D"__DIVIDE=
R__"><div data-marker=3D"__HEADERS__"><b>Van: </b>"fubog1" <fubog1@aol.c=
om><br><b>Aan: </b>"van mulders marcel" <van.mulders.marcel@telenet.b=
e>, "Mike Harmuth" <ofracer@gmail.com><br><b>Cc: </b>"fot" <fot=
@autox.team.net><br><b>Verzonden: </b>Donderdag 18 oktober 2018 22:39:39=
<br><b>Onderwerp: </b>Re: [Fot] Weber vs Mikuni<br></div><br><div data-mark=
er=3D"__QUOTED_TEXT__"><span color=3D"black" size=3D"2" face=3D"Arial, Helv=
etica, sans-serif" data-mce-style=3D"color: black; font-family: Arial, Helv=
etica, sans-serif; font-size: small;" style=3D"color: black; font-family: A=
rial, Helvetica, sans-serif; font-size: small;">
<div> <span size=3D"2" data-mce-style=3D"font-size: small;" style=3D"font-s=
ize: small;">Well I won't speculate on the cause, but I doubt that it's the=
SUs.<br>
</span></div>
<div><span size=3D"2" data-mce-style=3D"font-size: small;" style=3D"font-si=
ze: small;">My small crank 1300 w/1 1/2s on a eurospec manifold w/Stahls he=
ader, "big" valve head, would buzz easily to 9k, still making power, if I l=
et it.</span></div>
<div><span size=3D"2" data-mce-style=3D"font-size: small;" style=3D"font-si=
ze: small;">Normal shift point 7800-8000.</span></div>
<div><span size=3D"2" data-mce-style=3D"font-size: small;" style=3D"font-si=
ze: small;">FWIW...<br>
</span></div>
<div><span size=3D"2" data-mce-style=3D"font-size: small;" style=3D"font-si=
ze: small;">Glen</span><br>
</div>
<div> <br>
</div>
<div> <br>
</div>
<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black">-----=
Original Message-----<br>
From: van.mulders.marcel--- via Fot <fot@autox.team.net><br>
To: Mike Harmuth <ofracer@gmail.com><br>
Cc: fot <fot@autox.team.net><br>
Sent: Thu, Oct 18, 2018 2:12 pm<br>
Subject: Re: [Fot] Weber vs Mikuni<br>
<br>
<div id=3D"yiv1357758352">
<div>
<div style=3D"font-family:Verdana, Arial, Helvetica, sans-serif;font-size:1=
0pt;color:#000000;">
<div>-"...hitting a wall at that point..." : is it possible this is rather =
pointing to the camshaft than to the SU's? If it are the carburettors, mayb=
e the power would decrease more gradually above 6500 rpm.</div>
<div>-In general one choke per cylinder is better, and 2 Webers 40 DCOE isn=
't overkill I think</div>
<div>- what about trying HS6 SU's on your actual manifold?</div>
<div>At what maximum rpm is your engine still reliable?</div>
<div>Marcel</div>
<div><br clear=3D"none"></div>
<hr id=3D"yiv1357758352zwchr">
<div class=3D"yiv1357758352yqt0105059393" id=3D"yiv1357758352yqt73080">
<div><b>Van: </b>"fot" <fot@autox.team.net><br clear=3D"none"><b>Aan:=
</b>"fot" <fot@autox.team.net><br clear=3D"none"><b>Verzonden: </b>W=
oensdag 17 oktober 2018 15:49:45<br clear=3D"none"><b>Onderwerp: </b>[Fot] =
Weber vs Mikuni<br clear=3D"none"></div>
<br clear=3D"none">
<div>
<div dir=3D"ltr">
<div>I'm looking into switching out my twin HS4s on the 1296 race engine to=
either Weber or Mukinis. I know this has been done for years and I'd like =
to get close the best set up out of the gate. <br clear=3D"none"></div>
<br clear=3D"none">
<div>I don't think the SUs are up to the task of moving enough air with the=
new ported head and Stahl header. I've worked on the SUs and gotten them t=
o finally deliver a good AFR , 12.6, at 6500 RPM under load but I seem to h=
it a wall (figuratively) at that point. I suspect that the openings just ar=
en't big enough to deliver the mass of air required. (spreadsheet or other =
flow calculator link appreciated)<br clear=3D"none"></div>
<div>Biggest gate I suspect is the intake valve, 1 3/8" head (~35mm) HS4 is=
~38mm at best.<br clear=3D"none"></div>
<br clear=3D"none">
<div>Recommendations? I've seen all these setups at the track, each with pl=
uses, minuses and overkill cause it looks cool. <br clear=3D"none"></div>
<br clear=3D"none">
<div>One weber DCOE 40 or 2? what jets, tubes etc for a starting point? Bes=
t manifold? <br clear=3D"none"></div>
<br clear=3D"none">
<div>2 or 4 Mikuni 40? jet size?</div>
<br clear=3D"none">
<div>thanks</div>
<div>mike<br clear=3D"none"></div>
</div>
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tions/fot/van.mulders.marcel@telenet.be<br clear=3D"none"></div>
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