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Re: [Fot] Weber vs Mikuni

To: van.mulders.marcel@telenet.be
Subject: Re: [Fot] Weber vs Mikuni
From: fubog1 via Fot <fot@autox.team.net>
Date: Fri, 19 Oct 2018 11:23:38 +0000 (UTC)
Cc: fot@autox.team.net
Delivered-to: mharc@autox.team.net
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 Yes HS4 carbs.Glen
 
 
-----Original Message-----
From: van.mulders.marcel <van.mulders.marcel@telenet.be>
To: fubog1 <fubog1@aol.com>
Cc: fot <fot@autox.team.net>
Sent: Thu, Oct 18, 2018 5:48 pm
Subject: Re: [Fot] Weber vs Mikuni

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?
thanksmike

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<font color=3D'black' size=3D'2' face=3D'Arial, Helvetica, sans-serif'>
<div> <font size=3D"2">Yes HS4 carbs.</font></div>

<div><font size=3D"2">Glen</font><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 &lt;van.mulders.marcel@telenet.be&gt;<br>
To: fubog1 &lt;fubog1@aol.com&gt;<br>
Cc: fot &lt;fot@autox.team.net&gt;<br>
Sent: Thu, Oct 18, 2018 5:48 pm<br>
Subject: Re: [Fot] Weber vs Mikuni<br>
<br>

<div id=3D"yiv7557179423">
<div>
<div style=3D"font-family:Verdana, Arial, Helvetica, sans-serif;font-size:1=
0pt;color:#000000;">
<div>Glen,</div>

<div>With 1 1/2s carburettors, I suppose you mean HS4? The SU logic is a li=
ttle weird. 1" + 1/2" =3D 6/8" so you would think it are HS6s, but when tal=
king about HS carburettors, 1 + 1/2 =3D 1 + 4/8 and they took the 4 to name=
 these carbs HS4...</div>

<div>Marcel</div>

<div><br clear=3D"none"></div>
<hr id=3D"yiv7557179423zwchr">
<div class=3D"yiv7557179423yqt0596148954" id=3D"yiv7557179423yqt61649">
<div><b>Van: </b>"fubog1" &lt;fubog1@aol.com&gt;<br clear=3D"none"><b>Aan: =
</b>"van mulders marcel" &lt;van.mulders.marcel@telenet.be&gt;, "Mike Harmu=
th" &lt;ofracer@gmail.com&gt;<br clear=3D"none"><b>Cc: </b>"fot" &lt;fot@au=
tox.team.net&gt;<br clear=3D"none"><b>Verzonden: </b>Donderdag 18 oktober 2=
018 22:39:39<br clear=3D"none"><b>Onderwerp: </b>Re: [Fot] Weber vs Mikuni<=
br clear=3D"none"></div>
<br clear=3D"none">
<div><span style=3D"color:black;font-family:Arial, Helvetica, sans-serif;fo=
nt-size:small;">
</span>
<div> <span style=3D"font-size:small;">Well I won't speculate on the cause,=
 but I doubt that it's the SUs.<br clear=3D"none">
</span></div>



<div><span style=3D"font-size:small;">My small crank 1300 w/1 1/2s on a eur=
ospec manifold w/Stahls header, "big" valve head, would buzz easily to 9k, =
still making power, if I let it.</span></div>



<div><span style=3D"font-size:small;">Normal shift point 7800-8000.</span><=
/div>



<div><span style=3D"font-size:small;">FWIW...<br clear=3D"none">
</span></div>



<div><span style=3D"font-size:small;">Glen</span><br clear=3D"none">
</div>



<div> <br clear=3D"none">
</div>



<div> <br clear=3D"none">
</div>



<div style=3D"font-family:arial, helvetica;font-size:10pt;color:black;">---=
--Original Message-----<br clear=3D"none">
From: van.mulders.marcel--- via Fot &lt;fot@autox.team.net&gt;<br clear=3D"=
none">
To: Mike Harmuth &lt;ofracer@gmail.com&gt;<br clear=3D"none">
Cc: fot &lt;fot@autox.team.net&gt;<br clear=3D"none">
Sent: Thu, Oct 18, 2018 2:12 pm<br clear=3D"none">
Subject: Re: [Fot] Weber vs Mikuni<br clear=3D"none">
<br clear=3D"none">


<div id=3D"yiv7557179423">

<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"yiv7557179423zwchr">

<div class=3D"yiv7557179423yqt0105059393" id=3D"yiv7557179423yqt73080">

<div><b>Van: </b>"fot" &lt;fot@autox.team.net&gt;<br clear=3D"none"><b>Aan:=
 </b>"fot" &lt;fot@autox.team.net&gt;<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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