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What Ralph said............
I have some experience with carbs on Spifires so I will share about 2 cents=
(meaning minimal, I could probably write a book) worth if you don't mind.=
=C2=A0Dual Webers look really cool but will move you up a class or in SVRA =
to the next group, my Dyno says don't do it, it's not worth it. Makuni's? f=
orget it, price and parts are a problem, everyone at the track has Weber pa=
rts on their trailer. 1 1/2 SU's will do 9000rpm on a 1296 I know for sure =
but they are a pain to straighten out the fuel curve throughout the RPM ran=
ge, don't try this one at home boys and girls, you will end up throwing the=
m through the window. The easiest thing to do is purchase a single Weber ma=
nifold and 45 DCOE, a 40 would work as well and maybe better depending on y=
our state of tune. I have a box full of manifolds, 2 are actually within 2h=
p of the dual Webers on the top with way more bottom and mid range one I fa=
bricated and the other was purchased but only runs to 7000rpm. I would be g=
lad to help with jetting when the time comes.
All the best!=20
On Friday, October 19, 2018 4:53 AM, ralph hansen via Fot <fot@autox.te=
am.net> wrote:
=20
gee, my 1147 with HS's puled all the way to 8k with a 4:11 gear - stock b=
ore block, head work, A6 cam - its not the carbs, its either timing or cam
On =E2=80=8EThursday=E2=80=8E, =E2=80=8EOctober=E2=80=8E =E2=80=8E18=E2=
=80=8E, =E2=80=8E2018=E2=80=8E =E2=80=8E01=E2=80=8E:=E2=80=8E13=E2=80=8E:=
=E2=80=8E48=E2=80=8E =E2=80=8EPM=E2=80=8E =E2=80=8ECDT, van.mulders.marcel-=
-- via Fot <fot@autox.team.net> wrote: =20
=20
-"...hitting a wall at that point..." : is it possible this is rather poin=
ting to the camshaft than to the SU's? If it are the carburettors, maybe th=
e 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 a=
bout trying HS6 SU's on your actual manifold?At what maximum rpm is your en=
gine 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 eith=
er Weber or Mukinis. I know this has been done for years and I'd like to ge=
t close the best set up out of the gate.=20
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 fin=
ally 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 ~38m=
m at best.
Recommendations? I've seen all these setups at the track, each with pluses,=
minuses and overkill cause it looks cool.=20
One weber DCOE 40 or 2? what jets, tubes etc for a starting point? Best man=
ifold?=20
2 or 4 Mikuni 40? jet size?
thanksmike
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/pipermail/fot
arcel@telenet.be
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/pipermail/fot
com
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/pipermail/fot
tt.net
=20
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<html><head></head><body><div style=3D"color:#000; background-color:#fff; f=
ont-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font=
-size:16px"><div id=3D"yui_3_16_0_ym19_1_1539949984130_7456"><span id=3D"yu=
i_3_16_0_ym19_1_1539949984130_9159">What Ralph said............</span></div=
><div id=3D"yui_3_16_0_ym19_1_1539949984130_7456"><span><br></span></div><d=
iv id=3D"yui_3_16_0_ym19_1_1539949984130_7456" dir=3D"ltr"><span id=3D"yui_=
3_16_0_ym19_1_1539949984130_10854">I have some experience with carbs on Spi=
fires so I will share about 2 cents (meaning minimal, I could probably writ=
e a book) worth if you don't mind. </span>Dual Webers look really cool=
but will move you up a class or in SVRA to the next group, my Dyno says do=
n't do it, it's not worth it. Makuni's? forget it, price and parts are a pr=
oblem, everyone at the track has Weber parts on their trailer. 1 1/2 SU's w=
ill do 9000rpm on a 1296 I know for sure but they are a pain to straighten =
out the fuel curve throughout the RPM range, don't try this one at home boy=
s and girls, you will end up throwing them through the window. The easiest =
thing to do is purchase a single Weber manifold and 45 DCOE, a 40 would wor=
k as well and maybe better depending on your state of tune. I have a box fu=
ll of manifolds, 2 are actually within 2hp of the dual Webers on the top wi=
th way more bottom and mid range one I fabricated and the other was purchas=
ed but only runs to 7000rpm. I would be glad to help with jetting when the =
time comes.</div><div id=3D"yui_3_16_0_ym19_1_1539949984130_7456" dir=3D"lt=
r"><br></div><div id=3D"yui_3_16_0_ym19_1_1539949984130_7456" dir=3D"ltr">A=
ll the best!</div> <div class=3D"qtdSeparateBR"><br><br></div><div class=3D=
"yahoo_quoted" style=3D"display: block;"> <div style=3D"font-family: Helvet=
ica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <=
div style=3D"font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, =
Lucida Grande, sans-serif; font-size: 16px;"> <div dir=3D"ltr"><font size=
=3D"2" face=3D"Arial"> On Friday, October 19, 2018 4:53 AM, ralph hansen vi=
a Fot <fot@autox.team.net> wrote:<br></font></div> <br><br> <div cla=
ss=3D"y_msg_container"><div id=3D"yiv2262750899"><div><div class=3D"yiv2262=
750899ydp154784e8yahoo-style-wrap" style=3D"font-family:Helvetica Neue, Hel=
vetica, Arial, sans-serif;font-size:13px;"><div></div>
<div>gee, my 1147 with HS's puled all the way to 8k with a 4:11 gea=
r - stock bore block, head work, A6 cam - its not the carbs, its either tim=
ing or cam</div><div><br clear=3D"none"></div>
=20
</div><div class=3D"yiv2262750899ydpe7e79603yahoo_quoted" id=3D"yiv=
2262750899ydpe7e79603yahoo_quoted_0115294811">
<div style=3D"font-family:'Helvetica Neue', Helvetica, Arial, s=
ans-serif;font-size:13px;color:#26282a;">
=20
<div class=3D"yiv2262750899yqt7631504929" id=3D"yiv22627508=
99yqt02256"><div>
On =E2=80=8EThursday=E2=80=8E, =E2=80=8EOctober=E2=80=
=8E =E2=80=8E18=E2=80=8E, =E2=80=8E2018=E2=80=8E =E2=80=8E01=E2=80=8E:=E2=
=80=8E13=E2=80=8E:=E2=80=8E48=E2=80=8E =E2=80=8EPM=E2=80=8E =E2=80=8ECDT, v=
an.mulders.marcel--- via Fot <fot@autox.team.net> wrote:
</div>
<div><br clear=3D"none"></div>
<div><br clear=3D"none"></div>
<div><div id=3D"yiv2262750899ydpe7e79603yiv4783538815"><div=
><div style=3D"font-family:Verdana, Arial, Helvetica, sans-serif;font-size:=
10pt;color:#000000;"><div>-"...hitting a wall at that point..." : is it pos=
sible this is rather pointing to the camshaft than to the SU's? If it are t=
he carburettors, maybe the power would decrease more gradually above 6500 r=
pm.</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 reliab=
le?</div><div>Marcel</div><div><br clear=3D"none"></div><hr id=3D"yiv226275=
0899ydpe7e79603yiv4783538815zwchr"><div class=3D"yiv2262750899ydpe7e79603yi=
v4783538815yqt3904850125" id=3D"yiv2262750899ydpe7e79603yiv4783538815yqt498=
46"><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>Woensdag 17 oktober 2018 15:49:45<br clear=3D"none"><b>Onderwerp: </b>[F=
ot] Weber vs Mikuni<br clear=3D"none"></div><br clear=3D"none"><div><div di=
r=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 m=
oving 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 u=
nder 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 require=
d. (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>Rec=
ommendations? I've seen all these setups at the track, each with pluses, mi=
nuses 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? Best 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>
<br clear=3D"none">_______________________________________________<br clear=
=3D"none">fot@autox.team.net<br clear=3D"none"><br clear=3D"none">http://ww=
w.fot-racing.com<br clear=3D"none"><br clear=3D"none">Donate: http://www.te=
am.net/donate.html<br clear=3D"none">Archive: http://www.team.net/pipermail=
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tions/fot/van.mulders.marcel@telenet.be<br clear=3D"none"></div></div></div=
></div></div><div class=3D"yiv2262750899ydpe7e79603yqt3904850125" id=3D"yiv=
2262750899ydpe7e79603yqt23489">____________________________________________=
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