--===============2181258205424041173==
boundary=Apple-Mail-EA71D618-CC73-4F59-9D2D-8D67234ED50C
Content-Transfer-Encoding: 7bit
--Apple-Mail-EA71D618-CC73-4F59-9D2D-8D67234ED50C
charset=us-ascii
Content-Transfer-Encoding: quoted-printable
Make sure the bowl vents are clear and working properly. I don't know much a=
bout SUs, but how about float level? Is it simply running out of gas the lo=
nger you drive it?
I've also seen this happen when a coil goes bad. You might just switch out t=
he coil first to see if things improve.
Good Luck!
Chuck
> On Nov 28, 2016, at 3:58 PM, Mike Harmuth <ofracer@gmail.com> wrote:
>=20
> Thanks for the replies, here are the answers to some of the questions:
>=20
> Valve springs, - Dual springs with alloy retainers. The engine builder tes=
ted and shimmed them to a uniform pressure but I don't know the number off t=
he top of my head. I'll ask him tomorrow
>=20
> Silver springs in the carbs, the lightest they make I believe. I have a se=
t of heaver ones (red I believe) that I can try. The pistons are filled ~ 3/=
4 of the way, up with SU branded oil and the dampers are in place.
>=20
> The fuel pump, Holley red, all the lines, micron filter before the pump an=
d the regulator were changed last winter because I didn't know how old they w=
ere. I had the problem then as well, before and after the replacement. I ope=
ned the cell up two weeks ago. The foam is in great shape, the pickups and i=
ntake line look to be solid as well. The ATL cell is 6 years old.
>=20
> Fuel pressure is measured by a gauge at the regulator 2 feet from the carb=
s.
>=20
> I'm not sure that the problem isn't electrical but the car runs with a alt=
ernator (confirmed working). The distributor was built with a profile to mat=
ch my engine by Jeff at Advanced Distributors. I've changed the points (usin=
g his high speed set), rotor, cap, wires and capacitor over the summer, just=
in case, but with no affect. Timing is steady, double row timing chain.
>=20
> thanks for all the info.
>=20
> mike h
>=20
>> On Mon, Nov 28, 2016 at 5:05 PM, Sam Halkias <atr6racer@hotmail.com> wrot=
e:
>> What are you running for valve springs? Sounds like valve float to me.
>>=20
>> Sam
>>=20
>> Sent from my Verizon Wireless 4G LTE DROID
>>=20
>>=20
>> Mike Harmuth <ofracer@gmail.com> wrote:
>>=20
>> I'm tracking down a problem with the Spit race car (1296 Small Journal, 1=
2;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported a=
s per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles (mani=
fold and carbs checked for vacuum leaks), Advanced Distributor for spark (34=
degrees at full, mechanical only, advance @ 3.5K RPM)
>>=20
>> The problem I have has followed me on two different short blocks, I can e=
asily pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4=
th gear is 1;1, 4:11 locked diff ) gears. In 4th I'm struggling to get over=
6K, no matter how long the straight. Just before the last race of the seaso=
n, I installed an air fuel ratio gauge on the header (stahl) and found out I=
'm running (progressively) very lean (19:1) in 4th over 5K. At 2K I adjuste=
d it rich, to 12;1 and it keeps in the 13.5- 14.5 range until I get over 5K w=
hen it really leans out. If I pull the choke to 1/2 full over 5K, I get a g=
ood ratio again, 13.5- 14%.=20
>>=20
>> To me that seemed like the carb pistons aren't pulling all the way up so I=
drilled and tapped the manifold to get a vacuum reading. It was steady but l=
ow at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if I b=
lipped the throttle. Under 6K, it was in the 15 inch range. Normal air filte=
rs are K&N with stub stacks but I get the same results with open carbs.
>>=20
>> Am I correct in assuming that the vacuum is too low or is it that due to o=
verlap with a performance cam? Any ideas on where to look to get the ratio "=
normal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the en=
gine compartment and steady through all revs.
>>=20
>> I have dyno time scheduled in a few weeks but I'd like to use that time t=
o tune not debug things.
>>=20
>> thanks
>> mike h
>> 63 spitfire
>=20
> _______________________________________________
> fot@autox.team.net
>=20
> http://www.fot-racing.com
>=20
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/chasgee22@gm=
ail.com
>=20
>=20
--Apple-Mail-EA71D618-CC73-4F59-9D2D-8D67234ED50C
charset=utf-8
Content-Transfer-Encoding: quoted-printable
<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Make sure the bowl vents are clear and=
working properly. I don't know much about SUs, but how about float le=
vel? Is it simply running out of gas the longer you drive it?</div><di=
v id=3D"AppleMailSignature"><br></div><div id=3D"AppleMailSignature">I've al=
so seen this happen when a coil goes bad. You might just switch out th=
e coil first to see if things improve.</div><div id=3D"AppleMailSignature"><=
br></div><div id=3D"AppleMailSignature">Good Luck!<br><br>Chuck</div><div><b=
r>On Nov 28, 2016, at 3:58 PM, Mike Harmuth <<a href=3D"mailto:ofracer@gm=
ail.com">ofracer@gmail.com</a>> wrote:<br><br></div><blockquote type=3D"c=
ite"><div><div dir=3D"ltr"><div><div><div><div><div><div><div>Thanks for the=
replies, here are the answers to some of the questions:<br><br></div>Valve s=
prings, - Dual springs with alloy retainers. The engine builder tested and s=
himmed them to a uniform pressure but I don't know the number off the top of=
my head. I'll ask him tomorrow<br><br></div>Silver springs in the carbs, th=
e lightest they make I believe. I have a set of heaver ones (red I believe) t=
hat I can try. The pistons are filled ~ 3/4 of the way, up with SU bra=
nded oil and the dampers are in place.<br><br></div>The fuel pump, Holley re=
d, all the lines, micron filter before the pump and the regulator were chang=
ed last winter because I didn't know how old they were. I had the problem th=
en as well, before and after the replacement. I opened the cell up two weeks=
ago. The foam is in great shape, the pickups and intake line look to be sol=
id as well. The ATL cell is 6 years old.<br><br></div>Fuel pressure is measu=
red by a gauge at the regulator 2 feet from the carbs.<br><br></div>I'm not s=
ure that the problem isn't electrical but the car runs with a alternator (co=
nfirmed working). The distributor was built with a profile to match my engin=
e by Jeff at Advanced Distributors. I've changed the points (using his high s=
peed set), rotor, cap, wires and capacitor over the summer, just in case, bu=
t with no affect. Timing is steady, double row timing chain.<br><br></div>th=
anks for all the info.<br><br></div>mike h<br></div><div class=3D"gmail_extr=
a"><br><div class=3D"gmail_quote">On Mon, Nov 28, 2016 at 5:05 PM, Sam Halki=
as <span dir=3D"ltr"><<a href=3D"mailto:atr6racer@hotmail.com"; target=3D"=
_blank">atr6racer@hotmail.com</a>></span> wrote:<br><blockquote class=3D"=
gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-l=
eft:1ex">
<div>
<div>
<div>What are you running for valve springs? Sounds like valve float to me.<=
/div>
<div><br>
</div>
<div>Sam</div>
<div><br>
</div>
<div><font style=3D"color:#333333"><i>Sent from my Verizon Wireless 4G LTE D=
ROID</i></font></div>
</div><div><div class=3D"h5">
<br>
<br>
Mike Harmuth <<a href=3D"mailto:ofracer@gmail.com"; target=3D"_blank">ofra=
cer@gmail.com</a>> wrote:<br>
<br>
<div>
<div dir=3D"ltr">
<div>
<div>
<div>
<div>
<div>
<div>I'm tracking down a problem with the Spit race car (1296 Small Journal,=
12;1 compression, APT TR74 cam 295 duration and 0.324 lob lift, head ported=
as per Kas's book). Rebuilt European SU HS4 carb setup with AAA needles (ma=
nifold and carbs checked for
vacuum leaks), Advanced Distributor for spark (34 degrees at full, mechanic=
al only, advance @ 3.5K RPM)<br>
<br>
</div>
The problem I have has followed me on two different short blocks, I can easi=
ly pull 7500RPM in 1st-3rd ( Close ratio TR7 gearing in a Spitfire case, 4th=
gear is 1;1, 4:11 locked diff ) gears. In 4th I'm struggling to get o=
ver 6K, no matter how long the straight.
Just before the last race of the season, I installed an air fuel ratio gaug=
e on the header (stahl) and found out I'm running (progressively) very=
lean (19:1) in 4th over 5K. At 2K I adjusted it rich, to 12;1 and it keeps i=
n the 13.5- 14.5 range until I get
over 5K when it really leans out. If I pull the choke to 1/2 full ove=
r 5K, I get a good ratio again, 13.5- 14%.
<br>
<br>
To me that seemed like the carb pistons aren't pulling all the way up so I d=
rilled and tapped the manifold to get a vacuum reading. It was steady but lo=
w at 6K, ~20 Inches but would jump to ~28 briefly as the revs dropped if I b=
lipped the throttle. Under 6K,
it was in the 15 inch range. Normal air filters are K&N with stub stack=
s but I get the same results with open carbs.<br>
<br>
</div>
Am I correct in assuming that the vacuum is too low or is it that due to ove=
rlap with a performance cam? Any ideas on where to look to get the ratio "no=
rmal" at higher revs? Fuel pump is Holley Red, adjusted to 3 PSI at the engi=
ne compartment and steady through
all revs.<br>
<br>
</div>
I have dyno time scheduled in a few weeks but I'd like to use that time to t=
une not debug things.<br>
<br>
</div>
thanks<br>
</div>
mike h<br>
</div>
63 spitfire<br>
</div>
</div>
</div></div></div>
</blockquote></div><br></div>
</div></blockquote><blockquote type=3D"cite"><div><span>____________________=
___________________________</span><br><span><a href=3D"mailto:fot@autox.team=
.net">fot@autox.team.net</a></span><br><span></span><br><span><a href=3D"htt=
p://www.fot-racing.com">http://www.fot-racing.com</a></span><br><span></span=
><br><span>Donate: <a href=3D"http://www.team.net/donate.html";>http://www.te=
am.net/donate.html</a></span><br><span>Archive: <a href=3D"http://www.team.n=
et/archive">http://www.team.net/archive</a></span><br><span>Forums: <a href=3D=
"http://www.team.net/forums";>http://www.team.net/forums</a></span><br><span>=
sgee22@gmail.com">http://autox.team.net/mailman/options/fot/chasgee22@gmail.=
com</a></span><br><span></span><br><span></span><br></div></blockquote></bod=
y></html>=
--Apple-Mail-EA71D618-CC73-4F59-9D2D-8D67234ED50C--
--===============2181258205424041173==
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/archive
--===============2181258205424041173==--
|