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Hi WIlliam,
There will be as many answers to your questions as there are readers, as=
there are many variables involved.
It is my opinion that if the max advance, without vacuum connected, shou=
ld be 32 degrees at 3500+. That is shared by many. Another of my opinions=
is that 10% alcohol makes no difference to the engine=E2=80=99s performance=
. One can read adverts in British periodicals of the 1950s and 1960s in whi=
ch the brands advertise that they are better because of the alcohol. =20
As to the fuel choice, that very much depends on where you are driving (=
hills, dales, flat country) and how you like to drive. The workshop manual w=
as written years ago, so its timing specs may or may not be valid today. Fu=
els differ around the country, and certainly are quite different from those i=
n 1974, so you end up selecting one that seems to work OK for you. It is sa=
id, also, that fuel blends differ regionally in USA.
One ends up setting the timing to what keeps engine and driver happy. We k=
now that pinging/pinking is hard on the engine. One should avoid that by dow=
n-shifting as needed, checking that the timing is not over-advanced, or by u=
sing higher-octane fuel. =20
Mine is 1972 18V, home-market pistons, some cleanup of heads and ports, w=
ith HIF and distributor rebuilt by Advanced Distributors (Jeff Schlemmer). M=
ax advance, w/o vacuum, is 32 degrees. I find that alternating tanks of 8=
9 and 91 (sometimes the same pump shows 93) keeps it happy. We have some hil=
ls in CT, so I listen carefully at 2500 rpm.=20
Over the course of a driving season, perhaps 4000 miles, the annual diffe=
rence in cost of one fuel to another is slight. I try to err on the side of c=
aution.
Bob
> On Jul 9, 2021, at 5:47 PM, wkilleffer@epbfi.com wrote:
>=20
> Hello everyone,
>=20
> My car is a 1974 MGB with an 18GK engine and HS4 carbs. The evaporative lo=
ss control and anti-run on controls are connected. The smog pump has been re=
moved and the ports are plugged. The distributor is a Pertronix unit I bough=
t several years ago. It's equipped with vacuum advance, which is working. Th=
e mechanical advance is also freely working. Not too long ago, I read that t=
hese cars, even the high compression ones, should be able to run well on eth=
anol-free 87 octane. This caused no small debate on the local British car gr=
oup on facebook, but the consensus seemed to be that those who used E0 87 we=
re satisfied and didn't have any issues from it. My last fill-up had been et=
hanol-free 93, and I need not tell you that running E0 87 would be far prefe=
rable. It was time for a fill-up, so I filled at at a nearby station that se=
ems to sell decent quality stuff.
>=20
> It appears to run well enough, but I have had a couple of issues come up w=
here there was a low-speed but high load situation, like going up a short hi=
ll with a 15 mph speed limit. I could hear it pinging some. Downshifting wil=
l stop it, but that isn't always practical. So, I decided to check its timin=
g. The Bentley manual and several online sources state that an 18GK is suppo=
sed to have its dynamic timing set to 16deg BTDC at 1500rpm. It's been a few=
years since I last set the timing, so I disconnected the vacuum advance and=
plugged the manifold port, and then got the car running smoothly at 1500rpm=
as indicated by the tach in the dash. It's all I have, so it'll have to do.=
>=20
> I expected the timing to be too far advanced at that RPM, but if anything,=
it was slightly retarded. If 16deg is between the 20 and the 15, the car wa=
s currently set at around 12deg. I adjusted it to an indicated 16deg, re-che=
cked the idle speed, checked the timing again, was satisfied, tightened the d=
istributor clamp and shut off the engine. I haven't yet test driven it, thou=
gh at idle it sounded smooth at maybe an indicated 800 or 850rpm. For all I k=
now, it'll probably have a little more spring in its step, though it hasn't s=
eemed sluggish lately. I try to drive it at least twice per week, so it's no=
t sitting too often.
>=20
> Does anyone else run 87 in a high compression engine, or have I gone off o=
n a fool's errand here?
>=20
> Thank you,
> -William
> _______________________________________________
>=20
> Mgs@autox.team.net
> Donate: http://www.team.net/donate.html
> Suggested annual donation $12.75
>=20
> Archive: http://www.team.net/pipermail/mgs http://autox.team.net/archive
>=20
> Unsubscribe: http://autox.team.net/mailman/options/mgs/mgbobh@gmail.com
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div dir=3D"ltr"></div><div dir=3D"ltr">Hi W=
Illiam,</div><div dir=3D"ltr"> There will be as many answers to=
your questions as there are readers, as there are many variables involved.<=
/div><div dir=3D"ltr"> It is my opinion that if the max advance=
, without vacuum connected, should be 32 degrees at 3500+. That is sh=
ared by many. Another of my opinions is that 10% alcohol makes no diff=
erence to the engine=E2=80=99s performance. One can read adverts in Br=
itish periodicals of the 1950s and 1960s in which the brands advertise that t=
hey are better because of the alcohol. </div><div dir=3D"ltr">&n=
bsp; As to the fuel choice, that very much depends on where you are d=
riving (hills, dales, flat country) and how you like to drive. The wor=
kshop manual was written years ago, so its timing specs may or may not be va=
lid today. Fuels differ around the country, and certainly are quite d=
ifferent from those in 1974, so you end up selecting one that seems to work O=
K for you. It is said, also, that fuel blends differ regionally in USA=
.</div><div dir=3D"ltr"> One ends up setting the timing to what k=
eeps engine and driver happy. <span style=3D"background-color: rgba(255, 255=
, 255, 0);">We know that pinging/pinking is hard on the engine. One should a=
void that by down-shifting as needed, checking that the timing is not over-a=
dvanced, or by using higher-octane fuel. </span></div><div> =
; Mine is 1972 18V, home-market pistons, some cleanup of heads and por=
ts, with HIF and distributor rebuilt by Advanced Distributors (Jeff Schlemme=
r). Max advance, w/o vacuum, is 32 degrees. I find that a=
lternating tanks of 89 and 91 (sometimes the same pump shows 93) keeps it ha=
ppy. We have some hills in CT, so I listen carefully at 2500 rpm. </div=
><div dir=3D"ltr"> Over the course of a driving season, perhaps 4=
000 miles, the annual difference in cost of one fuel to another is slight. I=
try to err on the side of caution.</div><div dir=3D"ltr">Bob</div><div dir=3D=
"ltr"><br></div><div dir=3D"ltr"><br></div><div dir=3D"ltr"><br></div><div d=
ir=3D"ltr">On Jul 9, 2021, at 5:47 PM, <a href=3D"mailto:wkilleffer@epbfi.co=
m">wkilleffer@epbfi.com</a> wrote:<br><br></div><blockquote type=3D"cite"><d=
iv dir=3D"ltr"><div style=3D"font-family: arial, helvetica, sans-serif; font=
-size: 12pt; color: #000000"><div>Hello everyone,</div><div><br data-mce-bog=
us=3D"1"></div><div>My car is a 1974 MGB with an 18GK engine and HS4 carbs. T=
he evaporative loss control and anti-run on controls are connected. The smog=
pump has been removed and the ports are plugged. The distributor is a Pertr=
onix unit I bought several years ago. It's equipped with vacuum advance, whi=
ch is working. The mechanical advance is also freely working. Not too long a=
go, I read that these cars, even the high compression ones, should be able t=
o run well on ethanol-free 87 octane. This caused no small debate on the loc=
al British car group on facebook, but the consensus seemed to be that those w=
ho used E0 87 were satisfied and didn't have any issues from it. My last fil=
l-up had been ethanol-free 93, and I need not tell you that running E0 87 wo=
uld be far preferable. It was time for a fill-up, so I filled at at a nearby=
station that seems to sell decent quality stuff.</div><div><br data-mce-bog=
us=3D"1"></div><div>It appears to run well enough, but I have had a couple o=
f issues come up where there was a low-speed but high load situation, like g=
oing up a short hill with a 15 mph speed limit. I could hear it pinging some=
. Downshifting will stop it, but that isn't always practical. So, I decided t=
o check its timing. The Bentley manual and several online sources state that=
an 18GK is supposed to have its dynamic timing set to 16deg BTDC at 1500rpm=
. It's been a few years since I last set the timing, so I disconnected the v=
acuum advance and plugged the manifold port, and then got the car running sm=
oothly at 1500rpm as indicated by the tach in the dash. It's all I have, so i=
t'll have to do.</div><div><br data-mce-bogus=3D"1"></div><div>I expected th=
e timing to be too far advanced at that RPM, but if anything, it was slightl=
y retarded. If 16deg is between the 20 and the 15, the car was currently set=
at around 12deg. I adjusted it to an indicated 16deg, re-checked the idle s=
peed, checked the timing again, was satisfied, tightened the distributor cla=
mp and shut off the engine. I haven't yet test driven it, though at idle it s=
ounded smooth at maybe an indicated 800 or 850rpm. For all I know, it'll pro=
bably have a little more spring in its step, though it hasn't seemed sluggis=
h lately. I try to drive it at least twice per week, so it's not sitting too=
often.</div><div><br data-mce-bogus=3D"1"></div><div>Does anyone else run 8=
7 in a high compression engine, or have I gone off on a fool's errand here?<=
/div><div><br data-mce-bogus=3D"1"></div><div>Thank you,</div><div>-William<=
/div></div></div></blockquote><blockquote type=3D"cite"><div dir=3D"ltr"><sp=
an>_______________________________________________</span><br><span></span><b=
r><span><a href=3D"mailto:Mgs@autox.team.net";>Mgs@autox.team.net</a></span><=
br><span>Donate: <a href=3D"http://www.team.net/donate.html";>http://www.team=
.net/donate.html</a></span><br><span>Suggested annual donation $12.75<=
/span><br><span></span><br><span>Archive: <a href=3D"http://www.team.net/pip=
ermail/mgs">http://www.team.net/pipermail/mgs</a> <a href=3D"http://autox.te=
am.net/archive">http://autox.team.net/archive</a></span><br><span></span><br=
><span>Unsubscribe: <a href=3D"http://autox.team.net/mailman/options/mgs/mgb=
obh@gmail.com">http://autox.team.net/mailman/options/mgs/mgbobh@gmail.com</a=
></span><br></div></blockquote></body></html>=
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