Subject: [Mgs] Timing adjustment on an 18GK engine

From: [email-masked]
Date: Fri, 9 Jul 2021 17:47:12 -0400 (EDT)

--===============0078551136119302924==
	boundary="=_8f475dc8-4af6-40d4-a9ee-a51f2623595d"

--=_8f475dc8-4af6-40d4-a9ee-a51f2623595d
Content-Transfer-Encoding: 7bit

Hello everyone, 

My car is a 1974 MGB with an 18GK engine and HS4 carbs. The 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 Pertronix unit I bought several years ago. It's equipped with vacuum advance, which is working. The mechanical advance is also freely working. Not too long ago, I read that these cars, even the high compression ones, should be able to run well on ethanol-free 87 octane. This caused no small debate on the local British car group on facebook, but the consensus seemed to be that those who used E0 87 were satisfied and didn't have any issues from it. My last fill-up had been ethanol-free 93, and I need not tell you that running E0 87 would 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. 

It appears to run well enough, but I have had a couple of issues come up where there was a low-speed but high load situation, like going 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 to 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 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. 

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 was currently set at around 12deg. I adjusted it to an indicated 16deg, re-checked the idle speed, checked the timing again, was satisfied, tightened the distributor clamp and shut off the engine. I haven't yet test driven it, though at idle it sounded smooth at maybe an indicated 800 or 850rpm. For all I know, it'll probably have a little more spring in its step, though it hasn't seemed sluggish lately. I try to drive it at least twice per week, so it's not sitting too often. 

Does anyone else run 87 in a high compression engine, or have I gone off on a fool's errand here? 

Thank you, 
-William 

--=_8f475dc8-4af6-40d4-a9ee-a51f2623595d
Content-Transfer-Encoding: quoted-printable

<html><body><div style=3D"font-family: arial, helvetica, sans-serif; font-s=
ize: 12pt; color: #000000"><div>Hello everyone,</div><div><br data-mce-bogu=
s=3D"1"></div><div>My car is a 1974 MGB with an 18GK engine and HS4 carbs. =
The evaporative loss control and anti-run on controls are connected. The sm=
og pump has been removed and the ports are plugged. The distributor is a Pe=
rtronix unit I bought several years ago. It's equipped with vacuum advance,=
 which is working. The mechanical advance is also freely working. Not too l=
ong ago, I read that these cars, even the high compression ones, should be =
able to run well on ethanol-free 87 octane. This caused no small debate on =
the local British car group on facebook, but the consensus seemed to be tha=
t those who used E0 87 were satisfied and didn't have any issues from it. M=
y last fill-up had been ethanol-free 93, and I need not tell you that runni=
ng E0 87 would 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-bogus=3D"1"></div><div>It appears to run well enough, but I have =
had a couple of issues come up where there was a low-speed but high load si=
tuation, like going 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 practica=
l. So, I decided to check its timing. The Bentley manual and several online=
 sources state that an 18GK is supposed to have its dynamic timing set to 1=
6deg 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 das=
h. It's all I have, so it'll have to do.</div><div><br data-mce-bogus=3D"1"=
></div><div>I expected the timing to be too far advanced at that RPM, but i=
f anything, it was slightly 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 speed, checked the timing again, was satisfied, =
tightened the distributor clamp and shut off the engine. I haven't yet test=
 driven it, though at idle it sounded smooth at maybe an indicated 800 or 8=
50rpm. For all I know, it'll probably have a little more spring in its step=
, though it hasn't seemed sluggish 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 87 in a high compression engine, or have =
I gone off on a fool's errand here?</div><div><br data-mce-bogus=3D"1"></di=
v><div>Thank you,</div><div>-William</div></div></body></html>
--=_8f475dc8-4af6-40d4-a9ee-a51f2623595d--

--===============0078551136119302924==
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________

[email-masked]

Archive: http://www.team.net/pipermail/mgs http://autox.team.net/archive

Unsubscribe: http://autox.team.net/mailman/options/mgs/[email-masked]

--===============0078551136119302924==--