MGExp

MGB & GT Forum

Compression results for my 1966 MGB

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

Compression results for my 1966 MGB
#1
  This topic is about my 1966 MG MGB
CADDMAN04 J.P. Gauthier
Toronto, Ontario, Canada   CAN
1966 MG MGB
I have just completed my compression test on my MGB. It is 162(1) 161(2) 160 (3) 162 (4) . Are these results ok? I have a problem with my 3rd spark plug. It is always black, no oil just carbon, number 1, 2, and 4 are fine. I wonder was could be the problem, valves, or sticky ring? Could anybody please let me know if the compression test results are good , and how to solve the problem with the dirty number 3 cylinder plug.

Thanks

J.P. Gauthier

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
Compression is fine.
What plugs and gap BP6ES @ 25THO
Carbs might be slightly rich
Lean it out a tad



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

fast-MG.com Avatar
fast-MG.com Gold Member Dave Headley
Cortez, 4 corners, Colorado, USA   USA
What RobC said. Plus, verify carb balance both at idle and off idle before adjusting mixture.smoking smiley


Member Services:
Dave Headley, dba FAB-TEK offers full service race car parts and preperation for MGB & MGA race cars, SCCA and Vintage. Dave is a mechanical engineer and has raced MGBs since 1963.
CADDMAN04 J.P. Gauthier
Toronto, Ontario, Canada   CAN
1966 MG MGB
Thanks, everyone, the plugs are the spec Champion plugs. I will check the plug gap. The carbs were recently tuned with a vacuum gauge to sync the intake and idle. The mixture was set to spec appears to be running a bit rich, I can lean it out a bit to see if this helps.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
HiPowerShooter Avatar
HiPowerShooter Gold Member James Booker
Oshkosh, Wisconsin, USA   USA
1973 MG MGB
You should also see somewhere between 24-30 mpg depending on your city/highway driving under normal conditions. IF it's significantly lower...you're definitely running rich.



"One test is worth a thousand expert opinions"--Alvin "Tex" Johnston...Boeing test pilot.

73 MGB. Tires: Round, black, hold air. Oil: Sometimes old, sometimes new...always slippery. Oil filter: Yellow, usually full of oil. Carbs: 2 SU HIF. Distributor: Yes. Headlights: Not that bright but bright enough. A bunch of other stuff most cars have but not really important enough to itemize. Oh, wait...it has a cool sounding exhaust with stickers on the chrome tips. Really slays the ladies...

nickj Avatar
nickj Gold Member Nick Jenkins
Novato, Marin Co, CA, USA   USA
1970 MG MGB GT
1972 MG MGB
A picture of the #3 plug might help. If it's black from not firing, could be the plug. If it's crusty, could be a valve guide or seal.

ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
I'd lean it out and try NGK BP6ES
Gappend correctly

Champions no moresad smiley



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
That plug, plug-wire, cap or rotor might not be firing consistently on that cylinder. Try swapping plugs to see if the probably follows the plug, if not do the same thing with the plug-wire, if the probably is still on #3, replace the rotor and cap. Also inspect the dizzy shaft to ensure it is not bent.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Cincinnati, Ohio, USA   USA
1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2012 Jeep Liberty "Tank"
2014 Hyundai Accent "Skate"
Intake valve guide seal would be myvote for one plug only being blackened.

It would be interesting to see a photo of all the 4 plugs.

In reply to # 3591263 by nickj A picture of the #3 plug might help. If it's black from not firing, could be the plug. If it's crusty, could be a valve guide or seal.



The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions

Members Sign In   or   Create an Account

Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster