MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Matter of timing?

Hi All,

Moved from Panama City, FL (about 6 feet above sea level) to Colorado Springs, Colorado (about 6700 feet above sea level) and just haven't been able to get my 73 B quite right. I realize I will lose some power at this altitude, but I'm wondering if I shouldn't make some timing adjustment to compensate? Some of the folks here say I should use another 5 degrees advance, some just give me a "deer in the headlights" look.

Any words of wisdom?

Thanks,

John
John Staub

John, the physics is simple. There is less oxygen for combustion. The solution is therefore just as simple. Either increase the compression ratio or use a supercharger. Sorry!

Andrew
A Mills

John-
Rather than experimenting with the ignition timing to treat the symptom (rich mixture), treat the cause by either readusting the jet height upwards or rejetting the carburetor to a leaner mixture.
Steve S.

I second Steve's opinion. Either raise your needles accordingly, or purchase the next larger size available from what you have now. You are running too rich. The downfall is that your engine is getting less fuel and oxygen. :-(


Jeff Schlemmer

John. The old rule of thumb was to advance the timing one degree per 1,000 feet of elevation. I used this when living in Cheyenne and did not seem to have any problems. If you get pinging, retard the timing somewhat until it goes away.

If you had needles set up for sea level, you definitely need to go to a leaner needle for your altitude. The jet height is set for idle mixture and the cruise settings are controlled by needle profile. Thus, you need to know what needles you are currently running and what ones are leaner. After you find out what you have, give Joe Curto a call at 718-762-7878 and ask what he would recommend. He provides full service SU repairs and parts. Les
Les Bengtson

Hi All,

I probably should have been a bit more explicit in my first post. The carbs are properly tuned for the altitude.

Think I'll try Les's timing advice next.

Thanks,

John
John Staub

John. What needles are you running? Les
Les Bengtson

We should all be running just short of pinking at any combination of throttle, load and revs anyway. Depending on the precise set of tolerances on all one's components you could well get better performance and economy that way than the book figures. I know I did on a different BL engine, but not on the one I have now.
Paul Hunt

This thread was discussed between 22/02/2004 and 23/02/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.