MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey 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 - 18 V Timing

Having run my re-built (by me) 18V for around 700 miles and today done some minor adjustments, tappets, timing check, dwell etc. I notice that with the dwell correct it requires about 25 deg BTDC to run smoothly. Setting to 15 is fairly undrivable with low power etc. Before anyone asks, I did not remove the timing chain and so this is as original. When I started it I had done it statically and all seemed well. It is running unleaded (which I thought required more retard). Any bright ideas??
Andrew Walton

25 deg BTDC static or dynamic at what engine speed? Vacuum disconnected?
M McAndrew

Tickover about 800RPM and vacuum disconnected. Dynamic strobe measurement. Thanks
Andrew Walton

Has the timing cover or crank pulley been changed?
Allan Reeling

Andrew. Sometimes, especially with older pulleys, the rubber portion begins to deteriorate and allows the inner and outer rings to slip in their relationship with each other. At that point, the timing marks on the outer edge of the harmonic balancer are no longer an accurate reflection of the true timing. If the timing was accurate when the engine was initially set up and, now, it is no longer accurate delamination of the harmonic balancer is worth considering.

Les
Les Bengtson

What Les said but if its not that the mechanical advance is frozen or advance springs dislodged.
Denis
Denis4

Check the true TDC using an old spark plug, knock off the electrode and ceramic insulator and screw in a stud or piece of wooden dowel.

http://www.4secondsflat.com/TDC.html
c cummins

This thread was discussed between 25/09/2012 and 26/09/2012

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now