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MG MGB Technical - Ignition timing

Who can help me? I have a 1972 MGB GT that has a modified engine. Not over modified but modified no the less. It started life as a 18V (not the rigional engine) and since has been rebored by 0.40 which makes it, no, you tell me as my maths is not that good. It has a nicely done stage 2 head that was gas flowed and polished. I have done the right thing and had it converted for unleaded fuel when the head gasket went some years ago. It also has a DCOE 45 but a standard stainless steel exhaust as my wife says the Peco was too noisy and thats good enough for me as I value my life. I have no idea what cam shaft it has as all the work was done by a previous owner. It starts thanks to a 25D distributor on points with a vacume advance and NGK triple electrode plugs (best buy I have ever made for the car). Right then. It runs OK as it is but I do think that it might go a little better. I am up for playing about with the timing but would be grateful for advice from anyone as to what the static might be with the setup I have described. Also what the strobe timing would be and at what revs even thought the rev counter died a while ago and has not been replaced yet.
All advice will be gratefully received and please no infighting among your selves when one person disagrees with the others reply.
Thanks Doug
PS I managed to copy and past this from the MGF section where I accidently placed it yesterday.
Doug E

A good point to start off with would be a strobe reading of 10 DBTDC with engine idling at about 600rpm. FRom there it is down to road testing and applying a little advance at a time until you can just hear the engine starting to pink when accelerating firmly in 4th gear at about 20-25 mph. That's as close as its possible to go but will nevertheless land you at the ideal position.
Iain MacKintosh

Alternatively, set timing at 34 degrees at high revs (say more than 3500rpm) and work downwards. You maight not manage an idle of 600rpm with a stage 2 head, cam and Weber!
Neil
Neil22

I know it has been said before but IMHO the best money you can spend on a modified car is a session on a good rolling road. Then you should have a record of all the best settings for your engine.All you have to do is find a rolling road you can trust, I am sure someone on here can recommend somewhere.

Good luck Carl
C Bintcliffe

Doug. I would echo Carl's advice. The early MGB distributor is a basic starting place for all engines. Peter Burgess speaks highly of it in his book. It should provide adequate performance for most engines and will be safe to use.

For optimal performance, however, one needs to put the car on a rolling road (chassis dynamometer) with the proper test equipment to hand to determine when the engine is working at its best. That will determine what the ideal ignition advance curve is for that engine. At that point, you decide what you want/can afford, in the way of an ignition distribution device. A mechanical distributor, with the advance curve set as closely as possible to the ideal curve--without ever having too much advancement in any part of the range, is the least expensive method. Computer controlled systems are the most expensive. Depends on how much money and effort you want to spend on the project.

Les
Les Bengtson

Doug-
I have to agree with Carl and Les. A rolling road session performed by an expert would bring what you have into optimal performance. I suggest that you book a session with Peter Burgess. He'll have your engine singingin no time.
Steve S.

Hi
Thanks to everyone for the advice. It looks like a rolling road session is the way to get the best out of the motor without waste particularly as I don't know what cam I have.
Does anyone know of a reliable place in sunny Devon, England? I live in Torbay.
Thanks again
Doug E

This thread was discussed between 01/03/2008 and 02/03/2008

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