Classic MGB 1800, massively over advanced ignition timing...

AG Classic Car Tuning, tune hundreds of classic cars throughout the North of England. When tuning classic cars, one of the most common mistakes that I see is 'over advanced ignition timing'. Sadly there are far too many out there who advance their ignition timing as much as possible whilst listening for 'pinking' occurring either at idle or on the road. The key problem being that many have absolutely no idea what 'pinking' sounds like and instead mistake it for a hidden throaty roar from the engine. In this example the ignition timing at idle, was actually beyond where it should have reached at maximum rpm. The owner was very lucky that the engine hadn't experienced a massive failure......scary!!
www.classic-car-tuning.com
/ agclassiccartuning

[@Mr.Pontiac-nx1lx]

Hey mate, I have a B with the same problem, I was curious if you ever figured out the issue with the old girl. Cheers

[@AGClassicCarTuning]

Yes, it had simply been set up incredibly badly. The owner had both a GT and Roadster, both cars were set just as badly by the same local garage. Now that the ignition timing has been correctly set on both cars, and tuned correctly the owner is enjoying both cars at every opportunity. Prior to my visit and resetting/retuning, I'm genuinely not sure how he even managed to drive them home from the garage.

[@lucsavoie9501]

the damper must have slipped. static would be around 30*, would have a hard time cranking over.

[@AGClassicCarTuning]

A good guess, but sadly No,.... I'm 100% confident that the damper hadn't slipped. I say this for 3 reasons...(A,B & C)..A) I physically check TDC using a dial gauge to ensure that the TDC markers on the timing chain cover and pulley are correct. I also went in with a digital borescope to observe and see if there was any damage. It also allowing me to see the peak of the stroke on cylinder 1 as a second form of verification of TDC markings. 2) Pulley slippage is extremely rare and 'near' impossible due to being indexed by the drift on the crank. 3) Believe it or not, the owner of this car actually had both an MGBGT and Roadster set to exactly the same by a local garage, with within 1 or 2.....very shaky degrees of each other. My concern was also in terms of resultant damage to key compression components...rings, valves etc. This surpassed the prior worst timing record which was a Porsche 356 at just under 30 deg out.....which yes it did struggle to crank over.

[@lucsavoie9501]

@@AGClassicCarTuning If it's the later low compression engine, you can advance that far without noticable pinking.

[@AGClassicCarTuning]

@@lucsavoie9501 ... My apologies, however I don't know your background or experience with these matters, so no offence meant if the following explanation is rather obvious. The video only shows ignition timing at idle, and equates to approx 42 deg BTDC (vac disconnected). The mechanical advance inside the original Lucas distributor will provide typically an additional 26 to 30deg by approx 4500rpm. Hence, at 4500rpm in theory the ignition timing would be at 68 to 72 deg BTDC. At light throttle or throttling off, the vac advance will then add maybe another 14 to 18 deg on top of the mechanical advance given. If the badly timed engine is capable of reaching 4500 rpm, then even with a modest 8.1 CR of some US spec cars to those of 8.8:1 or > 9:1 in other markets, 'pinking' will most definitely have been occurring. Sadly, that's where we encounter a different problem in that many people do not really know what 'pinking' actually sounds like. But one thing is for sure, no one should be looking for, nor expecting the hear pinking at idle. However, based on poor internet advice, or badly advised by a mate they advance the ignition timing as far as possible whilst listening for an illusive 'pinking' noise. I see and read it routinely time after time on the internet.....'advance it as far as you can, until your hear it pinking...then come back a couple of degrees'. Less than 20% of average enthusiasts out there actually know when they've reached an ignition timing position at which it is causing pinking to occur. If you're from the UK it reminds me of the classic Delboy phrase....'a nod is as good as a wink......to a blind man.'