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Timing advice please

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Mick from Scotland Avatar
East Lothian, Scotland, UK   GBR
Sun is suing time for driving!
Car running grand at lower speeds. Timing at 13 btdc at 900rpm. In 4th, on a steep hill, pulls smooth as you like with no pinking from 30 to 50mph. But, on even a slight incline, if I go to accelerate from about 50 to 60mph it pings a lot. After 65 all good again. Running 98 octane fuel. Should I regard timing a couple of degrees? I looked to see where timing is all in, and this occurs currently at approx 2800 rpm. Go gently with me because I am not as experienced as I would like to be.

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ghnl Avatar
ghnl Silver Member Eric Russell
Mebane, NC, USA   USA
1961 MG MGA "Calvin"
What is the timing when 'all in'? 2800 rpm for maximum advance sounds a little low - perhaps weak advance springs? Is the vacuum advance mechanism working correctly - and not sticking when vacuum drops (as happens when you open the throttle)?



Eric Russell ~ Mebane, NC
1961 MGA #61, 1981 Alfa Romeo GTV6, 1984 Alfa Romeo Spider, 1991 Honda ST1100

Mick from Scotland Avatar
East Lothian, Scotland, UK   GBR
I made an error. It was supposed to be 13 btdc at 600 rpm, not 900 as I had things. To be fair I didn't think It would make much odds, but regardless, set idle down to 600 and then timing to 13 btdc. Went a drive. Still not quite right. Gave the vernier wheel 11 clicks of retard and repeated the same uphill road, much better. Just the faintest of pinking now in 4th overdrive if I push the throttle uphill between 55 and 60mph......if I drop out of overdrive it's fine. Perhaps Eric isn't far from right though, as its the original distributer, never rebuilt......has to be getting pretty worn. Maybe treat myself to a new one soon, will see how the driving season pans out.

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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
13 degrees at a very low 600 rpm idle is always difficult to adjust on, on 1000 rpm it is much easier to do.

Your 1973 belonging to the non-smogged home market B's may have its 1000 rpm value on 20 degrees once. I personnaly found a value of 17,5 degrees on this 1000 rpm much safer with presentday fuels. But there is nothing wrong with setting the max value on your 2800 rpm to 32 degrees, the famous "safe" max value JT advises. After this double check the 1000 rpm value: is it near 17,5 now?

PS Once I tried 15 degrees on that rpm value, with my own 1972-1973 distributor for desmogged engines of the time it got me a less responsive engine.
You need the steep curve of an earlier 40879 (E) distributor in this type of setting as I am doing now. Your original Lucas will be different, probably the 41339 !

In reply to # 3717197 by Mick from Scotland I made an error. It was supposed to be 13 btdc at 600 rpm, not 900 as I had things. To be fair I didn't think It would make much odds, but regardless, set idle down to 600 and then timing to 13 btdc. Went a drive. Still not quite right. Gave the vernier wheel 11 clicks of retard and repeated the same uphill road, much better. Just the faintest of pinking now in 4th overdrive if I push the throttle uphill between 55 and 60mph......if I drop out of overdrive it's fine. Perhaps Eric isn't far from right though, as its the original distributer, never rebuilt......has to be getting pretty worn. Maybe treat myself to a new one soon, will see how the driving season pans out.

barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
I am far from an expert in the use of OD. Only my '74 is so equipped and I rarely use it unless cruising. For this reason it strikes me as odd to try and set timing based upon performance while accelerating uphill in OD. When setting timing for optimum acceleration without pinking, I would never be in OD.

Mick from Scotland Avatar
East Lothian, Scotland, UK   GBR
Not really setting timing with od On, just observed that that was a little noise as I cruised in od and then went to pass a slower car on dual carriageway......I agree with your post totally, and mentioning this here in case it confuses anyone. I use my od all the time though at anything above 50mph on roads that i wont be slowing down below thst speed.......given the price we pay for fuel here, every little helps!

In reply to # 3717339 by barry s I am far from an expert in the use of OD. Only my '74 is so equipped and I rarely use it unless cruising. For this reason it strikes me as odd to try and set timing based upon performance while accelerating uphill in OD. When setting timing for optimum acceleration without pinking, I would never be in OD.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
50mph or 80kmh is not a strange speed to use the OD on, although sometimes on so-called 80kmh max country roads the variation in speeds makes me select OD in 3d, not 4th. On the highways any speed upwards of 80kmh is always best with OD in 4th. The execption being last year when a contact failure on the OD solenoid forced me to 110kmh max without OD on the highway trip back sad smiley

But checks on pinking are normally executed without OD, e.g. just 4th gear....

PS I am confident that with max advance set on 32 degrees there will be no pinking at all in any situation

In reply to # 3717349 by Mick from Scotland Not really setting timing with od On, just observed that that was a little noise as I cruised in od and then went to pass a slower car on dual carriageway......I agree with your post totally, and mentioning this here in case it confuses anyone. I use my od all the time though at anything above 50mph on roads that i wont be slowing down below thst speed.......given the price we pay for fuel here, every little helps!

In reply to # 3717339 by barry s I am far from an expert in the use of OD. Only my '74 is so equipped and I rarely use it unless cruising. For this reason it strikes me as odd to try and set timing based upon performance while accelerating uphill in OD. When setting timing for optimum acceleration without pinking, I would never be in OD.



Edited 1 time(s). Last edit at 2018-04-16 09:52 AM by Donthuis.

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Footsoldier Avatar
Footsoldier Silver Member Dave Hughes
El Dorado Hills, CA, USA   USA
1974 MG MGB MkIII "Blew"
RE timing at low RPMS:

After installing Pertronix electronic ignition in my 74 B, using a timing light I timed following the under-bonnet spec sticker, which said 11 degrees BTDC at 1500 RPM (vacuum line removed). Then balanced and tuned carbs (HIFs). The car subsequently started and ran okay, but I noticed during road testing it lacked “oooompfh” during inclines and I found myself constantly downshifting to get the RPMs up to get up the hills. Every once in a while I’d also get an intermittent cough of unknown cause.

I just retimed using the 32 degree BTDC recommendation. Removed vacuum line and held the RPMs at 3000, then back-timed on the light 32 degrees. Matched pulley mark with first timing mark, locked in the distributor. Balanced and tuned HIFs again.

The difference is significant. The motor is now much happier and zippier. The car now aggressively pulls and on a drive last week, I rarely had to downshift to 3rd on hills I always had to drop down from 4th to climb. No more coughing and I can’t detect any pinging or complaining (yet).

I’m a convert; the 32 degree @ 3000 sweet-spot timing spec worked for my set-up.



“Money may not buy happiness, but I'd rather cry in a Jaguar than on a bus.”

B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB
2014 Dodge Charger
With a Euro-spec distributor, you should be able to run 14 BTDC at slow idle, if its in good nick. As the springs stretch out, you'll be set lower. A vacuum leak at the vac unit can push the mixture lean which will amplify any pinging. It sounds like its time probably for a rebuild, which would be money better spent than buying a Chinese made replacement. The Distributor Doctor can probably get you set up in short order!



jeff@advanceddistributors.com

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Mick from Scotland Avatar
East Lothian, Scotland, UK   GBR
Jeff - just saw your post now, after being on the Dist Doc's website! First thought was yourself, but its a long way away if there is someone closer, so your recommendation will do me. I agree, seems a better option than a new distributer, nice to have the original rebuilt I think......going to give him a call this week and see what the wait time would be though, as the Scottish season is too short to be having a lot of downtime - hopefully he might be able to fit me in with a fairly rapid turnaround!

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