Tuning Unleaded Engines?

[paulb2]

About to bite the bullet and finally convert my old Moggy (1098) to unleaded.

Can anyone advise me what are the differences in tuning/set up for an unleaded engine?

Thanks in advance

Paul

[57traveller]

The ignition timing may need to be retarded a bit from the normal 4 star leaded book figure. Modern unleaded has a lower octane rating. Both my cars run fine at 3 degrees BTDC. (set by timing light with vacuum advance disconnected and revs. about 400 so that centrifugal advance is less likely to operate).
My Traveller has of course run much better since it was changed from 17 deg. BTDC which I mentioned some time ago on the forum when complaining about bottom end rumble.
Unlike on my Traveller, there may be enough fine adjustment on the distributor to achieve the desired result.

[rayofleamington]

I've always set mine at 4°BTDC statically - all the cars have run happily on leaded, unleaded or unleaded with Castrol addititive.

Riley had his timing set at 20°After TDC when I bought him!! He made it on a 160 mile round trip the day after the MOT (had a rally to go to and ran out of time to sevice him).
However he nearly had a melt down at 80mph on the M1! The engine got so hot it stoped running completely and produced clouds of smoke from the rear....
A few gallons of water and a few stops later, the remainder of the journey was done (under 50mph) and he was fine.
Needless to say I was relieved to find the incorrect timing when I got home, and he's not overheated in the few thousand miles since it was set correctly.

So on the subjecty of timing, the A-series is a very resilient engine. I doubt anyone could tell the difference of an engine set between 2° and 5°.

A lot of cars have faulty or failed Vacuum advances, so it may be worth to check that is working if you drive hard and fast.

[Willie]

The rule with ignition timing is, and always will be, to set it
to where you get no pinking under normal driving conditions.
Fit your new head and retard eleven clicks at a time(equals
1 degree) until you eliminate any pinking,

[Benjy]

I could always tell if my vacuum advance wasn't working on the pickup (because I'd left it off AGAIN!), you put your foot down and the engine just didn't sound right. It still accellerated, but felt different and definately sounded different.

The Traveller is better insulated so I'm not sure I'd notice it, but I dare say if I ever check the tappets, I'll forget the pipe again and we'll see...

Ben

[57traveller]

Willie, other than the "rumbling" bottom ends and possibly better performance , I had no pinking at 17 deg. BTDC. It was only while routinely checking the timing that I really became aware that it was incorrectly set. So may be something to be aware of that pinking doesn't always, not in my case anyway, occur.

[winger300]

My ignition timing was really retarded once due to the distributer slipping in its clamp. Acceleration was really bad, but the car would still do 80mph, and the engine knocking sound went away completly.

Hasten to say i've replaced that engine now.

[Willie]

'57' can only assume that your noisy gearbox was masking the
pinking(joke) Having driven a car which had allegedly been set up
by an 'expert ' on a rolling road, which was about seventeen
degrees too far advanced I have to say that it was so rough
that you couldn't miss it. The smoothness when it was re-set
correctly was wonderful. BENJY...the vacuum unit only comes
in to operation when you are NOT accelerating, it advances the
ignition timing when the engine is on light load only, in the
interests of economy. If it is leaking air then the carburation
will be slightly effected.

[paulb2]

Many Thanks for the info.

Regards

Paul

[57traveller]

Gearbox Willie . No, more than likely it was the whining differential .

[Kevin]

No, more than likely it was the whining differential

Thats a good description for a back seat driver, not heard that before