Thread: What Timing Advance for Carby V8?

Standard setting is 3 1/2 degrees BTDC but up to 8/9 degrees is OK - I am currently running 8 with LPG/Petrol.

Garry

What advance would you use for a 3.5 V8 with carbies? It was at 6 degrees for a long time and I finally looked into this as maybe causing some hot running,

There is no way that 6 degrees advance will cause hot running but 9 is better, and some will run them up to 12 or so.

The limit of advance is in practical terms when pinging occurs under heavy load.
A 3.5 should be able to take 35 degrees total advance and as long as you are below that it will be OK. So measure that out on your pulley and see where it is at 4000RPM>
The centrifugal advance curve of a lucas diizzy is very conservative and total advance is only gained at 4000RPM so big gains can be made setting up the dizzy with a more aggressive advance curve. BUT then you have to be more careful of pinging, This is why many people think a Scorcher dizzy is superior to a Lucas.
Big gains in economy can also be gained by computerising the vacuum advance as the vacuum advance is also pretty conservative. There are several on the market. I think mine is running over 40degrees total advance at light loads.
So a few degrees of static advance makes a small positive difference but really is only the start, but overheating no.
Regards Philip A

The best way to set the timing is for the motor to be revving like the post below says. Around 2500rpm all your timing should be in.

Lpg, timing should be 16-18 degrees at idle and approx 28 degrees total.

At the end of the day you should use a dyno and play around with the timing to get the best performance.

Regards Paul

And Des Hammill's book goes on about getting the highest idle speed and then testing on a dyno. Unfortunately, it would appear my closest dyno is 1000km away.

I should have mentioned that it's not on gas, and an automatic, so the engine doesn't get particularly stressed. Anyway, thanks for the confirmation and yes, I didn't think the hot running would be the timing but I'm running out of bits to replace!

If you have changed the Radiator , viscous fan clutch, thermostat, then a likely candidate with a 3.5 with tin gaskets and bolts in the bottom row is that the head gasket is leaking into the valley.
This makes them get hot on the highway.
Regards Philip A

Yeah, I started a thread about it a while ago and have been working ever since through the list of possibilities. (I decided to update the thread when I have the answer - this should be in about 7 or 8 years at the current rate.)

A compression test looked good, (but I'll do another one), and the coolant level never drops. And all the plugs are white despite the carby needles being wound up. I might go over to that other thread and update it with more questions!

12 BTDC and suddenly it runs better, takes off faster, and the hot running problem where it would heat up under acceleration and then not cool down while cruising - is gone! Bloody high-strung, these engines.

Are you sure the centrifugal advance is working ? You should be able to move the rotor about 3MM and it should spring back. If not drop some oil down the shaft and move it occasionally .
Regards Philip A