Distributor regraphing for a 4.6

RoverP6B · Post by **RoverP6B** » Tue Jun 24, 2008 10:41 am

Some 18 years ago, I purchased a new Lucas 35D8 distributor, then as a spare for my 3.5 in the P6B. As it would come to pass, this distributor was to find iteslf a home in my new 4.6.

Given that the characteristics of both engines are different, the distributor had to be regraphed so as to meet those new requirments.

The rate of and total advance must meet the requirements of the engine in question. I do know that the primary and secondary springs within the distributor were changed, and that prior to regraphing the maximum advance as applicable for the 3.5 in the P6B was 30 degrees at the crankshaft @ 4800rpm.

For the 4.6, maximum advance is brought forward, and now occurs at 3700rpm. The exact amount though I am not sure of.

It is my understanding that the combination of ignition advance and air fuel ratio adjustment from off idle to red line will provide in essence the maximum engine performance in terms of torque and power at all points within that band.

Ron.

kiwicar · Post by **kiwicar** » Tue Jun 24, 2008 11:15 am

When I used to muck around with minis the way to sort out the timing was to use a fixed distributor (vac adveace disconnected and a self-tapper through the advance plate into the body behind, with the springs removed) and on a rolling road with the engine loaded to a fixed revs, plot about 8 points of timing advance against revs between about 2.5k and about 5.5k revs depending on the cam, by swinging the distributor for max power without detornation you could plot out an advance curve for the engine and then build a distributor with the same charictoristics (or better still get someone who had done it before to build one. Then back to the rolling road to check it against your plot.
Mike

ChrisJC · Post by **ChrisJC** » Tue Jun 24, 2008 2:39 pm

I was a bit concerned that it might involve a rolling road. That's something of a problem with an auto I believe....

Chris.

kiwicar · Post by **kiwicar** » Thu Jun 26, 2008 2:19 pm

you can get close with an auto by advancing it until it pinks at a given revs (under full load on a rolling road) then backing off 1 degree, do that for the 8 or so load sites to get the curve (ignoring power figures) build and install the distributor and set the overall position by running the car against the stopwatch accellerating up a known hill advancing the distributor a little each time until it don't go no faster.
Mike

Simon B · Post by **Simon B** » Sat Jul 19, 2008 12:41 pm

kiwicar,

being a thicko and lazy would you know who might have done this for a 4.6 in a Land Rover? JE are fairly close to me would they know or is it more a matter of ancient history for a company like that?