[Josh D]

I have an '80 RoW SC with the "optimized" 188 hp 3.0 930/09 big port, low compression (8.6:1) and K-basic CIS.

Problem: I seem to have too much mechanical advance. the only timing spec I have found on this one year only engine is 5* BTDC static and 24-29* @ 6000 rpm dynamic. This was found in Waynes engine rebuild book.

When I set the static at 5*, I'm getting 35* at 6000 rpm. Problem is I get detonation under heavy throttle in second gear at about 5800 rpm. This is on 91 octane. It will only tolerate about 30* total with summer temps and running A/C, and about 32-33* in the cooler winter months.

What I've done so far to counter this is to run it as rich as it would tolerate with off throttle idle dip of about 400 rpm with the drag of the A/C compressor on. This had some, but not much affect on the high rpm, high load detonation. Plugs are dark brown.

I tried an octane booster and that did make a difference, however this was more to test than a bonified solution.

Finally I bit the bullit and just dialed back the ignition timing to 30* max for the summer. This pretty much solved the detonation problem, but created others. 30* max advance puts my static timing at 0* BTDC. In this configuration, the car is noticeably down on power between off idle and 3500 rpm. It's also slow to restart when warm. Residual fuel pressure was tested and well within spec.

When set to the 5* BTDC static, throttle reponse is very good and the car pulls like a frieght train from off idle until the 2nd gear WOT detonation event.

So, what I would like to do is take 5* out of the mechanical advance. This would allow me to run the factory spec of 5* BTDC static and the 29* (+/-) @ 6000 dynamic in the summer. In the winter, I could advance it a bit (32-33* max) for a bit more power.

My question is, whats the best way to accomplish this? My thought is to bend the advance weight stops in towards the weights, taking away a bit out of their travel. Has anyone done this? What would the factory have done if the Mechanical advance was out of spec?

BTW, I have already done the dissassemble, clean and lube of the distributor. The plug wires are new Clewetts. The plugs are about a year old and are the factory recommended heat range (W4). The factory coil was replaced with an MSD Blaster II to rule out the coil as a possible suspect.

I've determined that this is clearly a timing issue.

What say you Pelican Brain trust?