Hey all,

Well, I got my Caddy back from the shop last week. A decent tune-up, timing all set, new dizzy cap, coil, rotor, ignition module, wires and a freshly rebuilt Q-Jet. Wow, what a difference! No more stammering, hesitating and near stalling when cold, and MUCH better throttle response. The only hiccup was the car took a few days longer as the guy who rebuilt the carb screwed up and it promptly haemorrhaged its fuel after one day. So it was rebuilt twice. I also bought a kit from Canada - just in case (can never have too many spares, especially when they all have to be imported). The rubber vacuum lines were in real bad shape so steel ones were fabricated. The car had sat for at least 6 years before I got it (its CA tag expired in 2002, and the original owner's registration card expired in 1997) so there was a lot of dry rot to sift through.

Suffice to say I'm pretty happy :cloud9:

BUT (here's the question part), the bloody thing STILL has a tendency to pre-ignite. Not as much as it used to, but now that I've had so much done to the car, I'm really starting to run out of ideas.

I'm hoping it's just a case of it needing a serious blow out, like 65MPH for several hours in one sitting maybe. But if not, then what???

I thought about turning the idle down a bit, maybe? There's no tacho, but it just sounds like a high-ish idle to me. Due to being stuffed, the EGR was removed and blanked off. My mechanic suggested putting STP octane booster down the carb, but I am always wary of any additives.

Regular fuel here is 91RON, mid-range is 95 and premium is 98. The handbook says "at least" 91. Would the car require re-tuning if I put 95 in it?

Cheers,
KiwiCadi

Here's some pics.....

Gee that carb looks new not rebuilt. Metal vacuum lines huh, that's something I've never seen, impressive though. It shouldn't have preignition with 91 octane. Is the distributer connected to ported vacuum or full vacuum? I would run a 180 thermostat. If it still pinged then I would back the timeing off a couple degrees. It wouldn't hurt to tromp the 4 barrel and blow the carbon out once in a while too. That engine looks nice, I'd love to put a power tune on that.

Not sure what you mean by ported or full vacuum??

It runs on/diesels just every so often, not after each stop. There is no knocking or pinging that I can hear, it runs super-smooth, hot or cold.

Would I need to retune it if I put 95 octane in? I thought I would fill it with that and a bottle of carbon cleaner, and perhaps lower the idle (if that's easy enough to do).