Ignition Timing Curve

Okay, I've heard a little here and there about timing curves when it come to the ignition timing on older vehicles. I think thats what the issue was with my caprice. Before I took it off the road, I converted the engine to a non-ECM engine with an Edelbrock carb, and vacuum advance HEI distributor. The thing is, I converted a V6 distivutor to a V8 with a different pickup coil w/ 8 points, and a different cap and rotor. But I kept the weights and vacuum unit from the V6. When I drove the car at the set ignition timing of 4 degrees OTC as recommended by the Hanes book it ran great except it pinged massively at certain speeds and throttle. Even when retarding the timing, it still pinged at those certain points. I bought a new Vacuum unit that was designed for a V8 and that helped, but the problem still persisted.

Now, after all that, I'd like to know if anyone here knows anything about timing curves, weights and springs in the distributor, and vacuum settings. If anyone does, THANKS IN ADVANCE! I'm currently in the teardown process in rebuilding the engine, and I'd like to understand and fix this aspect of it before running it when its done.

Well, you can play with the various spring and weight combos, or hook your ECM back up and let that take the pain out of it for you. :)

Replace the springs and weights with ones from an older Caprice with 305 in it - such as a 1977-80. Setting the curve is a black art, and I'm glad I've graduated to computer control.

Computer contol is great, don't get me wrong, but once the electronics get that old, everything stats going to hell. The car was running like crap, and I was getting numerous computer codes. Even after fixing something, something else electronic would go wrong. It was becoming more of a pain than it was a help. This forum is a great example of the troubles an old ECM can be... a large amount of the posts go for a long time trying to figure out which sensor or which solenoid is causing the car to not run at all, or die at random increments. In most cases if something goes wrong in a non ECM controlled vehicle it'll still get you home, even if it does run horrible.

Example: my Caprice has NEVER left me stranded in the four years I've been driving it, and after I ridded it of the EMC and emissions, it never randomly decided to run poorly either. It always got me where I needed to go. My neighbor's 2001 Impala left us (and him alone) stranded 3 times since he got it a year and a half ago. Once it died and wouldnt start b/c of the MAF sensor. Then some sort of transmission solenoid kept it stuck in 4th gear so moving from a dead stop was almost impossible, and again becasue the computer needed to be rebooted somehow. Not to mention two other times it was in the shop due to a "security failure" in the ECM. My boss's 2005 Chevy Silverado 3/4 ton pickup lost its brakes because of the ABS sensor, and he went through his garage door. My mother's '93 Grand Prix would randomly accelerate hard on its own, and after getting computer codes, and replacing a sensor and solenoid in the throttle body found it needed to have the $120 ECM replaced.

The ECM setup that I am most fond of though is that in the late 80's to early 90's pickup trucks. My '89 Sierra 2500 has no emissions except an EGR valve. It came stock like that. It does have the 2bbl TBI though. Aside from an O2 sensor, nothing electronic has ever gone wrong with that truck. Its provided my father with 17 years and 110,000 miles of reliable service, and now for the past few months of me now owning it, I have yet to find something I dislike about it. That, in my opinion is the best ECM setup out there. Practically emissionless, and so simple that its nearly foolproof, and yet requires little to no maintanence.

All in all, when they work right, ECM's are an AMAZING thing to have in a vehicle, and some of the things Ive seen in the newest of cars is incredible. But when anything fails, everything fails. Theres nearly no grey area.

But anyway, I've gotten way off topic here... so pretty much what you're saying is the timing cure is like a hit and miss. Should I try to get a collection of springs and weights and experiment until I get it right? Is there any way to measure the ignition timing? My father owns one of those old fasioned stand alone computers from the 80's designed to monitor things on NON ecm cars such as RPM, timing, dwell, etc. Would that help any?

P.S. I know this sounds strange, but I really do enjoy the tinkering and experimenting involved with a non ECM engine. Its like a hobby of mine, well sorta. I love to come home from work, and pop the hood and try to adjust a little something here and there to see if it'll affect anything, and improve performance or fuel efficiency.

Find a shop with a Sun distributor machine. Have them play with the springs, weights, advance cam, and vacuum advance/retard to try to get close to this kind of timing:

http://72.19.213.157/files/TimingTable.jpg

Find a shop with a Sun distributor machine. Have them play with the springs, weights, advance cam, and vacuum advance/retard to try to get close to this kind of timing:

http://72.19.213.157/files/TimingTable.jpg

Is that a WinALDL screen capture?

TunerPro

cool, thanks! Thats probably what I'll end up doing once the engine's done.

I was also reading up a little bit and read that if I get the detonation, my springs could be too weak and its advancing too far too soon.