A great friend (69MYWAY) helped me through my very first distributor/timing lesson showing me how to do this on my car. All went good and was a lot easier than I thought. A couple interesting things to note and would like comments from you all.

History Of Car: I know some of this stuff is backwards compared to the proper order of tune-up, but it is a learn as you go kind of experience for me. I bought the car from about a year ago and have never had the timing checked until now. The L46 was rebuilt 14,000 miles ago (back-in 1990) with 9~9.5:1 compression and updated with a electric tachometer and HEI distributor. I have put a very hard 6,000 miles on the car since owning it Oct. 05 enjoying it a lot. A shop 6 months ago set the carb AF ratio to around 12.5~13:1 as they said the secondaries were way out of line…..but they did not adjust the timing as they said the car ran fine as it was. I have always put 93 octance and never had a problem with the Miami heat with regards to the engine pinging/knocking, etc. and have had it to Moroso where I ran a 14.25@99mph in the hot August heat. After reading further into the Lars stuff I had a feeling the distributor/timing was not set correctly either. Well….here is what we found:

1. Timing reading 45* @2,500rpms.
2. We pulled distributor cap and found that somebody had taken the distributor to a machine and spun it up dialing in the timing to a specific setting. The ends of the weights were actually "custom drilled" but not all the way through to where you would see day light at exactly the same location on each weight. There were also 2 different size of springs used on each of the weights with it being marked "by a red marker" that a specific weight went with a specific spring so not to get the two confused.
3. The distributor did not have any play at all so we did not pull it puttingany "shims" on it.
4. We wasted no time in replacing the already modified springs & weights with the Lars gold springs and new weights that came in the kit. We did not lightly smash the "black bushings" that go around the pin holding the weights on as we felt that it was pretty secure just as they were.
5. We then rechecked the timing and it was at 33* @ 2,500rpms. We only had to advance the distributor a "hair-line" to get the timing at 36* @2,500rpms. The initial advance was at 10* and we left this alone for now.

I had did not have the opportunity to fully test out the car after we did this as it was very late for me and I had a long journey back too Miami. The car does feel stronger from 4,500+rpms as before I recall the power on the car would just drop off after 4,500rpms.

Would having the timing so much advance reduce the HP in the higher rpms?

Is there a "safety" limit on how much I can go with advancing the timing such as going with a slightly higher timing figure such as 39*?

Has anybody else ever seen a distributor with specific custom drilled wieghts and different size springs setup like this before?

I just moved this past weekend and my place is a mess so I will try to get some pics for you all to see how the springs & weights were setup.

Cheers….Rob

 

The use of different size springs is normal. This is a fine tuning adjustment to the mechanical advance curve. If you look at Lars information I believe he talks about this.

You should not go much more than 36 degrees total advance at WOT. Above this the engine will begin to "buck". That is, it will begin to fight itself. You need to remember that as the plug fires the piston is still traveling up on the compression stroke. This is to get a complete burn of the fuel/air mixture. If you light the fire too soon the pressure rise inside the cylinder WILL hammer the rod bearings into failure. This is a bad thing. You should stick to a max of 36 to 38 degrees. And no, that doesn't mean setting it to 39 degrees, 36 to 38, no more. Wouldn't want to see you scatter your engine all over the track.

I'm really not too crazy about the drilled weights but if they work, they work. I really don't think that is necessary. This can be done with springs alone.

What carburetor are you running?

It sounds like y'all got it running pretty good. Time to go back to the track.

BigBlockk

Later.....

 

Thanks for the info and tip….I certainly hope that no long term damage has been done running it this hard at 45* timing since it is the original engine. I will play with it this weekend getting use to the timing light and get it dialed in at 12 initial and 36 advance and then call it a day. I guess that is why the engine somewhat feels smoother on the way up to redline (6,000rpms) now vs. before.

I am running the stock quadrajet carb.

Yes…I need more time at the track is a must. I have to wait until Jan 20th for the next Corvette Series Challenge @ Moroso to begin.