I have a question..... I have never messed with the timing on my 72 riv 455 other then to check it. Stock motor, original distributor with a acell points eliminator. I was reading this thread so I started playing with the timing. Checked all the parts and both vacuum and mechanical advance were working properly. Fresh tuneup and carb is set well. Car ran very nice but I felt it was underpowered. Timing Was set a 4 degrees (factory for 72), bumped it to about 10. Immediately improved power.......so I ordered the crane kit as listed in the thread. Installed new springs (1 blue 1 yellow) per cranes paperwork that’s all in at 2600. Once again immediate power increase with a much stronger mid range. I’m pissed I didn’t do this along time ago! Car is no drag racer, I’m sure the rear end is a 2 something ratio and of course it’s a riviera so it’s heavy as heck So after all that......Should I go lower on the springs (silver silver all in at 2200) or would I be getting into idle timing? Would a stock 72 455 even benefit from a change at this point?
Stock distributor for the 1972 Buick 455 was the 1112110. Look at the specs, Total amount of mechanical advance is 14-18*. So at 4* initial timing, the most timing you could have would be 18-22*, far short of the 32* that makes best power. I would set your total timing without vacuum advance to 32*. Then see what your initial timing is. I'd leave it in at 2600, you don't want any mechanical advance in at idle.
Thanks for the info and the quick responses. I’m going to use my dial back light to get it to your recommend 32 tomorrow.
Finally got off my lazy ass and did the limiter plate mod. Car is definitely peppier. I've got about 8* of vac advance right now, 12 initial, 22 mech in by 2600. 42 total. Definite difference. If I remember I was getting something absurd like 55* of total timing before hand with the unencumbered vacuum advance. Each notch is 2* on the plate right, or thereabout?
Hi Larry, this is the best explanation of timing I have seen to date. However I do not have the tools or know how to adjust all these parameters accurately. Would I just adjust the existing setup a couple of mm each way and drive the car to see the results?
I would not touch it without the right tools. Leave it alone until you can do it right. You can do more harm than good.
Just bumping up the most informative thread on any forum anywhere. Got my pro-touring build timed correctly and feel like I added 30-40 HP. It cold starts without a choke much better now. Thanks Larry!
Excellent topic. One question, can you also use 1 stock spring? Instead of lighter springs. According to the manual my full advance is in at 4600 rpm. Springs are linear, so removing one should mean full advance in the 2300 rpm range.
You can run with one weight and one spring. It will work, but the advance will not be all in at half the RPM. That one weight has less total leverage than 2 weights.
I have read that by combining 2 springs of different settings, it will result in your advance occurring between the 2. This is a way of customizing your distributor, it was claimed. BUT what Ray said makes sense, so I'm not sure whether the sources I read are correct.
It can be done, but yeah, it isn't optimal. One year at Cecil County, one of my weight pins fell out. I removed that weight and spring, and used the lightest spring on the other weight. It worked pretty good for the rest of the day.
I was actually thinking about 2 weights and 1 spring. With a circlip the weight shouldn't come off. I know it's hillbilly, but it's something I have at hand
Well, when you have a running engine, you can actually observe your results with a tachometer and timing light. Will be interesting to see.
I have a question about the effects of bringing all of the mechanical advance in at lower RPMs. My 70 Stage 1 runs at 190F-195F while cruising when the total timing is 33 degrees (12 initial, 21 mechanical) all in at 4,800 RPMs (looks like "stock springs"). I'm playing with different spring kits and I have a set that's all in at 3,500 RPMs, but the engine now runs at 200F-210F when cruising. Right now my vacuum advance is capped. I'm playing with spring kits still and haven't found a combination that's not in the advance curve at idle (850RPM) and gets to the full total advance under 3,500 RPM. I'm concerned that further dropping the RPMs where total timing is all in will increase the engine temperature above 210F. The MSD spring kit from page 1 of this thread is one of my next kits to try. The above results were achieved with a Grainger 1NAT4 spring. I'm also going to try a Grainger 1NBF6 spring.
