Hi guys, in the process of reviving a 77 Buick Estate Wagon which has the R code 350 Olds motor and I have a timing question. This is all stock mind you.
I replaced the dead vacuum advance pod and set the base timing at 600rpm to 20B@1100RPM as per my trusty old Chilton's manual. Trouble is I don't observe much in the way of mechanical advance. The mechanism isn't stuck, but seems kind of.. floppy for lack of a better word. Do the springs wear out in these? I have a suspicion it's always advanced, which is why I don't see much more with any increasing RPM. I plan to go buy a tuning kit with springs and weights and see if I can get it functioning again.
Can anyone give me some advance numbers to shoot for at various RPM?
I've read 36 degrees by 3000 with the vacuum unplugged, is this pretty universal for a stock low comp motor?

Thanks..

 

I'm not sure I understand your question. If the mechanical advance is "floppy", it would provide advance at a lower RPM than normal. If you're not seeing mechanical advance, something is sticking or binding.

 

My theory is it's loose to the point where it's giving advance at idle or near to it. Increasing rpm to 3K or so I only saw maybe 5 degrees of advance.

 

Those HEI units are notorious for the plates sticking, I can't tell you how many I have seen that caused hot starting issues. With the cap off, gently twist the rotor by hand, it should load up then "snap" back. If not, remove the distributor, pop the gear off, separate the shafts and clean them up real good. Lube it and reassemble. The stock curve is slower, the timing will come in at more like low 4,xxx rpm. Here is my HEI recipe. If you get a kit, keep the stock weights, don't use the replacements. Use 1 light and 1 medium spring. Set total at 38, initial will fall around 23. Then, set the vac advance for 10 off of ported vacuum, then drive it. If you have no part throttle ping, add a few more degrees of vacuum advance. This has worked well for me in several low comp 350s.

 

That sounds like a plan, and the sticking sounds right on as well.
I'm off to the shop. Thanks...

 

Well it's defenantly better, but even back at 20 innitial I still have some WOT ping when the rpm get's up a bit. Would getting the mech advance in later help with that, meaning maybe both medium springs in stead of one light and one heavy?

 

You might have to, or you can ease off a couple of degrees and see what happens. Are you doing this with 87 octane? If so it might be worth it to try a tank of 89. Do you have a fresh air induction system? What temp thermostat?

 

Stock high temp t-stat, new rad a year ago with the t-stat and it runs 190 or therbouts. Regular 87 gas, I figured with an 8:1 comp it'd be enough, especialy since I have yet to hear any part throttle cruise pinging.
I'll try the spring swap sometime soon. After driving a few days it's really not that bad though all in all. Surprisingly not bad.

 

Good, sounds like you are pretty close. Did the kit have the stop bushings in it? Sometimes with the lighter springs you need to limit the total advance.

 

It had em but I didn't use em. I'll have another go at it shortly, my other old car is getting some wrench time this weekend while the weather is nice.

The Buick got 14mpg this last tank, up from about 11, hehe..