Also worth mentioning, when I was inspecting the distributor I noticed the rotor has some thrust movement, where it's able to to move up and down? I thought it was odd but I'm new to these cars so I don't know what's acceptable and what isn't. It looked like it needed a shim above the gear to keep the shaft from moving up and down. It just slipped my mind when I was posting earlier
That's what I originally had it set too but the distributor isn't original to the car, the casting number is 1112037 which I think is from a 1972 car? That's when I looked into recurving the distributor to get the timing more dialed
I just bought a rebuilt distributer for a 350 Chevy on a stand in my garage Might. Cost just under 100. Very little backlash when holding the body + turning the rotor very little. Also I would think any up and movement allows rotor to turn. Sloppy interface with cam gear.Timing variation with worn timing chain.Now I regret having shop install pertronix on 69.Hotter spark but doesn't start up right away like 68.
I'd start with Larry's thread! But I'd remove and plug the vacuum advance, for now and adjust the distributor it till it doesn't ping. Then get distributor springs in order. Good luck
I'll leave the subject of 68 buicks but for one last tale. I was returning from the country around kankakee river and something in rear view mirror caught my eye. A couple rednecks in an astro van were closing on me within seconds.At my second glance the driver was standing on the brakes van was swerving in between lines of lane and passenger had feet planted leaning back braced for impact. But in between I had put pedal to the floor activating the full throttle downshift and I put car on shoulder as engine responded - screaming. 50 60 70. I left shoulder at full speed now eased up and to right of them Ready.
I'll read through that post again tonight, thanks again for everyone's help and advice. I'll report back with what I've found when I get a chance
The biggest reason for my authoring the Power Timing thread was the enormous amount of confusion I saw surrounding the topic of ignition timing. One common point of confusion I have noticed over the years is that guys seem to think that initial timing is etched in stone for a particular year of BBB. It is not, it depends on the distributor specifications for mechanical advance. Change the distributor, all the year specific specs go right out the window. Over the years, a specific part number distributor was fitted to Buick engines, and those distributors varied, sometimes, greatly. I compiled the specs I could find in this thread, http://www.v8buick.com/index.php?th...specs-1965-66-66-67-68-69-70-71-72-74.329332/ If you look at the specs for distributors, you'll see that for the most part, maximum WOT ignition timing was limited to 30-34*, and that is where most Buick engines make maximum power. I'm sure considerable time and effort was spent by Buick engineers to get the ignition timing right. Most of the timing built into the various Buick distributors is consistent with regards to total WOT timing, 30-34* was it. Some distributors had most if not all that advance built into the distributor, necessitating an initial timing close to TDC (0*), and some had considerably less mechanical timing. In the 70's, emission requirements necessitated timing changes at the expense of gas mileage and performance, but the fact still remains, most Buick engines like 30-34*. Now the above was determined back in the day, with completely stock engines that ran on non ethanol fuels with octane ratings closer to 100 for premium gasoline fortified with one of the best anti knock additives, tetra-ethyl-lead (TEL). 50 years later, how many engines are still completely stock? If you haven't owned the car since new, how do you know? Today, our engines are running higher compression with gasoline that has 10% ethanol. That ethanol makes for leaner fuel/air mixtures, all else being equal. In a lot of cases, the engines are running at higher coolant temperatures as well. There are lots of factors that contribute to an engine's propensity for knock/ping. High temperatures, lean running, and insufficient octane fuels are the most common factors. Those factors are more easily correctable. Then there is higher compression, and the use of pistons that place the piston as much as .090" down the cylinder at TDC. Add to that the possible use of camshafts that increase cylinder pressures excessively because they are used with no regard for static compression requirements, and it is no wonder that knock/ping is a common problem. Some reading on that, http://cochise.uia.net/pkelley2/DynamicCR.html Every engine today is going to be different. It needs to be tuned for best performance with no knock. Ignition timing is an important part of that, but obviously, not the only part. One thing is for sure, you need to be able to measure the total timing as precisely as possible. Just moving the initial timing around willy-nilly is not going to tell you anything about where the timing goes as engine RPM increases. Tune the initial+mechanical separately from the vacuum advance. Disconnect the vacuum advance and plug it. Work with the initial + mechanical, and determine how much advance the engine will handle, and how soon it will handle it. Once you have that set up for best performance with NO knock, then add the VA and tune that for rate and amount. If you find that the engine pings with total timing less than 30-34*, there may be other factors in play.
Larry, that explanation cleared up a lot of questions for me. The notion that the timing specs are "set in stone" is what was throwing me off I think. Now I've got a clear step by step plan for me to execute, starting with confirming TDC is correct. Thanks again
So I have the next couple days off so I took another stab at getting the timing sorted out. First I made sure that balancer was still true and fortunately it hasn't slipped. TDC lines up with the piston and the distributor at #1. I also removed the distributor and inspected the advance mechanism and found that there was no limiter bushing on the mechanical advance, which would mean I'm getting waaaay more advance than I anticipated. If I had to guess I think I'm getting 25* or so of advance? I then set the total timing to 30* and the initial timing ended up being 2*. There's more work to do with getting the curve set but now it doesn't rattle it's brains out when accelerating. Tomorrow I'll get a new limiter bushing installed and try again
So tomorrow turned into weeks but I've taken another stab at getting the timing dialed. The limiter bushing was installed and with the timing set to 10* initial I'm getting around 25* total advance with the lightest springs installed. A quick test drive reported no pinging however I need to take the car to WOT to ensure no pinging. With 15* of advance I think I should be ok with 15* initial but ultimately the car will get whatever it wants. Vacuum advance is still plugged/disconnected but vacuum advance tuning will come later of course.
So I've hit a setback, since I work evenings usually my drive home ends up being a test/tune session and tonight I ended up getting the same rattle/pinging sound I've been hearing at WOT going uphill. To try and isolate whether what I'm hearing is indeed pinging, I'm considering retarding the timing back to 0* which is safe, but drive WOT up the same hill to see if the noise returns. If the noise returns then that would make me think its a rattle under hood or a component beginning to fail under stress. From what I've read on this forum 10* initial and 25* total shouldn't be an issue, vacuum advance is still disconnected too. Thoughts?
Have you looked for a vacuum leak checking everything with power brake booster power brake hose fitting to the intake manifold the carburetor gasket and intake manifold itself at one point I had a pinging problem turned out to be a cracked fitting on a brake booster on a manifold
Excessive coolant temperatures, and lean fuel mixtures will cause an engine to ping as well. In addition, using a piston that can place the piston as much as .090" down below deck will make the engine more prone to detonation. Using a small cam in combination with too much static compression will also be a problem. If you eliminate all the main causes, then you need more octane. At that point, I would try some race gas and see if that eliminates it.
I'll check for vacuum leaks then, I admit it didn't cross my mind since my idle vacuum is ok but if there's a leak then I might have tuned it out. I'll have to look around and see where race gas is sold in my area, maybe down or near Pacific Raceways (local racetrack)
So today before I ran out of daylight I fired the car up to check for any vacuum leaks. I checked the potential leaks that walts mentioned and I found a couple areas that I think might be a leak by spraying brake clean. First is the PCV grommet, the rubber is hard so it might not be providing a good seal? I also sprayed the intake manifold bolts with brake clean and the 2 center most bolts when sprayed with cleaner had a noticable change in idle rpm. Perhaps the intake manifold needs to be retorqued? Other than that I didn't find any leaks at the base of the carburetor or at the brake booster fitting/check valve. I also found a gas station a ways away that sells race gas, I'm going to try it out when I get a chance.
I always had an intermittent leak at my original pcv grommet which had become rock hard. New one cleared that up. Intake manifold leak can certainly lean out the mixture, which can cause pinging. Definitely want to seal those up before trying to diagnose anything else
