1971 Cutlass Vacuum/Timing
 

Hi everyone,

I was wondering if anyone here might have some tips or suggestions to help my 1971 Cutlass Supreme with the 350 Rocket engine. It is basically completely stock. It had a tune up before I bought it and everything seems to check out in terms of that. Dwell is at 30 degrees, timing is at 12 degrees at 1100 as factory spec says, idle is 600 RPM in gear, has new spark plugs gaped to 0.040, has professionally rebuilt carburetor installed, all new vacuum tubing with all unused ports plugged, and TDC on the balancer confirmed.

But, with all of that I am stuck at about 15.75" of vacuum, which is up from the 14.5" that I had when I first started looking into this. Adjusting fuel mixture screws helped to a point as did plugging some vacuum leaks that I found. I tried that method of taking an unlit propane torch around the manifold and carb but the RPM was never effected. I have heard taking carb cleaner and spraying areas prone to leaking is another method - would that yield different results than the propane?

As mentioned above I have confirmed TDC and checked the timing is to factory spec, but the vacuum gauge (connected to manifold) is in the red saying late ignition timing. I have read that as the cars age and timing chains stretch that the factory setting may no longer be what the car needs. I have not messed with timing in about 15 years and am a bit nervous doing this. I should mention that I still have the old points ignition system, some say that this and the HEI will require different settings. Having said that, I have also read that olds engines like lots of timing, to the point of finding a lot of people claiming to be running 22 degrees of initial timing. What do you guys think of that? Maybe the 12 degrees that I have mine at is just simply nowhere near enough. They said the risk is that if you have lots of initial timing, if you end up at really high RPMs factoring in the timing advance you can hurt the engine. This car is strictly a cruiser and short of maybe pushing it a little on the highway to pass a slow car will never see top end RPMs and certainly not on a consistent or regular basis.

The only thing left I can think of is to try the timing, but before doing that, especially if I am going to be going much higher than 14-16 degrees, I just wanted to get some advice from people who are familiar with these cars to make sure I am not going to break anything.

One other thing that might be worth mentioning is that the line from the carb to the charcoal canister thing has been disconnected and plugged. Will this have any effect on the vacuum reading?

Thanks in advance to everyone for taking the time, I really do appreciate it.

Adam