defiant1

Ok-a little confused on this one.

SBO 350
4BBL
Pertronix with factory weights and springs in distributor
Accel adjustable vacuum canister

I was setting the timing (vacuum capped) on the motor and was only able to achieve 30* (base plus mechanical advance) no matter if I advanced or retarded the distributor 30* is all I could get.

So, I turned the adjustable vacuum canister to 0* and tried the timing again. Vacuum still capped.

This time I got 35* Which does not make any sense to me because the hose was not hooked up to the canister. So I adjust the vacuum canister a couple of turns from 0* and my max base + mechanical advance was 33*.

So I turn it back to 0* and the timing went to 35*.

It also should be known when I actually hook up the hose to the vacuum advance canister, I do not get any additional advance.

As it stands right now, I got 17* initial and 18* mechanical (which seems low to me - I was expecting more like 22-22* for mech advance).

Anyone got any ideas why the adjustable vacuum canister directly affects the mechanical advance when it is not hooked up? I don't understand.

d1

oldcutlass

Disregard your curb idle timing setting. Run your rpm up to 3400 and thats where your mechanical + base timing should be @ around 34-38 deg btdc. Then do the same thing with your vacuum canistor connected, your engine will probably like total timing with vacuum somewhere around 50 deg btdc @ 3800.

defiant1

I guess I did not describe the issue well enough. I was establishing my base and mechanical timing at high rpm (until the advance stopped with the vacuum disconnected). I was only getting 30*. Unless I turned the adjustability of the vacuum canister to 0, then it increased from 30* to 35*.

I get no additional vacuum advance from the canister, in fact when I do adjust it to get more vacuum advance my timing decreases or stays the same.

So is the canister bad? Do I try and find my factory canister and see if that works ok?

I have used the adjustable vacuum canister when I had my 2BBL and it worked fine and I could adjust everything correctly and had 48* total overall timing. So I am a little perplexed on why it is not operating correctly now.

d1

defiant1

Well, I guess the Accel adjustable vacuum canister is junk. I applied vacuum (via MightyVac) and it did not advance the points plate. I took it off and tried it again and nothing. I pulled my 40+ yr old original vacuum canister out and it worked like it should.

Now when I set the timing (with vacuum plugged) I am still around 33.5-34* for base + mechanical timing (stops advancing around 2500 RPM). I can't get anymore out of it (unless of course I advance the base timing--right now it is at 16.5* @1100 rpm). So-why the mechanical advance is not higher, I do not understand.

Now with the vacuum advance hooked up the vacuum advance canister is working. But by virtue of the number stamped on the canister (24), that is exactly how many degrees advance it is giving me. So I am sitting at 57.5* for total overall timing (stops advancing around 3000 RPM). I have not driven it with these setting yet, but I assume 57+* is too much for cruise/part throttle before pinging will ensue?

So-
1. How do I limit the vacuum advance canister or what aftermarket setup should I buy?

2. Why is my mechanical advance (by itself) never higher than 17/18*??

Thanks for any insight.

d1

oldcutlass

Believe it or not I've seen engines set at 60 total advance to get the most performance on the highway!! Drive it and see if it pings!!

There is a limiter that comes with an accel vacuum adv kit!!!