Ok, is the formula
Static + Mechanical+ Vacuume advance? or for ex.

12* + 21* + 10* which could concievably give a motor 43* total
OR is the total amount of advance limited by the mechanical.

I started playing around with the can on my dist. for the first time in 3 years thinking I could cure a slight tip in but after doing so it felt like it was getting way too much advance. This was pulled from the ported area. I have Vortec heads and certainly 43 is over the top if I was pulling that much.

Thanks,
Mike

What does too much advance feel like?

Your timing looks right on for Vortec heads. 43 would be your cruise advance. When you floor it vacuum advance disappears. Your tip in problem could just be an accelerator pump adjustment. I like hooking vacuum advance to full time vacuum, it gives better off the line response.

[This message has been edited by 1978LT (edited February 25, 2005).]

Don't count the vacuum number in your total advance. You are right at 33* total with the 12* + 21*. That's right in line for Vortecs.

Like others have said.. You don't count vac. advance in with total timing. Just inatil + mech. = total.

The vac advance is only there at low throttle cond. When you got WOT, vac falls to 0 and so does the timing added by the vac can

32-34* is the range that seems the best with most vortec head combos

So, what is good cruise advance for a set of Vortecs? Seems like I remember 50 or so for cars that like 36 total. Any secret with the Vortecs?

43 is fine. Try the vac line on manifold and see how that works, you will have to dial down the RPM a bit with it setup this way.

I tried it both ways and right now I'm up on the ported side. I might go back to the manifold but my converter might not be loose enough since I cant get my idle below 1200 with the manifold vac. Car seems to like manifold but I don't like how it must be held with the brake and rocks pretty hard going into gear. Ported seems to be working alright as well, I'll probably continue to screw around with it. i did have to add some jet for the advance though. No doubt that was what I was feeling when I first tried it out yesterday, must have been lean missing a little.

Thanks for the comments.

Hey, what does that last post mean? Lean miss? I am going through this right now and cant seem to get it right. Also, what do you do when the mechanical advance is too much. Is that the weights? I know the springs control the rate, but what controls the max?

MaTt

Well, feeling a miss is sort of subjective but, in my case, before the car was running very smooth inbetween 1500 and 2500. After adding the advance I noticed that the car felt as though I was driving on a road that was a little bumpy. The car wasn't feeling particularly weak but it felt rough. I have solid mounts and poly subframe bushings so I feel almost everything the motor is doing. In this case it felt like it was shaking a bit, like it was fighting with itself.I attributed this to an uneven burn running through the cylinder causing it to fire off too soon, typically a lean condition causes this.

As for the advance max. I have never dealt with any other distributer than the MSD I have so I can't speak on any others. With the MSD there are bushings that can be replaced that limit the amount of travel allowed.

Niether of those probably helps much but I tried.

[This message has been edited by Michael Joslyn (edited February 28, 2005).]

I don't understand why you can't get the idle below 1200 on the manifold vac setting?

Probably because I keep my secondaries open a little bit so the transition slot is just showing.
At any rate, I have driven around with a Vac. gaugehooked up and cruising I'm pulling plenty of manifold vacuume just like I am with ported. The only real benifit to manifold for me would be slightly better off idle performance (very slight) and that the advance stays in when I lift rather than pulling out with ported.
Temperature isn't an issue since I run fairly cool anyway and my cam isn't big enough to require a lot of timing at idle.
I have some other carbs that don't have ported and if I decide I might want to run one of those I'll probably start screwing around with finding a lower idle.

Hook it up to full time vac. for sure, like others have said. I keep advancing the vac. can until I get detonation, then I back off a bit. This will usually give the best repsonse and fuel economy. I did this with my 383 and am getting 21.6 mi/gal! http://www.nastyz28.com/ubb/eek.gif

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Gordon

1979 Camaro Berlinetta