Vacuum advance

[j69302]

trouble shooting slight hesitation.. after trying many different accel pump cams and secondary springs I started to advance my timing some.

Is there a general rule of thumb as to how man degrees the vacuum advance will add after setting initial timing?

After setting my initial with it plugged, I only gained 2 degrees after hooking it up with no increase in RPM.

Last time I remember doing it, it increased much more with a couple 100 rpm increase as well.

I leak checked the vacuum advance and it appears to be good. Also with the carb port plugged, I put another hose on the vac adv and sucked on it and got a decent increase in RPM from it so It appears to be working.

 

[2+2GT]

If you're using ported vacuum, you should have little or no advance at idle when connecting the vacuum advance tube.

 

[j69302]

ok.. I always have it on the ported port..

Its a 302, edelbrock performer rpm heads, rpms air gap intake. Stock distributor with pertronix kit and a crane energizer 260 cam (I think at .050 lift it was something like 204 duration). Holley 600 vac secondary. Vacuum at idle is 18 inches..

There are 2 pops in the exhaust if I punch it below 2500-3000. Then at about 3000 it pulls much harder.. Accel pumps and vac secondary springs didnt seem to affect it..from the stiffest to the lightest... even tried different discharge nozzles.

Im not too sure what my exact timing is.. I pretty sure my harmonic balancer has rotated on itself and also my timing pointer probably isnt even in the right spot.. But i doubled the initial today.. The pops are still there just as much as they were.. but I did notice the throttle response was little better..

On a side note - Does anybody know of any shops that can re curve distributors in the Inland empire southern california area.

I know I can buy weight/springs but I want to setup on a bench and have settings verified and measured.

 

[2+2GT]

I do distributors sometimes, and rarely change springs. I've never needed to change weights. Tell the shop to use BOSS 302 specs.

 

[j69302]

how do you re curve them without changing those? I thought the weights and springs are what control the curve.

 

[2+2GT]

how do you re curve them without changing those? I thought the weights and springs are what control the curve.

You bend the posts they attach to. They're made for that. There's a hole provided in the breaker plate to insert a small screwdriver to bend the post. Spring tension is too sensitive to rely on spring changes. Besides, it takes so long to change the springs you'd be looking at several hours to do it that way. It's not like a Chevy, with the springs on top.

Almost all smallblock distributors had the same weights.

Here's the BOSS specs. I use the advance portions, and ignore the retard unless I am working on a BOSS distributor: