recently rebuilt 350 olds.intial timing set 12 degrees, new HEI distributor. When reving engine in park, no issues whether vacuum advance connected or not. When driving, no issues when vacuum advance disconnected, but when connected to vacuum (ported) I get noticable pinging on throttle tip in while driving. Advance can is adjustable and i followed summit directions by turning can adjustment all the way clockwise (i had pinging when driving at that adjustment. I backed it off 2 full turns and still get pinging ) Should i continue turn vacuum can adjustment back or reduce initial 12 degree timing. No issues with starting car hot with current timing. Also engine temp sits at 180 degrees.other than this car runs/idles great and has good pep to it. I also run 93 octane fuel.
erson e540121 hydraulic cam adv. duration 292/292, lift .0478/.0478
Another thing. whiile out on test drive, i remebered I had disconnected the vaccuum advance hose. I pulled over to connect and saw i didnt have hose plugged (ported vaccum port) but it ran fine. shouldnt it have run bad with vaccum leak.
thanks eric.

 

The adjustment on the vacuum can is a rate adjustment not an amount advance limiting adjustment. You need to make a physical stop to limit the amount of advance the vac canister can provide.

 

 

You can make a stop or buy one from places such as Summit.

 

If you use manifold vacuum the vacuum advance should retreat as soon as you tip in. It'll be slower with ported vacuum.

 

I thought it should be ported
how will that affect initial timing
figured stock style hei on stock engine shouldn’t be a problem

 

Is 12 degrees too much initial-

 

Vacuum advance connected to manifold vacuum will give full vacuum advance at idle, and connected to a ported source will have no impact at idle but will advance as soon as the throttle is opened. Either way, restricting it to around 10 degrees is recommended. Some vacuum canisters give 24 or more degrees advance.

12 degrees initial is not too much. It might not be enough with an HEI depending upon the distributor’s amount of mechanical advance, but the engine should run OK, it just might not make maximum power.