Thanks, and yes, this can kill performance...and your motor(s).

I know for a fact that gm crate engines, even though they are apparently "race motors", are built very very tight in terms of clearences... I know 572's are also too tight. So im just wondering, at 50 timing, id be effraid they started to be too hot, and they might start to to seize... Hopefully not for you.

But as said before, double check your tdc, take a camera and make sure piston did not start to melt, get a compression test to better understand what is going on in there, or leak down test, and let us know!

When I pulled the weights and bolted down the vacuum advance on my HEI distributors, at 6500RPM they would have about 46*-48* of timing, I never heard any pinging or signs of detonation. It was what the engines liked, When I switched over to the Crane HI-6M's (new cams and retainers at the same time) I now run 35* of timing and they run the same. I don't know if I was timing the HEI distributors right or wrong. On the dyno I set them at 3000RPM 36* of timing. Later I found out that over 4000RPM the timing started to increase with RPM's. I don't know if my cams were walking with the increased RPM's and my button was deflecting my timing chain cover to increase my timing or what. Still a mystery to me.

maybe these? http://performancedistributors.com/

don't think it would live long in a boat with that timing...as said better ck with another light...something is funky

I agree, something is not adding up. The motors runs perfect!! If they had truly been seeing 50 degrees timing at 3000 rpm's and up over the last two seasons I can't imagine these things not having some kind of issue if not blown up all together. I am going to check with another light before I get to excited. These have the factory GM hei distributor's, and ATI fluid dampeners (degree mark's stamped all the way around the dampener). Now just to be sure I am doing this right. Block off the vacuum advance, timing light pickup on number 1 spark plug wire, raise rpm until advance quits climbing, and notate reading? Nothing more than that is there? The light I have been using does not have the adjustable dial on the back.

Do not plug the vacuum advance nipple. Leave that open to atmospheric pressure.

What would need plugging is the vac line itself that goes to it, which a car would have, but yours doesn't.

Edit in: since the ATI balancer is marked completely around, a fixed timing light is better. Just make sure you can read the #'s on the balancer clearly, so you don't mistake numbers.

Would you also recommend leaving the vacuum nipples open to the atmospheric pressure under regular operating conditions, or plug them after timing is set?

Doesn't really matter. The only time it might move would be with a huge altitude change that you'll never experience. The vacuum advance is spring loaded to the advance position. It's not really vacuum advance, it's actually vacuum retard.

Thank you!!!