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cppursell · 01-21-2012, 04:07 PM

Hey folks,

I recently put a 307 in my '67 C10. I put on a 2bbl rochester carb, with an HEI distributor. It consistently hesitated acceleration, and wanted to die when cold. I eventually found out through a mechanic friend that the timing is way off because there's no port vacuum on the (older) carb, and that the manifold vacuum was messing up the timing on the HEI. I had retarded it myself so it wouldn't ping, but when it's set right, it pings a lot under acceleration and freeway speeds.

He said I can disconnect the vacuum advance and just change the mechanical advance curve until I find something that works. I bought a timing kit and plan to reduce the advance, but I wanted to know you're opinion of just using mechanical advance, or if I should just get a new carb with port vacuum, or anything else!
My goal is to have the most efficient option for better economy. Will mechanical advance alone run the engine efficiently enough?

01-21-2012, 04:07 PM	#1
cppursell Registered User Join Date: Dec 2008 Location: San Francisco, CA Posts: 144	Vacuum advance issues Hey folks, I recently put a 307 in my '67 C10. I put on a 2bbl rochester carb, with an HEI distributor. It consistently hesitated acceleration, and wanted to die when cold. I eventually found out through a mechanic friend that the timing is way off because there's no port vacuum on the (older) carb, and that the manifold vacuum was messing up the timing on the HEI. I had retarded it myself so it wouldn't ping, but when it's set right, it pings a lot under acceleration and freeway speeds. He said I can disconnect the vacuum advance and just change the mechanical advance curve until I find something that works. I bought a timing kit and plan to reduce the advance, but I wanted to know you're opinion of just using mechanical advance, or if I should just get a new carb with port vacuum, or anything else! My goal is to have the most efficient option for better economy. Will mechanical advance alone run the engine efficiently enough?