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burnin oil · 06-17-2020, 11:40 PM

Whats the base timing at idle? That is not a big cam at all and should have no vacuum issues. I have 250 duration cam in my truck and still have vacuum brakes that work. It sounds like you need a recurve of the distributer. I would hook the vac gauge back up and twist it to you get a good vac reading then limit the advance to the 32 degrees you want overall. Once the curve is set you can play with the vac advance if you like. I dont have it hooked up on my truck and milage is horrible. 7.5mpg on a good tank! I am willing to bet that it will run better with vacuum advance when the curve is set up correctly and gain a little mpg as well. I would not listen to GM here unless it is a track only vehicle. They are not always correct.

06-17-2020, 11:40 PM	#8
burnin oil Registered User Join Date: Jan 2013 Location: Eastern TN Posts: 1,921	Re: Cam Change Whats the base timing at idle? That is not a big cam at all and should have no vacuum issues. I have 250 duration cam in my truck and still have vacuum brakes that work. It sounds like you need a recurve of the distributer. I would hook the vac gauge back up and twist it to you get a good vac reading then limit the advance to the 32 degrees you want overall. Once the curve is set you can play with the vac advance if you like. I dont have it hooked up on my truck and milage is horrible. 7.5mpg on a good tank! I am willing to bet that it will run better with vacuum advance when the curve is set up correctly and gain a little mpg as well. I would not listen to GM here unless it is a track only vehicle. They are not always correct.