21.04.2009, 11:39
Carsten,
Holley 4150 style carbs usually have two vacuum ports at the front. One is usually on the metering block behind the front bowl and that is 'ported' vacuum, and the other is on the front of the baseplate under the bowl which is 'manifold' vacuum. The manifold vacuum will advance your timing with vacuum advance even though your carb's throttle blades are in the 'idle' position because it is pulling vacuum from under the baseplate. The ported vacuum will only apply vacuum to the distributor advance can when you open the throttle blades since it is pulling vacuum from above the baseplate.
Try both ports. Both will pull vaccum when you are cruising and should pull the vacuum to 50 some odd degrees when cruising in high gear on the highway. Is it 6 degrees at 1000 in gear or in park with the vacuum line to the distributor unhooked and the vacuum port plugged? What is your timing at 3000 rpm with the car in park and the vacuum line to the distributor unhooked and plugged? You want to check your timing without the vacuum canister hooked up.
Cheers,
Holley 4150 style carbs usually have two vacuum ports at the front. One is usually on the metering block behind the front bowl and that is 'ported' vacuum, and the other is on the front of the baseplate under the bowl which is 'manifold' vacuum. The manifold vacuum will advance your timing with vacuum advance even though your carb's throttle blades are in the 'idle' position because it is pulling vacuum from under the baseplate. The ported vacuum will only apply vacuum to the distributor advance can when you open the throttle blades since it is pulling vacuum from above the baseplate.
Try both ports. Both will pull vaccum when you are cruising and should pull the vacuum to 50 some odd degrees when cruising in high gear on the highway. Is it 6 degrees at 1000 in gear or in park with the vacuum line to the distributor unhooked and the vacuum port plugged? What is your timing at 3000 rpm with the car in park and the vacuum line to the distributor unhooked and plugged? You want to check your timing without the vacuum canister hooked up.
Cheers,