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1977 trans am hei distributer retarding.
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vermey
New User
Mar 30, 2013, 2:45 AM
Post #1 of 1
(1479 views)
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1977 trans am hei distributer retarding.
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1977
pontiac
trans am
400 cid (pontiac)
110,000 miles
Hello. my Pontiac 400 ci engine is not stock. I am running a hydraulic roller cam, 1.6 roller rockers, and a high volume oil pump. The distributor is a stock HEI, except for a bronze drive gear. the centrifugal advance is the stock weights , and center plate. I have put lighter springs on the weights. the cam reduces my vacuum to 10 in of vacuum at idle. cam spec, 110 lobe separation, 106 center line, duration at 0.05 lift 256/244. double roller timing chain, it has minimal slack 2 deg.
My problem:
I have slight miss in the motor at 30 mil/h that is continues at that speed. the throttle is just off idle, at that speed. if i accelerate, the motor smoothes out. this is with vacuum advance (ported) disconnected, and plugged. Engine at operating temperature, about 190 deg. timing light, with tach built in, hooked up. initial timing set, and timing mark set back too 0 on balancer. Transmission in park. I rev the engine to 1600 RPM, the timing mark will retard 8 deg, and stay there. when I increase engine to 1800 RPM, the timing jumps to, 8 deg advance. after that the mechanical advance, advances smoothly to 16 deg's, total mechanical at 2600 RPM.
I removed the distributor from engine. The cap, and rotor are in good shape. No sign of arcing, or miss alignment. The bronze gear is slightly worn. lower bushing has 0.045 side movement. Shaft end play is 1/16". Advance weights move freely. Advance springs hold weights tight in rest position. Magnetic pickup screws are tight. Upper bushing has minimal side movement, 0.006. vacuum advance unit has a limiter stop, so it can't move backwards, (retard).
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