I have a 1972 Mustang with a 351C, 4-V. I'm replacing the stock Motorcraft 4300D that's on it with an Edelbrock 750 cfm, because the Motorcraft float is screwed up and the secondaries are frozen shut. As the car is now, it won't start with the stock carb. I need to determine if the distributor vacuum port on the stock 4300D carb is timed (no vacuum at idle) or full (vacuum at idle). Since I can't start it with this carb on it, I can't do a simple vacuum test. Anyone know if this car has either timed or full distributor vacuum? Thanks.
Ford 351C question
Apr 13, 2005
2 Replies
Joe,
You might do well to post this and other questions about your car on alt.hi-po.big-block-ford-mercury. Your car and engine is definitely on-topic over there. There are lots of folks with lots of expertise with this stuff. I wish *I* had some to give you on this specific question... good luck, regardless!
I don't know what the specs say, but I always use the timed vacuum, aka ported. This gives you only base timing for startup, which makes it easier on the starter motor. Then you get the vacuum advance on tip-in, which is the whole purpose of vacuum advance: to give you more power with less fuel. Whether ported or full, the vacuum effect goes away at WOT.
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