77 351M issues
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Postmaster
Joined: Dec 2002
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From: Southern Oregon USA
77 351M issues
I've had this 77 F150 for 15 years and have always dealt with a low power issue, but have never really investigated it. After my father in law caught it on fire and burned most of the vacuum lines on the engine, I decided to get rid of it all and simplify with an alum intake and 4 bbl (1406 Edelbrock) It also has a new distributor.
It idles fine and runs decent enough to run down the road. But any time you step on the throttle, it bogs and backfires through the carb when the accel pump hits. It completely falls on its face past that with any throttle input. I would chock it up to carb tuning, except that it did the same thing with the stock 2bbl.
Compression is between 110-120 lbs on all.
I initially set the ignition timing to 10* which gave me total of 45* all in. Vacuum reading was around 15" and bouncing a little at idle.
I played with timing and could get the vacuum to 17, but it took 35* of initial timing to get there. Ironically, the backfire and the bogging went away, at least with no load on it.
I'm suspecting maybe the cam timing is off or the chain has slipped.
Any issues with the ring turning on the balancer?
Just looking for a little feedback before I pull it apart.
It idles fine and runs decent enough to run down the road. But any time you step on the throttle, it bogs and backfires through the carb when the accel pump hits. It completely falls on its face past that with any throttle input. I would chock it up to carb tuning, except that it did the same thing with the stock 2bbl.
Compression is between 110-120 lbs on all.
I initially set the ignition timing to 10* which gave me total of 45* all in. Vacuum reading was around 15" and bouncing a little at idle.
I played with timing and could get the vacuum to 17, but it took 35* of initial timing to get there. Ironically, the backfire and the bogging went away, at least with no load on it.
I'm suspecting maybe the cam timing is off or the chain has slipped.
Any issues with the ring turning on the balancer?
Just looking for a little feedback before I pull it apart.
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Joined: Apr 2004
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If you pull it apart, are you going to rebuild it?
As a 351m or a 400?
Lots of threads here on building a proper 400.
There are no easily available pistons for the 351m that will bring the compression up. A cam change will help, but it will still be weak and eat more gas than it should.
As a 351m or a 400?
Lots of threads here on building a proper 400.
There are no easily available pistons for the 351m that will bring the compression up. A cam change will help, but it will still be weak and eat more gas than it should.
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Postmaster
Joined: Dec 2002
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From: Southern Oregon USA
If I do need to go in that far, it will be a 400 when I'm done. I have a spare 400 crank and another block to work with.
Unfortunately for me, I'm a little short of money to build one the way that I want. So, I'm trying to just make the 351 work for awhile. If I just have to swap out the timing set, that's pretty simple and cheap.
Unfortunately for me, I'm a little short of money to build one the way that I want. So, I'm trying to just make the 351 work for awhile. If I just have to swap out the timing set, that's pretty simple and cheap.
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