Engine knocking at 55 mph
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New User
Joined: Sep 2004
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From: Houston,
Engine knocking at 55 mph
First of all, forgive my lack of auto tech knowledge. I'm just a wannabe mechanic and too broke to waste money at a shop.
Well to the problem: I just got a '82 f-150 with a 351. Today after I have gotten new electrical and ignition parts and a new fuel pump, I got it started, and took it for a test on the highway. first, the engine cut out at a light twice ( i have already boosted the idle speed, maybe a bit more?) and once I got on the highway, the engine started knocking (?) at 55 mph and wouldn't go faster. then it started doing it at progressively lower speeds
please help-
thanks
Well to the problem: I just got a '82 f-150 with a 351. Today after I have gotten new electrical and ignition parts and a new fuel pump, I got it started, and took it for a test on the highway. first, the engine cut out at a light twice ( i have already boosted the idle speed, maybe a bit more?) and once I got on the highway, the engine started knocking (?) at 55 mph and wouldn't go faster. then it started doing it at progressively lower speeds
please help-
thanks
Posting Guru
Joined: May 2004
Posts: 2,223
Likes: 2
From: Billings Montana
It sounds to me like your timing is off a little. That "knocking" you heard could just be spark-knock, meaning detonation. If it died out on you after you replaced ignition parts, look there first before you check anywhere else.
On the other hand, if you replaced the distributor, you might not have the oil pump shaft engaged all the way. Did you check to see if your oil pressure was good? Because if it was low or even zero, you might have heard the rods knocking.
IMO: I would check the easy things first. Check to see if your timing is within range. If memory serves, 8*btdc is a good place to start for a 351.
Check to see if all the ignition parts are connected right and go from there.
On the other hand, if you replaced the distributor, you might not have the oil pump shaft engaged all the way. Did you check to see if your oil pressure was good? Because if it was low or even zero, you might have heard the rods knocking.
IMO: I would check the easy things first. Check to see if your timing is within range. If memory serves, 8*btdc is a good place to start for a 351.
Check to see if all the ignition parts are connected right and go from there.
Elder User
Joined: Mar 2004
Posts: 517
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From: Texas
Knocking at 55 and below
big hoss 29 is right! Check the easy stuff first. Just from what you have written, I suspect a severe timing problem. Could be as simple as crossed wires, broken wire, or a not so simple leak. Time to go over what you installed and double check, then throw a timing light on it.
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New User
Joined: Sep 2004
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From: Houston,
Okay, about a week ago I decided to change the spark plug wires so I did the obvious thing and ripped them all out. Bad decision, I later learned. So after about five different ignition sequences and reinstalling the distributer (the other way around) I finally got it to *start* I'll go back and recheck the wiring and all, but could is there a way to fine tune the timing? I'm pretty sure I have the wiring right according to the chilton's manual.
Posting Guru
Joined: May 2004
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From: Billings Montana
8 degrees before top dead center is what the timing should be set at. If you look at the balancer, you'll notice the timing marks. At the center of the marks is ZERO. Anything before the 0 is before top dead center or BTDC. Those marks are graduated in 2 degree increments, so if you set your timing at 8 BTDC, it should make a world of difference.
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