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Hi i have a 1978 f150 with a 351 in it. Ive got the carborator set seemingly good but when ever i start it, it shakes the whole truck. once you get moving its fine untill you start to stop then it comes back. it does it in gear and also when not in gear. what do you think is wrong? thanks justin.
Does it start up right away? Maybe it needs a tune up. Could it be the driveshaft is unbalanced, or dented, or stuff is caked on it? Do a compression test and see what compression is. Could the timing be off? How does it run when driving? Smooth or kinda rough? Has the power dropped any? What did you do prior to it starting to run like this?
if you've got the 351M , I had the same problem. I was told that it was due to Fords' having used the 400 crankshaft and a longer piston stroke with smaller pistons.
Did I get that right? It's been a long time but it made sense to me at the time.
And mine did it before and after a complete rebuild. Drove me and anyone else who tried to set the timing crazy!
it has the 351M in it. its fine once you take off and smooth at all speeds untill you stop and start. when you have the brakes on like at a red light it pulls against them but its not constant it pulses. it feels like someone is pushing you from behind and the vibration is horrible. also why does this enginge require so much oil? i could take a bath in the oil pan. thanks justin
In that case from what you just decribed it sounds like your timing needs to be retarded. Mine did that when my friend and I were tuning my truck turned out we had it advanced too far.
-Chris
It should not shake. Sounds like it has a miss - remove one plug wire at a time and note if it makes a difference. If you find one that doesn't seem to make a difference when unhooked, then check the wire and plug on that cylinder. Let us know what you find.
Your engine should require 5-6 quarts of oil at oil change with new filter.
I would bet that it is either timing or a vacuum leak. Don't forget to check your vacuum lines and any plugs on the rear of the carb. I had some big cracks/holes in my lines and that's what caused my 351m to shake as you describe. Put a vacuum tester on the rubber lines to test for leaks. It might be easier and faster than testing and adjusting the timing.
ive changed all the vacuum hoses and im almost certain theres no vacuum leaks i just changed the plugs and wires last night and it still does it but its not as bad. ill check each individual plug and see for misses. then ill let you know. thanks justin.