351M/400 Valve Train noises.
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From: Rockport,TX
351M/400 Valve Train noises.
Hello Folks,
My 1980 Fullsize Bronco's 351M/400 engine has about 200 miles on the rebuild. Ever since it's been back in the Bronco I can hear the valve train making a ticking sound really bad while it's running (Passenger side valve train). I pulled the valve cover off the passenger side of the engine and notice the valves are not adjustable. I was thinking about swapping out the rods for longer ones but wonder how to figure out what length will work??? Do you all think this is the best route to go??? Or should I take the engine back to the machine shop where the engine was rebuilt and assembled??? As always , Thanks for your help and advice! The FTE forums rock! The best source of information I've ever seen! Thanks for letting me join!
Ron McCann
My 1980 Fullsize Bronco's 351M/400 engine has about 200 miles on the rebuild. Ever since it's been back in the Bronco I can hear the valve train making a ticking sound really bad while it's running (Passenger side valve train). I pulled the valve cover off the passenger side of the engine and notice the valves are not adjustable. I was thinking about swapping out the rods for longer ones but wonder how to figure out what length will work??? Do you all think this is the best route to go??? Or should I take the engine back to the machine shop where the engine was rebuilt and assembled??? As always , Thanks for your help and advice! The FTE forums rock! The best source of information I've ever seen! Thanks for letting me join!
Ron McCann
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From: Saraland AL
351M/400 Valve Train noises.
The valves on 351M/400s are non-adjustable. You should check the rocker arm bolts and make sure they are not loose. I've been told that some brands of lifters make a ticking sound.
Exhaust manifold leaks will sometimes make a ticking sound as will arcing plug wires.
Exhaust manifold leaks will sometimes make a ticking sound as will arcing plug wires.
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From: Porterfield
351M/400 Valve Train noises.
IF the motor was rebuild by a engine shop then I'd take it back to them to have it fixed .. either the rockers are worn or something in the valve train isn't right if there making noise.
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From: chicago burbs
351M/400 Valve Train noises.
have you identified which rocker is noisy?(or more) use a length of conduit or such,hold it to your ear and listen to each rocker. rest the end on the hold down bolt-you'll be amazed at how loud the noises are. if you find a loud one(or more),try removing a bit from the bottom of the pedestal. you can keep track by measuring w/a caliper or mic. just don't go too crazy, maybe .010-.020 at a time? what's the worst thing that can happen? or try a new rocker assy on the noisy position
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From: Hephzibah Georgia
351M/400 Valve Train noises.
What is it that makes the valves non-adjustable. I believe that the valves on my truck aren't sealing as they should. I remember the guy I bought it from replaced the lifters on the #1 and 2 cylinders which im not getting good compression on. Could he have put the wrong lifters in it.
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From: Saraland AL
351M/400 Valve Train noises.
Non-adjustable because you only tighten the bolts(notice is said bolt, not nuts) to proper torque and leave them. There is no valve lash to do. The rockers are what is called "pedestal mount". The rocker pivot actually bolts to a machined notch in a pedestal on the head. They don't use studs or pushrod guide plates.
If a valve isn't sealing, it could be burnt or cracked, possibly bent slightly.
If a valve isn't sealing, it could be burnt or cracked, possibly bent slightly.
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From: Hephzibah Georgia
351M/400 Valve Train noises.
You have the same idea i do about the burnt valves. The guy who replaced the lifters may have the wrong lifters or the wrong pushrods. If their too long they will let the valves hang open. So when I crank it up im roasting the freakin valve face. I guess ill have to get an adjustable pushrod and send it to Comp Cams so they can send me some custom pushrods that will work right.
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From: Saraland AL
351M/400 Valve Train noises.
I don't think pushrods will be the problem. I believe you will need to remove the heads and inspect them. Clean them good and have them checked for cracks. Clean and inspect the pistons also, there shouldn't be any dents or pitting.
If the heads were milled too much, that would make all of the pushrods too long. If the heads were not milled, the pushrods won't be the problem.
Also inspect the head gaskets. You may have a burn through between cylinders.
If there is nothing wrong with the heads, the problem is more likely in the valve train. Possibly a bad cam or lifters. I doubt if it has the wrong lifters. Unless somebody put solid lifters on a hydraulic cam.
Did you have this engine built or did you get it from someone else? Is there a warranty? If there is, take it back and have them fix it.
If the heads were milled too much, that would make all of the pushrods too long. If the heads were not milled, the pushrods won't be the problem.
Also inspect the head gaskets. You may have a burn through between cylinders.
If there is nothing wrong with the heads, the problem is more likely in the valve train. Possibly a bad cam or lifters. I doubt if it has the wrong lifters. Unless somebody put solid lifters on a hydraulic cam.
Did you have this engine built or did you get it from someone else? Is there a warranty? If there is, take it back and have them fix it.
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