79 f150 351m top end rattle

[04SVT-L]

ok so heres the problem. i got a 79 f150 with a 351m in it. now keep in mind this truck was sittin for a long time when i got it. i had bent 2 off the pushrods awhile back and when i had the valve covers off to replace them, this thing had so much slugde and grime in there it was unbelievable. ive done plenty of oil changes. and i now have 10w-40 oil in it. when i start it up, it runs great. no problems, besides a slight miss the never goes away. now after about 20 min of driving and after it warms up, wen cruising at about 2500rpms under normal throttle just to keep the truck moving i have a real bad rattle coming from the top end. almost sounds like when i had the bent pushrods in it. but i kno its not them again because they would start making noise instantly. it goes away when i accelate hard or let off the gas on decel. what is this noise!?? lol it doesnt sound good.

 

[blacksnapon]

ok so heres the problem. i got a 79 f150 with a 351m in it. now keep in mind this truck was sittin for a long time when i got it. i had bent 2 off the pushrods awhile back and when i had the valve covers off to replace them, this thing had so much slugde and grime in there it was unbelievable. ive done plenty of oil changes. and i now have 10w-40 oil in it. when i start it up, it runs great. no problems, besides a slight miss the never goes away. now after about 20 min of driving and after it warms up, wen cruising at about 2500rpms under normal throttle just to keep the truck moving i have a real bad rattle coming from the top end. almost sounds like when i had the bent pushrods in it. but i kno its not them again because they would start making noise instantly. it goes away when i accelate hard or let off the gas on decel. what is this noise!?? lol it doesnt sound good.

Just a stab at it, it will be related to the sludge. Lifters would be my first guess. Camshaft wear would be my next concern.

 

[d-kuzmen]

any idea what the oil pressure is. If you have that much sludge in the top end imagine what might be in the oil pan restricting oil flow, or the oil returns maybe blocked up in the heads not allowing oil to drain to the pan fast enough.

 

[04SVT-L]

but if a lifter was collapsed or something that would make the noise all the time. i kno its time to tear the whole thing down and rebuild the whole thing. just gota finish putting the rear in the lightning so i can get the 79 in the garage cuz its getting cold! o yea and i will check for oil pressure today if i got time