i need help,,engine trouble

[68GMC454]

ok today i got my dually together fired it up...at first she just purred, sounded great when revved up...then all of a sudden i got a slight knock in the front of the engine....now let me say this,,
all we did was replace all the gaskets and seals except for the head gaskets..but i didnt pull the heads...when i first started it, the intake gasket was leaking, so got it tightened up enough to quit leaking. but when i shut it down, the heatyer hoses and water hoses are darn near hot enough to burn your hand when you touch them...i was told there coupld possibly be a air bubble somewhere in it, and that wouldnt let the water circulate...

is this true...my motor is a 1984 454, 210 horsepower 340 torque..i think thats what the stock numbers for it are...

so what do i do,,need information asap...i appreciate any and all help.

also, i have 6 quarts of oil and a bottle of lucas in it now, and it is still showing low on the dip stick... need all the help i can get..
thanks
billy

[shadetree]

Hot hoses are normal, but overly hot could mean blockage or an "air-lock" (bubble). A small (1/8") hole drilled in the edge of the thermostat helps prevent the dreaded coolant air locks, by allowing trapped air to escape.
The knock would concern me most. I would investigate by pulling spark plugs, looking for coolant leaks & signs of damage.
Your oil level is low, with 7 quarts in it? Look for leaks. Look for signs of coolant in the oil (milky white oil).
Good luck, and keep us posted, I hope this works out.

[68GMC454]

so if i dril the hole, that should take care of the air bubble..yeah the knock worries me, sionce this motor has gave me no trouble for the 5 years or so ive owened it, and it ran fine when i took it apart to replace the gaskets... so far it has leaked no oil since i replaced the gaskets...will be checking tommorow to make sure the modified dip stick tube is in all the way, i had to cut the mounting bracket off it to get it to clear the headers.... will let you know what i find out...thanks

[old Rusty C10]

well does it sound like a bearing knock? does the oil level return to normal after a while? Do you have a fram oil filter on it?
First off id change the oil filter and see what happens . if that dont help then if it sounds like a bearing you may have gotten a blockage somewhere cause crud from the motor blocked up an oil passage or gallery you may have to pop the motor apart to clean it out and pop the pan maybe something from inside the motor is jamming the pickup in the pan
good luck and keep us posted

[68GMC454]

thought i would let you know it was cold and raining all day.. and since my crew cab only has a couple of inches to spare when it is in the garage, we didnt work on it today...i hate cold dreay rainy days....

[Big_Black]

Hey 68GMC454!

I am from northern Calif. and it was cold, too...I also have a dually, 1987 crew-cab. And a couple of years back, I heard some knocking in my engine, I kept on driving nuts because I couldn't pin point exactly, but it was near the lower, front. After talking to a few mechanics that I new, they told me the worst would be the bearings at the crankshaft and/or a broken valve. Well, it turned out that I had a broken valve and two worn out bearings, and I needed a new crankshaft.
I hope this isn't what you have because you have a lot of work ahead of you.

[68GMC454]

what concerns me most is, the motor ran great before i took it out of my 84..noise is in the front of the motor, not a hard knocking sound, like a rod, but more than a rattle from the heads. hopefully this weekend i will be over this cold and figure out what is wrong with it...i think should have just kept my 84, while i have always dreamed of haveing a crew cab dually this truck has turned into a night mare...

[old Rusty C10]

could you be out on timing?? if the distributor wasnt tightened down right it could have moved on its own

[chev74]

what about a lifter? mine has lifter noise since i know it isnt a rocker arm. i took both valve covers off to determine the noise and checked all the rockers, but it is a deeper sound than the rockers.

[derrickc]

Mine had a slight knock, valve covers were on backwards, done by a professional mechanic, so he said. Makes a very faint knock and will wear a hole in the valve cover, covers will fit on both ways, but one side is higher then the other.

[68GMC454]

well my freind looked into it today, and i stopped by he fired it up, definatly a rod knock now i belive...gonna pull the oil pan tommorow to check the bottom end, but more than likely gonna have to rebuild it from the ground up.....personaly i dont understand how a mtor i know had no problems goes south all of a sudden.. yeah i know it happens...i know i should have just kept the 84,, this 76 has been a night mare from day one..oh well..now im just mad so i will tear it apart and rebuild it...

[f.monroe]

I had an 84 454 3/4 ton . ran great . I started it one day to show it to a potiential buyer and it had a knock . Since it had been running perfect , we ran a can of GM top engine cleaner through it . Knock stayed . Pulled the pan and checked everything out . No problems found so we reassembled it and ran it . it still had the knock . We ran one more can of GM top engine cleaner through it and the knock went away . The carbon buildup in the cylinder head had come loose and lodged on top of a piston . When the piston came to TDC it would compress the carbon between the head and piston and the knock was there . The engine cleaner loosened it and all was good . Just my experience . I hope yours is something simple . Frank

[68GMC454]

well had fun today,, puled the oil pan while the motor was still in the truck..after some good cussing and finger smashing it came right out...oil pump looks good, bottom end looks ok,,no chunks in pan or oil, no metal shavings...so i dont know why i got a knock...we did pull some of the bearings out, while they are not new, they are not totaly wore out looking either.....so im not sure where im going from here, but im pretty sure, im gonna just put the oil pan back on it, and pull it back around in the field until spring and then rebuild the motor..