i have another issue with my 79 ford f350 400ci. the issue is at idle i hear a clacking noise its not a rod but more of a tappet or rocker. The issue is i've been told the rocker arms are non adjustible... The truck sat for 5-6 years before i revived it from the grave. Is there a certain weight oil that these engines like? nobody has been able to give me a straight answer when it came to the oil weight.

 

Check the rocker arms tomake sure all are tight. If they are, check for loosness for the pushrods, up and down movement. Check every pushrod with the rockers in the up position. I'm thinking a collapsed lifter. Sitting that long the engine sat in the same position all this time allowing the lifter to stick and won't pump back up.
As for oil, depends how many miles and the climate you're in. Warm climate (like southern states) under 150K miles, 20W50 oil is good. Northern states, 10W40. Hope this helps... BB

 

how would i go about to freeing up a collapsed lifter?

 

Lifters are typically not a rebuildable item, they are usually just replaced. I have had success letting them soak in PB Blaster for several days 20% of the time. It's rare that they can be unstuck. BB

 

im guessing the engine has to be torn down to remove the lifter?

 

Only the intake and valve covers need to come off. The rockers can be loosened and turned siedways and pull the pushrods out. Check the pushrods while you have them out for straightness also. BB

 

is there any chance i can get it freed up by putting some lucas in the oil?

 

No, Lucas is an oil additive that makes it thicker to reduce oil loss/burning/smoking. What is needed is a penetrating type liquid to get something freed, just like rusted/frozen bolts. BB

 

ok thanks for your help i will be tearing down the intake to remove the tappet if i find play on pushrods.. and lasty would 10w40 be good year round in WI?

 

I'm willing to bet you have a bent push rod more than a stuck lifter. I'm not saying the lifter isn't possible, but bent push rods are pretty common. Also, rocker arms have "Adjustments", too. If you take the rocker arm completely off, you'll notice shims under the rocker arm. Remove some of the shims to tighten up the rocker adjustment. If it's a loud "clack", then you can't remove enough shims to make that go away. That's why I suggested looking for a bent push rod.

It should be painfully obvious when you pull the valve covers. Wiggle the rockers. They'll all move a little, but the one that's clacking will flop around like a fish.

 

10W40 would be good for your location. When it's cold outside the oil will be 10 weight for easier starting hence the "W" is for winter. The oil will be around 40 weight during the warmer months. Down here in Fla I use 20W50 cause it doesn't get that cold here and have high mileage on the engine. BB

 

When checking the rockers like this, make sure they are on the up-stroke. If the rocker is on the down-stroke it could still be tight hiding a possible bent pushrod. BB