I had an issue arise about an hour ago I'd like some opinions on before I drive up to asher's tomorrow morning.
Truck Stats
1968 FJ40
F155 engine, never rebuilt
Weber 38 carb
Running 20w50 Castrol, coolant level's fine, oil pressure and engine temps are normal.
Problem -
Drove the 40 in to work today, it ran fine on the way there. On the way home I was coming down I-29 by the airport. The truck was up to temp and running fine when I heard a small bang (like a small backfire, but from the engine bay) followed by a drastic increase in engine noise. Now whenever the engine is under load (acceleration or uphill grades, 1/4 throttle or greater) I'm getting a very loud cam sound. It's a tic-tic sound, coming from the driver's side of the engine bay. It's not present at idle, reving in neutral, or during compression braking. Only under load. If you've ever hear an old tired full size farm truck accelerating, it's the same "metallic" cam sound, not the loping exhaust note.
My first thoughts are cracked exhaust manifold or manifold/exhaust connection. I've got the remote oil filter and carburetor in the way to really be able to see the manifold well. I'm going to let it cool down and poke around some more. The noise certainly sounds like it's coming from the driver's side. When it first occurred I was worried about valve or pushrod problems due to the type of sound, but as far as I can tell it's coming from the opposite (exhaust) side of the motor. I can't be certain because I can't reproduce it in the driveway - only when moving under load.
Any suggestions, ideas, or w.a.g's are welcome. I drove it home to Bonner Springs with no problems other than the noise, so unless I find something later tonight I'll be bringing it up tomorrow. However, I'd really like to have a better idea of what it is before I get it back out on the highway.
Thanks
Truck Stats
1968 FJ40
F155 engine, never rebuilt
Weber 38 carb
Running 20w50 Castrol, coolant level's fine, oil pressure and engine temps are normal.
Problem -
Drove the 40 in to work today, it ran fine on the way there. On the way home I was coming down I-29 by the airport. The truck was up to temp and running fine when I heard a small bang (like a small backfire, but from the engine bay) followed by a drastic increase in engine noise. Now whenever the engine is under load (acceleration or uphill grades, 1/4 throttle or greater) I'm getting a very loud cam sound. It's a tic-tic sound, coming from the driver's side of the engine bay. It's not present at idle, reving in neutral, or during compression braking. Only under load. If you've ever hear an old tired full size farm truck accelerating, it's the same "metallic" cam sound, not the loping exhaust note.
My first thoughts are cracked exhaust manifold or manifold/exhaust connection. I've got the remote oil filter and carburetor in the way to really be able to see the manifold well. I'm going to let it cool down and poke around some more. The noise certainly sounds like it's coming from the driver's side. When it first occurred I was worried about valve or pushrod problems due to the type of sound, but as far as I can tell it's coming from the opposite (exhaust) side of the motor. I can't be certain because I can't reproduce it in the driveway - only when moving under load.
Any suggestions, ideas, or w.a.g's are welcome. I drove it home to Bonner Springs with no problems other than the noise, so unless I find something later tonight I'll be bringing it up tomorrow. However, I'd really like to have a better idea of what it is before I get it back out on the highway.
Thanks
