(383) CAM SEIZED MOTOR AFTER REBUILD

[3500haulin]

I had a machine shop put a 438 stroker kit into a 383 block. I ran a comp hydraulic cam. Stealth head with roller rockers. first got the engine in and it cranked and seemingly was running good. Good oil pressure sounded solid. I go to restart it shortly after the initial runs/break in (mind you running good for all of this) and just click click. Long story short the CAM was seized. Pulled motor and removed cam/valvetrain. It would then turn over just fine. Took it back to the machine shop. They put new cam bearings in and the cam turned over great. Got it running again and seized the cam in the same manner as before. I am truly stumped by what could be doing this. Anybody heard of anything like this?

 

[RemCharger]

Which bearing seized?

 

[Kern Dog]

Hold on a moment....

With such little information, any response here will only be a stab in the dark guess. Did you ask the guys at the machine shop?
Was the camshaft damaged? Were the bearings installed with the oiling holes in the right position? Did the oil pressure drop off from say 70 when cold to around 20 when warm at idle?

 

[Don Frelier]

Likely they installed the cam bearings incorrectly and didn't line up the oil gallery holes.
Or there is something else wrong with the oiling system and no oil is getting to the cam

 

[HEMIB]

Lifters pumping up & valves hitting pistons

 

[3500haulin]

Hold on a moment....

View attachment 2028885

With such little information, any response here will only be a stab in the dark guess. Did you ask the guys at the machine shop?
Was the camshaft damaged? Were the bearings installed with the oiling holes in the right position? Did the oil pressure drop off from say 70 when cold to around 20 when warm at idle?

Cam wasn't damaged but bearing was galled up. the first time the oiling holes were correct. oil pressure never dropped. I am going to pull the motor and I will check it out further.

 

[Kern Dog]

The cam could be bent. It is rare but it happens.

 

[3500haulin]

Lifters pumping up & valves hitting pistons

I didn't see any signs of that but I will look again when I tear it down. I still got to pull it out of the car either tonight or tomorrow.

 

[3500haulin]

Which bearing seized

The Front most bearing

 

[3500haulin]

The cam could be bent. It is rare but it happens.

I was wondering if that could be it.

 

[3500haulin]

Ok looks like I will need to go pull this thing. I will and get some pics. I need a run stand. My 68 makes a terrible test bed for engine troubleshooting.

 

[QuickBpBp]

The Front most bearing

BOTH times?

 

[3500haulin]

BOTH times?

Im going to pull it and break it down. First time for sure but I assume it did the same thing the second time.

 

[Sedbld]

@Kern Dog may have your answer. Saw it happen in an 18 392 SRT right out of the box. Maybe got dropped at some point. But I have also seen a Pontiac 389 where the rear cam bearing was just too tight and once it got hot it locked it up. Installed another bearing set and took a brake hone and matched bearing ID to the journals OD and still running great today 12 years later

 

[pnora]

If the cam was bent it would not slide in or rotate. That would be something extremely obvious. If it is the same front bearing I would suspect some sort of blockage between the main gallery right off the oil pump and the cam bearing. Extremely odd failure. I would make sure that oil is feeding that bearing. With the front cover off you could run the pump off the drill and see the oil flowing.

 

[vance.dykes]

Let's look at the oil diagram and see what people think from there if you say the lifters pumped up and you had oil pressure what could be the problem by this diagram

 

[vance.dykes]

Is it possible the cam bearings are wrong or not lined up ? Or more likely the one that was scored on the cam journal is the one that's probably not lined up that's my guess or the hole could be plugged between the crank and the cam

 

[HEMIB]

How did you get the cam out if it was seized in the bearing did you have to pull it out or was it free when you took the chain off.

 

[1 Wild R/T]

How tight is the timing chain? any chance it's a undersized chain? When the front bearing fails twice it's sometime that should be considered....
Did the machine shop assemble the engine both times? Cause you mention the cam spun fine, but did you spin it? Or did you take their word for it?
BB Mopars are known to have cam bearing alignment issues, there are known tricks to assure a successful install... Scrapping bearings at tight spots, or my preferred method which consists of using an old cam, slicing grooves across each bearing journal then using the cam to shave any tight spots on the bearings...

 

[Kern Dog]

My preferred method which consists of using an old cam, slicing grooves across each bearing journal then using the cam to shave any tight spots on the bearings...