Engine rebuild time? Need opinions

[u0061914]

I have a 70 351C transplanted in my 75 Bronco. Last summer, it developed some engine noise, so I pulled the top end apart and found a cam lobe that went flat. I had good oil pressure and compression, so I decided to replace the cam, lifters, timing chain/gears, etc. and leave the rest alone.

This year and only 200 miles later, I have developed a similar noise/clatter. When I start up the engine, it runs smooth and quiet. After it gets hot and I rev it up to around 2500 rpms and hold it for a few seconds, then let it idle back down, it starts to clatter (top end somewhere) around 1200 rpms and will make noise at idle for around 20 seconds, then quiet down again.
Any ideas? I was going to pull the valve covers off tonight and see if there is anything obvious. I'm sure I'll never get that lucky, but you never know.

Now, I'm starting to plan for the worst, so I'm looking at options.

1. Pull the motor and have it rebuilt. Any idea what I should expect to pay?
2. Buy a remanned engine. Doubt I can get a 351C but a 302 or 351W
3. Junk yard motor and hope it runs

Not real excited about spending a ton of money at this time. Especially since I just got it back from the paint and bodywork. ya, good timing!

 

[bmc69]

Considering all the quality control issues that have surfaced with lifters over the last few years..that may be the whole problem in this case. Sounds like one is bleeding down and then lazy pumping back up (both would be related to a weak/bad internal lifter check-valve). I've had several do that in recent years (we build a lot of engines)..and getting real frustrated about it. Worth a look for sure.

 

[u0061914]

Is there a good way to verify whether or not that is the case? if it would happen to be the case, is there a better lifter available? Can I just swap the lifter(s)?