71 Chevy truck cam eater update

Posted a while back about my 71 Chevy Custom Camper 3/4 ton (10400 original miles) that ate a new cam at 4000 miles. Well , I said the heck with it (me with a bad back) and took it to a local guy who is a wizard with small blocks. My oil pressure had dropped off way down all of a sudden and the lifters were ticking away but the dang thing still ran like a top. He got it pulled apart and miced and scoped everything and got the block cleaned out. Said it had 8 lobes gone and the metal floating around ground out the bearings which I already figured. The good news was the crank was still in factory standard specs and the pistons and valves were in excellent shape which honestly suprised the heck out of me. Must have caught it right in the nick of time. The trans shop reported the trans was in good overall shape outside of the worn clutch packs. It had a habit of freewheeling when hot in drive. This old truck is so original and drives very nice and is one heck of a hauler. I almost sprang for a newer truck when it was acting up, but I am glad I didn't now. I will post the results when I get it back and drive the ol gal again later this week or early next week.

One reason some of those engines ate cams was because some ofthe holes for the lifters are not bored correctly causing the lifter not to rotate . It eats another one get a different block.

Use either synthetic oil or regular oil with ZDDP additive to break in cam. Run engine at approx 2000 rpm at no load for 15-20 minutes to break in flat tappets.

If using roller cam, forget what I just advised.

New oils lack the zddp additive and cams fail.

If it ran a hundred thousand miles on a cam I think the lifter bores were ok. also if worried about lifter bores or oil change to roller cam. end of problems.Paul

Bob,
I will still stick with what I said earlier. There are a fair amount of complaints about steel quality on cams right now.

ErnieDD mentions ZDDP additive. Break in is critical too, and proper lash.

Luckily it sounds like the rest of the engine is still clean. A good rinse will be needed to make sure you get all the junk from the 8 ground lobes out of that block.

I wonder if it wasn't lashed too tight, if you wiped out 8 lobes.

Keep us posted.
Rick

General Motors claimed they had two problems - #1 being a faulty Parkerization-process surface-hardening on some cams, and #2 a faulty break-in procedure at the factory at first engine start-up. What ever the problem was or is, we had to fix many back in the 70s - and on. Our standard procedure was to replace the cam and lifters with a Crane cam kit. I'm sure there are others just as good, but we had zero comeback problems with those aftermarket cams. My 64 Chevelle SS still has one in a 283 with 160K miles on it.
Many of those SB Chevys with failed cams also had failed cam drive-gears since they used plastic coated teeth. They fell apart and the plastic would often plug up the oil pump screen and ruin the engine. Hopefully you installed a set of all steel timing gears and new chain?

Jdemaris, you mentioned using Crane Cam kits. I just read an article where they appear to be going out of business. Another one down the tubes.
Crane Article

ya. 'cept NOTICE how he said 10,400 miles not a hundred thousand. and the current cam at 4000. problem is like stated above. block is junk. lifter bores are not oriented correctly, can be sleeved but expensive. real engine shops wont even install a flat-tappet cam in a bigblock chevy unless bushed cuz there off so bad they all eat cams, always have when goin bigger than stock.

I have been a mechanic since the early 60's and a Chevy is the only engine that I have replaced a worn out camshaft. Some had as little as 30K miles.

To add some more, The guy always uses a GM cam break in additive in the oil. I originally told him I wanted to go ahead and put a roller cam in and he said those roller kits for street engines don't hold up well. I think he means the kits for putting a roller cam in a block that was made for flat tappets. He said the rollers can break and then you have a big problem. So we are just going with a flat tappet cam. This guy had a 1st place, for 6 years running NHRA small block powered drag car years ago. I just hope this one does ok. It could be possible that I had it preloaded just a tad bit to tight, but certainly not by much as that was done while the intake was off and the engine rotated to valve closed position and lifters pre oiled or loaded. He said the engine bearings all had a 1978 date code on them so it did have some work done to it in the past but it had all GM parts in it when I took it apart last year. At least as far as cam and timing gears go. Last week when I was reaserching croller cams, I tried to call Crane and they are for sure closed as well as the Mikronite parent company. Guy at Summitt racing said he thinks Comp cams may pick them up in the near future. Some guys on an automotive message board said they went past the Crane shops in Daytona and there was just one car in the parking lot last week. Another guy posted the there were 4 cars in Mikronites parking lot in New Jersey. Sign of the times!

Was that a 305cu in?

ErnieDD has the key advice.

ZDDP has certainly been lowered in most new highway-rated oils - even the USA version of Shell Rotella-T. Still used in HD off-road oils as well as many European highway-rated oils. But, the GM cams in the 70s were failing often even with good oil and high amounts of ZDDP and other additives. And contemporaneously, others e.g. Ford and Chrysler were not having the problem.

Okay I missed the 10,400 actual. another option if one can find a cnc boring center is just have lifter bores trued to ford size. solves a couple problems. the bores are in the position they were designed to be in and they have a little more surface to run on. more reliable.that would probably cost less than an aftermarket roller setup .Paul

It is a 350 4bbl TH 350 trans with power steering brakes A/C cargo light,radio saddle tanks leaf springs in rear heavy front sway bar 2 tone blue and white paint, deluxe wood grain trim original cloth seat non ripped!

Sorry guys! I did make a mistake! it is 104,000 miles. Sorry about that! I wish it was 10k original miles!