GCD1962

On friday I was riding to an annual show in VT from CT in my '62. A few miles outside Rutland without any warning bam, pop and the engine immediately stopped. It was very abrupt with no signs of something about to happen, and no strange noises. I was cruising a steady 55-60 mph at around 3,200 rom. Before it happened the car was running great. The engine is a 70 LT-1 short block (all stock), Dart heads, headers, etc.

Before the flatbed arrived I pulled the distributor cap, cranked it over and the rotor did not move. My first guess was the the distributor gear cam un-done. After it was flat-bedded and towed to the tow company yard (the company was called Boondock towing !, but they were great). I had to wait a few hours for another driver to go back to CT (about 230 miles). While waiting I pulled the distributor and found that the gear was fine and intact. After a long day and $750 + tip lighter in the wallet, it was back in the barn.

Thought then was that the timing gear/chain let go. Got it up on the lift, took the pan off and there were no pieces of metal in the pan. Today I took the timing cover off and the chain/gear were fine. I then cranked to engine over and could see the cam also rotating. As I looked at the rear of the cam with the gear I could see it was not moving !! Only guess is that is broke at the last bearing before the gear on the cam. Never had that happen, nor ever heard of the happening to someone. It was the stock GM LT-1 cam that came with the shortblock.

Problem now is what to do. Do I take the heads off and try to get the cam out ? Do I pull the engine to get it out to rebuild ? or do I buy a crate engine (which one), or a new short block (no LS engines, just regular SB types) and use the heads, manifold, etc from the existing engine.

No a simple task and getting a little older so it takes a lot longer

Swept57

I would pull the intake to see where it broke. If it is a clean break with no metal debris, I would try to take it out and replace it. Not sure you can do that with the engine in the car though, but you shouldn't have to take the heads off. I would also have a metallurgist look at the break to determine cause. Might be possible that the rear cam bearing was starved for oil and seized?

Bluestripe67

Sorry to hear of the failure and associated trouble. I would pull the engine, tear it down or have it torn down by a shop for full inspection. If it's low milage and no critical issues, have it re-ringed, new cam (same cam?) new bearings, seals etc. Bolt on the previous parts and drive on. My two $ worth. Dennis

MikeM

I had a cam break in a 327 in 3-4 places. I pulled the intake and got the lifters out. Pulled the timing chain cover and oil pan and worked the broken pieces wither forward or down. No problem. Just tedious.

Be careful you don't skin your cam bearings.

GTOguy

What Swept57 said. Pull the intake, if a clean break, replace the cam. No need to tear everything apart....support the engine and pull the radiator....you can do it in-car. My bet is that the cam is not an original '60's-'70's cam, but that it's a reproduction late production cam of poor materials and craftsmanship. I'll bet it is a defective casting, made in China.

GCD1962

No it's the original cam. I bought the short block from Chev in 1973 - pink rods, forged crank and all.

tuxnharley

Hmmm - if the front part of the cam was turning and the back part wasn't there are likely to be some metal pieces/fragments/ particles in there some place. It's pretty unlikely it was a clean smooth break with no fragmentation, especially since it sounds like those parts have been grinding against each other a couple times now......

If it was me I'd do a complete tear down and clean out, just to be safe.

vettsplit 63

I guess we are the only two who think the same way. If he was running down the road at 3200 and it crapped the bed, I would be amazed if it didn't bend some valves, or at least pushrods along the way. That's what I would do if it was mine. And if the OP is running Dart heads, is there a possibility of stronger than stock springs, which may put a lot more strain on the shaft?

I am building a small block right now, and we are going to put a billet steel cam in the car. 8620 steel.

cardo0

Unless you gonna sell the car, pull that motor and blueprint it using modern parts and machine work. Or else bag it and drop in a nice crate engine. Too many better options than risking putting it back in service after a cam catastrophe.

Good luck.

Swept57

Well sure, if money is no object, just junk the whole car and buy another one.

desertpilgrim

I think God's trying to tell you to find a date correct 870 block and some heads and build yourself a "restoration Motor", 300 or 340.

GTOguy

Hmmm...the fact that it was an original 45 year old USA made cam changes things. Something caused it to fail....I have to agree with the others now. You need to tear it down at least enough to perform some forensics to find out WHY it broke, what locked up, and the extent of any collateral damage that might have occurred.

MikeM

GCD1962

I was expecting pieces in the pan, but there were NONE at all. The rest of the engine is in great shape. Doesn't appear so far that any valves hit the head or anything bent as it stopped abruptly when it broke. The heads do not have excessive valve spring pressure. No stretch in the timing chain.
I'll try and pull the cam out with the engine in the car

GCD1962

Can't. I've had the car for 45 years

JohnZ

Don't forget to remove the fuel pump actuating rod first.

cv67

Thats a long run, cant complain really how long do aftermarkets last?

Edit: see youve torn it down some get it back up & running, motor on.
Crane still make that blueprint cam? Time for an upgrade and some porting!

Swept57

Might be a little tricky getting the broken stub out, but worth a try! Maybe JB weld a rod to it and work it through the cam bearings.

GCD1962

Thanks for the reminder John.

The engine cranks fine with nothing binding. Nothing at all seems to be binding up and as I noted there were no pieces of metal found in the engine. Cam turns up to the area of where the last cam bearing is near the distributor. Look on the other side and the gear area on the cam is not turning

vettsplit 63

Well, at least run a leakdown test on the thing. Wont cost you anything but time, I guess if you are bound and determined to just replace the cam. (after you get a cam that is in one piece in it)