Just driving down the stree at 45 mph and click, click, click, (backfire noise), (backfire noise), whooch, whooch, (engines stops running).

Get it towed back to the house. Took off the distributor cap to check for movement and none.

What do I think the problem is?? I think the factory timing chain broke. But at 150k miles just moving at 45 mph(not accelerating, decelerating, or carring a load).

This is a 86' 305V8 which is now almost ready to come out, aall I got to do now is unbolt the tranny, exhaust, and motor mounts.

 

Probably not the chain, probably all the teeth stripped off the cam gear. But the end result is tha same.... you have to replace the whole set, no matter which part failed; and you can't change just one part, the whole set has to go.

Don't use the cheap "roller" chain sets. If it costs $20-30, it's not really a roller at all, it just looks like one, it's really bushings. Those wear ("stretch") worse than the stock Link-Belt style. Either put a regular stock-style one back, or bite off on a more expensive real roller one. The deal looks ot be Comp's at Summit, somewhere around $45 IIRC.

Also, be sure you have a new timing cover on hand... they have a nasty habit of wearing a hole in the cover at the bottom on the pass side where the slack of the old chain comes off the gear and hits the cover.

 

Today I had classes. Tomarrow is the day I will get the cover off as well as the engine out. Either way I'm going to check for farther damage(there was a clicking and I think a piston was hitting an open valve). If I get the heads off, I'll see about porting the heads. I painted(inside and outside of vehicle) it with no experience I think I can port/polish it. It's a 1986 Silverado, and I wet sanded and polished the brushed aluminum on the tailgate. I figure that if I get it moderately sanded(400-600grit?) it will be fine enough. What do you think?

 

Don't think the piston was hitting a valve, unless a spring broke and one dropped in (not impossible). SBC motors with stock cams won't have problems with valve-piston interference unlike some motors which will self-destruct if the timing thing breaks.

 

So I drained the oil and "clump". A piece of metal fell into the oil pan(this was yesterday).

Today I got the engine out and the intake and heads off. There was a lot of oil build up. We just got done rebuilding my dad's 302 and it had none of that(always put Havoline in it). This engine had 1 previous owner that often took it to oil change places. Strangly these ports in these heads are much smoother than the ports in the 302 heads. I don't know much about the ident numbers all over this thing. On the back of the block right were the tranny bolts up it's got this: GM5.0LG There are numbers on the heads and intake but I haven't cleaned them up enough to tell. Man, I'll say the flywheel was almost imposible to get off.

More when I get back from eating.:lala:

 

Ok next morning...

I got the balancer, oil pan, and timing cover off....

Lots of metal in the oil pan along with stripped gears on the cam gear, the chain and crankshaft look fine.

Funny thing is that with the balancer on, I could turn the engine over by hand...

 

New:

The valves where hitting the tops of the pistons. If the digital cam waasn't stolen(took it to fishing tourny) then I'd take pics of the marks on the pistons and on the valves. So now it's a toss up of if to change out the valves and get the block vatted or just changing the cam gear and put it back together.

 

So, I take it they didn't hit for some period of time, everything was fine, then suddenly out of the clear blue they began to interfere.

What changed? The valves didn't grow, the rods didn't grow, the block didn't shrink..... that's just a symptom of something else, which if you don't find what it is, it will just do it again when you put it back together.

How many pistons & valves? Just one? if so, it's probably a broken valve spring. More than one, look very closely at yout timing components.

If you'd tell us more about the car's history and what's in it, it would be alot easier to guess what went wrong.

You should be able to turn it over by hand; with no compression, it should take around 30-40 ft-lbs to turn the motor, not at all hard to put on it with a 3/8" ratchet.

 

Yes, every valve hit the pistons, but only 4 intake valves are bent. We took some valve grinding compound to each valve and put the back in and spun them with the drill(seating the valves?). 4 intake valves showed grinding on one side of the valve(thus bent). None of the springs were broke.

The guy that had it before me drove it to church and whatnot. Each time he changed the oil he took it to these local quick oil change places. When me and my dad bought it we cleaned the the top of the springs(in the truck). Other than that it hasn't really been "run". I mean, ya one time I let the radiator get low and it ran hot a little bit. I got it at 62k miles and now it's at 154k.

I don't know, this is the first rebuild it's ever had. My dad said he had the same problem with his 302 about the same milage. : </

The whole time we are taking this engine apart my dad's like "Man this is so much more engine than that junk sitting outside.". "See son, look in that box at my 302's intake valve size. See your valves are just a tad bigger plus you got dually springs. So much more engine."

If I had a digital cam I could show you the marks on the pistons and the marks on the valves. Then I could also show you the places on the 4 bad valves that didn't grind.

Look, the night it stopped running yes, out of the clear blue driving at about 45 it sounded like it took a bite out of something. The engine only ran for about 3-5 seconds after that moment and wouldn't crank again. I did have Z-Max in it, so I guess once it slipped 1 tooth it just kept slipping. When I got the timing cover off I took the chain off without having to turn or loosen anything. That's how loose it was. I think if I had a pic of the bottom of the oil pan you'd say "man that's a lot of metal". Take 8 AA batteries and put them in your hand and make a first. That's about how much metal there is in the bottom of it.

So me and my dad decided to just replace everything that needs replacing(the 4 valves, rings, bearins) and have the block vatted and the plugs redone. Local guy does that for about $88. When we get it back it will look like a new engine block.

Interesting though, I have been running it rather lean and all of the spark plugs where blrown with exception for #6 which had some carbon on it.