Freshen Up on a 78' GP LJ - Or, What to Do When the TIming Chain goes "Pop"

[PartsPile]

So, I frequently joked with my friends that my 78' Grand Prix only has a 5 digit odometer, showing what faith Detroit had in the Disco Era that their cars would ever see 100K miles.

Well, because the universe is cruel, the other week when I went out to start the car, I noticed that the starter seemed to be going around twice as fast as it should, and the motor was making absolutely no attempt to fire...

Uh oh.

Removed a valve cover and to my expectations, nothing moved under there when you hit the key. Adios timing chain... at 99,480 miles..... but at least you did it in the driveway, not the freeway.

Well, considering this was a one-owner mostly-garaged car when I bought it a few years back. It's never been restored, and a lot of the little stuff that's broken over the years, or worn, has never been replaced because of good ol fashioned "I'll get to that when there's time-itis" Well, there's time now. And, since the car is 99% original (only change I made was tossing the useless Sears tape deck for an MP3 player) I'm going to keep it as stock as I can on a relatively cheap resto.

First step, getting that motor out. (301 - 4B, stock) Fortunately, the only hard part was having to torch off the Y-pipe because 38 year old bolts on exhaust headers are just NOT gonna turn. And whaddaya know? Still a little of that factory blue hangin' on....

Keep you posted as this goes along, as I'm sure when it's time to go back in, there will be one vac line I forgot to label, and I'll have to swallow my pride and come here for the answer of where the sucker goes.

 

[theoldsone]

Paint the greasy little pig. Now that it's out might as well.

 

[pontiacgp]

I don't think it's the timing chain, I believe that engine has a nylon cam gear which is known to wear and break...

 

[pontiacgp]

and for the 5 digit odometer, back then we were taught math in school and never had a problem to add the 1, to the mileage of the car when the odometer turned over...

 

[shotgun]

Lock/block the flywheel so it cannot turn.

Then put a bar on the crank and see if it moves or turns.

My fear is the crank snapped, which is a known issue with 301. Been there,done that!

I got pictures of mine from years ago, there was a void/porous area inside one of the main that let loose.

Hate to see you clean it up and repair it only to find the crank went!!

Great time to swap in a 326-455.

 

[Bonnewagon]

You pulled the motor for a timing chain? I LOVE THIS GUY! So while it is out you might a well do the oil pump, water pump, seals, etc, power wash it and paint it. The 301 is perfect for our size cars, and I love mine. Note to Steve: GM hasn't used the plastic toothed timing gear since the 60's and the 301 never used it.

 

[PartsPile]

Yeah, I forgot to mention, the motor had a little bit of knock in it and while it didn't leak externally, it was using a bit of oil, probably from leak-down or rings.

So, I was going to do the whole thing anyway at some point in the future, it just came a bit quicker than I was hoping for. Doing the tear-down now to see if it's benign enough damage to rebuild

 

[GP403]

if nothing else you've got an empty hole waiting for a Poncho 350 or 400 to just drop in there. I think. More or less.

 

[shotgun]

The nylon gears made it to atleast 1970, lost the 350 in my LeMans Sport that way.

I am one of the few perverts that played with the 301.

The key thing with them is restraint and DO NOT build it like a small block chebby./

Enjoy the link: http://www.hotrod.com/cars/featured/hppp-0903-1985-pontiac-t1000/

 

[PartsPile]

Well, started tearing her down. Everything was routine until the moment of truth: time to take off the front cover.


I was a bit panicked there. When I popped the front cover off, the first thing that fell out was a chunk of irregular and broken cast iron... But, turns out that was a piece off the harmonic balancer. As you can see the gear on the crank end is in pieces and the chain snapped fairly clean. Not sure what went first in there, the gear, the chain, or the balancer, but once one of them got out of place, well, there's only enough room for ONE moving part at a time... you know the rest. Kinetic energy laughs at your puny Earth-materials!



Bright side, nothing damaged that's obvious, no cracks in the cover, crank, cam gear, etc. No bent pushrods, no cracked pistons, no damaged valve rims, maybe only the smallest little silvery nick in the top of the dome on one of them, (#8) but that could've been from last year when it broke an exhaust valve spring.


Next stop.. engine shop for a crack test and, assuming it passes, hot-tanking/machining. You can feel the out-of-round with a bare finger, it'll probably take the usual .030 to true up.