Guest Anonymous Posted October 9, 2003 Share Posted October 9, 2003 Well, it was bound to happen. I lost a timing chain. It really is a very sad story involving a throttle pedal getting stuck on a floor mat while shifting, redlining the engine (I mean really redlining the engine ) for about 2 seconds while I fumbled for the ignition key. I crank the engine over and the cam doesn't turn My question is, do the valves, when fully open interfere with the plane of the piston when at TDC? If so, it looks like a valve job is in my future (sounds expensive especially when considering 12 new valves) If not then perhaps just a new timing chain and gears. I would just like to know what to expect when I crack her open tomorrow night. Thanks in advance -frozen Quote Link to comment Share on other sites More sharing options...
Guest oldZguy Posted October 9, 2003 Share Posted October 9, 2003 Is the chain still on the cam gear? Guess I'm trying to see exactly what you are seeing. If the chain broke it probably be in the front cover causing all kinds of problems, if the chain isn't broken does it move when you spin the engine and not the cam or does the chain not move? If the chain is there and not moving then you probably sheared the key holding the gear to the crank. If you did hit any valves it would probably only be a couple of them, so you shouldn't have to be looking at replacing all 12. Quote Link to comment Share on other sites More sharing options...
Guest smoov280zx Posted October 9, 2003 Share Posted October 9, 2003 I dont have anything to add to help, just wanted to say "THROW THE DAMN FLOORMAT OUT". The same thing happend to me about 4 months after i bought my 83, but the chain held. Those thick zx mats are awful about getting behind the pedals. I tossed mine and just accepted the hole in my carpet from my heel in front of the clutch. Probably get the carpet shop to sew a special pad in when i get the carpet replaced. Mitch Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 9, 2003 Share Posted October 9, 2003 I couldn't see the chain, I just popped the oil fill cap off and watched as the cam didn't turn as I turned the engine over. I will be pulling the engine out and apart tonight and so I should be able to find out what damage was done then. Let me tell ya what smoov280zx, that floor mat is not worth it. The thing is that I just swapped that engine in. It had a lot less miles than the old one, and was in better shape. I slammed a new timing chain, gears, guides, tensioner, etc just last week before I did the swap. This drive was the final test drive before I declared the project complete. ALL RUINED BY A STUPID FLOOR MAT. Who would have thought, after carefully ensuring that the mechanical aspect of a vehicle was in good shape, it could all be ruined by a floor mat. I guess its a good thing that these cars are pretty easy to work on -frozen Quote Link to comment Share on other sites More sharing options...
David K Posted October 9, 2003 Share Posted October 9, 2003 Are you sure your cam gear didnt come off? A timing chain coming apart, thats rare, Good luck. Quote Link to comment Share on other sites More sharing options...
Guest oldZguy Posted October 9, 2003 Share Posted October 9, 2003 I would for sure pull the valve cover off before I pulled the engine! You may just have a broken cam, stranger things have happened. Quote Link to comment Share on other sites More sharing options...
Guest smoov280zx Posted October 9, 2003 Share Posted October 9, 2003 man, thats definitely a bummer. (happening on your final test) Good luck. Mitch Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 10, 2003 Share Posted October 10, 2003 Well, I pulled the engine last night, put it on the engine stand and pulled the valve cover. Good call David, the cam gear had somehow came off part way letting the dowl on the cam slip out of the hole on the gear. The gear teeth and chain looked pretty good. I'm not really sure how the gear came part way off, I know I torqued the bolt that holds the gear onto the cam pretty good. The 64 doller question is whether or not any of the valves contacted a piston. Any thoughts? My plan is to check compression on all the cylinders, and if any of them don't have compression I guess I will have to pull the head. Is there a better way to determine if the valves have hit the pistons? I appreciate the comments, keep em rolling in -frozen Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 10, 2003 Share Posted October 10, 2003 Check the valve lash. Should be way outta whack if the valves are bent. I suppose that if they just barely hit then they could still be pretty close, but if pistons and valves smacked hard they should be pretty easy to tell. Jon Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 10, 2003 Share Posted October 10, 2003 Also you could put a cyl at TDC then use an air gun in the spark plug hole. If the air comes right out the intake or exhaust port, that would be a pretty good sign. Jon Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 12, 2003 Share Posted October 12, 2003 Well, after putting the timing gear back on, and noticing that I didn't have compression, I pulled the head off and discovered that one valve in each cyl. smacked the piston. A couple of the valves were so bad that small birds could get past the valve when closed. There is a small indent at the edge of each piston face where the valve hit it. It doesn't look to bad, so maybe my pistons will be reusable. It looks like I will need new valves, any idea where a good source is for valves? I have a 78 L28 engine that died due to low oil. I am not sure what part of the engine died, but it seized up, so I would imagine that its a lower end issue. I could put the 78 head on the 76 block, using the 78 manifolds. The only problem with that is the 78 engine probably has 120k miles on it min. I would hate to put a worn out head on an engine. Any idea what it should cost to replace all the valves? Will the little ding along the edge of my piston face cause any problems? Thanks again for your advice -frozen Quote Link to comment Share on other sites More sharing options...
Guest oldZguy Posted October 12, 2003 Share Posted October 12, 2003 Pistons should be OK. The manifolds from the 260 will fit the 280 head. Considering that in effect you will have to have a complete valve job done on the 260 head to put the new valves in, along with the cost of the replacement valves, I would give serious consideration to doing a valve job on the 280 head and put it on to save money. It may be a better head to go with performance wise depending upon what head you have on and what you would be going to... Quote Link to comment Share on other sites More sharing options...
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