Timing Chain Replace

Ok, so I’m getting a leak down tester from Autozone, and I’m going to see if the valves are bent open. I have the valve cover off, and I can rotate the cams so that the valves are “closed.” Do I just put the piston at TDC and connect the tester to my air compressor and the spark plug hole? What am I looking for?

Couldn’t get a leak down tester (they said they can’t find one???)

I have the valve cover off. I put the first cylinder at TDC, made sure the valves were in ?closed? position, and blew through a tube into the spark plug hole. I could hear an audible hissing, and it did not get any harder to blow. This seemed to me to indicate that I have no compression in that cylinder, which means my valves are shot. Is that correct?

Yes. Timing chain replacement is useless on this engine.

I must agree with Caddyman and recommend finding a reputable shop to install a low mileage salvage engine if valves are bent. Those engines often become bottomless pits when there is a timing chain failure. It would be worthwhile to check for compression loss at this point and if lucky replace the chain but if valves are bent the salvage engine is a very good option.

Yuo do not need the piston at TDC for the test you’re performing. You’r enot checking to see how much compression the cylinder provides, as in a traditional compression test, you’re only checking to see if the cylinder will hold air. You can do this with the piston at any point in its cycle as long as both valves are closed. A cylinder with a bent valve stem will not hold any air pressure at all.

I’ve never tried OK4450’s “blow in the tube” test, but even that should work. If you can blow into the tube without the resistance of backpressure with both cam lobes NOT pushing on the rockers, then you probably have a bent stem. But, can a smoker (or an old fart like me) blow with that much force remains to be seen…

It makes me sick reading this cause my 02 grand am just broke the timing chain 2 days ago we bought the car for $500 about 6 months ago and this is this 1st real problem we’ve had so I’m just gonna pull the motor and keep it for parts lol thanks

Use of a car for less than $100/month “investment” is a bargain, and better than most well-used cars.

1 Like

I was thinking the same thing. If I paid $500 for a car and it broke down after 6 months, I’d have the salvage yard come tow it away and feel lucky if they’d give me $50 for the car.

1 Like

If you’re going to pull the motor anyway, why not replace the timing chain, and put it back in? If the compression is good, no engine knocking, pretty good chance you’d be good to go for a lot more miles.