I'm trying to find TDC on my car (yes, still... I only get to work on my car once a week, if even that). I've got my piston stop and degree wheel all ready to go. I'm going to use the method where you hit the stop from one side, then rotate all the way around and hit it from the other, and then find the halfway points between the two spots. And, lacking the proper tools to do it otherwise, I've decided to rotate the crank from the flexplate bolts.

My only other concern is: no matter how hard I try to keep it from happening, the crank tends to want to only move in "jerk increments". That is, it's nearly impossible to move it *slowly*, as it's either moving or it isn't. Wouldn't bother me, except that I'm trying to intentially stop a piston top with a bolt (the piston stop). I've rebuilt this engine with hyperkineutic pistons, and I've heard those pistons described as "brittle" when compared to forged or cast.

Granted, I'm not putting a tremendous amount of torque into the crank (I'm only rotating with a standard 15mm wrench), but I'd really hate to punch a hole in one of my pistons because the crank "jumps" and slams the piston into the stop.

Should I be concerned about this, or would that be pretty tough to do?

Thanks

 

Take all the spark plugs out. Make sure you remove the rockers for the cylinder that the piston stop is in. If not then the valves will hit the piston stop and either damage the piston stop or possibly bend a valve.

Most piston stops are made of brass. They will bend or break long before you hurt the piston unless you crank the engine over with the starter.

 

Do what Stephen 87 IROC said, if it's still (jerky) there is a special wrench that that you could borrow or buy that grabs the teeth of the ring gear, that makes it really easy to turn the engine from underneath, if you can't borrow one of those your regular wrench will work a lot better if you put a cheater bar on it (a long piece of pipe) that will give you a lot more leverage and you will be able to turn the engine smoother without the jerking, but it might loosen the screw when you turn it backwards? Just turn it slowly and you won't have to worry about the stop hurting the piston. I wish Chevy had put a big *** screw on the front of the crank pulley like Chrysler did with there engines, that makes it really easy to turn the engine over with a breaker bar, even with the plugs in it!!

 

I know they aren't exactly cheap, but those nifty crankshaft truning sockets that slide over the crank snout are really nice to have, and when used with a long breaker bar that will give the the advantage of a lever, you should be able to turn it over nice and smooth (or at least close to it!) I just finished assembling the rest of my engine, and it is so nice to have that socket. I have also found that some socket to fit a few other applications, therefore I keep it at the shop!

 

Stephen 87 IROC: THANK YOU for reminding me to loosen the rocker arms... you probably just saved me from having to pull the head for a bent valve!

As far as how to turn the crank smoothly... I did get a link on an earlier post of mine to that tool that you put on the harmonic balancer. Problem was, I didn't want to wait all week on shipping because I've got all of this week off to work on the car and I didn't want to waste it waiting on the tool. So I called around at some local shops and somebody gave me the number to a local Snap-On rep. He just suggested that I remove the inspection cover and rotate the crank using the torque-converter bolts (duh... why didn't I think of that? ). I just used a 15mm ratcheting wrench and then put the handle of my brakeover bar in the open end of the wrench, which allowed me to have more lever arm.

Anyway, I just finished up finding TDC (turned out that the balancer was only ~2.25 degrees off), and I don't think I broke any pistons .

Thanks for the replies.

 

Glad to hear it worked out. Last year when I put my engine together, the timing marks were out 8*. I just got my short block back together and rechecked the timing marks with a degree wheel and a piston stop (no heads on yet). The timing marks are only out 2* now. It pays to have an adjustable pointer. Move the pointer to point at the 0* line and it's done.

Now you'll know the exact ignition timing. A few degrees out doesn't sound like much but can make a big difference in the amount of performance an engine can make.