73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: Unofficial on August 18, 2009, 01:59:11 pm
-
Lately, I've been trying to diagnose some problems with my '87 TBI 350. My friend gave me a harmonic balancer that would work on my motor, because I suspected that mine had slipped on the rubber ring. I was right, because I compared the marks, and they were different. I get the new one on, unpluged the EST wire, and got a timing light hooked up. I had it a little advanced, and the idle sounded good, but when I took it for a ride, it was terrible. When I came back to adjust it, I tried to take it to 0 degrees. It WILL NOT go to 0 degrees at TDC. It won't run, it will die before it gets there. So my friend and I popped the cap off the rotor, and looked at where it was pointing at TDC, and redid the spark plug wires. It still won't run. So we turned the motor another 360 degrees to TDC again, and redid it. Still not right. I'm starting to think that it's something internal. Can anyone help me diagnose this? If more information is needed, I can provide it. I just want to try and figure this out without having to take it in...
-
You compared the marks and they were different. How much different? When I did mine, I tried 2 different balancers, one with the timing mark @ 12:00 the other at 2:00. It will depend on where your timing tab is aligned on the timing cover.
Check TDC @ number 1 cylinder, then go from there
-
I had to set my timing at @10 degrees BTdC. It sounds like you're going the wrong way when you move your distributor.
-
I had to set my timing at @10 degrees BTdC. It sounds like you're going the wrong way when you move your distributor.
No, I had a friend holding the timing light while I turned the distributor. It would run when it was advanced quite a bit, but it wouldn't run at 0 degrees. Shouldn't it be capable of doing that?
-
Both could be slipping, or you put one on that was slipping.
You best bet is to get a piston stop. Put the piston stop in the #1 hole crank it over till it stops, compare that to the pointer and see how far they are off.
If you want to find definite TDC with a stop, wrap tape around the balancer and mark where it is at TDC then turn it backwards with the stop still in it and mark it where TDC is again. In the center of those 2 marks will be TDC. If your timing marks is nowhere near it, you know it slipped.
-
As usual, good advice from CaptK.
My take on the 0 degrees- the ignition has to occur at the right time, and timing that's too much retarded will cause the detonation to take place too late. So the timing has to be advanced to allow the ignition to occur before the piston gets out of its power band. There's a really small amt of time between ignition firing and explosion in the cylinder- enough to allow the piston to move out of the power band and get poor detonation if the timing is retarded too much, especially when the rpms are higher. ( Now don't forget- I'm no mechanic) I always say the real mechs will be along in a minute..
-
Both could be slipping, or you put one on that was slipping.
You best bet is to get a piston stop. Put the piston stop in the #1 hole crank it over till it stops, compare that to the pointer and see how far they are off.
If you want to find definite TDC with a stop, wrap tape around the balancer and mark where it is at TDC then turn it backwards with the stop still in it and mark it where TDC is again. In the center of those 2 marks will be TDC. If your timing marks is nowhere near it, you know it slipped.
You might want to add that you would crank this over slowly by hand not using the starter.
These engines are easy enough to see or stick a coat hanger on the piston while an assistant rotates the crankshaft to find TDC for your pointer.
-
Your right, I tend leave out certain steps that I take for granted.
-
You might want to add that you would crank this over slowly by hand not using the starter.
LOL, I would hope that someone wouldn't install a piston stop and then crank the engine over with the starter. :o But, then again, you never know. ::)
-
Don't worry, I'm not that careless. I'm getting it fixed for free tomorrow at a shop, so I'll just let them take care of it and report back here with the results. Thanks for the suggestions guys. I'll be sure to try them if this doesn't work out with the shop.