Thread: My engines timing marks...Are these right?

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Hey fellas I was monkeying around last night on my chevy 400 when I realized that my timing marks were off. What I mean is that TDC is actually at 13 BTDC. I verified this by bringing the engine up on it's compression stroke and then turning the engine back COUNTERCLOCKWISE, I then inserted a fat drill bit that fit in the #1 cylinder perfectly. Finally I turned the engine back by hand CLOCKWISE and the engine stopped turning over and the damper mark lined up with 13 degrees BTDC on my timing tab. Is this the true TDC mark? I also have a MSD timing tape on my stock 400 8" damper and I set my timing this way.
12 degrees intial w/ the vacumm advance and carb port plugged and then 36 degrees total with the advance hooked up again at 3000 RPM. The engine runs good not much vibration at all, idles good at 1100 RPM and when I put it into gear about 750 RPM. So in conclusion does it really matter what TDC falls on as long as you know where it actually truly is? and is what I explained correct? Also my Damper looks to be in good condition so I don't think think it slipped, but I do know that after 1970 dampers on SBC actually moved the TDC mark to 8 or 9 degrees BTDC. Anybody have any thoughts.

Originally posted by onemangang
Hey fellas I was monkeying around last night on my chevy 400 when I realized that my timing marks were off. What I mean is that TDC is actually at 13 BTDC. I verified this by bringing the engine up on it's compression stroke and then turning the engine back COUNTERCLOCKWISE, I then inserted a fat drill bit that fit in the #1 cylinder perfectly. Finally I turned the engine back by hand CLOCKWISE and the engine stopped turning over and the damper mark lined up with 13 degrees BTDC on my timing tab. Is this the true TDC mark? I also have a MSD timing tape on my stock 400 8" damper and I set my timing this way.
12 degrees intial w/ the vacumm advance and carb port plugged and then 36 degrees total with the advance hooked up again at 3000 RPM. The engine runs good not much vibration at all, idles good at 1100 RPM and when I put it into gear about 750 RPM. So in conclusion does it really matter what TDC falls on as long as you know where it actually truly is? and is what I explained correct? Also my Damper looks to be in good condition so I don't think think it slipped, but I do know that after 1970 dampers on SBC actually moved the TDC mark to 8 or 9 degrees BTDC. Anybody have any thoughts.

if you had true TDC with your drill bit then it should have been on 0 degrees. i think your timing is right but the way you checked TDC is wrong. you need to stop the piston before it gets to the top turning the motor both ways, mark the damper and split the dif. the tool in the plug hole need to be stationary while you do this.

I guess that doesn't make much sense to me. I was always told that TDC is when the Piston makes it to the top of the cylinder and you are able to stop it with a tool or something, I actually bought a tool for this from Jegs...It didn't screw in in the damn hole on the #1 cylinder though so that's why I stuck the smooth end of the drill bit in there. So what your saying is that my mark is just a little off? because If I were to split the difference my TDC mark it would still not line up with the 0 degree mark on the timing tab. I think I have the wrong tab but it still shouldn't matter because once you find the true TDC no matter what the tab says you should be able to set the timing accuratley as long as your damper is degreed correct?

Originally posted by onemangang
I guess that doesn't make much sense to me. I was always told that TDC is when the Piston makes it to the top of the cylinder and you are able to stop it with a tool or something, I actually bought a tool for this from Jegs...It didn't screw in in the damn hole on the #1 cylinder though so that's why I stuck the smooth end of the drill bit in there. So what your saying is that my mark is just a little off? because If I were to split the difference my TDC mark it would still not line up with the 0 degree mark on the timing tab. I think I have the wrong tab but it still shouldn't matter because once you find the true TDC no matter what the tab says you should be able to set the timing accuratley as long as your damper is degreed correct?

you cant set the timing right until you know where TDC is. why wouldn't the tool work? screw something into the #1 plug hole, long enough to hit the piston, needs to be stationary. turn the motor clockwise until it hits your tool. mark the damper in line with the timing tab. turn the motor counterclockwise until it hits the tool then mark the damper at the timing tab. now you have 2 marks on your damper. split the dif. between the marks and that's you true TDC. wish I was a better teacher.

Originally posted by techinspector1
Sorry Mike, I was typing my answer and wasn't fast enough.

no problem, im a better do'er than teacher i think

I dont think your so bad a teacher...... I understood it.

Originally posted by Smokin65
I dont think your so bad a teacher...... I understood it.

thanks, i needed that.

I got it thanks guys, everything does line up with the damper. Now I got to fix the damn dizzy hold down which is stripped.

Originally posted by onemangang
I got it thanks guys, everything does line up with the damper. Now I got to fix the damn dizzy hold down which is stripped.

sounds like a walk in the park.