My engines timing marks...Are these right?
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.
Re: My engines timing marks...Are these right?
Quote:
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. :cool:
