What's this dimple on the flywheel for?

[bgbmxer]

What's this dimple on the timing mark of the flywheel mean. My flywheel has two slots for timing one is just a regular slot the other has this dimple. What does it mean. Thought it only bolted on one way. The flywheel is off an 88 and this is a common block but same amount of bolts

[cordes]

When the one with the dimple is in the timing window #1 is at TDC. When the one without it is in the timing window #1 is at BDC.

[bgbmxer]

Figured just making sure just put the clutch on and mating the trans to it as we speak. Thanks

[turismolover22]

When the one with the dimple is in the timing window #1 is at TDC. When the one without it is in the timing window #1 is at BDC.

Cordes is spot on. Good way to make sure you arent 180 degrees out.

[ajakeski]

I love learning.

[GLHS60]

It's impossible for the cam timing to be out 180 degrees.

Thanks
Randy

Cordes is spot on. Good way to make sure you arent 180 degrees out.

[turismolover22]

It's impossible for the cam timing to be out 180 degrees.

Thanks
Randy

False. If you timed your motor with #1 at BDC, thinking that was the TDC mark, would that not make either your crank, or cam, 180 degrees out of time? Technically if everything else is lined up to spec, then only the crank is out of time, but its just in how you look at it.

[raccoon]

^^ yea but the flywheel can only go on one way, aren't 2 holes slightly closer together.

I know from personal experience, if you have the firing order backwards and the distributor 180degrees out, it will run...

[cordes]

^^ yea but the flywheel can only go on one way, aren't 2 holes slightly closer together.

I know from personal experience, if you have the firing order backwards and the distributor 180degrees out, it will run...

Right, but the two hashes on the flywheel are directly across from one another. I think this whole thing is about semantics. If you set the timing with the #1 piston at BDC it will be 180* out relative to where it should be. If someone is talking about the crank position relative to something else then that could be different. After all the crank and the cam don't rotate the same due to the sprocket differences.

[bgbmxer]

i always stick a screwdriver down the hole anyways to verify tdc.

[jonnymopar]

When I did my clutch, I put some bright orange paint in the TDC groove so you can really see it with the timing light. We'll see how long it lasts until it's covered with clutch dust.

[bgbmxer]

When I did my clutch, I put some bright orange paint in the TDC groove so you can really see it with the timing light. We'll see how long it lasts until it's covered with clutch dust.

I use a paint marker and do the same

[GLHS60]

My comment is still true, not false, it's impossible for the cam timing to be out 180 deg, any other #, just not 180. I was just trying to make this point as I often hear the "cam timing is off 180 deg."

In this case, where the flywheel is out 180 deg, the "cam timing" would be out 90 deg.

Thanks
Randy

False. If you timed your motor with #1 at BDC, thinking that was the TDC mark, would that not make either your crank, or cam, 180 degrees out of time? Technically if everything else is lined up to spec, then only the crank is out of time, but its just in how you look at it.

[cordes]

My comment is still true, not false, it's impossible for the cam timing to be out 180 deg, any other #, just not 180. I was just trying to make this point as I often hear the "cam timing is off 180 deg."

In this case, where the flywheel is out 180 deg, the "cam timing" would be out 90 deg.

Thanks
Randy

If the crank was at TDC and you spun the cam so the little dot was facing 180* of the direction it should, then wouldn't the cam be 180* out relative to where it should be when properly setting the timing? Without stating 180* out relative to... I think a case could be made for just about anything.

[GLHS60]

If the crank was at TDC and you spun the cam so the little dot was facing 180* of the direction it should, then wouldn't the cam be 180* out relative to where it should be when properly setting the timing? Without stating 180* out relative to... I think a case could be made for just about anything.

No, then the cam timing would be correct. As the cam turns 1/2 the speed of the crank, it takes 2 turns of the engine to complete one 4 stroke cycle. At every TDC the cam dot is either straight up, or down, depending on which TDC. (TDC compression or TDC exhaust) That's why its impossible for the cam timing to be out 180 Deg. The only case I'm making is the cam timing can not be out 180 deg.
There is no case in disregarding this fact.

Thanks
Randy

[cordes]

No, then the cam timing would be correct. As the cam turns 1/2 the speed of the crank, it takes 2 turns of the engine to complete one 4 stroke cycle. At every TDC the cam dot is either straight up, or down, depending on which TDC. (TDC compression or TDC exhaust) That's why its impossible for the cam timing to be out 180 Deg. The only case I'm making is the cam timing can not be out 180 deg.
There is no case in disregarding this fact.

Thanks
Randy

I know exactly what you are saying. I understand how the cam and crank turn with the belt on the motor. Do you understand what everyone else is saying? I'm thinking that you've misconstrued what everyone else in this thread is talking about or you're trying to prove a point about something which nobody else was discussing for no apparent reason.

ETA: My post previous to this one could have been more clear I guess. Supposing that the crank is at TDC and the belt is not on it because you're going to set the cam timing, if one were to rotate the cam 180* about it's axis from the position it is normally set at and then one puts the belt on and tensions it, then the cam will be 180* out relative solely to the position it should have been set at with reference to nothing else.

[GLHS60]

Sorry if you think I turned this into an argument, but if one person gets the point that the cam timing can not be out 180 deg. then it is worth it to me. Agreed, the dimple is 180 degrees from the TDC mark, but when I hear, 180 deg. out and cam timing, I have to respond.
I have heard over and over that someone thinks their cam timing is out 180 deg, and I like to try and help get the point across that it is impossible to have cam timing out 180 deg.

Thanks
Randy

[cordes]

Sorry if you think I turned this into an argument, but if one person gets the point that the cam timing can not be out 180 deg. then it is worth it to me. Agreed, the dimple is 180 degrees from the TDC mark, but when I hear, 180 deg. out and cam timing, I have to respond.
I have heard over and over that someone thinks their cam timing is out 180 deg, and I like to try and help get the point across that it is impossible to have cam timing out 180 deg.

Thanks
Randy

I didn't think there was ever an argument. I really wasn't sure whether or not you knew what everyone was talking about or if you were making a random point about something. It was the latter. Although confusing, not a big deal really. There could be people in here that don't know that the crank and cam turn at different speeds due to the size of the sprockets.

[GLHS60]

This is the statement that got the ball rolling. If you installed your belt at BDC your cam timing would not be out 180 deg, but 90 deg.
The BDC slot has no meaningful purpose in respect to cam timing. My point wasn't random, it was responding to this inaccurate post.
"Good way to make sure you aren't 180 deg. out". 180 deg. out of what?? The only thing to be concerned with is cam timing, and cam timing can not be out 180 deg.

Thanks
Randy

Cordes is spot on. Good way to make sure you arent 180 degrees out.

[cordes]

This is the statement that got the ball rolling. If you installed your belt at BDC your cam timing would not be out 180 deg, but 90 deg.
The BDC slot has no meaningful purpose in respect to cam timing. My point wasn't random, it was responding to this inaccurate post.
"Good way to make sure you aren't 180 deg. out". 180 deg. out of what?? The only thing to be concerned with is cam timing, and cam timing can not be out 180 deg.

Thanks
Randy

And that's the whole point. I guess I've always assumed that people are referencing the crank from where it should be when in that context. As with most language and writing, context is everything. I think the BDC slot is nice. You know when you're at BDC so only half way around to go!