Underdrive Pulleys

[_-Night-Shade-_]

I'm just wondering: do aftermarket underdrive pulleys have the little ridge on the lip so that you can see your timing with a light? Also are the stock crank pulleys the same from our I4s and V6s or not?

[marcdh]

As in the 6 ridges that give you your crank sensor input? If so yes.
I believe they're different between Ks and Bs.

[_-Night-Shade-_]

No, you know when you check your timing? The little ridge on the crank pulley lines up with the timing cover to see the degrees BTDC.

[marcdh]

ahhh sorry I get you now, that punched circle. I don't think so. Here's mine:


Easy enough to make your own mark though really.

[_-Night-Shade-_]

It's gotta be in the right spot though, how do you know where that spot is? I'm just wondering if you lose the ability to check your ignition timing when you put on a UD pulley. Also anyone got an answer to my 2nd question?

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Anyone?

[umcamara]

It's gotta be in the right spot though, how do you know where that spot is? I'm just wondering if you lose the ability to check your ignition timing when you put on a UD pulley. Also anyone got an answer to my 2nd question?

There wouldn't be a RIGHT spot. Mark it on the pulley, then install the pulley with your newly acquired mark. it's just a circular pulley right? There's no reason why it has to be on any particular part of the circumference if the pulley is off the car.

Then set your TDC or whatever floats your boat...

Right?

[onlytrueromeo]

I would not recommend a UDP unless you balance your rotating assembly upon a full rebuild.

[_-Night-Shade-_]

It's gotta be in the right spot though, how do you know where that spot is? I'm just wondering if you lose the ability to check your ignition timing when you put on a UD pulley. Also anyone got an answer to my 2nd question?

There wouldn't be a RIGHT spot. Mark it on the pulley, then install the pulley with your newly acquired mark. it's just a circular pulley right? There's no reason why it has to be on any particular part of the circumference if the pulley is off the car.

Then set your TDC or whatever floats your boat...

Right?

Ummm no... because when you shine the timing light it strobes on and off and that's why the mark appears in a particular spot. If you just make that mark wherever on the pulley, your timing might not seem to be what it really is because that mark will be off.

[umcamara]

Okay... I realize how a timing light works. The point is, how do you think that mark would be made if it was done by the manuafacturer, or if we're talking about the OEM pulley? It's just placed anywhere on the edge of the pulley.

It's when you put the pulley on that makes the difference, you put it on so the mark you make mates up to the mark on the timing cover when the piston is at TDC. How does this not make sense??

[_-Night-Shade-_]

Okay... I realize how a timing light works. The point is, how do you think that mark would be made if it was done by the manuafacturer, or if we're talking about the OEM pulley? It's just placed anywhere on the edge of the pulley.

It's when you put the pulley on that makes the difference, you put it on so the mark you make mates up to the mark on the timing cover when the piston is at TDC. How does this not make sense??

Ahem. How are you not understanding this? Do you see the little gap on the inside hole of pulley in the pic that marcdh posted? That can only line up and bolt on one way to the crank. That's why it spins together with the crank. SO THEREFORE there is only one spot on the pulley that would indicate correct timing. Make sense now?

[umcamara]

Okay... now I'll counter with line up the keyways in the UDP and the OEM pulley, and mark the UDP.

May bad, I completely forgot about the keyway machined into the pulley.

[_-Night-Shade-_]

That's okay, no worries. That's the thing: if there's no other way then you'd need some precise measuring tools to mark it right and such. I guess these aftermarket UDPs aren't car-specific or something...

No one about the I4s and V6s still???

[onlytrueromeo]

I think they are different - if you want an I4 get one for mx3/protege/miata, if you want one for a v6 get one for a mx3/probe/mx6.

Either way, I think UDP's are not worth the money, they give you like 1/2hp and have a possibility of destroying your engine if you like to rev high. They are "bling: only, and why have a blue or purple pully in there w/o having colored cam gears, alternator casing, valve covers, intake, etc.

I would take that money and save it for something different...like getting better brake pads, or stainless steel brake lines, or buying an extra set of VC's so you can get them powder coated.

[marcdh]

Indeed! ^ I already have a UDP and I don't even use it on my KLZE. Fidanza makes things revvy enough for me. Maybe if I was getting a full balanced high revving setup, but nah... I like it on my k8, but that's because I don't care about that engine.

Making the timing mark isn't that hard IMO though.