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Why the positive piston stop?

How to Degree a Cam

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Hey guys maybe someone can help me out dialing in my new kelford cams for my Evo IV. I don't get the point in turning the engine around a positive piston stop after having set true-TDC using the centerline method. Isn't that redundant? Or what important part of the piston stop do i miss? I've watched the cam degreeing course several times now and still don't get it.

Thanks in advance

Marius

You need the positive piston stop to find the same angle (piston position) before and after the true TDC, so you can determine the true TDC. How do you do the "centerline method" without dead-stopping he piston?

If you know stock center line angle of intake and exhaust camshafts you can install aftermarket camshafts using those figures as basline to start from and adjust new camshafts accordingly providing that cams are cemetryc. I checked this method once when a guy asked me to double-check his new camshafts done with dial indicator- I calculated how the new cams should be positioned and the actual position exactly matched my theoretical calculation...

Evo IV stock is 105 intake and 109 exhaust so knowing recommend center lines of new camshafts you can easily adjust their position by advancing or retarding them.

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Lets say your new camshafts recommended center lines are 109 for intake and 113 for exhaust. In that case you need to advance intake camshaft 2 little marks in adjustable intake sprocket (2 marks = 4 degrees on crankshaft since 109-105=4) and you need to retard exhaust camshaft 2 little marks in adjustable sprocket (2 marks = 4 degrees on crankshaft since 113-109=4).

You may be conflating things a little?

The piston stop is used to give a fixed height from TDC that will be an equal number of degrees from TDC BTDC and ATDC and the centreline of those is the true TDC.

If you have used another method, such as a DTI down the spark plug hole, it isn't needed. They're just different ways of doing the same thing.

Maybe I didn't get what Marius was asking but I thought he wants to know how to dial in his new camshafts without having to physically find true TDC?

Thanks for all the answers till here:)

To specify my question further... When i've found true TDC using my dial gauge moving the crankshaft in both directions from the point of highest travel (where i've zero'd it) for example 1mm, divided my measured crankshaft degrees from both sides by two, why do i have to do that procedure again with the positive piston stop basically doing the same thing? As i've found true-TDC using my dial guage i feel like thats redundant or is it just another technique to find true-TDC using the piston stop? I still couldn't figure it out watching the course once again.

@georg thanks for the information you posted my car is actually an evo 4 using a built evo 7 block and head i've built by myself and i didn't start degreeing my cams i am still at the point of preparing for it and figure everything out until i feel confident to not make a 3 day job out of it👍🏼

Thanks to all of you didn't expect even a single person to reply as i know other forums where people just come to get rid of their frustration and don't give valueable answers. :D

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