measuring cam lobes

[highflyer]

If one takes a new cam never run..measures the lobes from the base to the top of the lobe at lifter contact point should they all be the same....yes ...but how much of a tolerance is acceptable since grinding is just about the most accurate way of machining how much do manufacturers allow... ?????j

 

[TrailBeast]

I probably don't know the answer, but are you asking what variance in specs from any given manufacturer is acceptable in the industry?

If that is the question I would think it's a pretty tight tolerance.

 

[OldmanRick]

I probably don't know the answer, but are you asking what variance in specs from any given manufacturer is acceptable in the industry?

If that is the question I would think it's a pretty tight tolerance.

I don't know the answer either, but I agree with TrailBeast. Then again, their acceptable tolerance's and what gets out the door, could be two different things.

 

[Hebrews10:26]

Stones wearing out was the rumor for varied lobes.

 

[RustyRatRod]

Cams cannot be measured accurately at all by that method. If you want something accurate by "backyard" standards, you need to cut some V blocks from wood, set the cam on them on the journals, put a dial indicator on the base circle of the lobes and gently rotate the cam in the blocks.

Cam grinders can and do put lobes wherever the hell they want to on the core. This is why you cannot just mic a lobe from base circle to apex and get it right. They'll likely come up different every time.

 

[frosty_the_punk]

Agreed, and even with the dial indicator you're going to be looking at the small dial not the big one.

be sure to let us know what you find. I will be surprised if there's any measurable variance in actual size between lobes though.

 

[highflyer]

ok doing it today..

 

[highflyer]

ok got it done..to anyone interested this cam I checked is a 274h comp cam that has few miles on it..like a few hundred that's all..i set it up in my mill using mitutoyo precision v blocks shimmed so the center line was parallel and straight with the table travel ...found tdc and set it at 0 on the dro...all the lobes were within .002 of each other ..pretty accurate I think..got my questions answered...j

 

[67Dart273]

I don't know how you'd get more accurate than that, LOL

I've got an unknown cam in my car. I'd love to know "what it is" but last time I pulled it out of the 360 and stuck it into the 318, I was in a hurry.

 

[pishta]

You also have to measure the edge of the lobe as its cut on a crown to rotate the lifter. Also cams will have different lifts for intake and exhaust and don't assume the lobes are ieieieie, they are eeiiiieeeeiiiiee... iirc..lol. the lobe top doesn't vary much, its the base circle that drops for more lift.