WTF! how do i tell if my LT4 hotcam is legit?
02-10-2008, 01:05 AM
#25
I sold my Hotcam kit on here not too long ago and I had pics up on it, maybe you could search for it, but ti definitely had a yellow stripe on it. Sorry for the luck and the cam is definitely much larger than the stocker.
02-10-2008, 12:08 PM
#27
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The most accurate way to measure true lobe lift is to measure the cam base circle dimension, cam lobe lift dimension, subtract base circle# from the lift# = true lobe lift, X 1.6 for hotcam RR's or 1.5 for stock rockers = valve lift. If you dont get .525 when using the 1.6 multiplier, then it not a hotcam.
Another alternative would be chuck the cam in a lathe and use a dial indicator to measure lift, zero the dial on the cam base circle and slowly rotate the cam by hand.
Another alternative would be chuck the cam in a lathe and use a dial indicator to measure lift, zero the dial on the cam base circle and slowly rotate the cam by hand.
02-10-2008, 12:11 PM
#28
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hey guys so i was thinking if the hot cam's part number is 24502586
and my cam's p/n is 586FM67 doesn't that prove it's a genuine hot cam?
because dosesn't the same go for the "847" whose part number is 12370847
ehh this crap is confusing
and my cam's p/n is 586FM67 doesn't that prove it's a genuine hot cam?
because dosesn't the same go for the "847" whose part number is 12370847
ehh this crap is confusing
02-10-2008, 02:43 PM
#30
I would not give up on the cam yet. It might very well be a hot cam. Like was said above one way to tell is put a dial indicator on it. Now if you think about it the Hot Cam should have less lobe showing on the dial indicator than a stock cam. The back side of the lobe is ground away putting the base closer to the center of the cam giving more lift. Just think if the lobe was a circle you would have no lift. However the dial indicator would have a big number.
02-10-2008, 03:19 PM
#31
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Its hard to tell the color of that once was painted ring, however I would think the lobes would measure around 1.460 on a 12370847 cam. Only way to know what the exact specs of that cam are would be to run it out in an engine with the ratio of the rocker arm.
Maybe the camshaft is really old and the paint has somewhat baked away, perhaps you are reaching, one thing for sure it is a performance camshaft of some sort.
Maybe you got a ZZ4 roller camshaft. But then you would have the same PN as I gave.
That band looks really burnt but if you got the numbers what the heck are you worried about?
The one that I posted a photo of was a 071FM15 (ZZ4) part number 10185071 and has an advertised lift of .474 that really runs out @ .477 (Intake). So maybe that white band was once yellow, but your part number theroy seems to hold water.
Maybe the camshaft is really old and the paint has somewhat baked away, perhaps you are reaching, one thing for sure it is a performance camshaft of some sort.
Maybe you got a ZZ4 roller camshaft. But then you would have the same PN as I gave.
That band looks really burnt but if you got the numbers what the heck are you worried about?
The one that I posted a photo of was a 071FM15 (ZZ4) part number 10185071 and has an advertised lift of .474 that really runs out @ .477 (Intake). So maybe that white band was once yellow, but your part number theroy seems to hold water.
Last edited by Checkmate007; 02-10-2008 at 03:47 PM.
02-10-2008, 03:49 PM
#32
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alright guys here's what i did to figure out the lift:
I measured the height of the lobe (top of lobe to bottom of base) then i measured the base circle and subtracted the two numbers and then i multiplied that number by my rocker ratio 1.6 to come up with .5248 and .524 the second time, throw in some slight mechanical and human error of .0001-.001 or so.....then doesn't this calculation prove its a genuine hotcam?
i then proceeded to do the same with the stock cam measured lobe height and base with subtracted and multiplied by 1.5 (factory rocker) to come up with .444 -.447 lift (some lobes are more worn than others.. 100k cam)
then for shvts and giggles i used the stock calculation and threw in 1.6 instead of 1.5 to come up with about .477 lift, which is what the corvette's came with i believe (could be wrong)
SOOOO what do you guys think ?
I measured the height of the lobe (top of lobe to bottom of base) then i measured the base circle and subtracted the two numbers and then i multiplied that number by my rocker ratio 1.6 to come up with .5248 and .524 the second time, throw in some slight mechanical and human error of .0001-.001 or so.....then doesn't this calculation prove its a genuine hotcam?
i then proceeded to do the same with the stock cam measured lobe height and base with subtracted and multiplied by 1.5 (factory rocker) to come up with .444 -.447 lift (some lobes are more worn than others.. 100k cam)
then for shvts and giggles i used the stock calculation and threw in 1.6 instead of 1.5 to come up with about .477 lift, which is what the corvette's came with i believe (could be wrong)
SOOOO what do you guys think ?
02-10-2008, 04:05 PM
#33
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there should be a code 845 on the end of the cam, unless it was ground by crane. I bought a cam here a while back what I was told was an lt4 hot cam from a member, i went to a dealership in winchedon ma, and they told me it was not a hot cam part 845, but it was actually an 846. So I smiled returned the lt4 valve springs I'd purchased in exchanged for some ls6's. It always sucks to feel taken advantage of, but if the seller is trying to make it right (instead of fleeing the counrty, and wouldn't blame him you seem quite displeased) I'm sure it will work out, bring the cam to a GM performance parts dealer, they will be able to track down exactly what cam it is and the maker whether it is them or not. Good luck
02-10-2008, 04:19 PM
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alright guys here's what i did to figure out the lift:
I measured the height of the lobe (top of lobe to bottom of base) then i measured the base circle and subtracted the two numbers and then i multiplied that number by my rocker ratio 1.6 to come up with .5248 and .524 the second time, throw in some slight mechanical and human error of .0001-.001 or so.....then doesn't this calculation prove its a genuine hotcam?
i then proceeded to do the same with the stock cam measured lobe height and base with subtracted and multiplied by 1.5 (factory rocker) to come up with .444 -.447 lift (some lobes are more worn than others.. 100k cam)
then for shvts and giggles i used the stock calculation and threw in 1.6 instead of 1.5 to come up with about .477 lift, which is what the corvette's came with i believe (could be wrong)
SOOOO what do you guys think ?
I measured the height of the lobe (top of lobe to bottom of base) then i measured the base circle and subtracted the two numbers and then i multiplied that number by my rocker ratio 1.6 to come up with .5248 and .524 the second time, throw in some slight mechanical and human error of .0001-.001 or so.....then doesn't this calculation prove its a genuine hotcam?
i then proceeded to do the same with the stock cam measured lobe height and base with subtracted and multiplied by 1.5 (factory rocker) to come up with .444 -.447 lift (some lobes are more worn than others.. 100k cam)
then for shvts and giggles i used the stock calculation and threw in 1.6 instead of 1.5 to come up with about .477 lift, which is what the corvette's came with i believe (could be wrong)
SOOOO what do you guys think ?
02-10-2008, 04:20 PM
#36
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there should be a code 845 on the end of the cam, unless it was ground by crane. I bought a cam here a while back what I was told was an lt4 hot cam from a member, i went to a dealership in winchedon ma, and they told me it was not a hot cam part 845, but it was actually an 846. So I smiled returned the lt4 valve springs I'd purchased in exchanged for some ls6's. It always sucks to feel taken advantage of, but if the seller is trying to make it right (instead of fleeing the counrty, and wouldn't blame him you seem quite displeased) I'm sure it will work out, bring the cam to a GM performance parts dealer, they will be able to track down exactly what cam it is and the maker whether it is them or not. Good luck
and my cam says 586FM67
and like shawnzr2 stated the calculations checked out okay so im pretty sure its genuine
02-10-2008, 04:28 PM
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I was able to zoom in on the camshaft and there is a good chance that yellow ring may have just faded. It sure is dirty compared to that other guy's photo and the photos I have of new ones. Maybe your not so *ucked after all. If cams are anything like women, maybe dirty is a good thing! 
02-10-2008, 04:41 PM
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I was able to zoom in on the camshaft and there is a good chance that yellow ring may have just faded. It sure is dirty compared to that other guy's photo and the photos I have of new ones. Maybe your not so *ucked after all. If cams are anything like women, maybe dirty is a good thing!
damn im relieved
thanks to everyone!!!
