Cams And Spring Advertisement

Timebomb

Timebomb

Bootney Lee Fonsworth
Just curious as to why cams for one are advertised with lobe lift numbers and not valve lift ? The other is why springs are advertised with numbers that seem to be just that numbers. I think guys are educated enough to use the advertised numbers that all large aftermarket spring and cam companys use. Just my thoughts
 
Better question is what those lift numbers are at. There really is no standard. In the gasser world it tends to be the somewhat standard to measure duration at .006 cam lift or lobe centerline then valve lift at .050 or max. So with those slight variations its no wonder noone knows whats going on. Atleast if you get both numbers you can see how aggresive the lobe profile is assuming that it is somewhat linear. Then there is the diesel world where you have even tighter clearences and they dont tell you hardley any specs. As for your question, lobe lift is a better measure to go by becuase the cam grinder cannot know what rocker arm ratio you are running or how off the factory rockers where to start with. Many engines are manufactured off by 10% right out the door, usually to the smaller side of the ratio.
 
Advertised duration @ .050", seat timing & LSA are given more for marketing reasons than anything else - they don't accurately portray the 4 valve events... primarily because most folks have no idea how to reconcile IVO, IVC, EVO & EVC with their power production goals.

There's no way to know lobe profile from just a couple of numbers, since different orders of valve motion can be linear - best way to "see" a lobe is by graphing lift area under the curve in relation to crank rotation...

Lift
Velocity
Acceleration
Jerk
Snap
Crackle
Pop
 
xlr8r said:
advertised duration @ .050", seat timing & lsa are given more for marketing reasons than anything else - they don't accurately portray the 4 valve events... Primarily because most folks have no idea how to reconcile ivo, ivc, evo & evc with their power production goals.

There's no way to know lobe profile from just a couple of numbers, since different orders of valve motion can be linear - best way to "see" a lobe is by graphing lift area under the curve in relation to crank rotation...

Lift
velocity
acceleration
jerk
snap
crackle
pop
Click to expand...


LOL LOL :Cheer:
 
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It just sounds dumb to me that a spring is referred to as a 60# or a 110# what part of the spring is 110# ?
 
i agree with you Coop, if you using a aftermarket cam with more lift, technically you have just now changed your spring "pressure" at max lobe lift. has anybody tested that? Zach???...
 
Lift
Velocity
Acceleration
Jerk
Click to expand...


spent a few days back in college pondering what the integral of acceleration would be, only to learn that it is indeed a real thing
 
94 12valve said:
I think that refers to seat pressure above stock
Click to expand...

I wondered that, same deal with the 60# I told folks that 5 years ago. 200lb on the seat seems high but Im no cam guy. Its just like the 60# spring though,people have called it that for years but had no clue what was 60# about it. More info is needed on the springs but in all honesty then we could just buy them from Comp or whoever. So I guess I understand
 
wdimig said:
i agree with you Coop, if you using a aftermarket cam with more lift, technically you have just now changed your spring "pressure" at max lobe lift. has anybody tested that? Zach???...
Click to expand...


There are a few reasons we name springs #110 and use lobe lift on the cams.

In the past people just called springs sportsman or maxspool or whatever they wanted. There was no designation as to how much seat pressure a spring had at installed height. Due to this fact there were several manufacturers that used springs from other applications in the cummins realm that were not better and actually worse in some instances. There was a "performance" spring set that sold for right at $400 that had 11lbs less than stock pressure. instead of the valves blowing open at 5x psi the blew open in the 4xpsi range. You are right in that the name #110 does not tell the full picture but it is not meant to. That is why we publish all of our pressure at .xxx" height and coil bind height on all of our springs. If you know your rocker ratio and lobe lift you have all of the information to figure out your spring pressure at any height.

As far as higher lift cams adding more pressure to the lobe, that is correct. This is why we lowered nose pressure on our new 110# springs, all of our newer designs feature much higher lift. Also duration plays a big factor in potential journal wear. Higher lift adds more pressure and higher duaration at higher lift can cause the cam to eat into the block if you don't have bushings installed. This is the reason we require bushings on our biggest cams regardless of steel or cast core.


As far as lobe lift. We use this to describe our cams because I have seen people use differing rocker ratio to describe 24v rockers which will make a cam look different and give a false lift number. I chose lobe lift because there are 12v rocker ratios at 1.69to 1 and 1.38 to 1 on 24v's as well as a bunch of custom ratios. Giving lobe lift, assumes that customers are somewhat intelligent and that they know how to multiply lobe lift times whatever rocker ratio they have. It also cuts down on b.s. marketing.

On a side note there was a very popular cam sold in the past for a lot of money that was pretty horrible. The cam grinder stated that the cam had so much lift that stock springs would bind if used. No lift numbers were given and people spent a crazy amount on springs that had a fancy name and were not much different than OE springs. The funny part is that the cam easily fit with stock springs. I give lobe lift, rocker ratio, and spring pressure charts to help you make better choices.
 
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