Rocker Ratios...variances
 

Interesting information here. Shows how different brand of rockers, can have quite a bit of different ratios from their advertised ratio. Obviously ratio effects full lift, but it also can affect valve acceleration. Here you can see how each rocker differs.

The 1.8 Ratio's are really interesting. According to this chart, the differences are substantial.

Harland Sharp .127/.649

Crane .131/.649

Comp .126/.638

Scorpion .138/.680

While they are all 1.8 Rockers, the scorpion has .680 peak lift, and the comp, .638. Thats a .042 difference in peak lift at the valve.. plus, a faster accelerating valve opening.

how old is that data?

Feb 2015 publish. Considering they are testing the Comp Cams 1828 Ultra Pro Magnum XD, I wouldn't think its that old. That rocker hasnt been out that long. Looks like it debuted at 2010 Sema show. https://www.youtube.com/watch?v=NSLIIrujyzo

I can attest, that there is a significant difference, in the geometry of a Crane Gold, Scorpion, and older style Comp Steel rocker when studied back to back on icdedppls engines, doing valvetrain geometry checks. The sweep patterns, and roller tip placement varied quite a bit between the 3, when setting the rockers up using the mid-lift method.

Good reads! I've been interested to find out why some cams/builds use a 1.7 and 1.8 rocker combo. I understand what they do but the benefit would be interesting to see.

Wow !

I believe because generally speaking, the BBC likes intake valve lift, more than it does exhaust valve lift. I also believe, it was very common for cam companies, to use an intake lobe, for an exhaust lobe. Like when you see cams with .630/.630 lift. The modern trend in cam lobes for bbc stuff, seems to be going with more intake lobe lift. From what I have seen, most bbc's respond better with 1.8 intake rocker, and 1.7 exhaust rocker, on those older cam grinds. You not only gain more peak lift, but more throughout, and a quicker opening valve.

The author of this particular book, mentions how normally a 1.8 intake rocker, is a way to go when using a dual pattern camshaft, with 6-8* more exhaust duration.

Given that these are new production items I'll assume that they used modern manufacturing methods to build them, Cee-N-Cee, basically ruling out tolerance issues.

Does the article make any mention of the arm's installation method or the spring's installed height? I'd also like to know how they measured the valve lift. Small geometry changes from setup to setup will definitely show up in the results. Fr'instance, maybe they used a dial indicator to measure travel and didn't get it back in the exact same spot every time.

He does not get into the specific details of the test.

I am always purchasing new literature regarding engine building, cylinder head porting/design, blueprinting and machining, to attempt to educate myself further on these topics. Mainly, because I am not interested in "opinions", or "theories" any longer. I like graphs, charts, data, and results. I have several of David Vizards books. Each one, I have found vastly informative, on all aspects of things. As far as big block chevy stuff goes, not only does he have vast experience in all types of build combinations, he has tested thousands. He is familar with, used and ported, Darts, AFR's, Brodix, RHS, Trick flows, and tons of stock offerings. From cranks, to rods, to blocks, to valvesprings, he's been around them all. Not a guy who's only dealt with one brand , and thinks its the best. He rarely has a negative thing to say about any brand, he simply gets to the point, and shows his results with data. The man started porting cylinder heads in 1950's, and has intensely studied the effects of the actual combustion process, heat transfer, airflow turbulence, and so on. He has over 500,000 dyno tests under his belt in his day. Spent a lifetime testing theories.

With that being said, I have no reason to doubt his procedure of this particular rocker arm test, or his knowledge of valvetrains. I am pretty certain, the man has learned valvetrain geometry basics, and how to use a dial indicator by now, considering he speaks at events like PRI, writes tech articles for engine builder magazine, etc.

Basically, I just thought it was interesting information, some may like. His contact information is on the web, as he has a website. I'm sure one can email him directly, and ask him about his test procedure/accuracy.