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Discussion Starter #21
IT Manta, do you have a side view pix of these rockers (like taken from the front end of the head), showing the rocker angles relative to valve axis, with valve closed and open?

Any further info on cam lift, spring pressures and rates, and rocker ratio would be appreciated. Or point us to another thread if it is already documented. Many tnx.
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IT Manta, do you have a side view pix of these rockers (like taken from the front end of the head), showing the rocker angles relative to valve axis, with valve closed and open?

Any further info on cam lift, spring pressures and rates, and rocker ratio would be appreciated. Or point us to another thread if it is already documented. Many tnx.
This is the only other picture that I currently have. I have not taken one from the viewpoint that you are asking about.
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I use ENEM cams and have used roller rockers with all of them at some point.

I use the I10 for mild 9:1 motors. 280/109/10.9/2.2 mek.
I am using the P2 in a 12.5:1 2l motor. 304/106/12.1/4.0 mek.
I am using the I3 in a 12.5:1 2.3l stoker. 300/107/12.0/4.0 mek.
 

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Opel Rallier since 1977
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Thank you for all the good info. I was just curious to see the angles of the rockers vs the axes of the valve and lifter. It is a geometry thing.

Is the I10/9:1 SCR engine for street driving or what, if I may ask? And do you know at what lifter lift ENEM lists their cam durations? Tnx
 

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Discussion Starter #23
Gotcha. That motor was a race motor similar to ITB rules, but with a few motor allowances. Very streetable cam and motor though. I believe Jan uses valve lash (.30mm) + .20mm = .50mm. See image...
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When calculating actual valve lift, be aware that the HS roller rockers are 1.6:1. Not the 1.53:1 stock Opel ratio.
Opel is ‘listed’ as 1.5:1 by most folks, but it is in fact variable due to the sliding tip. Figure 1.44 to 1.48 on average. I’ve measured as low as 1.41.

Longer valves and/or a reground cam with a smaller base circle will reduce the ratio. Shorter valves, full base circle cams, and longer lifters will increase the ratio.

My old roller rockers calculated out to 1.557:1 on most cams I measured. I actually had +1mm and +2mm lifters to be used with big cams with smaller base circles to maintain the desired ratio.

The Harland Sharps are based on my old design, so I suspect they are a similar ratio.
 
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I would have to measure ctr. to ctr. To find the actual offset. Per RB's post above, Harland Sharp tech said final ratio is closer to 1.6:1. That is probably with the added height of the lash caps. I don't have them, but I'm thinking seriously about getting a set of these from IT Manta here in Portland. Here is the side pic.
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