In my opinion and on this particular motor I will not be shimming the comp-910s.
This is on a factory cam.
To break it down.
In the previous post I showed that the valve head recession was fine, and the valve I called out was recessed greater than spec rather than potruding more than spec into the cylinder.
The unloaded spec on the valve springs is 52.705mm +/- 3.8
The unloaded factory spring is 52.08mm
The unloaded comp 910-16 is 53.00mm
This means the comp910 is within spec and does not need to be shimmed.
If those measurements were flip flopped, for example, if the comp910 was 52.08 and the factory was 53.00 then I would shim the comp910 by 0.78mm since it's shorter and my head deck to valve recession is already on the money.
The comp910s unshimmed pressure on the seat is greater than the pressure of the factory spring.
The valve tips will wear faster on an unshimmed 910 spring and faster than that on a shimmed.
I'm boosting and don't have concerns of floating the 910s.
I saw about 5-8 years of posts on various forums to just shim 0.78mm on comp910s on 7.3 IDIs and I just wanted to throw my 2cents in.
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Next, few comments on removing the valve springs.
I tried the overhead valve tool.
Couldn't get it to work to remove the retainers.
I was then tired of spinning it on and off by hand, so welded it to be automatic.
Still didn't work.
One thing was it didn't fit over the bottom part of the spring.
I then grounded and welded the longer lip to be able to go under.
Still didn't work.
So I decided to do it the old fashion way.
7/8 socket, hammer, something soft under the valve.
Popped the retainers on the first swing, all of 3 seconds.
I won't be user the tool for removal again on an IDI.
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