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Old 01-11-2013, 03:03 AM
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Originally Posted by techinspector1 View Post
intake closing point 36 + 15 =51.000

The intake closing point is where my concern is. If I use the closing point, at .050, of 36 deg and then add 15 deg, then all is well, BUT if I use the actual closing point at .006 of 78 deg then all is not well.

Should I assume that the KB calculator is saying that the intake valve is closed at 15 degrees past the .050 lift point? If that is the assumption, then my DCR is actually much lower because, according to cam card, my intake valve isn't closed until 78 deg. Unless, the intake valve is considered closed for DCR calculations at 51 degrees.

What do you think?

FYI - I tried to word my question so that it isn't confusing - I can't say that I succeeded, but I tried.

When I put this engine together, I relied on the machine shop to recommend the cam and pistons. He thought the engine should easily make 1 hp/cube, but I haven't been able to pull it off. The best I've done is a little less than 310. The 310 was calculated from the dyno owner's software based on actual rwhp. I realize that all dyno's are not alike, but, this got me checking into the DCR just to see whether it was OK. When I found the discrepency between the two calculators then I thought this could be some of the issue. But I don't have a good enough understanding of exactly how DCR is calculated. And that is how I got into this conundrum.

Do any of you know what happens when the DCR is at or below 6.7:1? Will the engine still run well and be low on power, or will it run poorly all the time, certain RPM ranges, or what?

For some background, this engine was put together in the spring and driven for most of this last summer and fall - about 4000 miles. I can say safely, based on driving it, that I need more stall for launch, but other than that it seems like a rocket in the car. The is quite light, around 2600 lbs. At 40 mph it feels like it's shot of gun when you lay into the throttle.

Thanks - Jim
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