I'm wondering how each affect power in their own ways. I seem to understand that SCR is basically how much cylinder pressure is built up, and I've read a lot here that almost flat-out cylinder pressure=torque. I'm wondering where DCR would fall into how it affects power. Does it? I know it plays a critical role in determining what octane you can run. Other than that, though, how can it affect power? I know typically if you have a high SCR you will have a high DCR, but know that the numbers can sometimes work independently of each other too. I could be wrong on how I'm understanding this (which is why I'm asking), but my question may have a bigger answer than what I might expect.

Also, any good big-block books out there? I know I've heard something like 'How to Hot Rod the Big Block Chevy' or something, but on an Amazon.com review someone said it's information was kind of out of date, and was wondering if it's still a pretty good book (and if it includes anything on big-block stroker motors, or what does). Thanks a lot in advance.

Taylor, it's still a good book and I would highly recommend it. So many design features of the rat are timeless, so 1970's info is still valid.

Re your other question, all I can add is that I was shooting for the highest DCR practical to overcome the low speed softness of the big port heads. So I do think that + dcr = + tq.

You might have heard of low compression , cammed motors that never see the rpm potential the cam needs, so it's not only low speed torque that is affected, but clearly higher rpm operation as well by not having adequate cylinder pressure to make power. Event times are shortened so much at higher R's that cylinder filling is affected. Therefore you don't have the same 'squeeze' as a lower rpm cylinder filling event, hence the engine poops out before the cam card would indicate.

Get a copy of Ed Staffel's BB book "Building Max. Horse Power Chevy BB Motors" or whatever it is called??

I'm not at home so caN'T LAY MY HANDS ON MY COPY.

iT AND THE OLDER bb hpbook DO GREeat together!!

DARN CAP'S!!!! pdq67

No, SCR alone does not dictate cylinder pressure. In fact, it's DCR that more strongly influences cyl press.

Think of it this way, your SCR dictates what the max DCR will be; i.e. DCR will never be more than SCR. Almost always, DCR is lower than SCR.

If you look at 2 extreme examples: Let's say you have a cam that is so small (like 180 deg adv duration) that it closes the intake valve at the very start of the compression stroke. Assume your SCR is 10:1. That intake closing event will then trap all of the compressed mixture, resulting in a DCR of 10:1.

At the other end of extremes, let's say you have a cam that is so big (like 360 deg adv dur) that the IC is at the very end of the compression stroke. None of the compressed mixture will be trapped, resulting in a 0 DCR.

Normal engines run somewhere in between the two, and so do DCR's, determined by the intake valve closing and SCR. HTH.

Pat Kellys write up should answer your questions.

Pat Kellys DCR explained (http://webpages.charter.net/darrell1/dynamiccr.htm)

Yes, read Pat's work, and if you noticed, I never mentioned SCR in my above post.