Hey a discussion!! Eventually a few cam choices will surface. Gotta agree with what was said about establishing a bit of background info for everyone to work with and see from..
as far as..
You made a very good observation about terminology. I might be confusing others in my use of the term "low end". Midrange, if we're talking about maybe 2000-3500 or so, is where alot of around town driving is done, even with my tall gearing.
I checked out the Wallace Racing site, and hadn't realized someone had actually done a calculator for Vizard's formula. It, and the dcr calculator, are both very cool. I"m a bit unclear about the result with the dcr calculator though. When I filled in the data for my old 396 I had to use 12.25 cr in order for the cranking compression result to jive with what I actually read on the compression gauge. Something's not right with that..... If I can get it to make sense to me, I could use the calculator to target a certain ccr result. The reason I'd be focusing on ccr is because it's a value I've actually tested on an engine I actually ran, so it gives me a real world frame of reference to work from with my current build.
By the way, not sure why you've seen so many bbc having issues with propane. Many of my friends and family used bbc's on propane, so I personally was around probably 10 or a dozen bbc's, both stock and modified, over extended periods of time, and never heard of heat or gasket issues. In my experience they were even more reliable than the sbc's - and those were awesome!
Burb, you have portrayed your expectations quite well now.. I even get it.. The clicker for me was when you described flooring the engine you have in your suburban for the first time. I am just getting old enough now to appreciate certain engine characteristics other than the all out power side. I am a slow learner in that regard, I don't think I've ever owned a vehicle that I haven't wound out no matter what it was. One does have to remember that we don't all drive the same or want the same..
In regard the low end. From what I have seen all the modern torque cams really do create torque especially in combination with higher compression. A big cube engine can easily get into the too much zone if you don't watch for it. But they can be very responsive and have a fun side, paying attention to gearing is a must. The 700r4 transmission has a very low first to get things moving.. It can also break things.
I"m a bit unclear about the result with the dcr calculator though. When I filled in the data for my old 396 I had to use 12.25 cr in order for the cranking compression result to jive with what I actually read on the compression gauge. Something's not right with that..... If I can get it to make sense to me, I could use the calculator to target a certain ccr result. The reason I'd be focusing on ccr is because it's a value I've actually tested on an engine I actually ran, so it gives me a real world frame of reference to work from with my current build.
That is a good approach, I like to feel the results of the theoretical before I actually believe. I just meant for that calculator to demonstrate the static cr link to dcr and cranking pressure. Change the intake close point in seat to seat duration, not 50 thou specs if that is what happened. You do need the real numbers off the cam card. Advance or retard position of cam changes the ivc too which changes the results. Its good to understand where you've been before going to the next.. Keep playing with that stuff til you get it to match real world results. The next will be more predictable.
As far my experience bbc well that may be a bit misleading.. Our family owned a service station back when gov subsidies were available for propane conversions. We were near a big dam project where money was flowing. In the narrow segment of years I was around that business, there may have been a lot more gm trucks than fords being used in that area in those years. I recall one bbc head in particular being the suspected culprit. These were mostly all heavy use work type trucks and included the odd motorhome and camper. So it may just be my experience which had some extreme use and coincidental factors that I should have considered. But that is where it began. I have a brother running the 454 now. 200,000 miles on it, pulls like a freight train. Not apples to apples though, he changed to a 6 speed trans and it is a heavy work truck. But it rekindled an interest.
So OK, cam choice.. Should be done with an eye to making the entire package work together.. A cam range, a compression range, a head choice, intake man etc.. To match burb's driving style..
Do a quick test on Vizards formula.. I'm pretty sure that is close to max torque but would you want to drive that? What could be done to tame it enough and for the mileage to improve? hmmm