[johnsongrass1]

The internet is good at making it a much bigger deal than it is. If it's a side benefit than good, go for .040 or whatever......I wouldn't build around the arbitrary .040 idea.....
Stick to the 10:1 rule and it'll be fine.

 

[johnsongrass1]

Only a controversy by those confused on it.
Those guys are talking about IVC, intake valve closing point, there isn't anything dynamic about it. Everything else is fluff trying to make it make sense.

 

[johnsongrass1]

Compression pressure changes with RPM so at 200 cranking rpm you might get your 205, it goes up through the rpm range, untill a restriction happens then it goes down again.
For example a big CI engine with a small 2v carb would still push 205 for example at 200 rpm cranking BUT what happens when the little carb becomes a restrictions and half the air needs at 5500 reduces the volume? pressure goes down again.
Thats why the math doesn't work.

 

[johnsongrass1]

Send it at 10.3 and worry about something else

 

[johnsongrass1]

Cometic C5245-023 is .023. Pretty close if you prefer MLS

 

[johnsongrass1]

1000 percent.

 

[johnsongrass1]

Love ya to death, but you missing something more important than justification of an arbitrary number.
When the fine begins over scavaging the cylinder....your DCR is thrown out the window. In different words, your DCR number is derived from IVC, and your DCR number is is calculated in the cam power range.
oh, but the thing is cams often operate way outside the range. Throwing the DCR out the window. Try swapping heads to a very small very good flowing port, then to a very large poor flowing port and think about what's happening. IVC didn't change, DCR didn't change. The engine is radically different in both characteristics and power curves.
Now you COULD estimate a typical street engine and make the assumption of DCR and be within the tolerances but to use the BS math for all engines, you would wrong more than right.
Remember this....not one single professional head porter or cam designer uses DCR calculations. Why not?
The real recipie is the smallest port that flows enough, then opens and closes the valve the fastest without breaking something, and the highest compression ratio the fuel will tolerate in the rpm range it's intended to use.
DCR as it's commonly calculated simply assumes way too many things to be of use.

 

[johnsongrass1]

I don't care push a theory that saves guys from themselves. That's their responsibility.
The problem as I see it, is pushing a narrative to save guys from themselves quickly becomes the gold standard and when the time comes, a professional builder laughs and smirks in their faces because the hotrodder guys tells the professional engine guys they read it on the internet, and its a fact.
It's junk science, it's junk math. I see this crap walk in the shop all day everyday.

Guys looking for a high rpm screamer 327, 3/4 race cam, high rise intake elderbrok, double bump heads, and a 850 double humper carb. (Misspelling on purpose)
I always ask Why? Are you trying to go slower?

Lets educate, and help guys put in the correct parts, instead of just preventing them from chasing the really wrong ones?
Maybe it's just me.