Don Terrill’s Speed-Talk

gmrocket wrote: ↑Wed Apr 03, 2019 9:25 am

Carnut1 wrote: ↑Tue Apr 02, 2019 9:14 pm Resized_20190402_132441_9944.jpeg I decided to radius that bottom cut in.

What did your throat % ending up being?

Maybe it's an optical illusion but that long wall looks like it really necks down in size just under the bottom cut....dont look much different than the original shape .

Gm, I made a mistake yesterday. The narrowest part of the port measures 1.28" x 1.33" now this is not the exact port I flowed yesterday but it will be damn close. Now for some wonky stuff, that figures to 1.3 sq" x 147 equals 196cfm. Ok, so it is impossible to flow over 200 cfm? Interesting discussion point. Thanks, Charlie

Making chips, "wonky" St has many super genius types that can do calculus in their sleep. They like the "wonky" stuff. They may not even read my threads to be honest.

Carnut1 wrote: ↑Wed Apr 03, 2019 7:23 pm

gmrocket wrote: ↑Wed Apr 03, 2019 9:25 am

Carnut1 wrote: ↑Tue Apr 02, 2019 9:14 pm Resized_20190402_132441_9944.jpeg I decided to radius that bottom cut in.

What did your throat % ending up being?

Maybe it's an optical illusion but that long wall looks like it really necks down in size just under the bottom cut....dont look much different than the original shape .

Gm, I made a mistake yesterday. The narrowest part of the port measures 1.28" x 1.33" now this is not the exact port I flowed yesterday but it will be damn close. Now for some wonky stuff, that figures to 1.3 sq" x 147 equals 196cfm. Ok, so it is impossible to flow over 200 cfm? Interesting discussion point. Thanks, CharlieResized_20190403_191536_6185.jpeg

That straight on pic looks like it's even smaller to me...how far down in the bowl did you get the 86%?

The nice thing with these castings as opposed to some of the others is the spark plug position.
It allows for generous angle milling to set the chamber volume to pretty much any you want.
What was the final chamber volume ? (Before any milling)

gmrocket wrote: ↑Wed Apr 03, 2019 11:40 pm

Carnut1 wrote: ↑Wed Apr 03, 2019 7:23 pm

gmrocket wrote: ↑Wed Apr 03, 2019 9:25 am

What did your throat % ending up being?

Maybe it's an optical illusion but that long wall looks like it really necks down in size just under the bottom cut....dont look much different than the original shape .

Gm, I made a mistake yesterday. The narrowest part of the port measures 1.28" x 1.33" now this is not the exact port I flowed yesterday but it will be damn close. Now for some wonky stuff, that figures to 1.3 sq" x 147 equals 196cfm. Ok, so it is impossible to flow over 200 cfm? Interesting discussion point. Thanks, CharlieResized_20190403_191536_6185.jpeg

That straight on pic looks like it's even smaller to me...how far down in the bowl did you get the 86%?

Right under the lower cut of valve job. Which gets radiused in. Thanks, Charlie

gmrocket wrote: ↑Wed Apr 03, 2019 9:25 am

Carnut1 wrote: ↑Tue Apr 02, 2019 9:14 pm Resized_20190402_132441_9944.jpeg I decided to radius that bottom cut in.

What did your throat % ending up being?

Maybe it's an optical illusion but that long wall looks like it really necks down in size just under the bottom cut....dont look much different than the original shape .

Pic of exhaust from flange. If you look you can see the paste ooze line around the bowl. So the exhaust port is not enlarged much from stock. So nobody will call b.s. to this port flowing over 100% efficiency at it's mcsa? So how is this possible? Thanks, Charlie

Carnut1 wrote: ↑Wed Apr 03, 2019 7:23 pm

gmrocket wrote: ↑Wed Apr 03, 2019 9:25 am

Carnut1 wrote: ↑Tue Apr 02, 2019 9:14 pm Resized_20190402_132441_9944.jpeg I decided to radius that bottom cut in.

What did your throat % ending up being?

Maybe it's an optical illusion but that long wall looks like it really necks down in size just under the bottom cut....dont look much different than the original shape .

Gm, I made a mistake yesterday. The narrowest part of the port measures 1.28" x 1.33" now this is not the exact port I flowed yesterday but it will be damn close. Now for some wonky stuff, that figures to 1.3 sq" x 147 equals 196cfm. Ok, so it is impossible to flow over 200 cfm? Interesting discussion point. Thanks, CharlieResized_20190403_191536_6185.jpeg

isnt mcsa 1.28"x1.33" is 1.70 sq" ,not 1.3sq" ? why are you averaging the the two measurements and calling it sq inches?

1.3 x 147 equals 191.1 anyway, not 196

so 1.7 x 147 = 249.9

I averaged two circles. One 1.28" and 1.33" that is 1.3" true the opening is not 100% round that is why I thought of it as two circles. Thanks, Charlie

1.3" circle has 1.325 sq in area × 147 = 194.6 cfm.

Carnut1 wrote: ↑Sat Apr 06, 2019 3:03 pm 1.3" circle has 1.325 sq in area × 147 = 194.6 cfm.

why not do it exact then? plot it out on paper if you have to and add it up. it sure isnt round. ....there are flat areas. or get a piece of solder and do a circumference measurement to get your area. thats what i do to figure area of odd shaped ports

Forgot to ask why you think it's so efficient?

gmrocket wrote: ↑Sat Apr 06, 2019 5:49 pm Forgot to ask why you think it's so efficient?

I was trying to prove a point but I am over it. You stated it looked very small almost stock. Which in reality is true. It just sounds and flows better. Thanks, Charlie

I have a question on if the double crossover exhausts on heads like this are that much of a detriment? Exhaust cylinder #1 without crossover vs. Cylinder #3 with crossover.
Cylinder #1. Cylinder #3
.05" 31.2. 31.4
.1" 66.2. 69
.15. 100. 102.2
.2. 124.8. 129
.25. 143. 148
.3. 157.3. 162.3
.35. 169.4. 173
.4. 177.8. 178.3
.5. 185.3. 183.8
.6. 188.1. 187.4
.7. 188.6. 189.1

I should add that the air that actually exits the crossover has an average velocity of 60ft/sec @ .5" lift. 183.8cfm.
This has to do with how I designed the exhaust. I have tested other heads that had very fast air passing through the crossover. This is the first time I measured the air speed. I get that the exhaust will work better if they are filled as far as tuning but is it really worth the effort?

Charlie,

What about my, stock, 2.02"/1.60" valve, way OLD, -461 heads?

They are '63 or '64 heads.

I know you wanted to get your hands on my new EQ 200 cc intake port 50 cc chambered heads that I am going to run on my 4.155" b x 3.00'" s = "325" engine if I live long enough?

pdq67

pdq67 wrote: ↑Sat Apr 13, 2019 9:34 pm Charlie,

What about my, stock, 2.02"/1.60" valve, way OLD, -461 heads?

They are '63 or '64 heads.

I know you wanted to get your hands on my new EQ 200 cc intake port 50 cc chambered heads that I am going to run on my 4.155" b x 3.00'" s = "325" engine if I live long enough?

pdq67

461's have a single exhaust crossover so two less ports are affected.