Airflow to Cubic Inches
- Thread starter nes4pres
- Start date
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PRH
Well-Known Member
TF270’s are the default head choice for that type of build.
Uses std offset rockers and has std height ex ports.
Indy EZ295 is basically the equivalent.
Uses std offset rockers and has std height ex ports.
Indy EZ295 is basically the equivalent.
PHR said it best above. The formula for getting the max and beyond are one thing, and average hot rodders just need to look at what others have done and do a basic copy of it.
This is where I see so many people use a formula and get pissed at the results and why I say formulas don’t work well and are not for everyday or even pretty hot builds. People get lost in them and choose based on what the math says only to be disappointed.
The only time I see people happy with the math is when they’re building a very specific certain something to do a specific strain something. By the standards of this forums routine chatter, this would be the extreme end are really hot engines.
If off the shelf parts can do the trick, you really don’t need the math.
This is where I see so many people use a formula and get pissed at the results and why I say formulas don’t work well and are not for everyday or even pretty hot builds. People get lost in them and choose based on what the math says only to be disappointed.
The only time I see people happy with the math is when they’re building a very specific certain something to do a specific strain something. By the standards of this forums routine chatter, this would be the extreme end are really hot engines.
If off the shelf parts can do the trick, you really don’t need the math.
Also u have to realize the machine work that goes into this type engine. These are the results u get with a high end pro engine builder. Like the old saying goes: u wanna play u gotta pay. Kim
Very true. There are in my head “Levels” if you all get the drift.
Stock rebuild
High performance
Race
This applies to the parts and combinations used. OEM parts can go far. (Totally subjective) Then there are HP parts and race parts as well as machining.
Please tell us about your build.
Dartswinger70
Well-Known Member
Yeah but what do 318 heads flow after Uncle Tony gets done with his HF grinder...? 
Darin's talking actual airflow demand in a running engine and they're talking what they see on a flow bench, 2 totally different worlds.
A quick bowl and short side job like he did could be in the 210 area easy. The heads don’t flow much as cast but do respond well to some work.Yeah but what do 318 heads flow after Uncle Tony gets done with his HF grinder...?
I don't see that calculating an actual displacement of air over time. It calculates estimated cfm at 28" which is airflow on a bench. cid x ve% x rpm / 3456 = cfm calculates a close approximation to actual volume of air used/needed.
And get rid of that God awfully large 3/8 valve size and use an 11/32 or even 8mm valve and that goes for all the OEM heads.
Never said it did, just that calculation suppose to predict flow bench cfm reading needed not actual physical amount of air in cfm.
Bingo!
A more efficient head makes a more efficient engine.
(Along with what’s below and above it line up with it.)
Please explain, are you saying changing only the cylinder heads won't make an engine more efficient.
Difference is were talking over time (rpm) not just one sitting (cid x ve%).
At full throttle (demand) you only run out of supply
That's a great analogy
Piston demand and piston speed is what fills the cylinder not the heads ability flow. Like I've pointed out earlier static flow on a flow bench is not representative of what happens in a real running engine.
Well, that's a good way not answering the question.
You need some one to explain to you why a 300 cfm W2 head will make very little torque in a 273?
What's the piston demand and peak piston speed of that little bore and little stroke?
Here watch this:
Improving cylinder fill improves power.......Piston speed, Rod Length and Stroke and Bore Size all affect the cylinders ability to fill. The bigger the port and intake valve the easier it is for the exhaust to travel up the intake tract PREVENTING cylinder fill when the intake valve opens.
Improving cylinder fill improves power.......Piston speed, Rod Length and Stroke and Bore Size all affect the cylinders ability to fill. The bigger the port and intake valve the easier it is for the exhaust to travel up the intake tract PREVENTING cylinder fill when the intake valve opens.
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