damn cosworth gives good head

 

Does anyone know the estimated cost of the machine work if all other parts are purchased on stock heads?

 

Just thinking out loud....

Admittedly, I don't know much about this but I'll assume that even though the Intake is good for 411 CFM it is limited by the Exhaust at 274 CFM. I suppose this must be true unless there is a big leak somewhere. An engine is just a glorified air pump.

3.5 Liters = 0.124 cubic feet.
It takes two revolutions to process 0.124 cu.ft. of air OR 0.062 cu.ft. per revolution.

There are 6 exhaust ports so the total flow is times 6.

The stock exhaust side is good for 225CFM x 6 = 1350CFM or...
1350CFM / 0.062 cu.ft. = 21,774 RPM

The Cosworth exhause side is good for 274 CFM x 6 = 1644CFM or...
1644CFM / 0.062 cu.ft. = 26,516 RPM

Seems silly... somethings wrong....
Oh...
The exhaust valves aren't open all the time.

Let's assume JWT cams with a 260 deg duration. Does this mean that the valve is open for 260 degrees?

If so that's about 3/4 of a revolution but only every other revolution so it's open for about 36% of the time.

If I assume rise and fall times for the valves is near zero (a little optimistic) then the best flow for each is:

Stock: 36% of 1350CFM = 486CFM
Cosworth: 36% of 1644CFM = 592CFM

Stock: 486 CFM / 0.062 cu.ft. = 7839 RPM
Cosworth: 592 CFM / 0.062 cu.in. = 9548 RPM

It's certinly possible that I completly screwed this up but it seems at first that high flow heads don't help much until you get to the very top end. Even then maybe only when allowed to go over the stock redline.

It's hard to imagine these being much help for anything but extreme applications. Also, do these numbers change for FI? It doesn't seem like they should.

I'm sure there are secondary effects that come into play also.

Ken

 

estimated numbers(high end):

Clean heads/disassembly: $100
oversize valve seats to accomodate oversized valves: $15-20 per hole: $480
quality port & polish -flowbench tested (not just intake and exhaust runners): $800-1500
Redeck heads: $80
assembly/clearancing/adjusting: $200
Ferrea valvetrain: $1800

this would total: $4160 (using highest of numbers)
I mayt be missing a few little things...

lowest: $3340

 

Fito, I cant wait till you put these things to the test. You guys are radical out there in PR...keep up the good work. I expect to see at least 750whp from you guys.

 

Right on the numbers Sharif!