Cracked Valve Spring Retainers/ Head Flow
Thread Starter
Joined: Mar 2002
Posts: 251
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From: Covington, LA
I have some flow numbers at 28" H20.
Int. Valve Lift ..... CFM @ 28"
0.100 .................. 112.5
0.200 .................. 165.0
0.300 .................. 265.3
0.400 ............... ... 302.0
0.500 .................. 338.7
0.550 .................. 342.0
The Ex. is approx. 90% of intake at low lift (~0.100) and transitions to approx. 74% at high lifts.
Greenlight
Int. Valve Lift ..... CFM @ 28"
0.100 .................. 112.5
0.200 .................. 165.0
0.300 .................. 265.3
0.400 ............... ... 302.0
0.500 .................. 338.7
0.550 .................. 342.0
The Ex. is approx. 90% of intake at low lift (~0.100) and transitions to approx. 74% at high lifts.
Greenlight
Thread Starter
Joined: Mar 2002
Posts: 251
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From: Covington, LA
The head data was obtained on a Superflow 600 and the Superflow supplied calibrated orifice was used prior to the test. We tested at 36" H2O and 28" H2O. The numbers I gave you are the 28" H2O numbers.
On another flow bench I tested at 10" and 28" to see how much difference it made. It makes a HUGE difference in the air speed, turbulence, and air separation at the short turn near the seat when checked with a pitot tube.
An 88 mm adapter was used, because an 87 mm adapter was not available.
The head was flowed prior to any cylinder head modifications with a radiused entry that we made out of a 3/4" plastic plate that we added a 1" radius.
After all of the head modifications were complete (as well as during the modification process) the test was repeated with the radiused entry and with the manifold/throttle bodies assembly in place.
The flow loss with the manifold assembly in place showed ~2% loss at high lifts and no loss at low lifts.
The stock head flow was in line with flow figures that I have seen on this forum, as well as other locations.
By the way, I have approx. $7000 invested in the cylinder head/cam assembly.
Greenlight
On another flow bench I tested at 10" and 28" to see how much difference it made. It makes a HUGE difference in the air speed, turbulence, and air separation at the short turn near the seat when checked with a pitot tube.
An 88 mm adapter was used, because an 87 mm adapter was not available.
The head was flowed prior to any cylinder head modifications with a radiused entry that we made out of a 3/4" plastic plate that we added a 1" radius.
After all of the head modifications were complete (as well as during the modification process) the test was repeated with the radiused entry and with the manifold/throttle bodies assembly in place.
The flow loss with the manifold assembly in place showed ~2% loss at high lifts and no loss at low lifts.
The stock head flow was in line with flow figures that I have seen on this forum, as well as other locations.
By the way, I have approx. $7000 invested in the cylinder head/cam assembly.
Greenlight
Thread Starter
Joined: Mar 2002
Posts: 251
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From: Covington, LA
On a highly modified engine it takes ~3 cfm to make 1 hp.
On a street engine it takes ~ 5 cfm to make 1 hp.
The stock head averaged ~232 cfm and the modified head averaged ~ 254 cfm (when using the flow numbers in the previous reply).
This roughly equates to 29 extra horsepower over the stock head.
When you add the fact that the stock intake reduces the flow by ~ 6% (avg.) and my setup reduces the flow by ~ 1% (avg.) there is ~ a 45 hp gain in the porting and manifold alone.
Remember, these are JUST ROUGH ESTIMATES.
Greenlight
On a street engine it takes ~ 5 cfm to make 1 hp.
The stock head averaged ~232 cfm and the modified head averaged ~ 254 cfm (when using the flow numbers in the previous reply).
This roughly equates to 29 extra horsepower over the stock head.
When you add the fact that the stock intake reduces the flow by ~ 6% (avg.) and my setup reduces the flow by ~ 1% (avg.) there is ~ a 45 hp gain in the porting and manifold alone.
Remember, these are JUST ROUGH ESTIMATES.
Greenlight
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Joined: Jul 2002
Posts: 93
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Thanks Greenlight. I didn't mean to sound doubtful, just wanted to be sure. It is good news.
Just to confirm again, the numbers you mentioned..
Int. Valve Lift ..... CFM @ 28"
0.100 .................. 112.5
0.200 .................. 165.0
0.300 .................. 265.3
0.400 ............... ... 302.0
0.500 .................. 338.7
0.550 .................. 342.0
.....these are for the MODIFIED head yes?
Would you mind providing the numbers at the same lift intervals for the STOCK F20C head?
Thanks again!
Just to confirm again, the numbers you mentioned..
Int. Valve Lift ..... CFM @ 28"
0.100 .................. 112.5
0.200 .................. 165.0
0.300 .................. 265.3
0.400 ............... ... 302.0
0.500 .................. 338.7
0.550 .................. 342.0
.....these are for the MODIFIED head yes?
Would you mind providing the numbers at the same lift intervals for the STOCK F20C head?
Thanks again!
Thread Starter
Joined: Mar 2002
Posts: 251
Likes: 0
From: Covington, LA
Int. Valve Lift ..... Ported ...............Stock .......CFM @ 28"
0.100 .................. 112.5 ...................92
0.200 .................. 165.0 ................. 158
0.300 .................. 265.3 ..................238
0.400 ............... ... 302.0 .................283
0.500 .................. 338.7 ................. 302
0.550 .................. 342.0 ..................304
0.100 .................. 112.5 ...................92
0.200 .................. 165.0 ................. 158
0.300 .................. 265.3 ..................238
0.400 ............... ... 302.0 .................283
0.500 .................. 338.7 ................. 302
0.550 .................. 342.0 ..................304
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