Time to go Stage II!
- Thread starter Alky V6
- Start date
Donnie I have a set of MA heads here, my guy said they flow 255 intake and 185 exhaust seems right to me. However every flow bench is different, I think this is the issue, and you guy's is showing too low for all his tests. How come stage 2 heads according to the power source book flow 340 cfm unported for iron s2 heads?
What are the test pressures in the Power Source book?
The copy I have in front of me, titled "How to Hotrod your Buick V6", which is basically the same as the Power Source book (I have both) is showing that they are checking the flow of the heads using 40" water.
OK Donnie whats the conversion factor from 40" to 28". The MA heads I have have extensive porting, so I do believe those numbers.
Here I found a chart to do the conversion.
http://www.centuryperformance.com/airflow-conversion-chart-spg-135.html
Here I found a chart to do the conversion.
http://www.centuryperformance.com/airflow-conversion-chart-spg-135.html
To convert from 25" water to 28" water, multiply the cfm by 1.06. I only know this because my porter made that note on the flow sheet for the heads for me. I don't know what the conversion is for 40 to 28.
Norbs. Please use your numbers. We'll just pretend that my head porter worked on a set of M&As for the first time in his head porting career and came up with the best flowing set of M&A heads that has ever been produced. That seems realistic enough to me. 
Still,... you will not come close to 1130 bhp.
Still,... you will not come close to 1130 bhp.
So, using this conversion chart, what does that do to your 40" water numbers?
Based on the power source book Iron stage 2 heads flow 292 cfm@500 instead of 350 cfm. Now reading more it says the heads were modified not stock. Those number seem more realistic to me.
The Power Source book shows a modified stock intake port flowing 243 cfm @ .600" at 40" water. If you convert that to 28" water, you get 203 cfm @ .600".
My head porter got 209.5 @ .600" at 25" water. Convert that to 28" water and you get 222.07 @ .600" lift.
Now that doesn't seem that far off to me for a first time attempt on a new head. As a matter of fact, that seems pretty exceptional for a first time attempt.
My head porter got 209.5 @ .600" at 25" water. Convert that to 28" water and you get 222.07 @ .600" lift.
Now that doesn't seem that far off to me for a first time attempt on a new head. As a matter of fact, that seems pretty exceptional for a first time attempt.
The modified Stage II intake port in the Power Source book shows 364 cfm @ .600" valve lift at 40" water. Convert that to 28" water and you get 305 cfm @ .600" valve lift.
The Chapman head that was flowed for me came in at 304.3 cfm @ .600" valve lift at 28" water.
That doesn't seem too far out of the realm of reality to me.
The Chapman head that was flowed for me came in at 304.3 cfm @ .600" valve lift at 28" water.
That doesn't seem too far out of the realm of reality to me.
The numbers you have for the stage 2 head are most likely dead on!! I have flowed quite a few of them and that would actually be a very good set. What is the porting program number?? It is usually stamped on the rocker stand boss somewhere along with the date. The difference in power will be substancial and you will need chassis work to control the new found power. Also I would recommend that you use the standard stage 2 heads and not the square ports. The square ports will cause you to get VERY creative with the entire valve train to miss those ports. Looking forward to watching you progress with this project , it will be like christmas for everyone!!! Thanks for posting Mike
J-B Racing
Forced Induction
- Joined
- Sep 16, 2003
My Heads are Chapman Stage II, and the Ports are Huge. Porting is not as detailed as I would of done, but maxed out like I would of done.
I would go with those. They Flow well over 300 CFM............... 7's no doubt with your insane mind..
I would go with those. They Flow well over 300 CFM............... 7's no doubt with your insane mind..
The Stage 1 headers are 304. They've held up extremely well. The plan is to stick with the 304 material.
