Bigger valves?

[John B]

What cfm gain do you get going from a 1mm (stage 2) to 44/37 (stage 3) head?

[amoparacer]

Post your flow sheet be a hero. I really dont understand why the vendor's dont have there flow sheets on the web store. Seems to me to be important pre purchase info.

[Speedeuphoria]

Because flow sheets are not proof of anything, just like dyno numbers with correction things can be fudged to get better results.

[BadAssPerformance]

Every head is different, but a general estimated % of increase would be helpful to the prospective buyers out there.

[glhs727]

Several years ago, we had the same guys that used to port LRE's heads, also do some for us. The big valve head gets a little more work than the +1mm heads so it isn't an exact comparison, but flowing both the big valve and the +1mm heads on the same superflow bench on the same day, one after the other, the big valve head flowed approx 10% more than the +1mm (about 20 cfm at .500 lift). I will try to find the old flow sheets but that was way back in 2001 or 2002, so I'm not even sure if we still have them.
The +1mm is a great head for people on a budget, and the big valve head is a great head for someone looking to extract every ounce of hp they can. But if you ask 6 people you will get 6 different answers and opinions are rampant on these forums. Make your choice based on what you feel is best for YOU.
later,
Cindy

[turbovanman²]

Flow numbers mean squat unless you do a comparison, IE before and after, then you know how much difference there is, :thumb:

[glhs727]

Simon,
These numbers were comparing both swirl heads, both on the same bench, both on the same day. The only difference was one was +1mm valves, the other was 44/36.9mm valves. That is the question the OP asked (what is the flow difference from a +1mm head to a big valve head?) and it was answered.
Flow numbers don't mean squat if the question was "what does a +1mm head flow?" and everyone threw out all sorts of numbers that doesn't mean anything. It would be important to have a stock head versus +1mm head numbers done on the same flowbench on the same day etc... if again the question was what does xyz head flow? But that was not the question.
later,
Cindy

[glhs727]

Post your flow sheet be a hero. I really dont understand why the vendor's dont have there flow sheets on the web store. Seems to me to be important pre purchase info.


because flow benches are like dynos and can give different numbers. If we posted a flowsheet and said a stock head flowed 100 cfm and the ported head flowed 200 cfm for a 100cfm gain, but the customer took it to another guys flowbench and the stock one flowed 50 and the ported flowed 150, it would still be a 100 cfm gain, but the customer then slams us on the forums because his head didn't flow 200 cfm...... it's a no win situation.

[turbovanman²]

Simon,
These numbers were comparing both swirl heads, both on the same bench, both on the same day. The only difference was one was +1mm valves, the other was 44/36.9mm valves. That is the question the OP asked (what is the flow difference from a +1mm head to a big valve head?) and it was answered.
Flow numbers don't mean squat if the question was "what does a +1mm head flow?" and everyone threw out all sorts of numbers that doesn't mean anything. It would be important to have a stock head versus +1mm head numbers done on the same flowbench on the same day etc... if again the question was what does xyz head flow? But that was not the question.
later,
Cindy

I am agreeing with you, flow numbers on there own don't mean anything.