Stock head flow cfm?

[SquadX]

I had a pair of 00 GTS heads put on a flow bench and they flowed 198 cfm. Does that sound extremely low as I remember hearing the stock GEN 2 heads flowed around 225 cfm. Can anyone clear this up?

I had the heads port/polish and valve and they got 50 cfms out of them so there are now seating at 247 cfm. But if they truely 225 stock then Ill have a bone to pick with the shop.
The heads were on another car (GTS 00 with headers and side exhaust, T & rr) and made 475 rwhp.

[SquadX]

and yes, I know I should have gone with Greg good but had heard good thing about the shop from some road course guys.

[RTTTTed]

A flowbench is a tool, not really good for measuring hp, just airflow at certain settings. Different settings and setups means different numbers. Like a dyno it gives and indication of performance that may be available.

A 25% increase in flow is great. Of course that depnds on the rest of the chart. What lift? What pressure? etc.

The main purpose of a flow bench is for measuring and correcting flow differences between ports in the heads for YOUR engine. If all the ports have equal flow the engine will produce max power for what you've done. If one port is slow compared to all other ports, it will drag the power level of the engine down.

Ted

[TexasPettey]

247 sounds a bit low, but not too far out for a basic porting job. I believe that the ROE heads are ~270 cfm.

By way of comparison, Greg Good got my Gen1 heads to flow 305CFM! I think he get's Gen2 heads near 320, but I don't have direct experience.

[SquadX]

247 does sound low. Shop said the heads keeping flowing as they go up but I am waiting for the flow chart.
If anyone has cfm for stock GEN 2 heads, let me know.

[RTTTTed]

If you wnat bigger numbers you could just ask for a higher pressure for measuring the flow. Like a supercharger higher pressure means higher numbers. Like a dyno, different benches will show different numbers.

How fast is the car? You've put on a 1,000mi. Feel any difference?

Ted

[SquadX]

Let me correct myself. My concern is that if stock heads flow 225 cfm and they are claiming a they got 50 cfm out of the heads then osmething is off. They said my heads flowed 198 cfm so are my heads just bad or....
I understand what you mean about different flow benchs yield different results but I would think all stock heads would flow the same. I will post the flow chart when they send it. Thanks for all the advice/help.

[RTTTTed]

So if the numbers are that important to you you can send your heads to Greg Good and have hom flow them on his bench for HIS numbers, or take another set of stock heads to your porter and get them flowed to compare your OLD head numbers.

Maybe Greg's machine will show huge numbers? Probably another stock set of heads will flow the same numbers as yours (unless they told you that the heads you gave them had bad casting flaws all stock heads are close) at that machines settings.

My point is that they're just numbers. If you want to compare to GG's numbers you should have your heads measured on his machine, not compare someone else's numbers to Greg's.

If your heads were ported properly, you'll feel a difference. If you had OS valves and seats installed you'll feel a bigger difference, etc.

There's different types and levels of head porting. A street car (without supercharger) will lose mileage, power and torque if a set of race ported heads are installed. Sometimes the numbers lie.

Ted

[2001 GTS]

Stock numbers were 227, Roe was 267, and Greg's were anywhere from 300 to 320.

I have Roe Heads and now am having a set of stock heads ported by Greg.

[KenH]

Here is a flow chart from JMCylinderheads website which show stock numbers over different valve lifts for both intake and exhaust to give you an idea of typical numbers on a stock head and then in this case compared to their Stage 3 heads with porting and larger valves.

50CFM increase, especially if the valves stayed stock, seems pretty reasonable to me and I doubt the factory castings are fundamentally flawed. My guess is that it is just the way they have their flow bench setup. In this chart, the pressure is set at 28" H2O. Factory valve lift is about .541.

[plumcrazy]

i think mine stock were 260

[ruckdr]

The answer to your question is in the form of a question:
Are all flow benches the SAME? NO
One flow bench relative to another flow bench has very little meaning.
One flow bench relative to itself has significant meaning when making port/combustion chamber changes, valve size changes, valve grind angle changes, valve seat angle changes, and other considerations; not to mention atmospheric differences.

Later,

[SquadX]

Well to clarify more on why I am so on numbers. I just want to make sure the shop is not just telling me they got the heads to flow 50 additional cfm. I know alot goes into port/valve job on a head and vary for different applications.

I should have the heads back late next week and will swap them out with my current heads on my car.

[plumcrazy]

talk to GG. he will tell you its NOT all about flow, its not the size of the chamber,its not the size of the valves. its a combo and the way the chamber is shaped has something to do it with it too im pretty sure.

[Russ M]

Originally Posted by SquadX

Well to clarify more on why I am so on numbers. I just want to make sure the shop is not just telling me they got the heads to flow 50 additional cfm. I know alot goes into port/valve job on a head and vary for different applications.

I should have the heads back late next week and will swap them out with my current heads on my car.

The only way to know the answer to your question is to have witnessed the air flow first hand. Problem is all it takes is a knob adjustment on the flow bench and the numbers can look completely different.

The other thing you can do is send your heads to someone you trust, and have them flow benched after you receive them. That way you will know for sure if they are what you paid for.