Wanted: flow numbers for stock heads

[AtomicDog]

All,

Searching has been unsuccessful. I am looking for flow numbers for large and small port 3.0, and 3.2 heads.

Same depression is great, same bench better, same operator on same bench is best.

To reiterate, I am not looking for your performance secrets. I just want to know what "They flow pretty good from the factory" means.

Thank you.

Chris

[AtomicDog]

bump...

Nobody willing to share baseline data?

Chris

[AtomicDog]

Somehow, I feel like I'm talking to myself...

I made some calls. Here's what I have for the 3.2 and large port 3.0 heads.

In stock trim, 28" H2O depression, intake side:

0.200" lift ~127 cfm
0.300" lift ~192 cfm
0.400" lift ~228 cfm
0.500" lift ~240 cfm (PEAK FLOW)

No one mentions exhaust flow numbers, as its percent of intake flow is their secret...

One head porter mentioned that you only pick up about 10-15 cfm on peak flow with a streetable port & polish, but the flow at 0.300-0.400" is much improved.

Would really love to get some data on the small port 3.0 heads.

Would also like to talk to someone other than myself...

Chris

[afterburn 549]

maybe post in eng rebuild section ?

[vreference]

This is a subject I'm really interested in as well. I'm from the domestic performance world where heads are the single most important performance part one can buy not counting forced induction.

I've never seen any numbers for the 911s but I assumed they must be good as no one gets too excited about heads.

If your numbers are correct then yes; that's pretty good flow for a stock motor. These numbers are very similar to the more street oriented heads offered by AFR and TrickFlow.

[AtomicDog]

I decided to post here, as the engine rebuild board doesn't get as much traffic.

There seems to be this general assumption that certain components can't be improved. It would be nice if everyone were a bit more willing to understand the status quo, then go out and challenge it.

Chris

[afterburn 549]

Then your exp. has been dif then mine........................................

[ChrisBennet]

You miight find this article interesting http://www.mototuneusa.com/think_fast.htm Find out why the auther says:
"It turns out that a flowbench measures the least important aspect of intake cycle efficiency !!"
-Chris

[vreference]

Originally Posted by ChrisBennet

You miight find this article interesting http://www.mototuneusa.com/think_fast.htm Find out why the auther says:
"It turns out that a flowbench measures the least important aspect of intake cycle efficiency !!"
-Chris

I would argue that it probably is unwise to go in and root around in the head of an engine that already produces 140+ naturally aspirated HorsePower per Liter. On an engine that's turning 7000 RPM (rather that 12-14K) and making 67 Horsepower per liter, flow rates are a much more accurate way to predict output and you can bet money more (at least when more is compared to factory heads) is better. But yes, even on automotive engines port volumes effect charging and one has to account for desired RPM Range.

The way this guy's article reads one could come away thinking that lower flow numbers are always better and, for obvious reasons, this cannot possibly be true.

[AtomicDog]

Some comments:

afterburn 549 - I will not attempt to dispute your experience on the forum. I merely suggest after reading through about a hundred posts about cylinder heads, the majority of those posters decided to do nothing without asking for any sort of test data.

ChrisBennet - The first thing that came to mind was that Sham-Wow commercial. It may really work - and I know that port velocity is of paramount importance. Flow at maximum valve lift is very, very misleading. Any of the domestic engine guys will swear that improved "swirl" has a greater role in engine response than the highest flow numbers. What the article references is indicative of both a head problem AND a cam problem.

Google "Engine Masters" or similar. There is an annual competition among engine builders which demands the most balanced and thorough integration of system components. These guys get unreal volumetric efficiency numbers by ensuring that all the parts contribute to the whole. Area under the curve is king and peaky engines don't come close to the top 20. I will find the link, but most of the top builders use smaller volume, conservatively but expertly ported heads. Similar to your link, no?

More on this later...

Thank you for the discussion, however.

Chris

[afterburn 549]

I did not say anything worth a hoot, but thanx.

[mytoy]

Originally Posted by afterburn 549

I did not say anything worth a hoot, but thanx.

You are correct.

[AtomicDog]

mytoy,

Neither did you, but your participation is welcome...

Chris

[racing97]

Reliable info on Porsche performance is always hard to find. I flowed some 3.8 factory race head 15 ye ars ago with 51mm intakes and got 230 cfm @ 25" which is pretty comporable to a typical Chevy at a depression of 25". The Porsche cross flow Hemi is tricky and responds to little, leaving it alone is as good as pouring money into it. Check out this data base-

http://users.erols.com/srweiss/tablehdc.htm#Porsche

regards

[afterburn 549]

Mytoy now you ruined my day,was the only glory I ever had .Your mother wears combat boots

[AtomicDog]

racing97 - I saved your link. Tons of good info. I just wish there was more Porsche data.

ChrisBennet - Try this one - http://racingarticles.com/article_racing-72.html
Although centered around domestic performance, much of the wisdom applies...

Chris

[ChrisBennet]

Originally Posted by AtomicDog

racing97 - I saved your link. Tons of good info. I just wish there was more Porsche data.

ChrisBennet - Try this one - http://racingarticles.com/article_racing-72.html
Although centered around domestic performance, much of the wisdom applies...

Chris

Thanks for the link!
-Chris

[Lukesportsman]

This seems to be the trouble of getting aftermarket heads off the ground.
CMW
Extreme
NineMeister

CMW seems the more budget oriented answer. As they use both billet and domestic engine experience to create their product. If they could slow the head speed down and create a "better" impression, I'd give them a go. (or obviously good feedback from others on here)

Extreme: Cast, great reputation, yet I haven't heard any numbers on the heads or engines yet.

9M is likely the best known and documented. Very impressive numbers and have yet to see anything in production beyond their 993 heads. They have been promising 911/930 heads for sometime. Likely from my research the best product, but do to exchange rate.....rather pricey for a non comp car.

Then again, these may all be great and its just the fact that so many Porsche Racers run in classes that won't allow such things leaving it mainly to a few with budgets allowing this for open track days. As a comparison, I was recently qouted about $4500 from a very respected builder on this board for a comp setup with my 3.2 heads.....no flow numbers presented to after there done and flowed before return.

[Bart_dood]

Originally Posted by AtomicDog

bump...

Nobody willing to share baseline data?

Chris

I don't have any numbers for you but perhaps its the case that there is little to be gained from opening up the ports by any appreciable amount? some cars have ports that are on the large side and sometimes there is little to be gained from making them any larger, you might just slow down the inertial ramming effect and lose mid range torque.
If the 3.2 is such an engine then a clean up of any casting marks etc is all you need, larger valves might be worth exploring if the ports are already large, the main restriction in 99% of heads is the valve curtain area.

[RWebb]

surprised nobody has mentioned the extensive head porting done on some smaller heads in a recent post by kenik or kenikh -- I think that is his user name.

search terms include oval + D'ed + offset