General Cylinder Head Flow Numbers discussion

[Stan Weiss]

Originally Posted by SSDiv6

"unless otherwise specified" refers to the NHRA approved aftermarket cylinder heads.

Since in stock eliminator you can not fill the port. How many of the after market replacement heads in the NHRA Acceptred Products list have a port volume that is legal?

Stan

[Dissident]

There are some heads out there that have been welded prior to reshaping. Cylinder port volume varies a great deal on castings, but can be closely controlled after being "tuned up" as it were.
Although such things might be beyond the regular guy's interest or budget, others have done so (paid to have it done).

Regards,
HB2
Dissident

[HawkBrosMav]

Originally Posted by SSDiv6

"unless otherwise specified" refers to the NHRA approved aftermarket cylinder heads.

A) I see how you are reading that and I don't disagree with your statement, BUT I still don't see how this addition to the wording of the rules changes how they can be applied. The sentence already had "etc." in the verbiage which opened it to any interpretation NHRA could come up with...

B) if you read that and ignore the cylinder head addition it clearly deems literally every single Stock Eliminator car illegal... name me one single car that is running Stock factory OEM unaltered pushrods... in addition to that find me the rule that says we can even run larger diameter or thicker wall pushrods. At least there is a whole section on what can and cannot be done to cylinder heads.

The Blueprinting rule is written to basically say you can only use aftermarket parts when they are listed on the "NHRA Accepted products list" otherwise you have to use OEM unaltered pieces. We all know this isn't the case based on the multitude of rules that follow this statement so them adding cylinder heads to the verbiage doesn't make any sense and unless they can explain to me what it actually changes in application means absolutely nothing..

now that we had this little tangent about a rule "change"... i'd like to try and steer this post back on topic... Other than flow holding past max vlave lift and a quiet port are there any specifics you're looking for from head A to head B to determine one is a .500 under head and one is a record setter? I want to restate.. I'm not looking for the HOW you did it or what you did to to find the best cores to start with...I simply want to have 3 sets of heads.. all starting from an equal "these three heads are the BEST i can find"

-Head A stock completly untouched
-Head B has flow characteristics that make me feel like it will be okay (.5 under)
-Head C has flow characteristics the make it a record setter

Knowing all 3 heads will pass tech what does Head C's flow numbers, port velocity, or anything else you can use to analyze a head on paper look like that makes it the one you chose over Head B.. Again physical things done to the head I'm not asking about. If I handed you the flow printout of 2 separate heads ported by 2 separate people and told you to pick the one you thought would be fastest cause you were headed to INDY tomorrow what is the most important thing on that print out that would sway you to pick one over the other. Or how do you rank the things you look at when making that choice.. as I'm sure it's not just one thing going into that decision.

This might be too much to ask as I'm sure there are many people out there that probably make a bunch of money knowing why stuff goes fast and what their intended goal is when they flow something to know they've got a winner, but if someone is willing to talk about it that's why im asking.. Thanks

Brad

[Adger Smith]

Sure looks like my old Boss has been at work on the rules.
Giving a little and taking a little with things camouflaged. LOL WR

Brad,
You would need to send me a little more info than 2 flow sheets.

[Glenn Briglio]

Originally Posted by SSDiv6

I should have explained better. Optimize the velocity, and like Ralph Powell said, go at least 0.100" ~ 0.150" past your maximum lift and you want a quiet port.

Seen too many heads with big flow numbers and low velocity that do not make power. Your valve job angles are also critical and different for each head manufacturer.

The reason why you want to have a good flow past your maximum lift is because you can make more power by doing a controlled loft of the valve past your maximum allowed lift. The cam lobe is designed to toss the lifter and increase valve lift to make more power while still checking legal during a static lift inspection.

So how much valve loft are we talking about?

[SSDiv6]

Originally Posted by Glenn Briglio

So how much valve loft are we talking about?

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

[Stan Weiss]

Originally Posted by SSDiv6

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

Do you have an idea how much more area under the curve there maybe verses the dwell type setup we ran years ago?

Stan

[Glenn Briglio]

Originally Posted by SSDiv6

On circle track restricted engines, with a combination of a specific valve guide height and lobe design, I have seen a valve launched as high as 0.160" during Spintron testing. Because of valve to piston clearance, it is a bit of trial and error.

Got to be pretty destructive application and not for roller lifters.

[Ralph A Powell]

Yes they have one they got it image the fuel heads and we’re going to use it on the the Factory Showdown cars but the further they got into the deal they just through up the hands up and gave up on them but still use it on the Fuel cars.


QUOTE=Stan Weiss;629202]Ralph,

Thanks. Didn't I hear a couple of years ago NHRA got something like a FARO, touch probe / laser scanner for checking stock ports?

Stan[/QUOTE]

[SSDiv6]

Originally Posted by Stan Weiss

Do you have an idea how much more area under the curve there maybe verses the dwell type setup we ran years ago?

Stan

Stan,

I will have to look at my notes and I will share the info.