General Cylinder Head Flow Numbers discussion
 

Hi All,

I'd like to keep this discussion as general as possible to encourage dialogue on the topic. If you're open to disclosing specifics that is totally up to you, but I feel like there are probably a few opinions on this topic and it could be a bit of an interesting discussion.

Basic question here is when you have your heads done or you do them yourself in legal stock eliminator form (whatever that means in this day and age to you individually) what is the most important improvement in flow characteristics you are looking for? 80-90% of us have less than .500 lift, so are you looking to see the numbers from .400-500 to jump? Are you looking at port velocity? are you looking at average from specific lift values? something else?

This isn't really a discussion on "HOW TO GET THERE" but more with your end results compared to where the heads started stock what makes you decide the heads are going to make you .800 .900 1.00 under capable verse the stock castings?

Brad

Re: General Cylinder Head Flow Numbers discussion
 

Port velocity and optimize the valve opening and closing events.

Re: General Cylinder Head Flow Numbers discussion
 

Curious what you man by "optimize the valve open and closing events" when it comes to the valve job or flow characteristics of the cylinder head. Maybe I'm just completely naive, but wouldn't this been completely controlled by camshaft design after you already know the flows and velocities of the ports?

Re: General Cylinder Head Flow Numbers discussion
 

On the V6 truck engine I went to core suppliers to get the best sets of heads for each approved casting number. How I judged the heads by valve protrusion into into the chamber. I bet I looked at 200 + pairs of heads. I think I had 4 or 5 sets of heads of each casting number to clean and test on my flowbench. Most of my winnings from Atlanta were used to buy the bench Jimmy Bridges did my first set heads for the truck. I think he picked the two best out of six.

Re: General Cylinder Head Flow Numbers discussion
 

You want a port that continues to flow well past your max lift point and not go turbulent and is quite on the bench!

Re: General Cylinder Head Flow Numbers discussion
 

Was that to minimize chamber volume?


Rick Thomason
GTOMayhem

Re: General Cylinder Head Flow Numbers discussion
 

I’m not a head guy but with the valves hight in the head, if you had to sink one to get the cc’s correct it usually didn’t hurt the flow real bad. In most of the old cast heads one or two runners are just turds and are difficult to get to respond. I have made a few test valves.

Re: General Cylinder Head Flow Numbers discussion
 

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.

Re: General Cylinder Head Flow Numbers discussion
 

I have not done an stock eliminator heads but looking at the rules, I do find it interesting what is being talking about. It looks to me the only area one can get creative is the valve job.



Stan

Re: General Cylinder Head Flow Numbers discussion
 

You need to read the gray area part of rules. Most of the heads are ported( acid and others ways the camouflaged) to pass tear downs!

Re: General Cylinder Head Flow Numbers discussion
 

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

Re: General Cylinder Head Flow Numbers discussion
 

Folks,

One should realize a few points in a cylinder head discussion of NHRA stock eliminator head and manifold components.:D "trust but verify" is a good methodology to follow.

1) The rule book might state one thing but in practice the "passed tech" cylinder heads are quite another and many examples of ported/reshaped and covered up have passed with abandon. That includes manifolds. It is sometimes a discretionary call as it states in the rulebook. Methinks that there was (is) at least one lawsuit that reflects same.:rolleyes:

2) Cylinder head rules indicate that the valve job is "legal" all the way down to the valve guide. This area can be very creatively used by something like a single point cutter that can re-contour the area described. Other methods can also be used.;)

3) Starting off with primo castings is the best beginning, but not totally necessary if one goes the route mentioned in 1) above.

Regards to All that like this kind of stuff,
HB2:)
Dissident

Re: General Cylinder Head Flow Numbers discussion
 

With core shift and with the high number of different cylinder head part numbers for the same engine combination, it would make it very difficult.

This is a true story...
Many years ago I got a call from NHRA asking me about technology to shrink metals, especially cast iron. The reason was that there was a particular engine combination that every time the engine went through tear down, the cylinder heads were compliant and at the next race, the car would go faster.

So, NHRA purchased a pair of the suspect cylinder heads from a junkyard, sends the cylinder heads to a trusted shop to have them built to the rule book guidance and when they poured the cylinder heads, the port volumes were bigger than the suspect cylinder heads!

I explained to NHRA that during the casting process, a temperature differential or the abundance of Ferrosilicon will cause shrinkage of cast iron. The reason why many racers check and flow lots cylinder head castings. ...or the cylinder heads were spray welded to add more material.

Re: General Cylinder Head Flow Numbers discussion
 

Ralph not being in the room when the heads are being flowed and not owning my own stuff to do it... is there a way to know if the port is quiet by looking at CSA and port velocity? Do I just need to ask the head guy if they were quiet?

How far past max lift would you like to see it "flow well" .050?.0100? more? and by "flow well past" do you mean the CFM should still be increasing or just not backing up a lot? if it just holds the peak CFM from say .350-.500 at a fairly constant CFM but isn't gaining anything or dropping off at all is that okay?

Thanks
Brad

Re: General Cylinder Head Flow Numbers discussion
 

Brad,

It needs to be on the flow bench and the quietness is the sound of the air. Usually test 0.100" ~ 0.150" past your required maximum lift and don't worry about the behavior past that limit.

Re: General Cylinder Head Flow Numbers discussion
 

Folks interested in flow bench testing::D
These days I can't hear worth a dip, but I do know a fair amount about flow bench testing and there are multiple ways to discern the stability of airflow in the cylinder head or manifold without hearing....;)
The cylinder head should be tested with the manifold and carb/throttle body attached so the "real" flow test is indicative of what the system is doing.:cool: That kind of testing is a bit more difficult, but much more meaningful. From that flow data, potential power can be predicted as can the rpm at which peak power will occur. Measuring a load of intake manifolds is worth the effort. Unless one follows the outline that I posted previously. You might find some worthwhile tips in HPBooks, Engine Airflow

Regards,
HB2
Dissident

Re: General Cylinder Head Flow Numbers discussion
 

You guys might want to take a look at the "odd" little rule change that's in the 2020 to 2021 rule changes. It just might have been put in there for a reason.

Re: General Cylinder Head Flow Numbers discussion
 

Saw that...inconspicuously and discreetly placed...

SECTION 11A: STOCK CARS: 1, BLUEPRINTING (Page 2) (12/3/2020)
Permitted per NHRA Specifications available from NHRA Technical Services
Department headquarters. Stock factory OEM Components (unless otherwise
specified) must be retained and remain unaltered (i.e., cylinder heads,
connecting rods, pushrods, crankshaft, etc.).

Clear as mud especially when aftermarket cylinder heads are allowed.

Re: General Cylinder Head Flow Numbers discussion
 

I guess I don't how that wording changes anything with the way the rules were written before... It already spells out what can be done and what can't be done as far as "alterations" so that would fall into "unless otherwise specified" meaning that all the heads that passes last year will pass this year just the same..

Re: General Cylinder Head Flow Numbers discussion
 

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

Re: General Cylinder Head Flow Numbers discussion
 

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

Re: General Cylinder Head Flow Numbers discussion
 

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.:eek:
Although such things might be beyond the regular guy's interest or budget, others have done so (paid to have it done).:rolleyes:

Regards,
HB2:)
Dissident

Re: General Cylinder Head Flow Numbers discussion
 

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

Re: General Cylinder Head Flow Numbers discussion
 

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.

Re: General Cylinder Head Flow Numbers discussion
 

So how much valve loft are we talking about?

Re: General Cylinder Head Flow Numbers discussion
 

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.

Re: General Cylinder Head Flow Numbers discussion
 

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

Stan

Re: General Cylinder Head Flow Numbers discussion
 

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

Re: General Cylinder Head Flow Numbers discussion
 

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]

Re: General Cylinder Head Flow Numbers discussion
 

Stan,

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

Re: General Cylinder Head Flow Numbers discussion
 

Just on restricted travel and solid lifters. As long you have good quality lifters and checked the spring pressure often you are good. Prior to the allowance of aftermarket roller rockers, you needed to have a box of spare OEM rocker arms because the tendency of the pushrod to go thru the rocker arm cup. :D

Re: General Cylinder Head Flow Numbers discussion
 

Been there done that. :D


Stan

Re: General Cylinder Head Flow Numbers discussion
 

-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

IMHO
And Head C has correct port volume, but probably has a larger CSA at several key places in the port.

Re: General Cylinder Head Flow Numbers discussion
 

Let me add a little more specific question to this:

.444 valve lift cam.

Lift -------- Head A -------------- Head B

.050 -------- 50.8 -------------- 35.1
.100 -------- 81.0 -------------- 57.6
.150 -------- 108 --------------- 88.2
.200 -------- 129.9 ------------ 117.12
.250 -------- 142.3 ------------ 136.6
.300 -------- 157.0 ------------ 158.0
.350 -------- 161.8 ------------ 172.6
.400 -------- 166.8 ------------ 175.6
.450 --------- 166.4 ----------- 175.6
.500---------- 165.8 ----------- 174.5

Which head would you rather have? Head B is a bit better up top but Head A is substantially better down low. I would still say looking at it from an area under curve stand point that Head B would be slightly larger but very small difference.

Re: General Cylinder Head Flow Numbers discussion
 

Low-lift flow is very important in a "restricted" engine.

Re: General Cylinder Head Flow Numbers discussion
 

You need to take into consideration the intake manifold and throttle body flow also. No matter how much air flow you have on the cylinder heads, the intake manifold and throttle body/carburetor, can become a restriction.

Re: General Cylinder Head Flow Numbers discussion
 

exhaust port flow is going to come into play in this too

Re: General Cylinder Head Flow Numbers discussion
 

When doing comparative testing, it is imperative to use the same radius inlet guide (not rolled up clay method) as the specific entry has influence on results. On the exhaust side, one should always use a short length of pipe for the same reason.

The methodology of area under the curve is best evaluated by graphics and using the cfm/sq in rating. One should have a graph of the cam / valve lift for that evaluation as well. It is in these types of details that gains are sqeezed out of otherwise run of the mill components.

After the heads are evaluated, then one can begin sorting out manifolds and carbs and placement of same.
Notes, lots of notes so you can take a look at what items worked the best. This is particularly important when you are evaluating valve jobs.
Lots of patience, study, and thoughts with coffee will help get the job done.:D

Regards,
HB2:)
Dissident

Re: General Cylinder Head Flow Numbers discussion
 

I get that, but would you run a set of heads you knew flowed less air intentionally knowing the TB and intake may be a restriction larger than the heads or would you put the "best" flowing heads on regardless?

I think I'm more curious as to what people are more concerned with if area under the curve is similar between 2 sets of heads. Having the larger peak numbers or giving up a little up top to have much better down low numbers. Obviously there are other factors to consider... mainly possible restrictions before the port and then the relation to exhaust port flow as mentioned in the next reply. But at this point for a simplistic questions and answer.. would you prefer a head that peak flows more or flows down low more given the overall "area under the flow curve" is generally equal.

Billy seems to lean towards low flow potentially with his response.

Re: General Cylinder Head Flow Numbers discussion
 

I'm playing with those curves now. That is one reason I am asking the questions I'm asking. Trying to determine if area under the curve if just area under the curve and doesn't matter where it is.. obviously where the curve moves will determine other pieces like cam and timing events, possibly converter as well and potentially effect header lengths and sizes, but I have to choose a set of heads first to match those things to the flow curve.. If area doesn't matter as long as the other parts are matched well to the system as a whole... great.. if having the flow low but giving up some up top is better.... great... if wanting the great numbers around peak lift while giving some up early is best... great.. just thought I'd pick the brains of others that have had to think about this stuff before I did.