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Old 12-25-2006, 01:19 AM
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Valve Stem Angles, Do they Matter? Truth or Fiction?

A while back a person made this comment:

"We have built Pontiacs, Fords, Chevies, Olds, Buicks, Hondas, Mopars and others over the years. Most all have been on the dyno and the heads always on the flow bench. 14 degree valve angles have no bearing in this conversation and are meaningless. In fact, stock 14 degree Pontiac big block heads are TERRIBLE flowing heads and to claim that's something special makes their actual flow even more laughable. Even Stock Edelbrock heads are NOTHING to right home about. Almost any decent aftermarket 23 degree Chevy head is either going to equal a stock Pontiac head with the better CNC variations blowing away even the Edelbrock head, all 14 degrees of them. NOW, step up to a RR 23 or 21 degree or 13-18 degree Chevy small block head and your in a different ballpark compared to the typical Pontiac aftermarket head. Only the very best Pontiac big block aftermarket heads are going to be in the same range as what these upper level types of heads offer."

Now my question is which is it? In one sentence this person says 14 degree valve angles are meaningless and in another sentence s/he says step up to a 21 degree or 13-18 degree chevy small block head and you’re in a different ball park. Now I take different ball park to mean superior, untouchable, to create a gainful advantage.

Now we all know that the stock gen 1 sbchevy has a stock 23 degree valve stem angle but nearly all top dog aftermarket heads tilt the valve stems closer 10 and 4 degrees. For example Dart race series heads claim “Dart 15’, 16’ and 18’ aluminum small-block cylinder heads offer a dramatic performance improvement over conventional 23’ designs.” When moving up the ladder to a pro stock style Little Chief head (notice the Indian’ish name given to this head, kind of remind you of a brand P engine) the valve stems are further pushed to 11 degrees where they claim “The huge flow resulting from the 11 degree angle”. They say that if you want to build the “ultimate bad-nasty small block race motor, you want the Little Chief.” Does valve stem tip angles matter?

A flow test @28 of water showed that a sbchevy head casting # 462, 156cc, peaked at 218/142 cfm @ .600 lift, a 23 degree head. Going to a 13 degree valve stem angle TFS 200cc was able to squeeze out 265/211 cfm @ .600 lift. To keep it even, a WP Sportsman II 201cc, same valve size and port size flowed at 243/156 cfm @ .600 lift. That is a 22 cfm difference in intake flow comparing to approximately 45HP difference on a 8 cylinder engine.

Another flow test of mid to late 1970’s model Pontiac head 6X-8 with 153cc intake ports came in at 214/158 cfm @ .550 lift, 28 inches of water. A #16 head ported flows 250cfm @ .550 lift on the 160cc intake.

Before and after tests of Edelbrock 2.11/1.65 Pontiac heads flowed 290/208 cfm @.600 lift, 215cc and 299/217 cfm ported.

For comparison Edelbrock 2.02/1.60 Performer RPM sbchevy heads flowed 227/176 cfm @ .600 lift, 170cc and 248/192 cfm ported.

Now if remember, the above professional engine builder claims that “In fact, stock 14 degree Pontiac big block heads are TERRIBLE flowing heads and to claim that's something special makes their actual flow even more laughable. Even Stock Edelbrock heads are NOTHING to right home about. Almost any decent aftermarket 23 degree Chevy head is either going to equal a stock Pontiac head with the better CNC variations blowing away even the Edelbrock head, all 14 degrees of them”.

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By the way, a Edelbrock/Chapman 6104 head w/236cc intake will flow 314/250cfm @ 28”. These are 18 degree high dollar heads. What happens when we tilt these valves another 3 degrees with the Edelbrock 15 degree 283cc intake head? 363/254cfm @.600 lift.

I guess valve stem angle don’t matter?

This thread will only deal with Gen 1 Chevy small block 23 degree valve stem angle head vs. all other non 23 degree valve stem angle wedge/compound wedge Gen 1 Chevy small block head. This is going to be done to keep from stepping on other's toes or breaking someone's heart.

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Last edited by QuenchPiston; 12-25-2006 at 10:07 PM.
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Old 12-25-2006, 02:19 AM
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They can both be correct. When talking about valve angles, it depends on the head around them. You can't compare valve angles on a chevy to valve angles on a mopar any more than you can compare port volume between the two.

Just like port volume, valve angles are meant to be compared within similar heads. A 23* chevy head might not flow as well as an 18* chevy head, but trying to compare a pontiac's 14* head has no bearing on the subject.

Like with port volumes. I hear people talking all the time about how this SBC head flows more with 200cc than this BBC head with 300cc. That means nothing, since the distance from the port opening to the valve on the BBC head is so much longer. A 300cc BBC port might have a smaller cross-sectional area than a 200cc SBC.

In general, each head has a "sweet angle" that is a compromise between shallow valve angles and short turn radius in the port. As a vague generalization, less valve angle makes better flow, but only up until the point that the sharp bend in the port starts choking it off. That might be 20* on a chevy head and 4* on an Olds head, but comparing the two is pointless. One way that folks get around that sharp turn is by raising the intake port. That maintains the same radius in the port, but provides a favorable, straighter shot at the cylinder. Higher ports have been used on factory engines, like the vortec and the LT4 with great success, even at the factory 23*. One of the downsides is packaging. The Vortec carb intake is a full 1.5" taller than the GM-issued non-vortec intake to accomodate the higher ports.

But I digress. Suffice it to say, when dealing with valve angles, comparing them ONLY works within the same engine family and its only a relative comparison at best. Way too many things factor into net flow to say that one head will definitely flow better than another with simply an angle change.
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Old 12-25-2006, 08:37 AM
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Going to a 13 degree valve stem angle TFS 200cc was able to squeeze out 265/211 cfm @ .600 lift. To keep it even, a WP Sportsman II 201cc, same valve size and port size flowed at 243/156 cfm @ .600 lift. That is a 22 cfm difference in intake flow comparing to approximately 45HP difference on a 8 cylinder engine.

Same engine family, same valve size, same cc ports. This is the closest similarity in heads to compare different valve stem angles and its a chevy vs chevy in this comparison.


WP
vs.
TFS http://64.233.161.104/search?q=cache...s&ct=clnk&cd=7
Oh yea, check out "A Death in the Family" at the bottom of the article.

Again, my consensus and others is that valve stem angles do not contribute to horsepower or flow gains. What do you think?
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Old 12-25-2006, 03:11 PM
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The straighter the port, the better the flow.
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Old 12-25-2006, 07:06 PM
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Comparing the valve angles of SBC heads to the valve angles of another engine is useless; too many differences exist like port geometry determined by pushrod location, head bolt locations and such.

There’s no question that with all things equal the reduction of valve angle can provide benefit. I consider the potential benefits to fit into four groups.

With a reduced valve angle:

1. The port approach to the valve can be changed.

2.The flow cone inside of the cylinder has a superior location with less obstruction with the cylinder bore.

3.The combustion chamber shape and size (determined by valve layout and angle) can be altered taking on a smaller shorter geometry.

4.Valve relief in the pistons can be reduced.
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Old 12-25-2006, 07:33 PM
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Quote:
Originally Posted by automotive breath
Comparing the valve angles of SBC heads to the valve angles of another engine is useless; too many differences exist like port geometry determined by pushrod location, head bolt locations and such.
.
Ok, lets move this discussion off of the "Comparing the valve angles of SBC heads to the valve angles of another engine is useless" over to a sbchevy vs sbchevy. I used that portion to set up a historical relationship of what was being used back in the 60's and 70's and where it was coming from. It seems that comparing a sbchevy part to another brand xyz engine part that it touches a nerve especially when the brand xyz part performs better, even if its just perceived that way.

For the rest of this discussion we'll keep it all chevy and examples like this:

Going to a Chevy sb 13 degree valve stem angle TFS 200cc was able to squeeze out 265/211 cfm @ .600 lift. To keep it even, a Chevy sb WP Sportsman II 201cc, same valve size and port size flowed at 243/156 cfm @ .600 lift. That is a 22 cfm difference in intake flow comparing to approximately 45HP difference on a 8 cylinder engine.

Same engine family, same valve size, same cc ports. This is the closest similarity in heads to compare different valve stem angles and its a chevy vs chevy in this comparison.

WP
vs.
TFS http://www.hotrod.com/techarticles/t...ead_dyno_test/ Oh yea, check out "A Death in the Family" at the bottom of the article.

Last edited by QuenchPiston; 12-25-2006 at 09:06 PM.
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Old 12-25-2006, 07:59 PM
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Quench, you're comparing apples to oranges again. Just like in the original thread that this discussion came up in.

The Pontiac Performer RPM head has 215cc intake ports and the SB Chevy has 170cc ports, a 45cc difference.

How about comparing a SBC head with a similar port size to the Pontiac RPM heads? A 210cc AFR SB Chev head will flow 289/220 int/exh at .600 lift. Compare that with the 290/208 on the Pontiac heads. At least these heads have similar port sizes...

Price?
Pontiac RPMs: ~$1700 through Summit
SBC AFR: ~$1500 through Jegs

The AFRs also have 2.08/1.60 valves instead of the 2.11/1.65s on the RPMs.

The 205cc AFR LS1 head has a 15 degree valve angle... AFR says they'll flow 298/230 at .600" lift. Their 225cc heads are rated at 320/250 at .600.

Your link brings me to a Google search page and it shows nothing about TFS heads. TFS does have a 13.5 degree head for LS1 (Gen III) engines, these are totally different than Gen I/II engines.

Last edited by Blazin72; 12-25-2006 at 08:09 PM.
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Old 12-25-2006, 10:01 PM
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Quote:
Originally Posted by Blazin72
Quench,

How about comparing a SBC head with a similar port size
.
The link is fixed.

I already addressed how this discussion is going to move in post #6 so the only thing that is relevant in your post is what is left of your post in the above quote.

This thread will only deal with Gen 1 Chevy small block 23 degree valve stem angle head vs. all other non 23 degree valve stem angle wedge/compound wedge Gen 1 Chevy small block head. This is going to be done to keep from stepping on other's toes or breaking someone's heart.

Question, was the switch or demise of the 23 degree valve stem angle head to the other less than 23 degree valve stem angle heads destined in order to remain competitive in top endurance speed events SUCH AS NASCAR?
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Old 12-25-2006, 10:31 PM
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Top level NASCAR engines don't use 23 degree heads either. They use SB2.2 heads, or at least they used to. They may have something else now, I don't know. The SB2.2 valve angles are 11 deg intake and 8 deg exhaust. BUT, heads like these also use raised runners which alleviate the sharp turn in the port you'd get if you kept the "standard" port location. Again, I believe somebody explained this in the thread you originally brought this up in.

When was that Hot Rod article written? A while back I asked about the Twisted Wedge heads and was told that those were becoming a thing of the past...

Also, I can't think of too many people on this board, or anywhere else for that matter, that actually have a small block built to take advantage of the MASSIVE size of those Victor 15 and 18 degree heads you listed in your original post. Those heads have a 250+ cc intake port, they are far beyond anything you, myself, or just about anybody else would have a need for.

I don't think the Gen III engine is being used in NASCAR either...

Last edited by Blazin72; 12-25-2006 at 10:39 PM.
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Old 12-25-2006, 10:49 PM
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Blazin, you can't compare a 250cc runner on a SB2.2 or other altered RR head to a 23 degree casting because the port is longer. To determine what will work you compare cross sections.
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Old 12-25-2006, 11:04 PM
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Quote:
Originally Posted by Blazin72
Top level NASCAR engines don't use 23 degree heads either. They use SB2.2 heads, or at least they used to. They may have something else now, I don't know. The SB2.2 valve angles are 11 deg intake and 8 deg exhaust. BUT, heads like these also use raised runners which alleviate the sharp turn in the port you'd get if you kept the "standard" port location. Again, I believe somebody explained this in the thread you originally brought this up in.

When was that Hot Rod article written? A while back I asked about the Twisted Wedge heads and was told that those were becoming a thing of the past...

Also, I can't think of too many people on this board, or anywhere else for that matter, that actually have a small block built to take advantage of the MASSIVE size of those Victor 15 and 18 degree heads you listed in your original post. Those heads have a 250+ cc intake port, they are far beyond anything you, myself, or just about anybody else would have a need for.

I don't think the Gen III engine is being used in NASCAR either...
No where in my post did I say that NASCAR is currently using 23 degree heads.

There are raised port 23 degree heads as well, so whats you point? This is a discussion about "valve stem angles". If you cant stick to the topic then you should either start your own thread or move on.

"Again, I believe somebody explained this in the thread you originally brought this up in." (Blazin72, 2006). Again, you are trying to jump topic and bring something up you are trying to turn into a win/lose competition instead of a discussion about "valve stem angles". If you cant stick to the topic then go else where.

"When was that Hot Rod article written? A while back I asked about the Twisted Wedge heads and was told that those were becoming a thing of the past..." (Blazin72, 2006). Again, you are trying to jump topic and bring something up you are trying to turn into a win/lose competition instead of a discussion about "valve stem angles". If you cant stick to the topic then go else where. Your point is illogical since the Gen 1 was designed back in the mid 50's and still popular with hotrodders.

"Also, I can't think of too many people on this board, or anywhere else for that matter, that actually have a small block built to take advantage of the MASSIVE size of those Victor 15 and 18 degree heads" (Blazin72, 2006). Again, you are trying to jump topic and bring something up you are trying to turn into a win/lose competition instead of a discussion about "valve stem angles". If you cant stick to the topic then go else where.

Again, this is only dealing with GEN 1 SMALL BLOCK CHEVY, NOT GEN 3.

Blazin72, if you are trying to turn this discussion around into something else then start your own thread on how to kill a discussion thread. If you have something that pertains to valve stem angles then do so. I am trying to figure something out or learn something here one step at a time.
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Old 12-25-2006, 11:13 PM
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Take a look at the picture below. The head on the left is a camel hump head while the one on the right is a Vortec. Both are 23* heads, whereas Pontiac uses about 14* and Olds uses about 6*.



First lets look at the three major angles that come into play: The angle of the valve compared to the stroke, the angle of the valve compared to the port, and the angle of the port to the intake runner.

First of all, Automotive Breath is right. In most situations, the straighter the valve is in relation to the bore, the more efficiently it will be able to deliver charge to the cylinder. Its also usually true that a smaller angle from the port to the valve delivers more air. All things being equal, decreasing the valve angle in relation to the stroke (like going from 23* stock angle to 15* aftermarket) INCREASES the angle between the port and the valve. The secret is finding a valve angle that maximizes one while not crippling the other. Too little valve angle will make too much of a turn in the port. Too much valve angle makes a nice straight shot at the valve, but then it has to turn more in the bore and it cripples flow. That's why many aftermarket performance race heads have raised ports. It softens the angle between the valve and the port.

Now, let's use the photo as an example. Those are both 23* heads. In the case of the Vortec, they have raised the ports. This doesn't improve the valve-to-cylinder angle, but it does improve the port-to-valve angle. So, even in the same manufacturer we see that saying one valve angle is the best or worst is pointless. The vortec head has more "room" to play with port location compared to the early camel hump.

The third angle comes into play as well, however not nearly as importantly. Unless you're using a tunnel ram intake, the intake has to make two turns; one from the vertical flow of the carb, and then another as it enters the head. Raising the port often increases the angle that the flow has to take as it enters the head. Its pretty mild, and manufacturers sacrifice hood clearance with taller intakes to combat it nicely.

But, back to valve angles. As you can see, heads that are low and compact typically have low port roofs. Combining small valve angles with heads like this can create a really sharp short turn in the port and create flow problems. The olds heads are a prime example of this and, to a lesser extent, the caddy and pontiac heads as well. Whereas stock Chevy heads could be described as having too much valve angle, I would describe the Olds heads as having too little. If someone made alternate-angle perfromance heads for Olds, they would probably INCREASE the valve angle to ease up the turn in the port and improve flow.
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Old 12-25-2006, 11:37 PM
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Quote:
Originally Posted by curtis73
Take a look at the picture below. The head on the left is a camel hump head while the one on the right is a Vortec. Both are 23* heads, whereas Pontiac uses about 14* and Olds uses about 6*.
.
That was really good Curtis and the kind of discussion I am trying to establish in this thread. However, lets at least use brand A, B, C, D, E, F, etc in the posts so as not to turn this back into a brand war if you know what I mean. Maybe you could edit the brand names in your post.

This is along the lines of what Curtis is talking about: http://64.233.161.104/search?q=cache...s&ct=clnk&cd=5
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File Type: bmp port3.bmp (79.9 KB, 102 views)

Last edited by QuenchPiston; 12-25-2006 at 11:43 PM.
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Old 12-26-2006, 07:52 AM
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Interesting stuff. I allways wondered how the different valve angles effected the heads.

Check this out. I was reading some NSCA rules about Pro comp and all motor class.


In the rules for weights

BASE WEIGHTS
• 2,800 lbs - Small Block, Inline Valve, 13-21 degree valve angle, 7.8 lbs/ci to 360ci, 4.0 lbs/ci over 360
• 2,800 lbs - Small Block, Inline Valve, <13 degree valve angle, 8.1 lbs/ci to 360ci, 4.0 lbs/ci over 360
• 2,800 lbs - Small Block, Inline Valve, >21 degree valve angle, 7.1 lbs/ci to 360ci, 4.0 lbs/ci over 360

Looks like they show >21 degree heads having a disadvantage in an all out 8 second race motor. I wonder if the same is true with say a 450hp small block.
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Old 12-26-2006, 08:45 AM
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I think it's been more or less stated already -- valve angle alone is meaningless. So is port volume/size. The entire head design is a compromise, and all parts relate to the other. For example, I'll use what I know best and hasn't been mentioned: AMC/Jeep six cylinder heads! Nothing I say about them should offend anyone!!

Early AMC/Rambler heads (the basic design used for the 4.0L came out in 1964) use very large ports with only slightly tilted valves. I don't know the angle, but they are nearly straight up. The ports have to make a near 90 degree turn down to the valves. These flow great at idle, but don't flow well at high speeds because of the sharp turn.

Now lets jump way up to 1987 and the first 4.0L. Well, actually, to 1984 and the first AMC four, which was derived from the six cylinder block. The "new" engine received a new head (as stated -- block is basically a six with the two center cylinders cut out -- some other changes were made, but that's irrelevant to the discussion). The new head design featured smaller, raised intake ports (compared to earlier six cylinder ports, which did get smaller and slightly better in the 70s) with a little more valve angle and new combustion chambers to match. When the 4.0L was designed, it got a stretched four cylinder head along with EFI. The difference was a jump from 110 hp in 1986 with a carb to 177 hp in 1987 with the new head and EFI. The power jump can't be attributed all to the head, of course, but the head definitely made a big difference.

Now go to 1991 and the 4.0L H.O. There was a 13 hp increase in power due to the intake ports being raised another 1/8" (approximate!) over the 87-90 design. Valve angle remained the same. The only other change was some minor reprogramming of the computer and advancing the stock cam by 2 degrees (IIRC). Advancing the cam moved the power peak up a little higher, and along with the reprogramming allowed Jeep to eliminate the EGR valve (the main purpose for the advance and tuning changes). Most of the power increase, especially at lower rpm, can be attributed to the port change. I arrive at this conclusion due to reports from Jeepers who run the H.O. head with carburetors on earlier 258 block. They report gains of 20-40 hp from the head swap alone. There is a little compression gain in most cases, but the wide power change is due to variations in engine builds.

Valve angle alone is meaningless. If you could change the angle in a head designed with a specific angle in mind, I doubt there would be much (if any) change in performance at all. The whole package -- angle, port, and combustion chamber -- has to be taken together.
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