[65nss4spdGTO]

Originally Posted by john marcella

I here a lot of people talking only about CFM. There is so much more to a head than the flow #s. Correct cross section and design. Then CFM.

And by the way I/Ex flow ratios are crap. Ex area vs HP and rpm and desirable Valve timing. Most of the good stuff on the exhaust side will happen when cyl pressures are so high the the air speed will be at the local speed of sound witch will react to area ,not flow #s. And as long as you can decrease the air speed to less than the local speed of sound by the time the piston is at BDC, there should not be much pumping losses. JMO

This is true, but a 2.200" valve will only flow so much air, a 300 CFM head can only make so much power. Pontiac's turn down style exhaust changes the direction of the air in a way it doesn't want to go at high air speed. We've done minimal intake work and worked the exhaust a great deal on some specific heads and have picked up HP and improved ET's.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

[cfmcnc]

Originally Posted by 65nss4spdGTO

If square ports or tall thin ports were most efficient, the Pro-Stock guys would cast the heads that way. That's why the lifter bore and block positions have been designed the way they are. With the success of the Edelbrock performer head, the best improvement made is moving the push rod out of the way and using offset stuff. If the lifter bores position didn't create this problem, we wouldn't need the offset stuff. It's all about usable real estate in relation to the bore size and bore spacing.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

Exactly Calvin... but we're working within limited spacings and positions...not creating new ones from the drawing board like the prostock stuff is . I downsized your statements a little to focus on what others here have missed in this discussion. It's all about AREA and speed for a given displacement underneath the cylinder head . And given the design of our beloved Pontiac limits the ability of scratch designed lifter postions and bore spacings...to achieve effective area to feed the growing displacements... the port that will work the best in a high end application will probably end up rectangular. As you need 4.100-4.300 of AVERAGE CSA to feed 535 c.i. at 7300 rpm (and that's conservative) and make any sort of competitive power to what's already out there...1,080-1,120 with cast intake and one carb . Pushing the limits with a Pontiac presents it's challenges...think cramming a large BBC port (conventional) into the Pontiac head. It really can never be big enough to keep up with the evolution . I think the approach angle is almost right for an oval...just not the area. I'm speaking of course of a max effort version of the head. Smaller c.i. or application specific stuff like Jim is working on is another story . Johnny

[BruceWilkie]

Originally Posted by john marcella

I here a lot of people talking only about CFM. There is so much more to a head than the flow #s. Correct cross section and design. Then CFM.

And by the way I/Ex flow ratios are crap. Ex area vs HP and rpm and desirable Valve timing. Most of the good stuff on the exhaust side will happen when cyl pressures are so high the the air speed will be at the local speed of sound witch will react to area ,not flow #s. And as long as you can decrease the air speed to less than the local speed of sound by the time the piston is at BDC, there should not be much pumping losses. JMO

Perhaps the way I've worded it is crap.

Yes All the exhaust "wants" to leave when the ex valve 1st cracks open. It cant due to restriction. A large % of exhaust AND pressure IS relieved by BDC even on a stock motor. But even on a race motor we are not likely hitting 100% pressure relief at end of bdc dwell. What doesnt get relieved adds to pressure on the upstroke due to exhaust restriction. This creates a pumping loss and also impacts intake column movement at overlap, overlap requirement, cylinder purge etc..

An "ideal" "goal" would be all exhaust pressure relieved by end of bdc dwell and no new pressure created on the upstroke. That would leave only swept volume to deal with.

Flow "balance" DOES play a role here. But not in the way most think. Also flow capability at low lift on the opening "side" of the exhaust is important. The more exhaust and pressure that can be relieved by end of bdc dwell the better. You can only open the exhaust valve earlier to a point untill it negatively impacts the power event. You can only open the ex valve so fast before you have issues doing that.

And you cant flow into the cylinder until the pressure in the intake port is greater than in the cylinder. Exhaust pressure influences that.

That leaves reducing restriction to flow as the next means to get to that "goal" of swept volume only on the upstroke of the exhaust. On the closing side of the exhaust event better flow can assist the purge that occurs during overlap. Until cylinder pressure is lower than intake pressure the intake charge cant move in. Good exhaust flow influences the purge at overlap and aids VE

Please, no offense to anyone,.. stating "I've acheived "x" with a low exhaust percentage" is ok for bragging rights. However it doent answer the question "what could I have acheived if I had better exhaust flow?". IMO you should look at percentages... but in a far different way. Perhaps from differing ends!

[pastry_chef]

Originally Posted by BruceWilkie

An "ideal" "goal" would be all exhaust pressure relieved by end of bdc dwell and no new pressure created on the upstroke. That would leave only swept volume to deal with.

This would be FAR from ideal!

that scenario would have a severe negative impact on what is commonly referred to as the "5th cycle" near TDC to draw intake charge.

[BruceWilkie]

Originally Posted by pastry_chef

This would be FAR from ideal!

that scenario would have a severe negative impact on what is commonly referred to as the "5th cycle" near TDC to draw intake charge.

Dont bet on it. 1st off it would not likely be possible to acheive that condition and if you did it would pretty much accomplish the same effect. Study "5th cycle" a bit more closely. It occurs on running engines even granny's car to a small degree. Cylinder fires near tdc, as it approaches bdc the ex valve opens. A large pressure front begins to head out the exhaust. By time piston nears tdc that high pressure front is somewhere down the pipe. Behind that high pressure front is a lower pressure "front". Lows always follow highs. the charge is literally being "pulled" by the high. This is how the intake charge can begin moving into the chamber while the piston is still in TDC dwell.

Yes header tuning/valve timing can enhance the effect. However if you did accomplish no pressure on the upsweep you wouldnt need to enhance the scavenge effect as it would already be accomplished.

[pastry_chef]

I would indeed bet on it and win as always.

Unlike yourself, I do not make statements unless I know for absolute FACT; Meaning repeated REAL WORLD results.

Sorry to say you show a consistent trend of "speaking above yourself", I never understand why people have that need.

I will let you believe you are correct.

[BruceWilkie]

Some minor editing within the quote...

Originally Posted by pastry_chef

I would indeed bet on it and win as always.

Unlike yourself, I do not make statements unless I know for absolute FACT; Meaning repeated REAL WORLD results.

Sorry to say you show a consistent trend of "speaking above yourself", I never understand why people have that need.

You are contradicting yourself. Sounds like opinion to me

I will let you believe you are correct.

I'll restate it this way. A zero cylinder pressure through the upsweep of the exhaust event would enhance what you refer to as 5th cycle, not defeat it. No one is likely to ever acheive that zero pressure condition. However, the closer you can get to zero on the upsweep of the exhaust event the better the cylinder will be able to purge. Especially during overlap tdc dwell.

Again, most that discuss 5th cycle discuss the high speed scavenge effect and how it can be enhanced. Seldom discussed is that the purge is already there at tdc dwell (if you have overlap), unless you defeat it by opening the intake after the exhaust is fully closed.(The impact of the purge itself can be very minimal on a basic everyday motor but it exists regardless and can be enhanced) Again the intake charge cant enter the cylinder until its pressure is greater than the cylinder pressure. Again when the exhaust valve 1st opens it sends a high pressure out of the cylinder into the port/pipe. Behind that initial high pressure is a lower pressure. The "high" is literally pulling the "low" behind it.(analagous to weather fronts) That creates a condition where cylinder pressure can be brought lower than than the pressure on the intake side, allowing chamber fill/purge to occur while the piston is virtually parked at tdc dwell.

I'm not asking you to think outside the box. I'm suggesting that you dont box yourself in and look at it more closely.

The intent is to share and learn not jab at each other. Sorry if I've jabbed back.
If you want to discuss further, PM me or start another thread. We are taking this too far off topic. The exhaust event is a worthy topic though.

[cgeise]

Originally Posted by pastry_chef

I would indeed bet on it and win as always.

Unlike yourself, I do not make statements unless I know for absolute FACT; Meaning repeated REAL WORLD results.

Sorry to say you show a consistent trend of "speaking above yourself", I never understand why people have that need.

I will let you believe you are correct.

What an ass --- the vast majority of competitive heads being built today are trending towards an oval shape intake and a I/E ratio in the 68 to 74 percent range, those are facts.These are heads that are being done by the largest and some of the best in the country but you seem to know better. Yes, there are specific applications that require different approches but for most of the guys here on this sight its just not applicable. Bottom line -- time will tell who "wins" and what that winner will look like. This subject had some good imput from some well recognized porters -- even they don't agree on everthing, but they dont come on here and display there self importance by talking down to other.
And now I will "let you" believe you are correct in your little universe

[slowbird]

Originally Posted by cgeise

-- time will tell who "wins" and what that winner will look like.

You will never know what the fastest guys have!!

[slowbird]

Originally Posted by 65nss4spdGTO

I'm actually offended by this comment. First off, we have a port that is pretty decent, but it doesn't exceed my CV-1 head, KRE HP's I've worked or the Tiger head coming from AP. I also had a new set of 12.6's for sale almost a year ago, no takers here on this board when at the time, no one else could get them. As far as the amount of time we have in this port, it would cost well over $5K to cover the hours spent in development and we don't have the port digitized for CNC yet.

We should be able to post final flow data and final pricing by the end of next week, at this point we have a head flowing:

216 cfm @.300
347 cfm @.500
441 cfm @.700

Thanks.

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

Calvin how are things coming along on your head? Interested in hearing what the final flow numbers are and the pricing.

[65nss4spdGTO]

Originally Posted by slowbird

Calvin how are things coming along on your head? Interested in hearing what the final flow numbers are and the pricing.

It's been idle, we are giving a 555ci engine away at the PRI show and had to make that the priority the past week.

Nice shot of the wheels up!

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

[dda72]

Originally Posted by 65nss4spdGTO

It's been idle, we are giving a 555ci engine away at the PRI show and had to make that the priority the past week.

Nice shot of the wheels up!

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

Ditto on the wheels up pic!

[Dragncar]

So, what ever happened to Bartons 450cfm "oval port" High Ports. He made them and we never heard of them on a running engine. There was a thread on them over at PZ.

There should be no reason a Pontiac could not exceed the HP of any sbc. Its a physically larger engine. The biggest head gasket should win. As has been stated in this thread, more real estate to work with. What would it take, a real short deck Pontiac with further head development ? At least there would not be a problem calling a short deck Pontiac a "Pontiac" with inline heads.

Those are some very nice numbers Calvin. One could make some good power with those.
A better than Victor intake would be needed.

[johnta1]

we are giving a 555ci engine away at the PRI show and had to make that the priority the past week.

Cool!

What booth are you in?

[65nss4spdGTO]

Originally Posted by johnta1

Cool!

What booth are you in?

The engine will be on display in the Project 1320 booth, just look for Don Garlits.

http://www.project1320.com/

Calvin Hill
Hill Performance / Mondello Tech Center
708-250-7420

[johnta1]

I looked for project 1320, Don Garlits, and Mondello and didn't see any booths?

Do you have a booth number?

[BruceWilkie]

Last I saw was http://www.ebay.com/itm/Mondello-Eng...sories&vxp=mtr

The winner will be drawn by Mary Mondello and Traci Hrudka at the World Products booth at the PRI Show December 3rd, 2011.

World is supposed to be at booth 2523

[johnta1]

Thanks, Bruce.


I added it to my list.

[slowbird]

Anyone know if extra head bolts can be added to the pro ports like the Tigers?

[John Langer]

Originally Posted by slowbird

You will never know what the fastest guys have!!

My junk has a CSA of around 4.40", I have a 1" cam, I make peak hp around 7900 and shift at 8600. What else do you want to know...