Push-rod through the port

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SchmidtMotorWorks
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Push-rod through the port

Post by SchmidtMotorWorks »

I have seen pictures of an old Pontiac head called Ram Air V that had a pushrod that went through the middle of the port. Things were wilder then and the ports were really large and the tube around the pushrod was simple round.

Call me slow, but 30 years later I am wondering if there would be any advantage to a wider shorter port (in a BBC or SBC) with a pushrod going through it if instead of a tube around the push rod, a very nice fairing that blended into the valve guide boss were used.

Any thoughts?
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Re: Push-rod through the port

Post by OldSStroker »

SchmidtMotorWorks wrote:I have seen pictures of an old Pontiac head called Ram Air V that had a pushrod that went through the middle of the port. Things were wilder then and the ports were really large and the tube around the pushrod was simple round.

Call me slow, but 30 years later I am wondering if there would be any advantage to a wider shorter port (in a BBC or SBC) with a pushrod going through it if instead of a tube around the push rod, a very nice fairing that blended into the valve guide boss were used.

Any thoughts?
"Tunnel port" was the term for that. Pontiac copied it from Ford. (You don't know how much it pains me to say that. :) )

http://www.thecarsource.org/fords/engin ... gine.shtml

Here's another:

http://www.wallaceracing.com/ultimatehead.htm

If you look at the Pontiac flow numbers, remember the tests were at 12 in. H2O (not in. Hg) and should be converted to 28 in H2O, but that isn't always comparable data. Note that Pete McCarthy gives the RA V head the "Worst intake/exhaust ratio" award.

I think Pontiac just started dabbling in flow benches around 69-70 era. They didn't have one in early 68.

The RA V intakes had enough flow capacity to support a ton of rpm on a Pontiac, but with the huge bearing sizes they used, the bottom end didn't like rpm. The "small" mains were 3.00 inches which gave bearing speeds at 5700 equal to a SBC at 7000. Large mains also cause other oiling problems.

As to whether we should "reinvent the wheel" with tunnel ports, current practice seems to indicate no. Larry (maxracesoftware) might have some opinions as to why or why not.

Sometimes "thinking like air" isn't easy.
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Post by tjs44 »

there were 2 diff designs for the tubes,round and foils for the later design.I have the round in a set and foils in the other.Been told that they will flo pretty close but the foils have less turblance.The thing that helps V intake ports the most is putting a flat floor in them like a sideways D.Mendoza at Flotech did mine,they flo in the 370 range at .700 if I remember correctly.Tom
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Re: Push-rod through the port

Post by Darin Morgan »

[/quote]
As to whether we should "reinvent the wheel" with tunnel ports, current practice seems to indicate no. [/quote]

The tunnel port was a band-aid for poor air flow in that era. Jr Johnson thought that the old antiquated tunnel port idea was great because he saw the old Pontiac head run so well back in the day. He commissioned Ford to build some tunnel port heads 1990 and they did. They where monsters even by today's standards. The port where 2.5 inches off the deck and the exhaust ports where high and strait. They flowed as much air as todays best canted valve heads. Bottom line, they killed 100+ hp. Why? The tube ( even with an aerodynamic wing design) separates the air fuel mixture and deposits it on the adjacent walls. Its absolutely THE worst wet flowing head design on planet earth. After doing preliminary testing in 1992 I gave up on them even before I had perfected the prototype and told them it would never work. They didn't listen and tried it anyway. They never got within 100 horsepower of the Yates style heads on unlimited engines and it was almost as bad in the Winston Cup engines at the time..
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Post by SchmidtMotorWorks »

Interesting information, does the splitting of the port on four valve engines have a similar problem? If so, does that argue for using non-siamesesd ports on four valve engine?
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Post by bc »

There is guy right now working on making an alumimun version of the RAV heads for Pontiacs. He is hoping that they will support 1000hp from a 500cid+ engine. His name is Lynn McCarty. It will be interesting how it works out.
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Post by ClassKing »

McWho? This is truely the funniest thing I've read today. If you made a Model T head out of aluminum, and didn't change the any of the design features, would it be more efficient? No. Only an inexperienced person would waste time today with such a bad design. What would you improve? Let's see. Take out the tree trunk in the middle of the port. Now you're left with a DEAD slow intake port shape. And like TJ44 found out , it takes a approx. a 20% floor fill to make the head to begin to function - a little. And his combo still didn't make any power that a well done set of Edelbrocks couldn't embarrass. (I know him)

Leave the RA5's to the collectors, keyboard bench racers, and car show gawkers. If you want to make power, at any level, you'll use something modern.

www.PontiacEngines.com
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Post by tjs44 »

like a IA II block,W heads,moldex crank,BME rods and a sheet metal intake! Oh wait!Not a pontiac part to be found!LOL,Tom
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Post by ClassKing »

Maybe the cam retention plate.... 8)
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Post by tjs44 »

nope,want a timkin bearing plate to go against the billet cam!
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Post by ClassKing »

Oh, ha! - and all of those 12 second roller cam bearing engines out there just "gotz" to have that latest trick. I laughed my ying off when that nitiwit Himelick brought his 428 GTO out to Carlsbad and ran 12.20.s - and bragged to me that HE had ROLLER cam bearings. :lol: :shock: :roll:

That was the same day my 8.2 Cr 400 was running 11.40's. The same one you ran against. YOU - are my witness to that neat little combo.
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Post by tjs44 »

NEVER seen the motor apart,cant swear it was a 400 or 8.2CR!As far as taking ANY racers word,NFW.The car did run the 11.40 and also I never mentioned roller cam bearing?
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Post by Parkhurst »

SchmidtMotorWorks wrote:Interesting information, does the splitting of the port on four valve engines have a similar problem? If so, does that argue for using non-siamesesd ports on four valve engine?

Four-valve heads isolate each intake port using a knife-edged wall between them which tapers into a thicker divider as the port approaches the valve. This allows each port to be developed independently and one has little to do with the other. The tunnel port with a tube running through it is completely different, as each side of the port is trying to feed a common valve. The four-valve stuff works so well because it's not like the tunnel port. The individual ports on a 4-valve setup also allow for other tricks, like different cam profiles on adjacent valves on the same cylinder. Opening the intake valves at slightly different times has an effect on the incoming air/fuel charge and promotes tumble. If its a high-swirl design, adding some tumble motion has shown to help even more by keeping fuel in suspension when the swirl motion tries to force the heavier fuel out of suspension.

Darin knows much more about this than I do since he's been doing so much wet flow testing. Maybe he can chime in and add a few more facts.

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Post by ClassKing »

Tj : it wasn't your car with the roller cam bearings - it was some "engineer" that wanted to let us all know how smart he was.
Now don't go acting like you'd doubt me bout the 8.2 Cr engine, or any engine I've built. At least Westech took the 350 apart to verify it. Now THAT was a fun day. 8) :D
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Post by tjs44 »

Bruce,with ALL due respect if MY mother was racing and she told me what was under the hood I would not believe her!I have been around this block since 1962,cheated,been cheated on, so I would not beleive you know matter how much you preach UNLESS I was actually was doing the meas.NO malice intended!Tom
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