Porting the new Hamilton 12v head.

Don't worry about the bashing - any good head porter wouldn't argue with what you stated.

Your percentages are fine (though every chef has a different recipe ;)), you can never go wrong with the Coanda Effect, and your port velocity position is fine for daily drivers... but for competition mills that don't see a lot of off/low boost operation, it's important to remember that the air just wants to get in. :evil

As far as lobe profiles, I don't want to get in any more trouble. :)
 
you are correct... "hogging out" a head does NOT mean it's optimal!!!

as Zach stated, Greg Young designed the ports and has a leg up on optimizing them for higher flow applications

when I stated that any good head porter with a sonic checker could max out the head, I deleted the comment that it would be a tedious and expensive endeavor :o

lenahan05 said:
Ron. this is just my opinion and i know im guna get bashed by someone one here who disagrees with me but ohh well. with a head flowing this much over a stock 12v cast and an enlarged port of this size on a stock or competition motor i would try to remove the least amount of material possible if your going to do portwork over whats already been fixed in this casting. without seeing what this casting looks like stock i could not help you but i would imagine there would still be some cfm gains picked up in the troat and seat of the port. cut your throat size (area just before the seat) 90-91% of your intake valve size and on the exhaust 89-90% smaller than your valve. this rule works well on any high rpm/high HP diesel. for example....your intake is 1.850 on these heads...1.850x.90%=1.670. and get as many angles on your seat as possible. it will always pick up cfm. if you remove to much area in the actual port and runners....you will lose port velocity which intern= lower rpm. i am guessing with a head of this caliber, many who are currently running high duration competition cams will want to get a smaller duration cam and will notice bigger gains from these heads with lower duration.....Ron...rather than me continue posting on here and getting bashed for my thoughts...if you have any questions just pm me and we can get in contact with each other.
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lenahan05 said:
if you remove to much area in the actual port and runners....you will lose port velocity which intern= lower rpm.
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I've been lurking these forums for about 4 years after coming from the motorycle side and I've been waiting for the day that someone mentioned port velocity.

Theres more to porting than touching up the seats and making the holes bigger, I'm hesitant to send my head to most shops.
 
thank you all for being honest and truthful in your opinions with this.. it will benifiet us all in the performance market.
 
I talked with the Banks crew a while back on the subject. They said the head that flowed the most didn't make the most power, and it smoked like a SOB on the dyno.
 
straight 6 roar said:
I've been lurking these forums for about 4 years after coming from the motorycle side and I've been waiting for the day that someone mentioned port velocity.

Theres more to porting than touching up the seats and making the holes bigger, I'm hesitant to send my head to most shops.
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I've said it before, but I'm shy. :hehe:
 
One thing to remember, most motorcycles are not running turbo'd engines. I agree that port velocity is important when building a natural aspirated engine. I had the discussion with several head porters before sending my Harley heads to the guy I selected. In our conversation, he told me that he has had to actually slow the velocity down because it was too fast.
 
jedeka said:
One thing to remember, most motorcycles are not running turbo'd engines. I agree that port velocity is important when building a natural aspirated engine. I had the discussion with several head porters before sending my Harley heads to the guy I selected. In our conversation, he told me that he has had to actually slow the velocity down because it was too fast.
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whatch you talk'n bout willis?
 
port velocity at midlift numbers is most important, as the valve sees that point twice in its travels.

velocity is what fills the cylinder at low boost and even high boost situations, making more power and torque EVERYWHERE in the powerband. if velocity was too "high" perhaps a different camshaft is in order with less overlap.
veolcity also = swirl and turbulence in chamber with more complete combustion being an excellent side effect of that.
 
jedeka said:
One thing to remember, most motorcycles are not running turbo'd engines. I agree that port velocity is important when building a natural aspirated engine. I had the discussion with several head porters before sending my Harley heads to the guy I selected. In our conversation, he told me that he has had to actually slow the velocity down because it was too fast.
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I am not familiar with Harleys but I would assume the port sees fuel running through it. A big issue with wet flow ports is keeping velocity consistant in all areas of the port or you can get into fuel separation issues. Obviously with a direct injection diesel this is not the case.

In naturally aspirated engines excessive port velocity can also cause pumping losses. The magic number tossed around by some premier head porters over on speedtalk was usually around 350 fps. If the number gets too far over that you will have excessive vacuum on the piston during the intake stroke and hence, pumping losses.

That said I would think there is a point where too much velocity even in a forced induction application becomes a problem. Everything is a compromise. Port the head too large for max flow and as a previous member said you may end up with a smoke machine never getting up on the turbos etc. due to horrible velocity being maintained prior to max boost. Port the head too small and velocity may reach a point where the air becomes super hot, mashed up, etc. trying to make its way into the motor.
 
nick...i believe if you leave the exhaust port fairly small on the turbo engines that you can still gain more port area and flow on your intake side. with a smaller exhaust your velocity will still be there to drive your charger. depending on your camshaft grind of course. with a smaller exhaust and a higher flowing intake you can use overlap on your intake stroke to help push out your exhaust gases and drive the charger harder. that's why typically a 105-107LSA normally runs better on these cummins engines overall. too much LSA tends to get lazy/smokey at low rpms.

crackerman...you start bringing the word swirl into this discussion and your guna open a bag of worms. lol. swirl in these diesels is a big thing when your running low rpm and tryin to build a low rpm effiecient motor in stock form. the high swirl is put in there to eliminate the gases on exhaust stroke. personally i think in a high rpm diesel build with the kind of cylinder pressure and boost in the hole these engines are producing these days...you couldnt convince me that when the piston is compressing the air/fuel thats in the hole that there would be any swirl happening with that kind of pressure in the cylinder. whatever swirl is in there on the intake stroke is going to be slowed down dramatically if not all together on the compression stroke. please dont bash just my opinion. if someone has more explaination on this thats directly opposite of my thoughts please correct me. i'm always wanting to hear other peoples thoughts on the swirl issue. hope im not derailing this thread. haha. but swirl only seems to be important in my mind on the exhaust stroke for gas scavenging.
 
i know that unless any of us can spend the money and time to find out, then none of us will know for sure, and ANY two cummins, even if prepped near identical running the same perfect tune on the same day at the same time will most likely NOT give anyone identical numbers, ust oo many variables when it comes to high hp tuning, turbos or fuel...

i say "swirl" but in all reality mean tumble, or turbulent air in the chamber.

the mercedes commonrail i6 in 2005 used tumble flaps in one of the two runners to create violent air tumble on one side, and smooth on the other. they did switch "off" a aroudn 2700 rpm, promoting great low engine speed characteristics, as well as decent higher rpm too. (5,000 rpm out of the box)

any time a fluid flows from a high speed low cross section port around a valve of some sort to a low pressure large area, its gonna slow down, lose direction and tumble. giving it a direction to go is a whole different bag of worms as you have said.

dart cylinder heads, in the last couple of years, have gone to a "wet" test bench, flowing air and atomized simulated fuel, to create the best swirl and atomization possible for wet airflow. granted that has nothing to do with dry flow diesel cylinder heads, it could result in gains (however narrow in the rpm range) on a diesel head.
 
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Good info here. I have been thinking about getting one of these heads for my next car project. We'll see though. LOL
 
crackerman said:
i say "swirl" but in all reality mean tumble, or turbulent air in the chamber.

the mercedes commonrail i6 in 2005 used tumble flaps in one of the two runners to create violent air tumble on one side, and smooth on the other. they did switch "off" a aroudn 2700 rpm, promoting great low engine speed characteristics, as well as decent higher rpm too. (5,000 rpm out of the box)
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i dont believe that was to "tumble" the air, the flap made the runner smaller in turn making the velocity faster for low end power
 
why are they called tumble flaps then? i went to school for that engine when i was a tech for mercedes. and that was the explanation we were given in training.

but i believe they are more for the intention of increasing velocity of the unrestricted port. essentially giving it two runner sizes, alot like the mustange cobra svt 32valve or mitsubishi cyclone manifold. exccept those compreletely close the port runner vs necking it down.
 
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