head intake port

[Jeanda]

Is there a purpose for that protruding lobe just after the matting surface of the head-intake? A friend of mine said it had something to do with smog.
Also- is it hollow or solid?

[viper98885]

It is solid and the purpose is to enhance the airflow into the combustion chamber. Some people say to get rid of it when you P&P and some say do not. I would suggest that you leave it there, but polish it so that it is very smooth and offers little restriction to the incoming air.

[Jeanda]

thanks, I was jus curious to hear what someone else might have to say bout its purpose.

[StudlyCamaro]

i agree that it should be left there , however i dont believe that it should be smooth, the bump is on the lower side of the intake runner, a smooth bottom of the intake runner will promote fuel puddling in the runner.. the gas need to be atomized for proper combustion

[viper98885]

By smooth, I meant that it should not be ground down, but smooth so that it does not create air turbulance.

[Jerriko]

Grind it down!!! It is an old wives tale! It is not needed at all. I ground the ones on my 3.4 down and I didn't reject it.

[Jerriko]

Originally posted by viper98885:
By smooth, I meant that it should not be ground down, but smooth so that it does not create air turbulance.

I am confused by this. GM's logic for having the vane was to create air turbulance. But if you try to change it so it doesn't create any, you might as well just get rid of it.

[StudlyCamaro]

the purpose of the vein was allways explained to me as a way to keep the velocity of the intake air high thru the port

(mind you i havnt looked at one of these heads in person in a few years)

the vein is in the part of the port just before the bend into the bend where the port is rather large comparitivly to the rest of the port

this enlargement will cause the intake air to slow down.... however with the bump in the port this will take up room and allow the air to continue moving quickly

jim im not sure what you mean by create turbulance, the hump is a very aerodynamic shape it wont make much turbulance at all


however i dont we will ever have a solid conclusion on this discussion until someone ports a head with and without removing one of the bumps and then has them flow tested (im just gonna stick with my heads that never had a bump in them to begin with [img]tongue.gif[/img] )

[Jeanda]

:cool: ...I know what you ment viper/ "take out the wrinkles and keep the hump"

[oil pan 4]

To each is own.
If you want to grind it down do it.

[Jerriko]

You have to realize with flow dynamics, anytime your passage goes from a slow to large opening, you will lose pressure (and volume). With the vein there, that part of the port is smaller. That just makes the loss that much greater. Come on, if that vein ACTUALLY made a difference, they would be using it in the 3800s.