I am porting a TPI aftermarket intake from First - larger runners with matched base and plenum.

I'm only matching the ports of the intake, but what do I do with the big lump upstream of the injector inlet.

My first instinct is to "hog it out", but I think that would affect the spray pattern.


Thanks in advance.

 

i doubt vader ever sees this. someoen posted a long thread about this a month or so ago, do a search for madmax and kevin91z i tihnk it was one of them, kevin i think.

------------------
ICON Motorsports

1st & 3rd
MM Black Diamond Lodge 538 F&AM

 

Never underestimate the power of the Dark Side...

The "humps" you are referring to are in place to direct air flow downward at the point of entry to the head. This downward air flow helps carry the fuel mist into the port instead of depositing the mist on the top side of the head ports, where it would condense and not become part of the fuel/air charge. I would suggest NOT modifying the "humps" unless you are changing to a different injector design that would spray a tighter cone of fuel into the head ports. The little disturbance in air flow at that point is intentional and to some exttent necessary at higher intake velocities. What little turbulence is caused there can more than be compensated for by the enlargement of the ports and runners on the opposite (bottom) side.

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader

 

Well I'm gonna have to put a disturbance in the Dark Side and tell ya... Who cares. Personally I'd grind em off, they are casting marks. You'll find an identical set of marks at the other end by the runner. If you are worried, leaving them or taking them probably wont make much of a difference anyway.

The alignment of the port in the manifold to the port in the head is terrible. The port in the manifold is very low, too low really. Theres a few ways around it, but the port is quite a bit smaller than the head, leaving material to put a sharp radius in the bottom area of the port in the manifold, something similar to the short turn radius on the head by the valve. That will help the intake-head transition some.

 

Max,

Are we talking about the same "humps"? The ones immediately upstream of the injectors? I always noticed these and understood them to prevent intake air from sweeping directly over the injector tip and plastering all the fuel droplets against the top side of the runner and port.

You're right about the pitiful little openings. Almost anything on the bottom end would have been an improvement, and air flow is not directed at the back of the valve very well at all. the LT1 intake is much better at aiming the intake air, and the LT4 is even a little better than that. I'm guessing the base plate runners were kept low to provide hood clearance for the relatively tall TPI unit, so the GM Powertrain guys sacrificed port location improvements in the heads due to space considerations in stock vehicles.

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader

 

Yep, I agree that they went the packaging route and that decided the height of the TPI, so the base suffered.

I dunno if we are talking about the same thing. The ones I am referring to are about 1/2" in diameter right in the center of the roof of the port. At least thats all that I see... maybe I'm going blind in my old age

I'll have to see if I have a pic around here somewheres...

 

Let the confusion begin!

This is an 85 base, notice there are no bumps at all... cept for the ones from the runners going the other way...
If you look real close in the first pic, you can see the round spot that on my 86 manifold is much more prominent.





Here's my tach... red at 5500

 

Max,

That isn't like the step I thought we were talking about. There shoudl be a mound of aluminum dead center in the top of the intake runner and upstream of it to shroud the injector tip from air inrush. Looks like I'm gonna be digging for pictures, too.

P.S. - Zero RPMs in a TPI is not nearly as much fun as a bigger number. At least you have the "good" cam to get you to those numbers.

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader

 

These humps



[This message has been edited by a73camaro (edited April 16, 2001).]

 

Oh... hmmmm
What sorta base is that? Didnt realize they changed the roof that much.

I would leave that alone.

 

73,

Thanks for finding a photo! THAT'S more like what I was accustomed to seeing. That's what I would leave alone if possible.

------------------
Later,
Vader
------------------
"What a Day..."
Adobe Acrobat Reader

 

It is an intake from or named FIRST. I'm planning on leaving the lumps there.

Here is the other side of the runner.



[This message has been edited by a73camaro (edited April 18, 2001).]