UIM Porting
#1
Senior Member
Posts like a Corvette
Thread Starter
Join Date: Feb 2009
Location: Jersey Shore
Posts: 1,511
Likes: 0
Received 0 Likes
on
0 Posts
UIM Porting
SO I have a L26 Upper, I notice after I pull the runners out there is casting that holds the runners inline. Would it behoove me to Port my intake. I am going to be installing a HV3 insert.
#2
Senior Member
Certified GM nut
Wish I had a real answer for you, but here'* what I know about the UIM (besides the fact that it gets old and leaks coolant before you discover the joys of GM Forum and socket sets).
The runners seem to direct airflow through the UIM. However, like the MAF post in your throttle body, directing airflow means either reducing volume due to obstruction, or reducing velocity*due to directing. At high RPM'*, there'* enough air velocity that the runners actually slow things down (hence the existence of the HV3); however, at low RPM'*, the runners are needed to properly move air through the manifold; otherwise, the air would just slow down and stagnate. Proof: It'* been shown (by ZZP themselves, I believe) that completely removing the runners adds high-end horsepower but absolutely kills low-end torque.
Long story short, it seems doubtful that you can port the UIM to get more power out of it. On stock runners, I think reducing its height and therefore shortening the path the air takes through the manifold would be your best bet. (But bear in mind that I studied computer science, not mechanical engineering.)
However, I would look into polishing. I forget what the inside of a UIM looks like, but like a LIM, smoothing out the air channels would help a tiny bit.
The runners seem to direct airflow through the UIM. However, like the MAF post in your throttle body, directing airflow means either reducing volume due to obstruction, or reducing velocity*due to directing. At high RPM'*, there'* enough air velocity that the runners actually slow things down (hence the existence of the HV3); however, at low RPM'*, the runners are needed to properly move air through the manifold; otherwise, the air would just slow down and stagnate. Proof: It'* been shown (by ZZP themselves, I believe) that completely removing the runners adds high-end horsepower but absolutely kills low-end torque.
Long story short, it seems doubtful that you can port the UIM to get more power out of it. On stock runners, I think reducing its height and therefore shortening the path the air takes through the manifold would be your best bet. (But bear in mind that I studied computer science, not mechanical engineering.)
However, I would look into polishing. I forget what the inside of a UIM looks like, but like a LIM, smoothing out the air channels would help a tiny bit.
Last edited by SignOfZeta; 01-06-2011 at 12:00 AM. Reason: Clarification.
#3
Senior Member
True Car Nut
Join Date: Sep 2006
Location: Indianapolis, IN
Posts: 4,606
Likes: 0
Received 0 Likes
on
0 Posts
Zeta, the L26 can't crack and leak coolant because it'* metal. I mean, it could crack with enough tons of weight on it, but then you've got other problems.
Polishing actually messes with the air velocity. You don't want very smooth stuff. The finest you should go is 120 grit if you are going to touch the intake ports, but it all depends on how the HV3 lets air out into the LIM. Could we have some pictures, please?
Polishing actually messes with the air velocity. You don't want very smooth stuff. The finest you should go is 120 grit if you are going to touch the intake ports, but it all depends on how the HV3 lets air out into the LIM. Could we have some pictures, please?
#4
Senior Member
Certified GM nut
#5
Senior Member
True Car Nut
Join Date: Sep 2006
Location: Indianapolis, IN
Posts: 4,606
Likes: 0
Received 0 Likes
on
0 Posts
I remember my good old days with the nylon upper manifold. It cracked by the throttle body, and it didn't look as awesome as the metal one I have now. So, when are you top-swapping?
#7
DINOSAURUS BOOSTUS
Expert Gearhead
#8
Senior Member
Posts like a Corvette
Thread Starter
Join Date: Feb 2009
Location: Jersey Shore
Posts: 1,511
Likes: 0
Received 0 Likes
on
0 Posts