Porting LIM; do any good for a Series II n/a? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 02-01-2007, 03:36 AM   #1
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Default Porting LIM; do any good for a Series II n/a?

I've read a few threads about porting the LIM. Most (if not all) seemed to be geared toward Series I supercharged engines.

So, would porting the LIM do anything for a Series 2 normally aspirated engine (199?
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Old 02-01-2007, 04:05 AM   #2
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Yes, the port exits on the LIM do have very noticeable casting flaws.
It will make a difference, but not as much as if you were boosted.
IMO its a 'while I'm in here I may as well' kind of mod for an L36.
Basically, I wouldn't go ripping it apart unless you have to replace the LIM gaskets anyway. And you can only go so far because the inlet on the head isn't gasket matched either. So, you don't want to create a lip or step to the head in the port.
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Old 02-01-2007, 04:54 AM   #3
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Oh yeah, I intend to replace the LIM gaskets very soon...that'* why I got interested in porting the LIM. Seems all it takes is a Dremel with carbide bits (got that), and a micrometer (borrow from work).

So, is it accurate to say that I want to measure and match the port in the head, rather than gasket-match when LIM porting? I haven't actually had the LIM off yet to see for myself...are the head ports significantly larger than the LIM ports in any (or all) dimensions?
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Old 02-01-2007, 05:16 AM   #4
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Calipers may be easier than a inside mic.
Yep, you want to create an outlet similar to the size of the head port.
You won't be taking material off the LIM ports the same in all directions. The shape of the exit on the LIM ports is loosely based on a rectagle... Some sections of the outlet protrude more than others. It will be pretty obvious once you have everything apart.
You should also polish the runners in the LIM to improve flow.
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Old 02-01-2007, 06:40 PM   #5
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I don't know if the series I NA and series II NA have similar LIM, UIM, or heads but I have all three sittin at home waiting for me to port this spring/summer if you would like me to send you some pictures to give you a preview idea.
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Old 02-01-2007, 06:43 PM   #6
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Quote:
Originally Posted by Regal_Kid_05
I don't know if the series I NA and series II NA have similar LIM, UIM, or heads but I have all three sittin at home waiting for me to port this spring/summer if you would like me to send you some pictures to give you a preview idea.
They are pretty different.
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Old 02-01-2007, 10:54 PM   #7
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My thoughts...
when you pull it apart, and look at the ports, you will see the outline of where the gasket was mated to the surface. You can use this to position the gasket, draw lines, and remove the material from the correct places. Also, when you are reassembling, you can set the LIM in the valley, and then stick your fingers down the ports to try and align it the best you can. The bolt holes have just a little play, so you should be able to pull it off.
My two cents.
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Old 02-01-2007, 11:15 PM   #8
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One L36 LIM has been ported and tested with my instructions. I'm porting another. Do NOT port to the gasket opening. Port to the HEAD opening size only. You're just cleaning up casting variances and matching things up.
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Old 02-02-2007, 07:45 AM   #9
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On the tools, add a couple of the drum sanders to your arsenal. I found they are easier to work with.
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Old 02-02-2007, 09:32 AM   #10
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The drum sanders aren't much help in the L36 runners. The inside corners are too small of a radius.
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