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Old 10-23-2007, 11:31 AM   #1
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Default Porting the LIM

Well, I'm putting the Bonne to rest for the winter in a week or two and plan on doing the LIM gaskets in the spring. Don't have any problems yet, and only have 107K on her, but I'm tired of watching the temp gauge so closely and checking coolant level before every drive. Also, changing them before they leak will make the job easier with no crap baked on. A local JY has several LIMs priced reasonably so I picked one up just for the heck of it. Thought I would clean it up and have it ready to go in the spring. I've read some threads here about porting the LIM on the L36, and figured since I have all winter, I should give it a go. Question is, how do you size the exhaust port to the head? I can only figure you use the gasket set for a template, correct?
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Old 10-23-2007, 11:39 AM   #2
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No, the gasket is not a good template. The gasket openings are larger than the head ports.

You want to port it to JUST UNDER 0.9" x 1.9" on each port. Even as possible on the spacing. You can use the gasket as a GUIDE for your centering/spacing, but as a general rule, if you're careful to take the same amount of material from each adjacent side, you won't have a problem.

Do NOT over-port. You're better to be JUST under, or to have it 'taper' down to the dimensions I listed above for each port.

The L36 manifold is a little more difficult than the others due to the ugly nastiness of the casting/port quality. You also have a 'mouse bite' in one corner for the injector. This should be smoothed inside, but not altered in shape. Your end result will be a rectangular port with a round 'bite' in one corner.

Inside corner radiuses should also be matched the heads. No more than 0.125" inside radius on all 6 ports.
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Old 10-23-2007, 12:57 PM   #3
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Thanks Will. I'll be careful not to overport. Just really wanted to clean it up and smooth it out somewhat being I have alot of time to do it. You're right on about the quality of the casting...nasty.
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Old 10-23-2007, 01:07 PM   #4
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I told Bill about the quality of the casting one time and he didn't believe it was that bad... He thought I was making it out to be worse than it was...

The he had the Oh so fun liberty of working on an L36.... Next thing you know I get this phone call, something like this..

" Holy ****..... This thing it terrible.... OMG there is a lot of room for improvement here... OOooOOooHhhhhh you are so going to notice it once ported "


He was right the Top end came on quicker, and the midrange pulled stronger... I got a tad bit more Low end out of it too... Made me happy..

Just like he said the trick is to not over port, you want the air to be able to flow in a smooth pattern with no lip in the path, you want to be able to transition into the head with the least amount of turbulence..


After the ported intake, it made my drive through the mountains much better... I had less lag than I had noticed before.. So there are benefits to be had..


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Old 10-23-2007, 01:21 PM   #5
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Glad to hear that jr. I just put a caliper on the ports, and you surely don't have to take much more that the burr to get to Will'* specs. Does anyone make an aftermarket performance intake that is ported and polished that will just bolt on for the L36? Christmas will be here before we know it and the wife never knows what to get me!
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Old 10-23-2007, 01:56 PM   #6
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There'* alot more to remove than you might think. It'* the inside corners that get you.
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Old 10-23-2007, 02:06 PM   #7
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Barry...your mention of getting an UIM from a JY scares me. You will want to install one that is sleeved or has the coolant ports blocked.

The LIM gaskets typically look bad, but don't fail in a catastrophic method like the UIM on the L36'*
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Old 10-23-2007, 04:14 PM   #8
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Bill: I said I got the LIM from the JY. I bought a new UIM several weeks ago from APN, so I should be good. My UIM was replace at 36,000 in '01 and is not causing any problems, but I'll be switching that anyway also. The replacement they put on then is from Delphi and when I pulled the TB to clean it, I noticed they installed the smaller EGR pipe as there is a gap between it and the UIM port, but it is not sleeved and I want to go with the APN.
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Old 10-23-2007, 04:28 PM   #9
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Your're right Will, I see that now. Thanks.
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Old 10-23-2007, 05:01 PM   #10
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These guys make a LIM for your L36. not sure if they port the runners to the head or gasket. It would be cheaper to do it yourself if you have the time and feel comfortable doing it.
http://www.milzymotorsports.com/miva...ct_Code=L36LIM
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