What material is the LIM made of?

So, the L36 sitting in the shed...I took off the upper intake manifold off with relative ease, and pretty soon I'm going to take off the LIM and hope to do a mild DIY port and polish on it. Something that would help me get the perfect dremel bits is knowing:

I'm guessing it's made of cast iron and I should use mainly carbide bits?

or is it aluminum? I can't tell because of how much sludge the LIM has in it from a gasket that blew in my mom's old 97 bonneville :/

Aluminum!

Cast Aluminum. Carbide burr bits will cut through it no troubles. Thats what I've used for porting series one l27, series one l67, series 2 l67, and series 2 l36 LIMs. Take your time, be sure your hand is resting against a refrence point to keep it steady and it will be fine. Scribe out the runner ports with pencil so you don't over port. You want to shoot for just under the dimentions of the runners in the heads. No bigger at any point than 1.95" X .95". The rest of the runners just smooth out and take to 120 gritt smoothness. Any further opening upstream in the runners from the head will just lose you velocity.

are you going to use the gaskets as a guide?

Cardboard!!

rivparadise wrote:

Aluminum!

Karma wrote:

Cast Aluminum. Carbide burr bits will cut through it no troubles. Thats what I've used for porting series one l27, series one l67, series 2 l67, and series 2 l36 LIMs. Take your time, be sure your hand is resting against a refrence point to keep it steady and it will be fine. Scribe out the runner ports with pencil so you don't over port. You want to shoot for just under the dimentions of the runners in the heads. No bigger at any point than 1.95" X .95". The rest of the runners just smooth out and take to 120 gritt smoothness. Any further opening upstream in the runners from the head will just lose you velocity.

Awesome, Aloy-mini-ium is so much easier to work with than cast iron , the 1.95" X .95" is the same roughly as the gaskets and head gaskets as well, I believe?

robotennis61 wrote:

are you going to use the gaskets as a guide?

That was the plan :p

http://www.gmforum.com/performance-brainstorming-96/my-l36-lim-porting-pics-now-data-251838/

This will help me a good deal with informative pics and comments

flyineagle96 wrote:

Cardboard!!

No wonder all that sludge got in the LIM of my mom's old bonneville, ended up leaking and hydrolocked her motor


Lol, but another question I have is: How important is the upper intake manifold pressure sensor to the operation of the motor itself, just out of curiosity

Yeah, don't gasket match. You will lose flow and port velocity. If you do the heads, then you can gasket match both, but if not and the LIM runners are matched to the gaskets then you add a bunch of turbulence at the step to the head runners. Take it to exactly the head runner size tops.

Karma wrote:

Yeah, don't gasket match. You will lose flow and port velocity. If you do the heads, then you can gasket match both, but if not and the LIM runners are matched to the gaskets then you add a bunch of turbulence at the step to the head runners. Take it to exactly the head runner size tops.

Thanks for the tip

So basically, the LIM being ported more than the heads is bad, is what you're saying?

yup, the step that it would make from the head runners to the LIM runners will cause large amounts of turbulence.

That makes perfect sense, and I don't think I'd have made the runners bigger on one than the other, looking at it after taking it all apart. Looking at pics online, and holding things in person, is just so much different, ya know?