PontiacBonnevilleClub.com

OK, I have read a LOT of great info on the subject (and I think the most popular poster of that info has been Willwren, and he has described in great detail what needs done and some recommended bits for the job).

But, what I have not been able to find are pics of a successfully completed port matched LIM. Does anyone have any they are willing to share?

I recently bought a LIM that I intend to experiment with, though I feel I understand the desired outcome and how to achieve that outcome, I just wanted a peak at some one else's handy work.

Thanks!

You don't really need finished pics. The corner radius should match that of the cylinder heads, and the ports should measure 0.9x1.9" when done (with an exception for the injector boss bumpout).

They should be rectangular in shape, and those dimensions should carry up the port until it changes shape. If you dig through my photobucket accounts, you should find the pics you're looking for, but both accounts are nearly full and it might take awhile to find what you're after.

Basically you want to gasket match it and taper it back into the whole port.

00Beast wrote:Basically you want to gasket match it and taper it back into the whole port.

Negative.

He's not gasket matching the heads. He's trying to get the LIM port exits to match the head intake port inlets in size/shape.

Do NOT gasket match a LIM unless you're porting heads also! The above post is dead on. The one above it is way off!

Thanks guys.

Based on all my reading, I am just simply up to port matching NOT gasket matching. I'm not interested in working the heads at this point in time. Just a small massage on the LIM, nothing too terribly crazy.

And Willwren, I sifted through a LOT of photos you have and I think I came across what I was looking for!! Thanks for directing me there (you have a LOT of neat pics pertaining to these cars, I thought the adapting the Trans Am vents to a bonnie hood was really cool)! Also, thanks for the detailed info you've posted on the subject, past and present (I think I have sufficient bits for my Dremel to handle the task, but a site you referenced in a much older thread, I think Widget supply, yeah, I got some new bits on my "wish list").

Great stuff guys, thanks!!

What you are going to do is clean up some of the rough cast, and make the port opening straighter... Some of the L36 castings were really bad... Then give the ports on the heads a slight touch to allow for smoother port entry, or no ledges for the air to hit on its way into the port... This seems to help with overall performance to a certain degree... You can only use what you can flow..

So, I was inspecting my "donor" LIM tonight.... I noticed on the top of each of the runners (about halfway up the travel), on the opposite side of the injector boss is a little bump. Is it safe to say that "bump" should also be done away with? I don't want to say smooth, but a consistent/uninterrupted travel through the runner?

I'd have to look at an L36 LIM again to be sure, but I believe on the other side of that 'bump' is an internal coolant passage. LIGHT smoothing would be best.

In response to your hood vent comment above, you just reminded me I need to update my install with a little addition I put in there a couple weeks ago.

Glad my diggin' around in your pics came in handy!!

BTW - Did you do the hood vents purely for looks or do they actually provide any benefit to controlling the temperature on the engine??

I still love them, a really unique personal touch to the car!!!

He did it for engine bay temperatures, and it also has the added benefit of cutting down front end float too at high speed from what I understand.

Go with the 1.9x0.9" measure for porting it I did this on my L36 and I found that the measurement matched well to line it up I used a new gasket and used a few pens wedged in the mounting holes to keep it lined up and used a thin sharpie to mark the point to clean it up to. That happened to be the exact point to have it at 1.9x0.9" but measure often to check. On the injector boss I just smoothed it out with out changing the shape.

That's my game plan. I have a friend cleaning my donor LIM at his work (they have a good parts cleaner). I figure I can make some good markings and as stated frequent measurements (bought a caliper just for this task).

Looking forward to it.

Funny, I think I read mostly the Bonnie guys doing this (doesn't seem like a frequents mod for the Impala and Monte crowd). Odd....

That's because it started with a phone conversation between jrs3800 and I a few years ago, and the first LIM's came from there. Don's was the first I ever did.

I don't think that those guys see any advantage to doing it. Plus it seems like the guys who frequent the W-Body forums are into bolt-on stuff, nothing that requires real work or thinking.

00Beast wrote:I don't think that those guys see any advantage to doing it. Plus it seems like the guys who frequent the W-Body forums are into bolt-on stuff, nothing that requires real work or thinking.

Hard for me to say either way for those crowds. For me, I am a computer geek who's learned to wrench on my cars myself (to save on costly repairs by doing it myself). Basically, I am saying performance modding is NOT my area of expertise. But I've been doing a LOT of reading and trying to do a LOT of learning.

My Monte mod list is MOSTLY bolt on, but I'm branching out. I've re-conditioned a L67 T-body that should be a beaut to allow more air into my upper intake. And the metal work I've done on that with my dremel has opened me up to be willing to try out some other avenues (hence the interest in the LIM at this point).

People stay with either what they know OR what they are comfortable with. I'm not 100% comfortable with port matching the LIM, so I have a donor LIM to work with (figure that's "playing it safe"). And so far, I'm enjoying learning and branching out with my mod list. I'm anxious for SPRING!!!

We looked at it like this when we started this conversation years ago...

You can do an Intake, yo can do a Cam, you can do an Exhaust... But if you can only get so much air through the lower intake ( ports smaller than the head port ) you can only do so much, and that would be a limiting factor... If you don't deal with the intake you won't be taking full advantage of the Mods... At some point if you get really deep into the mods you's want to port the heads as well..


Not the greatest of Pics... But look close at the port on the right, then look at the other 2... This was a poor cast/cut from the factory... I ported my manifold as I knew the cam was going to want everything it could get...lol



The First PLIM that was done by Wren resides on my 95 SE Bonneville to this day...

When I saw the pics of the unported LIM and I think it was willwren who shoed a ruler against the ports and I now have a donor one to dable with, I understand the point of matching them. I also understand porting the heads (but at this point, I'm not ready for that, but that's my opinion coupled with what I'm up to).

Since I plan to rip apart so much of my Monte, I'm a matter of a few bolts and gaskets away from doing a LIM. Knowing the LIM ports could be better optimised for the stock head ports, pending I can successfully portmatch my donor LIM, adding this to my list of mods seems like an absolute MUST (it's a vitual freebie).

I know some people may feel that it's not that much larger of an opening, but in all honestly, every little bit matters, it all adds up.

JRS3800, thanks for the pic!! Seeing a finished port to an unfinished is just unbelievable!

I am so glad that I have signed up for more then one 3800 focused forum. Each one has given me insight to different modding ideas!

Like the saying goes, you can only use what you can flow....lol..

I think the Math came out to 10-15% increase in flow by port matching the LIM.. Every bit does help...

My 95 Bonneville is running a 97 Bonneville PCM with a 97 GP Tune, + 2* .... I have that ported LIM, High flow cat, Balanced Injectors, was running a PLOG on the front and will in the near future reinstall the Stainless PLOG... At most this car may get a Mild Cam...

But yes every little bit helps...