karldergrosse,

Those ported LIM ports of yours look awesome. Great job!

Could you do me a favor, and lay your aluminum GM LIM gasket centered over that port and snap a photo?

Thanks.

I was just about to request the same thing.

And very nice job on the porting.

OK here ya go. Sorry it took so long. Long day. Finished a job by a customers house and had to rush to the tinter to get the bonnie'* windows tinted



Thats pic 1. It seems the bolt holes are a little off but they are on on the other side. Now I'll line them up on this side.


There it is.

Note difference between gasket method:


and KDG method:


More material is gutted out with the gasket method with much larger radiuses at the corners than what is available at the radius of the heads. More than likely because you are depending on die stampings rather than finished ports at the heads using a factory set of dimensions to pour castings for the heads. Does this mean all castings are the same...H*** no. See the beginning of my post to see the difference I experienced after receiving LIM'* from two different sources. But center, AKA "centroid" of a port is center of a port. When designing castings for mating parts, this is what really matters.

This is still a work in progress so different people using different methods will have differnet results.I'm not saying you wouldn't see "seat of the pants" gains with the gasket method(stay away a 1/16 from the trace) as none have been reported as of yet. If seat of pants gains works with gasket method..good for you. That'* all I'm looking for anyway.

But we can all agree , the most precise method is the way to go if it doesn't take more time to do it. My layout method took perhaps 5 min. per port. Is that to much time to be more precise in your porting. I think not. I will say with the KDG method you are within .010" of the cyl. head ports finished measurements( if you follow "centroid" layout shown earlier). As repeated in other posts you don't want to create a "shelf" where the LIM port and the cyl. head port meet thereby impeding staight flow of incoming mix.

Long and short of it is, mine isn't on yet but will be by (hopefully) Monday. After it'* on I will try to compare mine stock vs. ported as JR3800 (Don) did. And let you all know for us NA'* if it'* worth it.

If you're like me......New(used) NA Bonnie and need to replace the LIM gaskets and UIM with a kit to stay away from DEX death of our rides. Why not take the time to port the LIM and get some decent gains......... NO BRAINER HERE.

More to come..........

Well, it may seem from the photos above that I've opened my ports more than karldergrosse using my porting method--perhaps even "overported"--however, I guess that a great deal of what you will wind up with depends on the original LIM casting (as mentioned by kdg already), and on gasket part number and/or manufacturing tolerances (like we've been told in this thread: http://www.bonnevilleclub.com/forum/...ic.php?t=72094 )

I took digital caliper measurements of the inside of the ports both before and after porting, as well as the inside of the gasket hole, at these points:



And the results are:
Point A (inside LIM port, at top, below corner radii): Before: 0.8125 in, After: 0.8880 in
Point B (widest spot in LIM port, at casting seam): Before: 0.9515 in, After: 0.9520 in
Point C (width of inside of gasket hole): 0.9670 in
Point D (height of inside of gasket hole): 2.0070 in

(Oops, also measured the height of the inside of the port hole, but forgot to draw a line for that in the pic above...that was: Before: 1.8750 in, After: 1.8955 in)

Being that the target is 0.9" wide by 1.9" high, my porting stayed within that...except of course for at point B, where it was wider than 0.9" to begin with.

I am curious kdg, since they change/update frequently, what is the exact part number of your GM gaskets (mine is 89017825), and could you take some calipers to the inside of your gasket hole? It could be that your gasket hole is significantly wider than mine...

Edit: Again, kudos on an excellent job...I think we'll both be OK with our respective portings (even if yours look better than mine )

It'* starting to look like we're getting some good feedback as this method is tried out by more members.

They look great!

semi-related stupid question (i can ask in another post if nessisary)

since the opening on the gasket is larger than both the head port and the intake port, couldn't the "pocket", however small, create turbulence in the runner? is there a method to avoid this? is it too small and the air moving too fast to even notice? or is the gasket squeezed so tight that the pocket virtually doesn't exist?

some stupid questions, fuel on the disscussion fire.

P.*. i'm hungry. :?

I've thought about that too.
Also, I can't remember seeing a pic of the head port but what'* the deal with that little "lobe" on the lower right corner of each port on the LIM? - the LIM ports aren't rectangular like the gaskets are.

With the manifolds torqued down to the proper ft-lbs, the gap between the head/LIM, and the LIM/UIM is minimal enough to negate any turbulance.

Those are the injector bosses added to the L36 LIM. The L27 LIM isn't like that.