Ok, right now I'm trying to port match my new SLP runners to my plenum. I assumed I would have to take some metal off of the plenum, especially to siamese them between the ports to match the runners, but what I didnt expect was that the ports on the runners just plain wouldnt match up with the plenum. Like they are cast wrong or something.

Here you can see how well they don't line up. I'm assuming I am going to have to take a significant amount of metal off of the runners to get the ports to match the plenum. If I likewise take metal off the plenum to match the runners, I'm going to end up with slightly oblong shaped ports. What the heck should I do?!?!

Here's another picture of the other side. This side was worse. All I've done to the plenum on this side is knock out the wall between the two ports. Again, they DONT line up at all. Has anyone else had this problem with their SLP runners? Are they all cast crappy like this, or is mine a unique case?
Should I just go ahead and port the plenum and runners to match, even though the ports will be much bigger, and no longer round? Jeez, I'd hate to think of how they line up with the intake manifold, seeing as how I can't see that.

 

I would cut them if they were mine. I bolted mine all together, and used some flat black laquer paint to mark where the gaskets were located. That way you can put them back like they were assembled and port them. The laquer paint will come off very easy. I don't have slp runners though. Just make sure you have enough material to port them.

 

Mine were like that too! After all the cleaning up and port matching my car ran slower with them on.Now they just collect dust on a shelf.

 

I second that. My car went slower after I put the SLPs on also. Even after port matching them and everything. So I took the whole thing off, sold it, and put a carb on it. Now the car is faster then it's EVER been.

 

Unless I'm not seeing something correctly, that doesn't appear to be much of a mismatch in the ports, and I seriously doubt that an slightly oval hole would detract from performance....no doubt matching even to a slightly oval shape will be better than leaving a step in the air transition.

Heck, once you siamese the ports...how "round" are they anyways?

 

I kinda agree with Mike.

I wouldnt worry too much about them being round, just give it your best shot and make sure they match each other. Take a close look at how each part transitions from one to another (or really in the case of TPI how theres a complete lack of transitions) and you might not be so worried about how round they are anymore. A good example is check the direction of the flow into the base with runners off, then stick a runner on there and note the direction of travel. Then look what GM did (or didnt do) to help the situation.

 

Isn't this WHY you port match in the first place? Things seldom line up perfectly and this is why the people that take the time to "port match" in the first place.

If it makes you feel good, you should have seen how much metal my buddy had to grind off his Miniram to port match it to his AFR 195s.

 

Man, don't look at the intake manifold to head connection. You'll really freak out!
As long as the plenum holes are not smaller than the runner holes, no foul.

 

Port the plenum to match the runners. Don't do it the other way around. It won't hurt a thing if the plenum is out of round. Just make sure you end up with enough material on the plenum for the gasket to seal the runners.

 

But the real question is:

Why did these cars run worse after the new SLP runners were installed.

Damn! I got a set on the way now.

There must be a tuning problem here???

What size engines were the runners added to?

Any other experiences out there with SLP runners????

 

Mine runs pretty good with the SLP runners....... but maybe the cam and heads and whatnot are responsible for that . I'm pretty sure it wouldn't run as good with stock runners though .

As for the mismatch.... That looks about like what mine looked like before I got started too. And as for just matching the plenum to the runners, it really is not possible to only remove plenum material and get them matched up very well... They just didn't match up very well in my experience either. But no worries on that - making them match as well as possible is the main idea here, so the flow will transition well from one component to the other, and not how round the port is, as 8Mike9 pointed out.

And like someone else said, you will really wonder what the he11 happened when they cast the manifold when you see the base/runner and to an even larger extent, the head/base joints . It looks like they just did not give even half a $hit when they created the mold for the base..... The engineers must have said, "Make it bolt together and not leak and we will call it good " I spent many many moons (well.......) in the garage getting full of AL when I cleaned up and matched the stock base to my TFS heads, matched the SLP runners to the base, and siamesed the plenum to the runners and matched them...... I also looked at the transition of each port and tried to help that out like madmax spoke of, but you would need a whole lot of material to get it to really flow like it should. That ended up being quite the project since I had no air for most of it and couldn't use my die grinder .....

So get after that stuff some more until it looks really good.... I knocked a lot more material out of the plenum divider walls than that..... And be sure to radius all of the holes nicely .



That's one of my setup somewhere during the process of siamesing the plenum.

Laterzzzz,
Matt

 

Very nice shot.

Do you have any other photos?