I just got this of a wrecked 91 Z28 350 car. Both runners are the same and look like you can put them on ether side. But my big question is what’s up with the porting on these one side has no divider at all and the other is just like notched out between the tow at the top. Has anybody seen this before?

 

It looks like they've been siamesed. It's done to help it breathe better in the upper RPMs.

 

You are lucky in my opinion. You have the first style SLP runners. If you are going for power these are the best to have. They are fully siamesed on one side and partially siamesed on the other. Those are what I'm running on my car and see the signature for my current power.

 

Ok they came that way from slp that’s good to know. I’ve been looking at them and I still don’t understand how you would get the same amount of air flow when 1, 3,8 &6 cylinders are fully done and 2,4,7&5 are different. And another thing the plenum and the intake are stock and unmodified. Any info would be greatly appreciated.

 

The SLP's runners were a compromise. They were trying to raise the rpm level for power on the TPI intake system. On the fully siamesed side they effectively shortend the runners 7 inches or so. With the other runners they would be somewhat less than stock but with much better air flow. So 4 cylinders would be making power in a higher rpm band than the other 4 cylinders to give a wider range of power.

The runners will work better with an aftermarket intake and a ported plenum. That is what I have done. My motor is right around the 400HP mark with TPI. Hopefully in the comming months I can up that quite abit with the next round of mods.

 

I remember back in the 70's looking at the injector stacks on the Can-Am McLarens. (big blocks) They were not all the same length, but alternated between short and long. I later read In a magazine that it was done to flatten out the torque curve. Otherwise the the engine tended to be too too peaky at one point in the rpm range, and would fall on it's face elsewhere. It helped to even out the power band over a broader rpm range.

Perhaps the original slp's had the same effect. Since we all are aware that 'Tuned Port" is tuned for a particular rom range. Maybe this is a way to keep some botton end but still allow better breathing at higher rpm's. Makes ya wonder if cylinder temps would be consistant and if there would be independant lean/rich issues per cylinder.


Then again I wonder why the Colts are only an 14 point favorite over the Bills.

 

One more thing to update the post. The runners are not the same. One is cast for egr as shown and the other is not. So one fits the passenger side and the other the drivers side.