I bought a plenum so I can port it and Siamese it without my car having any down time. My question is will I end up hurting/losing performance if I put on the siamesed plenum with the stock intake and runners?

I plan on buying an aftermarket intake and set of runners, but that won’t be for awhile, unless I can find a good deal on them. And since I siamesed the plenum, does that mean I have to have my aftermarket runner’s siamesed when I get them?

I have been searching all morning and haven’t found anything helpful, so any help would be greatly appreciated.

Thanks

 

Siamesing your plenum without the runners to match is a waste of time, you won't gain anything and it's just another tear down and rebuild to install it. But no, it won't hurt performance unless you get a leak.

No, you don't have to have your aftermarket runners siamesed when you get them. But you definitely want them siamesed prior to installation and match them to your plenum.

I siamesed my ports on my plenum to match the SLP runners. Make sure you grind down the humps in the floor of the plenum right behind the TB opening. Also blend in the flow at the opening.

Good luck with it.