I'm putting together an SDPC Vortec base and SLP runner setup for my 350. I've ported the base, but haven't opened up the mouth where the runners bolt. Likewise, the opening on the bottom of the SLP runners is untouched. Based on what I can see from peering in through the intake manifold, the SLP runner diameter is ever so slightly smaller than the opening in the manifold. My concern is that if I open up the port on the SLP runners without getting the baseplate opening identical, that I may end up with a ridge that could create turbulence. Right now with the runner diameter ever so slightly smaller than the baseplate, I'd expect turbulence to be minimal.

Does anybody have comments/experience with this? My guess is that I'm best off leaving the runner to baseplate transition alone and working on the top side of the runners by opening up the siamesed area.

 

Jim:
In it's stock shape that Vortec intake flows less than a stock factory manifold.
240 for the stock...236 for the Vortec.
So it needs work everywhere.
Flowed with this tool.

 

Don,
I've already done a lot of work to the intake base, based largely on some of the historical posts from your So Cal crew, along with some point-directed advice that you guys had provided to me a couple months ago.





An old pic prior to cleaning up the walls and pinch area that shows how I knocked down the injector bosses:


I've got the majority of the intake as open as I'm willing to take it. I've already run into the machined area where the runners bolt and had to fix it. Some of the other pinch areas may still have enough material to go a little wider, but I don't want to wind up cutting into adjoining ports or into water jackets.

To be honest, I didn't realize that the base flowed 236 cfm stock... I was under the impression that it was closer to 200. Since the stock vortec heads flow about 240 at .500 lift, if my runners and base can really provide an honest 240 cfm to the heads, I have to think that the intake & runners will have done their job.

 

I'd think you want the intake to flow considerably more than the heads so that the intake doesn't limit the heads. I've flowed intakes and heads together and unless the intake really hauls the mail, an intake will limit the heads quite a bit, especially if the intake flows the same as the heads..

 

That certainly makes sense. If that intake indeed did start at the 236 cfm range, then hopefully my modifications have helped to bring it to a sufficiently higher flow number. Unfortunately, unless somebody is willing to flow test it for me, there's really no way for me to know. Based on what Don & his crew have said, it sounds like the biggest restriction to that intake is the pinch area, and the transition into the cylinder head. Hopefully by cleaning up that pinch area and cutting those injector bosses way down, I've been able to make some meaningful improvements.

 

Agreed
With a LTR you almost cant do enough to those bases/runners you could kill a lot of time...lots as you know lol.

On matching the tubes to the base get them close. The gasket seems to be able to move a slight touch when lined up with the bolt holes so once tightened down there could move a teeny bit. I wouldnt get too wrapped up over making them "perfect"..real close will do imo.
Those runner lengths on these TPIs are so darn long a sligth something either way wont make a difference if that helps.