HI,after much searching I would like to ask a question, I have purchased some new SLP runners and have started to make some rough cuts and clean up some flashing, my question is how big can you port these without running into problems and can you remove the tangs inside the runners, it dosent look like if I remove them it will cause a problem or break through anything. If you know please help, and if you know any porting procedures that will help make this easyer please let me know.THANKS

 

Here is what can be done to SLP runners.

 

wow, just wow.

I bet that bad boy flows well past 4500 rpm

 

i've seen these before home much better over stock are these? they can fit a 305?

 

Man thats nice 89GTA, but how far did you cut the mid sections out on the base side, I think I have read that it causes a lean condition on some cylinders or is that if you port the base that way. Thanks for the photo it helps, what measurment did you get on that, and also were you able to cut out those tangs without cutting through something? And how much higher do you think that helped the engine to pull? Sorry for so many questions but I need all the help I can get....LOL. I also want to mod the plenum and intake, do you have anymore photos you cand post for me, I would really be very greatfull , thanks for your time.

 

Hi

On the left side the mid section is completely gone and fully siamesed. On the right side of the picture I went in a far as I could and there is maybe 2 inches at most of runner left.

As to the lean condition that "may" happen if you port the base. I did not but had it Extrude Honed. I did have to have the edges built up on parts of the base side of the runners so that it would match the Edelbrock base better with the holes opened up. I'm close to 1.70 inch on the base runner side.

The engine pulls strongly to 6000 rpm which is my 1/2 shift point. It shifts around 5600-5700 on the 2/3 shift.

On the dyno peak HP is about 5000-5100 rpm and peak torque is around 4600rpm. Kinda makes an LS1 out of a TPI.

There is no practical runner left in the SLP's. The runner length is now reduced to the manifold at 6.125 inches and the heads at 6.00 inches. Total is 12.125 inch which is quite close to the LS1 runner length.

Also the plenum volume was increased a solid 50%.

 

Another view of SLP runner

 

View of Plenum

 

On the car.

 

Thanks alot 89GTA, How long have you been running that combo, looks like you pull some good quarter numbers...That looks like a well done set up, really sharp. Have you had any tuning problems with it? I hope I can make mine half that good and then I know my combo will work good. How many hours do you think you have in them, and did you have to use any specialty tools besides just bits and sanding rolls? Again thanks so much for you help...

 

Sanding drums turned out to be the best tools. I also became good friends with my local welder. I have been running the combo for a good 6 months. Interesting in that I still gained torque across the board with the mods. I work slow so it took me a few weeks to do it. I have to stop and think about the next step. Mistakes cost me to much.

As to tools I have a small lathe and a small bench mill. I made the bolt guides on my lathe. Hogged out a lot of the plenum and runners with the mill. Made the bosses on top of the runners and plenum with my mill. This could all be done with hand tools and a friendly welder.

With my next round of mods I hope to be well past the 400HP mark. If the stars aline and the moon is in the right spot maybe even 425HP at the crank. That would put me well into the low 12's. This would still be with TPI although modified.

 

ZEEYAA,
That's what I was telling you about at the picnic yesterday. There's plenty of room in there. Hog 'em on out!

P.S. This is Johnny!
I mostly lurk, as you can tell by my severe lack of posts. (five years and I haven't even hit 200 yet)

 

just kinda wondering, and of course, I don't know any better.

I got (normal) SLP runnners on my 350 TPI with the Edelbrock base, and I did port-match the plenum to the SLP runner entries. I can see the rationale for big-time hogging out the top side of the SLP runners where they mate with the TPI upper plenum, to effectively shorten the runner length, create a bigger plenum volume, raise the RPM torque curve, etc. But not so sure I understand the benefits of creating an intermediate 2-runner mini-plenum bubble down by the TPI-manifold-base for each set of runner pairs.

I guess it works, regardless, lots of folks are doing it, seems like. Just wanted to pose the question, since I bought a set of SLP runners on e-bay that were agressively hogged out at both ends. Not sure if I would ever use them, bought them as extras, "shelf-spares". Not intuitively obvious to me the reasoning for going hog-wild on BOTH ends of the SLP runners, the plenum side I can understand.

 

WOOHOO JOHNNY G. now thats funny, Yeah I posted this along time ago before the cookout, Im still hoggin...lol.. but when I get closer to where I think they are o.k. I may get you to look at them and see what you think.. maybe just before I start polishing them. Thanks for your advise and help everyone and If anyone has more photos of plenum/runner/base set ups they can post please do, you know the picture/thousand words rule.... THANKS