I have been hearing that people are not porting the entire center out of these runners and porting the plenum to make it only 2 holes on each side. TPIS also makes gaskets for this right? My question is wont this mess up the flow into each individual port on the intake base?

Thanks

Chris
12sec305

 

someone help?

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1986 305 TPI
8.0 @88 in the 1/8
**Soon to be 355

 

I am not to sure what your question is , but let me twell you what I plan on doing. I am going to port my plenum to match the 58mm TB then goto the runner opening and port them to match a set of TPIS Large mouth gaskets. Then open the Siamese the opening for my SLP runners. The I will port out the runners to match the Intake and port all the way down but not remove the Center sections. This will help upper rpm breathing while not sacraficing too much lower end Power. I have enough low end torque right now to break my posi loose if I clam it and I only have 2.77 gears. So I am willing to give up some of that power becase when I get the 3.73's it will still feel like that power is there, but I will have more in the upper rpms. Hoe this helps

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86 Trans Am 355 TPI Rebuilt 700R4 with Corvette servo, modified valve body, and a B&M Torque Converter (2000 rpm stall w/ lock up), 87 350 block bored .30 with new crank, bearings, rings, and magnafluxed rods. Reworked 305 heads with 3-angle valve job. Added in the rebuild was an SLP TPI cam, BBK 58mm Throttle Body,SVO 24# injectors,MSD 6A, Hypertech Power Coil, 1.5 Crane roller tipped rocker arms, SLP Intake Runners and Port matching in upper intake including fully ported plenum, TPIS adjustable fuel pressure regulator @ 46psi, Hooker shorty style headers w/ Thermotech heat wrapping, Custom 3” exhaust with Flowmaster muffler and chrome quad tips, Hypertech Thermomaster Computer chip, K&N open element cone filter on modified MAF per TPIS specs, MSD Wires, removal of A/C hardware and a 1LE firewall cover installed. Also there has been a PST front suspension kit with Hotchkis strut tower brace
http://geocities.com/SunsetStrip/Garage/9548/kyle.html

Kills:
95 Talon TSI, 96 Probe GT, 91 T/A L98, 89 RS, 86 Mustang GT, 88 Mustang LX 5.0, 92 Thunderbird V8. couple or ricers that I think were Civics or Preludes not sure what year, 95 Celica GT-S, 94 Chevy 1/4 ton 350, one of those NASCAR F150's

 

I forgot... then I am going to match the enlarged ports of the runners to the Intake and port all the way through to as big as I can get it and radius the end of the intake for better air entry to the head.

 

Thanks that helped a lot. My question was based on whether or not to take the whole center section out or not when I port my intake. I thought that if you take the entire center(divider) out of the center the air going to the heads would be turbulent. Do you think that would hurt flow? I think I have the older(not a diveder in everyone. My motor will be a 355 or 383 so I will need lots of air.

Thanks

Anyone else that has done this mod?

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1986 305 TPI
8.0 @88 in the 1/8
**Soon to be 355

 

Yes it would not hurt flow if you remove the centers, but it would hurt your POrt Tunining. YOu will change the flow characteristics of the runner and I would say from the measurements the SLP specs out these runners are good to say 5300-5500rpm
So don't port the center out of the runner but make your Plenum match the runner. The big mouth openins are larger and I recomend portiong the SLP runner out to this inside diameter.

 

I pursued this question vigorously a few weeks back, I posted it on boards all over the place looking for some factual data and I actually called SLP twice about it. Second time I actually got somebody who knew what he was talking about. Bottom line is they do not reccomend cutting the plenum on a stock or near stock motor. But if it has been upgraded with heads and cam apparently there are some gains to be made in the upper RPM areas.
Roy

 

I bought a set of the old-style SLP runners that only have two dividers. I ported (gutted would be better word) the plenum to match the runners and removed the remaining dividers in the runners. I could not tell any loss of torque and gained 800 useable RPM, up to 5500. The motor dynoed the same before and after, but I found a vacuume line off after the second dyno run. This is all with the stock intake, no porting. Right now I'm finishing off the porting of the intake and have installed an LT4 Hot cam. Next spring I'll be able to see what I've done.

 

Does anyone sells the gasket set for the siamesed plenum openings, though?

 

I looked for a gasket set, but gave up. I just bought a roll of gasket material at the local Napa store. Not the cork stuff... this is more like very stiff dark cardboard. I just pressed the end of the runner against the material and traced out the outline. Trim to fit. Takes a while, but it will go a bit faster if you have a dremel tool with a small sanding drum attachment.

 

Mr Gasket has a set that seems to work well with 1.75" openings. While they are not siamesed, all you have to do is cut the center out. It's part #146 should go for around $12 or less.

 

I used a set of the TPIS big moth gaskets and cut the senter out.

 

I used the TPIS big mouth gaskets also. The problem I ran into though is that the old style SLP runners have an odd shape to one of the runners(one tube on each set.) The Big mouth gasket doesn't fit, it's too big. Of the 6 gaskets, I used four and made two more to match the odd runners.