What's your thoughts on SLP's Siamesed Runners? Are they worth it? Good/Bad Stories? How much 'real-world' horsepower/torque will I gain with my setup(below)? Driveability problems? Does it take away much or at all from my MPG?

I have a 1988 L98 GTA, ported upper plenum, SLP Headers, Flowmaster Exhaust, 3.73 Gears, MSD, Free Mods, Strut Tower brace, stock heads/internals.

 

well, I have those on my car....I notice I had a hard time to hook up at the track...no MPH increase...but that could be from alot of other things (like my fuel pressure that was to high...etc). I'm still not totally sold on them...but I got them with an edelbrock base for nothing.
I'm about to go to the track to test out the new 3.23's that I swaped in VS the 3.73's I had...3.73's were killing my car, and I got to say that the 3.23 pull extremly hard too...track will tell all

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85 Z28, 355, edelbrock base, SLP runners (old style) 58mmTB, ported plenum, stock cam, fuel reg, TES headers, flowmaster, 3.23's posi, rear disc, shift kit, MSD 6a, 305 hypertech chip (YUUUCK!) best prior intake mods: 14.6 @ 94, 2.02 60' temp: 78deg, 80% moist, on radials.
69SS, black, 3,73's, TH400, 402 BB, roller everything (solid 246@50 622 lift)+stud-guirdle, 67 Vette heads ported and o-ringed, about 10:1 cr KB pistons, should be done this summer, goals: 500hp and lots of fun

 

IMO, you are a long ways away from being ready to install a set of siamesed runners on your car. I would only install a set of runners (especilly siamese) if you have an aftermarket cam and intake base. Those runners flow too much, particularly up high for the stock cam and intake base to handel. If you really want to leave your cam stock, and want a set of runners, I would get LTRs.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

I agree with Dan. Siamesed runners like from SLP or AS&M work better with a larger cam and better heads than the stock ones. Go with large tuber runners from AS&M or Accel first, or save your money.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

The new design on the SLP runners are only about 1.5” shorter than stock and increase in diameter like .1”. Can’t see how that would be “too much” for a 350,, since the stock TPI system was designed for a 305 anyway. Just be sure to grind on the plenum to “gasket match” the large opening. If you’re talking the old design where the bottom of the runners were “siamesed” (like the Summit picture) they probably would not be a good choice for a relatively stock 350.

 

I am pretty sure that SLP includes the matching gaskets for their runners in the kit, I wouldn't think they'd make you have to grind down stock replacement ones.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

I'm pretty sure he was refering to porting the plenum to match the larger diameter of the runners

 

slp runners are only good if you have a bigger cam..

 

If I added 1.6 Roller Rockers, would it be enough to make up for the stock cam?

 

Just a correction, the stock TPI wasn't originally designed for a 305. Tuned port injection came first on the Corvette, which always had a 350. Just FYI...

 

another correction, the manifold base was designed specifically for the 305, GM had planned on fasing out the 350.(according to Lingenfelter's book on small block Chevys).

 

Night Hawk- I would think that for a temporay fix, the 1.6 rockers would work, since the stock cam in the 88 L98 is pretty decent for a stock cam. But, you will not see any huge gains in power until you install a bigger cam. I would recomend the LT4 HOT Cam or ZZ4 Cam, both are avilable for less than $200 from GMPP, so you don't have to spend an arm and leg to install a new cam, you can do it for less than $350 if you can get some inexpensive new springs and timing chain. I bought my LT4 HOT Cam for $165 from www.gmpartsdirect.com.


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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

I just purchased these runners for my 91 Z28. I have a set of comp cams roller tip 1.6 rockers, tes headers and 3in flowmaster cat back exhaust, ford svo 24lb injectors, Paxton s/c running 8lbs of boost, crane hi 6s boost retard. Will these runners help me at all?? I had these runners on my vett and had an acell base and noticed a huge diff! What do you think?

craiger