So called 1st run SLP runners?
Thread Starter
Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
Those are definitely SLP runners. They are of the first design as I bought a set exactly like those around 1991 from SLP. IMHO they are the best ones SLP produced. Maybe the best TPI runners made.
They have very little restriction in them compared to the SLP 2nd design. With the 2nd design they have bolt lug bosses protruding into the air flow and that cuts down on the cross sectional area. Plus they did away with the siamese on the one runner set.
I have modified mine since then by siamesing the other side and I'm making over 370rwhp with a 355. With my new build I expect to break the 400rwhp barrier but with an increase to 369 cubic inches.
Yes those are very good runners.
They have very little restriction in them compared to the SLP 2nd design. With the 2nd design they have bolt lug bosses protruding into the air flow and that cuts down on the cross sectional area. Plus they did away with the siamese on the one runner set.
I have modified mine since then by siamesing the other side and I'm making over 370rwhp with a 355. With my new build I expect to break the 400rwhp barrier but with an increase to 369 cubic inches.
Yes those are very good runners.
Should i fully siamese these?
Mods
1991 TPI stock long block 113 heads
Old style SLP runners gasket matched with Bigmouth intake gaskets.
TPIS Bigmouth intake
Ported plenum with 48mm TB
CC502 cam 218/224 @.050/495/503 lift 112lsa
Bosch III 24# injectors and AFPR
Scorpion 1.5 roller rockers
Flow master cat back and TPIS Ypipe
Racer
Joined: Oct 2007
Posts: 478
Likes: 1
The theory behind the design was to have two harmonic waves that would peak at different rpms. This would raise the usable rpm band for the motor. The peak torque would be somewhat less put peak horsepower would be higher and the torque band would be carried higher and not drop off so fast.
Whether or not to fully siamese the other side would depend on the desired operating range of your motor. You need to look into wave harmonics.
By the way I consider the last design of the SLP runners to be one of the worst aftermarket runners out of the box. However the good news is they can be modified to your hearts content.
The first design like you have is mostly already there from a modification stand point and requires a lot less work for all out mods.
Whether or not to fully siamese the other side would depend on the desired operating range of your motor. You need to look into wave harmonics.
By the way I consider the last design of the SLP runners to be one of the worst aftermarket runners out of the box. However the good news is they can be modified to your hearts content.
The first design like you have is mostly already there from a modification stand point and requires a lot less work for all out mods.
Thread Starter
Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
Race Director
Joined: Nov 2003
Posts: 12,221
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
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When you look at HP graphs for TPIs, LT TPIs, SuperRams, HSRs, Minirams, etc.... you'll see how the curve changes as tubes are shortened. As they get shorter than a superram, they essentially take on the character of a short-runner intake.
By having dividers completely removed, you'd have a short-runner intake with long-meaningless tubes on top. The TPI harmonics would be gone because of the length. (And, I'd question if the tubes become a detriment.)
When I calculated the optimal length (for my goals/rpms), I liked anything from the SR length to 2" longer. To me, anything shorter made keeping a TPI pointless. Anything longer meant sticking with ASM's, TPIS big tubes, the FIRST, etc....
Even if you hiding from the CA smog police, having a SR length divider makes the most sense for a street car.
It's all in the wave harmonics vs divider length. (If you'd like to see how the length's work, look at the last few posts of the active FIRST intake thread. Chris posted a link to a runner length calculator.)
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Burning Brakes
Joined: Nov 2004
Posts: 800
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From: Port Orange FL
The motor I had in my IROC was similar to what you have specked out there. I had siamesed the SLP runners as far in as I could get them. I would say I got about 1/2 way through. It would keep you planted in the seat until about 5500 RPM.
Roy
Roy
Pro
Joined: Feb 2005
Posts: 658
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From: Centerville OH
I spent some time cleaning them up, 2 days. Yesterday I siamesed the center runners in 5" another 4 hrs.What did you have yours on? Stock? Did you do any port work to them? Where did your rpms fall off?What is you opinion of these vs the new style?
Sorry, for all the questions
Sorry, for all the questions
I put them on the car when it was bone stock. I didn't port them, but I had to clean up the openings a bunch to make them even halfway round because the castings were so poor.
If memory serves (it's been a long time ago), the car ran out of steam at about 44-4500 stock, and the SLP's extended that maybe 200 RPM. Between the runners, a chip, and Flowmasters, I picked up about 2/10's in the quarter.
I ported my heads and put on an ACCEL base with these runners in 1996 and the car felt choked. I switched to AS&M large tubes and immediately picked up 2-3 tenths and almost 3 mph in the quarter.
I've seen the "new" style SLP runners and the thing I noticed most was that the casting quality was MUCH better. As far as function goes, I don't feel there would be that much difference as cast. I think the older style might offer more performance in a mega-ported state, but IMO the effort to mod them wouldn't be worth the gains over large tubes.
I still have the first-gen SLP's. I'm willing to sell if someone wants them. They are just collecting dust in my attic.
Pro
Joined: Feb 2005
Posts: 658
Likes: 1
From: Centerville OH
What...Waaaaooow! 
You never mentioned that to me. So you're saying the ASMs were .2 tenths faster than these? (Maybe that's why SLP said we never made those 
)
I thought your set went to another member. If you still have them, I suspect ekess would be interested in buying them from you.
gp
You never mentioned that to me. So you're saying the ASMs were .2 tenths faster than these? (Maybe that's why SLP said we never made those ) I thought your set went to another member. If you still have them, I suspect ekess would be interested in buying them from you.
gp
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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Todd: When you raced SLPs (vs ASMs later), did you run up the rpms quite a bit higher before shifting (vs ASMs)? How did the ceilings compare for each?
Last edited by GREGGPENN; Jul 3, 2009 at 09:51 PM.
Pro
Joined: Feb 2005
Posts: 658
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From: Centerville OH
Geez, Gregg, do you have to debate EVERYTHING???
I find it hard to believe that ASMs are faster (let along that much faster) than SLPs siamesed that far. The rpm ceiling's gotta be alot higher which would have let you say in lower gears longer. With similar power levels, staying in lower gears and go to higher rpms normally wins. TQ vs HP threads clearly show why.
Now, it's hard for me to see that config as being slower than ASM's -- unless the inner tubes are THAT bad. And, I mean horrible.
Now, it's hard for me to see that config as being slower than ASM's -- unless the inner tubes are THAT bad. And, I mean horrible.
BTW: When you raced SLPs (vs ASMs later), did you run up the rpms quite a bit higher before shifting (vs ASMs)?
Last edited by Z51L9889; Jul 3, 2009 at 10:09 PM.
Racer
Joined: Oct 2007
Posts: 478
Likes: 1
Let just say with my 1st design SLP runners that are siamesed I'm shifting at 6400rpm and the car is pulling quite well. On the dyno that is close to peak power but with valve float setting in I can't go any higher.
With my next motor and the same intake system I expect to up the shift point even more. Long live TPI.
With my next motor and the same intake system I expect to up the shift point even more. Long live TPI.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Actually, I had decided not to debate it. That's why I rectracted the post a few minutes after I posted it. Apparently, you copied it before I revised and removed it, then replied anyway. Geez, Todd...Do you have to reply to everything! 
O.K., now I have to complete my point.....When you combine (completely siamese 2 of the 4 SLPs tubes), that's a ton of flow. You're an engineer. Be a little more open-minded. I'm not trying to challenge what you ran, just that it doesn't make sense on the surface. I'd expect two (siamesed) SLPs tubes to suck way more air than one ASM tube. That's all I'm saying. It seems a significant point for people wanting to go down the siamesing road!
That's what I was thinking. Then, a few minutes later, I remembered a comment that MBDiag made recently. It was that the TPI tubes actually lower redline for a 350 block because of the "backpressure" they create (for the bottom end) at higher rpms. That's probably what the other two sets of tubes were doing. Not only weren't they contributing at higher rpms, they actually held it back.
So I answered my own question.
Originally Posted by Z51L9889
I didn't port the SLP's -- they have close to stock sized ports as delivered. The ASMs are quite a bit larger. I measured the ASMs at 1.7" and the ACCEL base at 1.68". My motor combination at the time obviously needed the additional flow that the larger diameter offered. Bottom line -- that combo of parts was mismatched and it didn't run very well.
That's what I was thinking. Then, a few minutes later, I remembered a comment that MBDiag made recently. It was that the TPI tubes actually lower redline for a 350 block because of the "backpressure" they create (for the bottom end) at higher rpms. That's probably what the other two sets of tubes were doing. Not only weren't they contributing at higher rpms, they actually held it back.
So I answered my own question.
