Tom400CFI

Eh.

Looks pretty blase' to me. Nothing really "interesting" to look at on it, IMO.

84 4+3

But it does get you what you're looking for curve wise. It ain't pretty.

Tom400CFI

Yep.


Nope.

GREGGPENN

If you're still interested in your original question, I might consider commenting. If not, I don't want to look up a couple of things for supporting comments (in addition to personal experience -- which requires "interpretation" due to my conversion from 350 to 383)....which porting the hell out of an SLP setup.

C409

….. FIRST Fuel Injection ….. https://firstfuelinjection.com/ … A little over a grand gets you most everything you need , including a Mono-blade throttle body and 1.75" runners and base (portable to 1.90") … slightly different look than TPI but still the same … I had one on a 409" sbc and it pulled well into the high 5000's rpm's but I never had it dyno'ed ….. several times at the track and car shows I was asked if it was a blower (GM Roots)

C409

….. Tom … You want something "different" ? … How about a Smokey Ram EFI Intake manifold … $600 with fuel rails …..

Tom400CFI

^That is very interesting. Let me think about it. Did you use the stock TPI fuel rails? That meets all my criteria, for sure.


:

cv67

Been wanting one of those forever but dont have $600 jumping out of the pocket. Some would hang ya for welding those bungs on lol
Neat piece.

MatthewMiller

There's also this Hogan intake: https://www.corvetteforum.com/forums...-not-mine.html. It's probably too expensive, too, but it sure would look bad-***.

C409

…. It uses universal SBC fuel rails … I have a pair of brand new Edelbrock's that will go with … you would need to plumb your fuel lines … Earl's has an affordable "kit" to convert the factory O-ring fittings to AN … the rail ends are 3/8ths pipe thread ….. I can pretty much guarantee that you won't ever be parked next to someone with the same intake set-up ! …..

Tom400CFI

Yep....beautiful though it is, that part is "not like the others" on the Kart.

C409

….. The base is still virgin … You can find Smoky Rams on Ebay for $400-500 if you're patient …..

cv67

Thanks.
Tom theres some goofy sheetmetal intakes on Alibaba, just got to find who is legit to buy from.
THey wont function as a tuned system like a Hogans would but "look the part". Lots of guys selling them on ebay for a few hundred.
I cannot see spending a grand or more on outdated TPi parts.

GREGGPENN

Brian provided a good link (you've probably seen) in post #19. Like most dynographs, we are deprived of sub 2500 RPM statistics. That said, you can see the fully-siamesed SLPs display the same torque (as stock TPI runners) from 2.5-4k rpms. Presumably below those rpms too. Peak increase would appear to be 400-500rpms though useful "area under the curve" is double/quadruple that -- especially if you look at HP numbers. As pointed out already, there is serious UNANSWERED questions on the benefits of "siamesing" intake cylinder tubes....and whether the siamesed area "acts" like plenum or runner? (That later presumably more apt to "pressurizing" which leverages reversion waves.) Back in 2010...when I looked at as many builds, charts, calculators, and theories I could find on the subject, it did see that siamesing the upper half of SLPs was beneficial. Beyond that (e.g., siamesing the entire runners) did not perform as well as a superram or even the Firehawk intake posted here. You can easily see this by comparing those intakes in the shootout.

Another question might include optimization. Are the comparisons made in the TPI Shootout FAIR if each intake wasn't optimized? The short answer is no (from my perspective). However, you easily see enough to make the correct selection for your individual goals! Changes in lift, valve timing, and duration could improve the advantages seen in the link. In my build, I worked with an engine-builder who was well-versed in optimization software. Using: the TPI shootout, his feedback from Engine Analyzer, anecdotal builds, and this intake runner calculator, I ended up determining the "ideal" siamese for my own 383 target build. Actually, here is another tool that I used. (When you input runner lengths to the "bowling" calculator, you must include head intake runner length too. Specifically, the 6.125" + 6.625" lengths that makeup the SLP runner "tract" don't include the distance from the head intake to the valve. (I can't find it, but it's probably around 6" more?)

Using a combination of these tools, you can easily target the approximate peak you're shooting for -- within any given intake. I will add that you can further effect peak with valve timing. IOW, installing a cam 4-deg retarded vs neutral vs 4-deg advanced should be considered in your build. IIRC, this alone, can swing peak at least 400 rpms. As eluded to above, I decided the "optimum" build (for me) was to choose a runner between the superram and TPI. I don't remember the exact length but I think the superram is only about 1" short from hitting the optimum 3rd harmonic (reversion wave). Opening SLPs about halfway down SHOULD achieve this result. Of course that "unknown" is whether the upper part of siamesed runners act like runners or plenum. My guess is both. It's not quite as good as plenum -- which give rise to the lauded benefits of the GIANT superram plenum. OTOH, it's not that bad either...especially if your choice is between a superram and a siamesed SLP setup.

Siamesing the base (to me) seem akin to building an LT1 intake. Personally, I think you'd lose all the runner/plenum benefit while inducing maximum turbulence between the adjacent cylinders mentioned a few posts up. One guy here (65Z01?) used to have a really good website posted that demonstrated track times between each detailed upgrade. I'm fairly sure I didn't see the benefit to his base siamesing...at least for my goals.

The biggest thing I get out of the TPI shootout (versus that skewed TPI vs LT1 graph you usually post) is how much power is "under the curve" for all these intakes. This is due to the scale chosen for the graphs. The TPI shootout makes the difference look closer to reality...though I would like it much more if the bottom half of each intake's graph were displayed.

In my 383 build, I ended up gaining about 500 rpms "peak ceiling" over stock. However, I'm fairly sure the stock 89 cam is 2-deg retarded vs the 4-8 deg setting I'm running. (That's right, I might have overshot my cam advance up to 4 deg!.....And, really, I chose an advanced setting because I thought it likely I'd end up swapping to a Stealth Ram intake...where I'd want more "bottom-end" leveraged with cam advance.). Had I installed my cam 4-deg advanced, I 'm fairly sure I would have gotten at least 1000 rpm more peak than stock. Plus, the overall "area under the curve" makes my 383 build's torque "bubble" nearly twice OEM in it's entire usuable range. I'm certain this is why one of our members consistently won more race brackets with a large-tube setup vs a Stealth Ram.

My final point will be tube diameter. As noted by Matt, larger tubes raise peak....and visa versa. It has been widely published that the Corvette TPI intake was meant for a 305 engine. It measures somewhere between 1.45-1.47" diameter. (which means a seller has this wrong in the 4 sale section of C4s! LOL). SLP tubes are around 1.55" .... making them the smallest aftermarket runner. IOW, Edelbrock, and TPIS tubes are bigger. FIRST FUEL INJECTION are the biggest. IIRC, they measure 1.6", 1.7", and 1.9" respectively. This might be helpful for those wanting to plug some numbers in the links I provided.

If you want an idea of runner diameter's effect on power, peak rpm, etc... look at this chart:


I think you can see the benefit of runner diameter as shown above. When I "mega-ported" and siamesed an intake for my 383 build, this is what it looked like.....

Tom400CFI

I didn't give a lot of weight to the article. I've read it before and found it informative, but not THAT relevent to my question here for two reasons:
1. It was a fairly modified 383....a "450 hp" engine, which is way out of the realm of the 'Vette Kart's engine and what most of those intakes were designed for. (eg, the T-ram looks not-so-great when it likely would look a lot better on a stockish 350 for which it was designed)
2. They hadn't fully ported the bejeezus out of the SLP's in the test.

I agree that there doesn't seem to be much good data on the wicket ported SLP's.

MatthewMiller

FWIW, I have some possibly-applicable theory to throw in. In an unrelated discussion about flat-crank V8s vs normal cross-plane V8s, a powertrain engineer with whom I'm acquainted noted that the flat-plane designs are far less sensitive to exhaust tuning (his emphasis on "far"). The reason he gave is that once you separate the firing order on each side by equal 180* intervals (as opposed to the highly uneven 90* and 270* spacing on each bank of a cross-plane V8), there is much less interference from one exhaust port to another. One port's pressure doesn't tend to disrupt the flow from an adjacent port. He says that the main reason long-tube headers work well on a cross-plane engine is that they give lots of separation between adjacent 90* cylinders, so that they don't interfere at the valve so much (that's right - it has little or nothing to do with resonant tuning).

That's on the exhaust side, but the same issues would apply on the intake side. I think it speaks directly to the concern I voiced in past #21. If you fully siamese the TPI upper, you may get into a lot of interference between adjacent 90* cylinders on their intake valves. This wouldn't be like short LT1 runners connected to a common plenum, because you're pairing the two runners (and only those two runners) together for the length of the siamesed portion of the runners. It seems to me that the deeper the siamesing goes, the more interference you'll experience. If you add a flat-plane crank to your engine, that would solve all the problems! That's probably budget-friendly, right? But seriously, the more I think about this, the less enthralled I am with idea of siamesed intake runners.

Tom400CFI

Flat plane crank. Hmmm.... The crank would cost as much as the entire project, thus far!

Yep, that all makes sense. I'm "over it" with the siamesed runner idea. I'm either going to do something retarded...like buy C409's crossram intake and make that work...or do something like that marine intake that I posted earlier with a custom plenum.

cv67

Take one of your LT1 intakes, weld a holley flange on top and stick a carb or TB on it. Going backwards at its finest!

Tom400CFI

Make that flange a 2bbl TBI flange and run a late 80's TBI on top...oh yeah! LOL....that would be some real internet fodder for the future, huh!

MatthewMiller

That's how I'd do it. A Holley Stealth Ram would probably even be better. For that matter, how about an old-school dual-carb tunnel ram converted to TBI? I bet you could find some L83 TBs (or some truck TB) for next to nothing, and those old tunnel rams can't be expensive on the used market. Polish that biotch up and get it running well and that would be pretty cool.