Marc 9118 said:
u think a 3.07 is a good comprise between fuel Economy and performance . i think i saw one of ur previews post on a lt1 intake it is a futur mod u Wanna add to ur vette
Well, 3.07's will boil both rear tires at will from a stop and shove you back in the seat hard enough that my passengers can't reach the dash until I either let off or we get up to speed, so they're good enough for me!
YMMV! LOL!
The LT1 intake is in the development stage right now:
That's it sitting in a Jig to get the critical dimensions right when I go at it with a TIG welder. Currently saving up for one. It could have been done much more simply, but it involves compromises that I just didn't want to make. I need an AC pulse Tig capable of around 250 amps for that sucker. That's around 2500 bucks on the low end (for a larger Chinese brand, if you want a Miller or Lincoln it's going to set you back around 5-6 grand). I've got a Lincoln 180 amp MIG with a spool gun, but it just doesn't have enough "punch" to deal with an aluminum casting this thick. Works fine on 1/8" aluminum stock though:
It built the cage for my Argo no problems, but just not enough punch for that cast aluminum. Close, but not quite enough. No big deal really, I've been "jones-ing" for a nice TIG machine for a while now and this gives me an excuse to get one. Between the MIG, TIG, metal lathe and plunge mill, I'll be pretty well set up for my retirement hobbies......
The LT1 intake is good for spinning an L98 up past the TPI intake limitation of about 4500-4800 RPM. You loose the peak torque that TPI creates,but you gain more average torque across the curve. Where the LT1 intake shins is over 5,000 rpm, where is where you start seeing higher HP numbers. It's my understanding that the LT1 intake will flow enough CFM to support somewhere around 400-500 HP, but you ned to do a lot of other work to an L98 to get it there. Heads, cams, etc....
This year, I believe I will be reworking the TPI to see what I can get out of it. I've picked up a used TPI lower intake to weld and port:
It would have been easier to start wit han edlebraock or accell TPI "big mouth" base, but they're hard to come by and if you do, people want stupid money for them. My stock 113 heads only flow around 240-260 CFM, so with some welding and raising the runner roofs, I should be able to get close to that. Ideally, you want your intake to flow more than your heads, but it's difficult with the TPI Long Tube Runner (LTR) design. The long tubes are what "tune" the intake pulses and are also what becomes the restriction (and flat tops the HP curve) around 4500-4800 RPM.
Here you can see a rubber casting someone made of a stock lower and a ported lower:
left to right; Stock, cleaned up and gasket matched, welded and port roof raised.
You need to weld to the intake and raise the roof at the head becuase o fthe way it turns into the head port/runner:
The rubber mold is taken from the 113 head runner, the tpi lower intake is what you see on the bench. The rod closest to the camera is the stock TPI runner roof angle, the sceond rod is the welded and ported runner roof. You can see how the stock runner essentially chucks the airflow into a wall, the ported one makes a "gentler" turn into the head port. This is important because any time you try to force air to turn more than approx 45 degrees, you get separation and turbulence, which kills flow and power.
The runner tubes also need to be enlarged, but hte problem is they are VERY thin walled and can't be made any bigger. You need to either buy an aftermarket set (most are out of production now) or make your own. I'm going to make my own.
I'm also going to "remake" the upper plenum to hold more volume. Generally, you want the plenum in an intake to be about the same size as the engine displacement and the OEM TPI upper plenum is about half the size of the 350 cu/in engine. I'm also going to take the opportunity to reduce the runner length a bit. Something like so:
You can also see the welding that is required to change the port roof. That's on an Edlebrock lower intake as well. It already has extra "meat" (compared to the OEM piece) that could be ported out and they still had to add material to the runner. They even had to add "bungs" for the injectors in order to raise them up out of the port area. It's all work I can do myself (once I get my TIG), it's just going to take a long time to get it done. Counting welding, reworking and porting, that guy easily had 100+ hrs of work into his intake.
That guy made max torque of 421 at 5000 rpm and max Hp of 413 at approx 6200 rpm. But it made pretty much that HP number at 5000 RPM, dropped a little bit at approx 6000 rpm and charged back up to 421 just after that, then started to fall on it's face after 6500 rpm. Here's the chart he posted:
That's dead serious territory....for an L98/TPI engine that is. And that's not an engine Dyno, that's RWHP! Figure another 15-20 percent for crank HP numbers. He had more work into his engine that just the intake though. AFR heads, cam, exhaust, ECM tuning, etc....
Changing around the runner length moves the hp and tq peak up a bit, but it also means it increases the RPM capability of the TPI. I'm not looking for much, maybe another 500-700 RPM to 5500-ish before the HP curve "flat tops". I've got some math to do though before I settle on how long they should be. I have to get the 1st, 2nd, 3rd and 4th harmonics right to get the power peaks where I want it and the proper RPM ranges where I use the car.
I'd like to say it is all my idea, but as you can see from the pictures above, I'm not the first. I'm just following someone else's patternand putting my own "twists" where needed.....
