DarthD

The TPI engine was rated at a max of 250 hp in the Corvette.
The LT1 only made 50 more hp at a higher RPM.

Most TPI haters credit the LT1's power advantage to the intake.

The LT1 had many other advantages over the TPI though.

Lighter pistons, lower tension rings, Higher compression, better cam, better flowing heads, sequntial injection, better flowing exhaust, possibly better programming and ignition.

Is is possible that a TPI engine, with all the advantages that the LT1 has would make 300hp? If so, it would be a lower rpm and make tons more torque.

If that alone would not reach 300, the think about adding a LTR setup. The stock TPI setup was designed for 305 cubic inches. If GM had the 350 in mind when the TPI was designed, there is a good chance that the runners would have been similar to the TPIS large tube runners and big mouth base. This alone, I think, is worth 20-25 hp on a stock L98. Adding every other advantage listed above should be worth more than 30 more hp.

What do you think?

PneumaticTire

Dyno the LT1 and then slap the TPI intake on, and dyno again. Find out for us all.

P.S. I see this is your first post, Welcome to the boards!

DuronClocker

iTrader: (1)

TPI style intake on the LT1? It wouldn't have been as great of a motor and we would probably just now be getting the LS1.

The L98 might make torque down low, but so does an LT1. The LT1 holds that torque almost all the way through the RPM band, while making more horsepower. Broader powerband.

You can get an LT1 car into the mid-12s with $1200 or so. Good 2800rpm stall, headers/exhaust, 3.73-4.10 gears (depending on auto/6spd), and drag radials. Add a cam and you're doing even better for under $1500.

I LOVE my LT1 heads/intake setup. Even on my 305 it was a blast. Not as much low end in the 305 especially because I over-cammed it. Well, not really, I planned to kill low-end and take a bunch of high-end and eventually get a better torque converter, but that didn't happen before I blew it up. Now that its on a 350 in my car, it pulls hard all the way down as low as 1800rpms and pulls all the way to about 6000RPM, and it's horribly out of tune. I only have 3.23s too. 4.10s will be going in along with a T-56 by spring.

Vader

The LT1s in Y-cars was rated at 330HP. Compared to the Y-car L98, that's 80 more HP, and across a broader, flatter curve.

You're right that the LT1 enjoyed better programming, better heads, and a lighter and better balanced rotating assembly. Even the iron heads for LT1s flowed better than the aluminum L98 heads. The LT1s also had more compression, lower emissions, and better mileage due in a large part to the cooler (reverse flow) heads.

The cam issue is on question, since some of the LT1s had a cam as mild as the Y-car L98s, and were still conservatively rated at 260HP. The tamer LT1 cam specs (.418/.430, 191°/196°, 111°LSA) were about the same as or arguably even worse than some of the the better stock L98 cams (.410/.423, 211°/219°, 117° LSA), so the power difference isn't necessarily there.

But even with the rest being equal, the "de-tuned" intake of the LT1 provides adequate low RPM torque and superior mid- and upper-RPM torque. Equip a "regular" L98 with a Mini Ram intake (LT1 clone) and you'll notice a difference. Some of it is simply in the intake design, and the sympathetic (resonnant) frequncies of it.

Ray87Z

Say whaa?? The LT1 was rated at 300hp in the Vette, the 330hp rating was for the LT4...

BadSS

Lingenfelter use to install the SuperRam on LT1 cars. If I remember an old tech article correctly they put the SuperRam on a stock LT1 Z-28 and picked up around .25 seconds. However, throw a big cam at the LT1 car/intake, add more gear, and add more stall and the LT1 car/intake will go faster with less money than the SuperRam swap would cost. That's why you don't,,, and didn't see a lot of people running out to swap the LTI intake over to the SuperRam (long tube runner system).

DarthD

If I was rich I'd do it just to see.

3.8TransAM

What about doing a search under "protoype TPI intake" and what if they used a Super TPI on roids like I have managed to acquire?

Has way more flow capabilities and a lot larger openings in base and runners and plenum.

Would be interesting to see something like that tested or even know what GM was getting out of it back in the day lol

Just a thought.

Sides Vader the LT4 was only avail. on 96 manual vettes(less u include the 20 or so hawks and a few more cam's)

I always love wonder what could have been lol

More than likely I would suspect had TPI evolved further it would have been a entire large tube setup like the First ir my prototype

later
Jeremy

kdrolt

The TPI intake would have been a flow impediment to the engine, so even with LT1 heads and all the other (minor improved) engine hardware you mentioned, the TPI would have made slightly better torque under 3500 rpm, but not as good above 3500 rpm. The engine team at GM designed the Crossfire, TPI and LT1 in that order over a nearly 15 year span, and in each case the later engines improved over the ones preceding them. So if it had been that good an idea to use the TPI intake on the LT1, the LT1 would have used it.

The L98 and LT1 cams are very close in specs, so the biggest (and only significant difference) is the heads and intake manifold. The LT1 heads/intake flow well enough that you can make over 400 fwhp with the HOTCAM and 1.6 rockers. The TPI would not do as well, because of the small area runners.

Remember that performance was abysmal in the early 80s, even in the Vette. It got substantially improved with the Crossfire (L83 engine, back into the 15s in the quarter mile, much better fuel economy than the 16 second carbed L82), and the TPI solved the mixture distribution problem of the Crossfire along with better airflow (more torque, more power) even though the designs were similar (long tube runners). What both of these lacked was big airflow, which was fine at the time because the awesome torque of the L83 and L98 still gave great street driveability and acceleration. And the Crossfire and TPI intakes didn't need to flow any better than they did because the head flow of the L83 and L98 wasn't all that great to begin with (in 1984, 1985) until the progressive improvements were made into the L98 head (1988-1991, and even after that for the GMPP version of the 113 aluminum casting). And even then the airflow was still not great compared to the LT1 head.

See this thread for more details on the Crossfire-TPI-LT1 evolution.

87TPI350KID

L98s are a great engine, just outdated. Just the same reason why we havent used carbs in 20 years. L98s were the LS1 of the 80's. I honestly don't think the LT1 was that much better. A few basic mods on an L98 can hang with an LT1.

DuronClocker

iTrader: (1)

And a few basic mods to an LT1 and you can beat an LS1.

Vader

Still an LT1 family engine to me. That's like saying a 350 is rated at 160HP. That's a broad category. There were multiple forms of L98s, LT1s, and the LS1s. Granted, teh LS2, 6, and 7 have different displacements, but the LT1 is in essence an LT1 with slightly better heads and cam - slightly. Lots of LT1s are doing 380 with head and valve work, and a real cam.