• Tuned Port Fuel Injection LT1?
  • Tuned Port Fuel Injection LT1?
  • Tuned Port Fuel Injection LT1?
  • Tuned Port Fuel Injection LT1?

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  1. #31
    Member Cadillac Tech's Avatar
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    Quote Originally Posted by Hib Halverson View Post
    There are a number of interesting assumptions in this thread...

    An LT1 cannot be converted to an L98.

    "Tuned Port Injection" like "Generation 2 Small Block V8" were marketing terms. "Tuned Port" was a name coined by Chevrolet marketing weenies back in the early 80s for the port fuel injection system used from 85-91 on the Corvette and until 92 on the Camaro and the Pontiac Firebird. It gets its name from its long intake runners, the lengths of which were selected or "tuned" to cause an increase in low-speed torque.

    The "Tuned" name was dropped in 92 in favor of another, even less descriptive moniker "Multi", but the 92 LT1 (along with the later L99 and LT4), also, used intake port length tuning to affect torque...but the port length was much shorter, which raised the rpm for which the runner length was "tuned". This also allowed the LT1 its higher rpm range and greater power.

    The Generation 2 (or "Gen 2") Small-Block V8 arrived in 1992 in Corvette and in 1993 in Camaro, Firebird and the GM B-car. While its block architecture was very much the same as the traditional small block (the so-called Gen 1 of 55-91), there was a big change in the cylinder head and cooling system to acomplish the "reverse flow" cooling discussed above.

    "Nelson84" is incorrect in saying the L98 (350 cuin version) of the Tuned Port engines are "easier to mod". Reality is each engine has good points and bad points as far as their potential for modification, but, if "modification" means significant increases in horsepower and an extension of the engine's rpm range, the L98s big problem is the tuned port system itself. The intake manifold, the runners and the plenum are highly restrictive and a big problem when modification for high horsepower and high rpm are the goal.

    "Nelson84" makes the misleading statment that the L98 makes "more torque". It is true that, in stock trim, the L98 engine has slightly more torque output between off-idle and the mid-range rpms but, if you consider the entire useable torque curve of the engine and the torque peak, the LT1 makes "more torque".

    As for "no Optispark" well....yeah, the L98 had the rear-mounted distributor, but that "no Optispark" is an advantage, I think, is debateable to a certain extent. I'll admit that the early ABITS distributors where flawed by poor moisture sealing but that flaw was eventually eliminated. The later ABITS distributors were not the reliability/durability problems the first ones were and were a much more accurate way to control ignition.

    No doubt, TPI systems look better under the hood. The long runners are pretty darn sexy.

    Another comment above that Tuned Port means one injector per cylinder is not correct. The LT5 has two injectors per cyinder. "Tuned Port" refers to the length of the intake runner not the number of injectors per port.

    Yet another comment above, the one about being able to backdate a Gen II with a Gen I distributor by changing the intake manifold, is not correct.

    Someone asked about the Vortec 350 truck engine. GM called that "Gen IE" and they were basically the Gen I engine with the best of the Gen II cylinder head, but no reverse flow cooling.

    Lastly, the final interation of the Gen II, the 330hp SAE net, LT4 was the most powerful production Small-Block V8 which used the traditional block design. If the old gross power rating system used in the muscle car era had still been valid, that engine would have been rated at about 410-430 hp. Such a power level would have been impossible using the L98 style induction and 2-bolt main cylinder block.

    Thanks for the information. It is nice to read posts from someone that really knows what they are talking about.

  2. #32
    Member 92BlackVette's Avatar
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    Reading these arguments between the L98 and LT1 remind me of listening to siblings argue.

    If were feeling like an idiot and wanted to act like the locals where I live, I would find a 1992(LT1) & 1991(L98) and hook a chain to their bumpers(more like the frames) and see for myself who pulls who. I know makes no sense, it's really what people with trucks do for fun I guess.

    See video for youtube example:
    YouTube - Mike@uspmotorsports vs. Chris@uspmotorsports Truck pull

  3. #33
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    Quote Originally Posted by 92BlackVette View Post
    Reading these arguments between the L98 and LT1 remind me of listening to siblings argue.
    It is a argument based on each's engines technical merits v one person's misguided personal opinion.
    As they say; you can lead a horse to water ......

  4. #34
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    Quote Originally Posted by nelson84 View Post
    But the LT-1 never reaches 350 lb/ft of torque. No wonde GM is bankrupt. They do a bunch of testing and make a crappy engine. Why didn't they make the runners a little longer on the LT-1 and atleast produce more torque than the L98. Even if they were able to get 360 lb/ft would have been decent. Good thing they dropped it after 4 years. Have you ever drove a LT-1 with a 2.59 rear gear, what a dog. Why did GM install granny gears in a corvette.
    Dog? I have an LT1 with a 2.59:1, and I don't call it a dog. You got a bad attitude talkin' trash about ANYbody's car like that.

    And LT1 wasn't dropped after 4 years either...

  5. #35
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    Quote Originally Posted by Schrade View Post
    Dog? I have an LT1 with a 2.59:1, and I don't call it a dog. You got a bad attitude talkin' trash about ANYbody's car like that.

    And LT1 wasn't dropped after 4 years either...
    I test drove a LT-1 with 2.59 gears with an auto and it was slow. The salesman told me before I test drove it that it was slow. But I thought he was an idiot, it was a new vette with 300 hp. It is obvious that the LT1 needs gears to get into its power range. With lower gears the LT1 is a good engine.

    Sorry if I said 4 years. It was 5 and it was the shortest run of any of the 350 engines for a reason.

    Don't get me wrong, if I could get a LT-1 vette cheap, say off ebay I would buy it in a second.

  6. #36
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    I am trying to figure out what you think of the LT1 and LT4 engines which were installed in MY 1997 Chevrolet Camaros and Pontiac Firebirds. By my math, that makes six (6) years of engine production. Not four (4) or five (5).

    The technology of the LS1 and subsequent later LS engines was so far advanced compared to the L98, LT1 & LT4 engines, GM was smart in developing the LS series and dropping the Gen I and Gen II engines.

    Hib is spot on about the definition of "tuned port".

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  7. #37
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    Quote Originally Posted by nelson84 View Post
    I test drove a LT-1 with 2.59 gears with an auto and it was slow. The salesman told me before I test drove it that it was slow. But I thought he was an idiot, it was a new vette with 300 hp. It is obvious that the LT1 needs gears to get into its power range. With lower gears the LT1 is a good engine.
    I'd say just about any Corvette with a 2.59 gear is a pooch, no matter what engine is in it. No on who drove even halfway hard bought that axle.

    Sorry if I said 4 years. It was 5 and it was the shortest run of any of the 350 engines for a reason.
    Corvette 350s in production less than 5 model years:
    L46
    L83
    LT1 (the original)
    LT4
    LS6

  8. #38
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    Quote Originally Posted by LT4man View Post
    I am trying to figure out what you think of the LT1 and LT4 engines which were installed in MY 1997 Chevrolet Camaros and Pontiac Firebirds. By my math, that makes six (6) years of engine production. Not four (4) or five (5).

    !
    "LT4 Man" is correct in that LT1 production in vehicles other than the Vette was longer than five years.

    In this discussion I was talking about Corvette.

  9. #39
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    My '92 has 2.59 gears and is a dog alright, a scalded dog
    1992 Auto. Arctic White coupe stock

  10. #40
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    Quote Originally Posted by nelson84 View Post
    it was the shortest run of any of the 350 engines for a reason..
    How many years was L83 Crossfire engine made?

  11. #41
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    One of my customers owns a 94 Vette with the 2.59 axle. His Vette is pretty quick. Of course, not as fast as my 92 was with the 3.07 performance axle.

    Even some Vettes with the L48 engine are quick. I guess the individual Vette has to be taken into account.

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  12. #42
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    Quote Originally Posted by vetteoz View Post
    How many years was L83 Crossfire engine made?
    From what I have been told: 82, 83, 84. Of course the 83 was only found in Camaros & Firebirds.

    I did see the "Only" 83 Vette this week at the National Corvette Museum. I did not open the hood, but I suspect the "Crossfire" was resting in there!

    AFTER TAKING A WELL DESERVED NAP, I WILL TRY TO SAVE THE !

  13. #43
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    Quote Originally Posted by vetteoz View Post
    How many years was L83 Crossfire engine made?
    Crossfire was in the Vette in '82 and again in '84

  14. #44
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    Quote Originally Posted by TWISTERUP View Post
    Crossfire was in the Vette in '82 and again in '84
    I know that.
    I was enquiring as to whether Mr Nelson was aware his engine had a shorter life span than the LT1 he is paying out on.

  15. #45
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    Quote Originally Posted by vetteoz View Post
    I know that.
    I was enquiring as to whether Mr Nelson was aware his engine had a shorter life span than the LT1 he is paying out on.
    Oops...my bad.....thought it was common knowledge for Vette fans...I understand now

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