Cool Runnings

These should have been designed with a 6,200rpm red-line. The 1970 LT1 was a much stronger motor. What gives ???

pologreen1

Emissions, Chevy sucks, mass produced vehicle, was still more performance than other American rivals, get what you pay for, etc, etc...

Thankfully the TPIS miniram came out for GM to model after... (Still being contested to this day I think)

Cool Runnings

So, Chev couldn't meet emissions with a solid lifter motor red-lined at 6,200 ???

Fiberbundle

It was about emissions and especially gas mileage after the gas rationing that occurred in the mid 70’s. So GM’s focus was on producing smaller, lighter more efficient vehicles. Government mandated emissions and mileage improvements continued even leading to the idiotic CAGS in our 6sp cars that we are forced to override. Thankfully there are now much higher horsepower cars that produce faster Corvettes than what was available in the past, and yield great gas mileage and low emissions.
Do I miss the raw power, sound, and fumes from the old days? Yes but not the 8 or 9 miles to a gallon when running 4:56 gears.

Y-bodluvr

First the L98 350 TPI was Never available in any “truck” from the factory it was Corvettes and F-bodies only and In 1985 when the L98 debuted even with just 230hp it was still one of the quickest and most powerful new cars on the road just a handful of FAR more expensive exotics like the 288 GTO, 928 S, 911 Turbo and Countach were faster it was the emission Restricted 80’s man

rblakeney

Paraphrasing from Wikipedia:

"The Chevrolet small-block engine is a series of V8 automobile engines used in normal production by the Chevrolet Division of General Motors between 1955 and 2003, using the same basic engine block. ... the family spanned from 262 cu in (4.3 L) to 400 cu in (6.6 L) in displacement. Although all of Chevrolet's siblings of the period (Buick, Cadillac, Oldsmobile, Pontiac, and Holden) designed their own V8s, it was the Chevrolet 305 and 350 cu in (5.0 and 5.7 L) small-block that became the GM corporate standard. Over the years, every American General Motors division except Saturn and Geo used it and its descendants in their vehicles.

"The small-block family line was honored as one of the 10 Best Engines of the 20th Century by automotive magazine Ward's AutoWorld.

"In February 2008 a Wisconsin businessman reported that his 1991 Chevrolet C1500 pickup had logged over 1 million miles without any major repairs to its small block V8 engine"


Since it was the corporate standard it did indeed go into light duty trucks as well as everything else. GM tuned the thing for the application just like any other manufacturer does. If you flip it over you could say "my truck has a car motor in it!"

Y-bodluvr

Yes the 350 cubic inch engine came on trucks BUT they either had TBI or a carburetor. duriing those times...

TorchTarga94

Not sure, but I wonder if we can swap optisparks on to them and beat C5/C6/C7r race cars?

Right Diz? Where ya at?

pologreen1

obijohnkenobe

The SB Chevy was designed in a different time for a different need... when the cost of exotic materials was far higher, and engineering prototyping was done experimentally and iteratively instead of virtually through computer simulation. It was a lot harder and more expensive to try things out. The GM engineers of the 1980s knew enough to know how to make horsepower and torque, but also knew their limitations. The evolution of Corvette engines from the C3 to C4 L98 to LT1/4, to C5, C6, and C7 with the LS engines shows the impact that computerization of ignition and fuel systems has had. When I was a teen in the 1970s, a fast car could produce about 1 HP per cubic inch, and it was very rare to see a factory car that could do 0-60 under 6 seconds. Today, it's not uncommon for a typical car engine to squeeze 2 HP or more per cubic inch, naturally aspirated, and of course turbochargers are now ubiquitous, and sub-6-second 0-60 is easy and affordable. My '91 C4 roadster was one of the fastest affordable cars available... you'd have to pay double the price or more to get an exotic that could beat it in terms of acceleration, braking, and cornering.

The key lesson I see from the evolution of Corvette engines is that street-capable horsepower comes from strokers… the LS series has a higher stroke-to-bore ratio than the SB 350. Stroking an L98 to 383 ci along with improving breathing via a decent cam and upgrade to the TPI intake system (larger runners, honed/ported plenum, runners, manifold) will give you at least 450 hp and over 500 lb-ft of torque at reasonable RPMs, and will make an L98 competitive, in terms of acceleration, with any modern naturally-aspirated Corvette. Put a blower or turbo on one and you'll be there with a new ZR1... which has a factory blower.

auburn2

Ok a few comments.

This was the 80s. With the exception of the 86-87 Buick Grand National, nothing under $50k (1980s dollars) was truely fast. A low end torque "truck engine" was the way to get power and comply with emissions laws. Compare the L98 to its contemporary V8s and it looks pretty good, as good as today's C7s compare to their contemporaries.

In 1970 there were virtually no emissions regulations. Everything was faster in 1970 than 1985. Even your full size Cadillac was faster in 1970 than 1985. One reason is the catalysts in the 80s were a lot more restrictive than today. They had not really figured out the dual-cat configuration and pushing extra air through a very restrictive converter was counterproductive. So the key was to generate power with minimal airflow - i.e. increase torque at low RPM.

Ironically the L98 actually has more low end torque then the later LS-based truck engines of the late 90s/early 2000s. So it was more of a "truck engine" than the actual trucks from a generation later.

The L98 vette was near the top of the pack in terms of performance, and nothing, except the formentioned Buick, could out accelerate it for less money and nothing period was faster around a road course for less money.

FAUEE

Its also worth mentioning, the LT1 was a pretty high strung extreme motor in its day. It wasnt a daily driver motor. You didnt buy an LT1 car to know itd be problem free every day.

Cool Runnings

In the 80's I had a 1986 BMW 325es for a few years. 5 speed manual. 126 bhp, 170 ft·lb torque . For the time, it was a pretty fast car. FYI: I grew up in the muscle car era. Nothing like the 1970 429SCJ I had in the 70's.

ghoastrider1

many truck engines in heavy duty trucks came with 4 ring lands, not 3.

vader86

They hadn't figured out yet how to get good power from a 350 and still pass emissions in California. Fuel injection tech hadn't come around yet, catalytic tech hadn't come around yet.

When they did figure it out, they built the new LT1 for 92. Better fuel injection, much better exhaust design and cat efficiency, higher redline.

Paul Workman

Tho the motor was never put in trucks, the reference to the L98 being a "truck motor" stems from its torque characteristics; i.e., more at the LOW end of the more typical rpm range of other sports cars - past AND present at the time.

The actual saga of the (Bosch) TPI induction system and how it evolved from the 305 cid SBC IROC Camaro to the 350 cid Corvettes is an interesting story in its own rite. It's one woven into the fabric of engineering limitations forced on the industry by government (EPA) requirements of the day.

Developed initially to put some reasonable spunk into the rather anemic 305 IROC Camaro motors, the success thereof made it desirable to extend the TPI design to the 350 cid motors for the Corvette. And, so, negotiations with Bosch to that end began. However, an agreement was not immediately forthcoming; resulting in GM having to pull a "retro" interim solution(s) instead: (81 saw the Computer Controlled Carburator (CCC), and in the 82 Corvette saw the TBI cross-ram which was carried over to the 84 model years before a deal was struck with Bosch to build the TPI for the 350 cid motors.).

Like the tubes of a pipe organ, the length will support the resonance of the column of air (and fuel in this case) at a particular frequency. The length and volume of what became the Tuned Port Induction system's runners were such that they resonated most efficiently at around 3800 rpm - chosen as the best compromise for the "sweet spot" for IROC events.

No free lunch. The main advantage of designing the induction runners near the first (F1) harmonic frequency is the peak pressure resulting from the resonating column of air reaches optimum amplitude (think pressure) at the intake valve. That's the good part. The not-so-good part is the resulting torque output tends to be "peaky" i.e., it builds quickly and once past the peak, torque falls off quickly as rpm increases. Such is the nature of the TPI. But, the TPI resulted in reasonably respectable performance in spite of low compression ratios ultimately related to using lead-free fuel coupled with computer technology of the day.

However, by using shorter runners, e.g., the "Mini-Ram", TSP plenums, and later the LT1 plenums, the torque curves produced by the (350) SBC were broader if not reaching the narrow peak of the TPI, but resulting in maintaining 90% of their peak torque from just off idle to just short of their "red line" (5800 rpm for the LT1 and 6300 rpm for the LT4). resulting in significantly more power* output.

*POWER, remember from high school physics, relates to the RATE at which work is done, i.e., HORSEPOWER = TORQUE X RPM / 5252

In terms of notable advances in engine development, the advances in computer speed coupled with cooling innovations, broader torque curves bolstered by higher compression ratios (10.5 for the LT1 and 10.8 for the LT4 vs. 8.5 for the L98), the later developed engines became more efficient and powerful in spite of those same fuel and efficiency requirements the L98s first dealt with.

SO! NO, the L98s never were installed in a factory truck application, The reference to the motor being a "truck motor" is more of a 'tongue in cheek' reference when comparing the L98s characteristics to modern sports cars vs. trucks.

OH! And, far as for that 2 hp/cid being "common" for NA motors goes, some examples might be nice (less I or others might wanna call WTF, or BS on that - far as auto applications go...not too many 350 cids making 700 NA hp!)

As for the LT1/4s being "high strung" and not intended for daily use? Oh, please. The second gen SBCs found their way into the Impala, Firebirds, Camaros, etc. ALL of which were intended for extended normal driving applications.

dizwiz24

if we could bring back the 80s - knowing what we know now, i would so do it.

now , everything is fast. It is not as cool or special to be fast - and theres always someone faster

back then , if you had the fast car (ie. 0-60 7.0 seconds, 15.1 1/4 mile) you were cool ! 😎

if i could transport my c4 with procharger, meth/inj , afr 195 comp heads and headers back to then.

i would be everybodys idol

aklim

I think I had this conversation with an older man. Only difference was that he wanted to go back further (50s or 60s) than you would when he was growing up and "things made sense" to him. He was certain that there was nothing he would miss from today's world. He had a son who had a certain type of terminal cancer as a young man. Apparently, the protocol to treat it (improved since then) only came out a year or two before he was diagnosed. That gave his son and extra 20 years of life before he finally succumbed to it again. Suddenly, THAT part of progress was an exception to the "Good old days" thing.

daverulz

Paul, awesome post but I think you missed one thing. He's not talking about the second gen LT1 - he's talking about the one from 1970 https://www.hemmings.com/blog/articl...corvette-lt-1/

FAUEE

Yup. The 1992 LT1 isnt high strung at all, haha. The 1970 LT1 the OP was referencing, was a very different engine.