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355 V8: The Mopar LA Racing V8 Engine

Starting around 1975, Chrysler built an LA engine designed for racing, and not used "on the street," because NASCAR had started penalizing any engine over six liters (366 cubic inches). In 1975, 355-powered Dodges won 14 of 30 Grand National races, and drove them to the winner's circle 13 times.

Motor vehicle Team Vehicle Crew Photo caption

Mopar was highly successful in Pro Stock in 1979 with the 355 in Plymouth Arrows.

Ramchargers in the engine lab with a 1,350-horsepower Hemi, 1962

Around 1978, a drag-racing version of the engine was developed, also at 355 cubic inches.

Ed Poplawski wrote:

The 355 engine was a bored and stroked production-340 6-barrel engine block (LA) that we modified for racing use. The modern 355 that we did in 2001 when we got back into NASCAR racing is a purpose-built race engine which has nothing in common with any of our old or new LA engines. [The 355 block was common to all racing applications before 2001.]

Back then, the engine block of choice was the 340 6-barrel block. However, by the late 1970s, 6-barrel blocks were hard to come by and we were scrounging the local junk yards. It was the same thing for the Pettys. We were using standard 340 blocks for dyno development and saving the six-barrel blocks for the race cars.

We wanted to use the 6-barrel block was because we had added material to the bulkheads for strength, so we could use 4 bolt main caps. Otherwise, the only difference between the engines was carburetion, camshaft, cylinder heads and headers. The NASCAR engine could only use a flat tappet cam (we used a mushroom tappet) and a single 4 bbl carb. The NHRA drag engines could use roller cams and multiple carburetion intake manifolds depending on the class.

Headers were chosen depending on the type of racing we were doing and the engine speed at which we were running. For example, for 1978 our goal for Daytona that year was 600 HP and the engine peaked at 7200 rpm. The 8-barrel drag engines peaked at 9600 rpm, so the header size and length was a lot different. The IROC engines were basically NASCAR 355 engines. Also, we used dry sump oil systems in NASCAR so there were some internal modifications to the block to make this work. Those were the major differences between all the series.
Marc Rozman wrote:

"Fast Eddy" [Poplawski] ran a 355 [drag] racing motor with a tunnel ram and dual quads [in the test cells]. He had a Chevy manifold on a Mopar, he made up little wedges that make a manifold fit the angle on the heads on the small block Chrysler. Back then, Ted Flack and Howard Comstock were driving those cars; Ted Flack was a dyno operator at one time, and he made the grade and became an engineer later on. Sharp guys.

They were still running the [NHRA] Pro Stocks, and if you look in the records you can see the Flack and Comstock cars, including a Dodge Dart Sport. They were doing development work on that motor still.
For 1976, Dodge had a complete W2 package, developed under John Wehrly; Willem Weertman credited Larry Rathgeb with creating a Kit Car which included that engine for racers. The Kit Car had a 340, 355, or 360 cubic inch engine, depending on the model year. The 355 had a slightly larger bore, with a stroke between the 340 and 360, and did well in short-track venues.

The engine had forged aluminum pistons, stress-relieved blocks with thickened bulkheads, and four-bolt instead of two-bolt main bearing caps. Weertman wrote that this package reached more than 600 hp, gross, with a single four-barrel carburetor.

In 1979, Mopar Performance started selling their "X block," a heavy duty racing small block which would displace 340 cubic inches; it could be bored out, as Larry Shepard suggested, to 355 cid. These were painted orange and a large "X" was cast into the end. It had standard and four bolt versions. The same block was used in Pro Stock during 1979 and in NASCAR racing, as well as ARCA oval track racing in the 1990-91 seasons. Numerous features in this block added strength.

The engines were also used when Chrysler sponsored the IROC (International Race of Champions) series, which uses identical cars; drivers ran with Dodge Daytonas converted to rear wheel drive, with the 355 under the hood.

When NASCAR added a truck series in 1996, Dodge entered with an updated version of the 355, including new aluminum cylinder heads. The engine was finally retired in 2001, when a brand new engine entered production - against, for racing only.

Marc Rozman added:

I [was working] in test cell 7A, and we ran the 440-3, the truck motor.

The guys next door in 6A had a higher RPM dyno, also. Fast Eddy [Poplawski]ran a 355 racing motor… I was doing certification work, it's not a high RPM deal. We had to put head muffs on, and run the stuff.

But then my buddy, Fast Eddy, would get a bug to run the engine. He'd fire up that bad boy, and the headers out the exhaust, and the exhaust all tied into the same trunk line for the exhaust. He fired up that 355 Pro Stock motor... and me, doing my little government certification work, kind of important... but, he'd fire his up and, oh man, it looks like a 747 coming in for a landing, because the exhaust pipes were all tied together. He's go, rev up to seven or eight grand.

I'd abort my test, walk out, because I couldn't stay in there, it was too loud, even with the headphones on. I'd go up and say, "Ed, at least can you ask me if I'm doing my test, at all? I mean, this is kind of important stuff… certification work, you know. At least ask me if I'm doing a test before you fire up and do your thing which can wait."

But he'd laugh and and the whole bit and he'd say, "Ah, you know…"

And I'd go talk to him and I'd help him read the fuel, because his higher RPM is a big motor. You have to be careful, and the fuel readout was behind you, so I'd just read the fuel for him, and kind of spot looking out the window, and make sure nothing's leaking or coming apart at all.

We'd do that for awhile, and he'd get done with his test, and I'd go and I test again. I would get my testing done, so I would get that engine certified, so we can sell some products. I thought that was kind of nice to do.
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