Avanti II Engines

[Guest dapy]

I just read an article about the changes from Studebaker to the Avanti II. I understand this except for the reason for the variety of Chevy engines used in the Avanti II.

We see the later II's with 305 engines. The article says II's started with 327cu.in. (300HP) then to the 350 followed by a few 400's to comply with emission regulations. No mention of the more common 305. Do owners have a preference?

Anyone able to time these changes and whether there were significant performance differences? Were there new car buyer choices?

The article said that the Avanti II had better handling, and the author considered them the Ultimate Avanti. No question that engine work is easier with the GM engines. One can buy a rebuilt 305 for $1200.

Edited October 22, 2012 by dapy

[Gunslinger]

Avanti Motors went along with whatever was available at a reasonable cost and still meet emissions and fuel economy standards. At first with the 327 and then the 350 engines which they promoted the Avanti fairly well in its literature as being equipped with the "Stingray" engine. GM replaced the 327 with the 350 so that pretty much made it necessary for that change. The change to the 400 may strictly have been a cost thing since Corvette 350's were certainly available. The 400 was essentially a sedan and station wagon engine which was probably less expensive. Since Avanti Motors had always been stressing the more touring car aspects of the car rather than pure performance this may have fit in with reality of government mandates.

The return to the 350 and then the 305 was again probably reacting to the reality of that times...smog controlled choked cars and the costs and availabilities of the engines. Somewhere I have a magazine article from the '70s where it states that Avanti Motors had already tested a car with a 305 and the performance was "roughly comparable"...whatever that means.

As far as performance, the earlier Avanti II's with few emissions equipment have the reputation for better performance...but so do all cars prior to the lowering of compression ratios and detuning by the early '70s...it's not exclusive to Avantis.

Avanti Motors always said in their advertising what the sole engine option was, but I've seen and heard persistent stories about they would install other small block Chevy engines if the customer wanted and would pay for it...the LT-1 seems to be the most common rumor, though I wouldn't hold out much hope for that without documentation to back it up. My '70 had the L48 Corvette engine when I bought it but it also had LT-1 valve covers which were on many engines...but valve covers do not an LT-1 make. Maybe Avanti Motors got a good buy on some LT-1 engines or later L82 engines and purchased and installed some...or maybe that was all that was available at the time they made an engine buy. Without testimony from someone who was there at the time or documentation those stories will remain stories.

I've also read where it was said Avanti II's had better handling than the Studebaker version. That's due to the fact that the small block Chevy engine was a good bit less heavy than the Stude V8, so the somewhat better weight distribution would account for that, but even then the difference might only be marginal.

As far as preferences in engines, that's a real arguable point. If you want a smooth boulevard cruiser, it probably doesn't much matter which engine. If you want performance a 327 or 350 may be better. The 400 can be built into a real torque monster. The 305 with the right rear axle ratio and transmission can do fine as well. Then there's the myriad of crate engines available...350's, 383 strokers and to me the ultimate way to go would be to install a modern LS engine, which has been done but it may have required some serious reengineering to install it correctly and add all the computer controls and wiring harnesses.

[IndyJimW]

I've also read where it was said Avanti II's had better handling than the Studebaker version. That's due to the fact that the small block Chevy engine was a good bit less heavy than the Stude V8, so the somewhat better weight distribution would account for that, but even then the difference might only be marginal.

As far as preferences in engines, that's a real arguable point. If you want a smooth boulevard cruiser, it probably doesn't much matter which engine. If you want performance a 327 or 350 may be better. The 400 can be built into a real torque monster. The 305 with the right rear axle ratio and transmission can do fine as well. Then there's the myriad of crate engines available...350's, 383 strokers and to me the ultimate way to go would be to install a modern LS engine, which has been done but it may have required some serious reengineering to install it correctly and add all the computer controls and wiring harnesses.

I know that there is a world of difference in the handling of 1987 and later Chevrolet chassis Avanti and earlier Avantis, but I would expect that from a suspension that is 25 years later.

With the popularity of LS swaps and the new oil pans, I wouldn't hesitate to install a LS in an Avanti.

[Skip Lackie]

Agree with everything Gunslinger said. GM brought out the 400 in 1972 to try to maintain somewhat higher horsepower numbers that were being reduced by two federally mandated factors: (1) the change from gross to net HP as the standard measure, which had the effect of reducing the advertised HP by about 20-25%, and (2) the lowering of compression ratios in expectation of the phase-out of leaded (premium) gas in 1975, which really did lower HP ratings by another 20-25%. Going from 350 ci to 400 ci gave GM another few HP to partially compensate for these losses, both real and imaginary. Avanti Motors was still trying to maintain the image of a quasi-sports/performance car at that time, and the 400 probably was a good compromise between settling for a gutless 307/305 or paying GM a premium price for a Camaro/Corvette 350 with only a few more HP than the 400.

As the 1970s progressed, (1) Avanti Motors began to stress the boulevard cruiser aspect of their cars, (2) the dreadful gas mileage of the 400 became a liability, (3) and the HP ratings of the GM 305 gradually began to climb a bit. So Avanti switched to the 305. They bought engines in lots of 50 or 100 at a time (about a year’s worth most of the time), and tended to buy whatever they could get a good deal on. That was typically whatever GM was using as a base V8.