Pushrod, cam in the block, just like millions of other Detroit V8s.
EDIT: Ninja'd by moments by Delta Force. Damn.
AHC/WI: Successful Chevrolet Corvair
- Thread starter Delta Force
- Start date
Pushrod, cam in the block, just like millions of other Detroit V8s.
EDIT: Ninja'd by moments by Delta Force. Damn.
Delta Force
Banned
I'm not sure when American automobile companies undertook widespread adoption of over cam head technology, but the most famous was the Ford 427 cammer V-8. The Ford cammer and cam technology in general was prohibited in many racing series, so General Motors wouldn't be able to promote the engine through racing.
They didn't, however aluminium and OHC is the sort of thing that can ameliorate the drastic performance losses that the anti-pollution equipment of the 70s imposed on American engines. IIUC aluminium's better thermal characteristics allows it to have higher compression than iron engines for a given fuel octane, which is good for power and economy not to mention being 1/2 as heavy as an iron engine. OHC is lighter and more efficient than pushrods and rockers, it reduces power loses in the valve train therefore giving power for free so to speak as well as allowing for higher revs. Pontiac offered an OHC for it's inline 6 in 1966-9. So it appears that Detroit developed exactly the sort of things in the 60s that would be handy to keep them competitive throughout the 70s, but dropped them just before they were needed.
Pontiac OHC 6.
They couldn't promote it in NASCAR, but at the time Detroit's attention in racing was moving beyond NASCAR - Ford's Cosworth DFV was in its gestation (and the Eagle-Weslake was proving to be something special), Indycars' Offy-powered era was ending, sports car racing had American champions in both Ford and Chaparral and the Trans Am Series was being born, so maybe one could see overhead-cam four-valve heads start showing up in Detroit iron around this time as racing units.
Delta Force
Banned
You mean the OHC has less moving mass, right? Some American car companies still use pushrods because they lead to lighter and more compact engines for a given displacement. To gain more power with pushrods, they simply increase displacement.
Of course, increasing displacement soon wouldn't really have been an option for the 1970s, when a third generation Corvair would have entered production. If OHC technology had been better developed for racing and performance in the 1960s, it could have been applied to regular cars more easily in the 1970s, helping to reduce the performance losses of that decade while allowing emission and fuel standards to be more easily met as well. Perhaps the 90 horsepower Mustang of the late 1970s and early 1980s could be avoided.
That could help develop the technology and show that it's nothing that unusual. I don't know if that was a common view of OHC technology at the time, but at a press conference following his decision to ban the Ford cammer, the head of NASCAR said that the series was supposed to be a demonstration of technology usable in regular production cars, not a showcase of "European exotica" like OHC technology.
Current pushrod engines use valvegear that 20 or 30 years ago was mentioned in hushed tones as the peak of hot-rodness, things like belt driven cam, roller lifters and lightweight pushrods. The latest LS3 also use canted valve heads like the old big block Chevs and the 335/385 Fords, but this took until about the early 2000s to refine pushrod mass production engines so much, its not really an option in 1970 when the rules really started to bite. As for the Corvair, when unleaded fuel came in perhaps with the alloy engine the compression doesn't need to be reduced quite so much, making the power drop not quite as drastic which makes the Corvair stand out from the crowd a bit.
As for the 427 cammer, recalling off the top of my head, the NASCAR rules of the time said that the engine had to be in production and available for purchase but stated no number or installation in a production car. Chrysler was virtually hand building Hemis at the time and only offering them for sale through the backdoor so to speak, so Ford took the next step. When NASCAR changed the rules Chrysler thought in for a penny in for a pound and put the Hemi into actual production and for sale in an array of production cars as well as a heavy duty boat engine. This approach wasn't going to work for the cammer so it was dropped and Ford used things like high rise and tunnel port heads on the 427 before plumping for the Boss 429 years later. So the European Exotica was a fair enough comment at the time.
As for the 427 cammer, recalling off the top of my head, the NASCAR rules of the time said that the engine had to be in production and available for purchase but stated no number or installation in a production car. Chrysler was virtually hand building Hemis at the time and only offering them for sale through the backdoor so to speak, so Ford took the next step. When NASCAR changed the rules Chrysler thought in for a penny in for a pound and put the Hemi into actual production and for sale in an array of production cars as well as a heavy duty boat engine. This approach wasn't going to work for the cammer so it was dropped and Ford used things like high rise and tunnel port heads on the 427 before plumping for the Boss 429 years later. So the European Exotica was a fair enough comment at the time.
Too bad Ford forgot about those thousands of 18L aluminum block and 32 valve aluminum head V8s with shaft driven DOHC they made during WWII for Sherman tanks.
A 40% scale of that would have been just the thing in the Horsepower wars
It wasn't design that was the problem, everyone knew that 4 valves per cylinder were possible and great since Peugeot and Alfa had used them before WW1 and the likes of Stutz and Duisenberg used them on road cars between the wars.
I think the problem is selling enough of these exotic engines to make it worthwhile for Ford to set up a proper production line with reasonable production costs to make it a worthwhile engine to fit into Ford cars available for sale to the public. Chrysler built about 11,000 Hemis between 1965 and 1971, so that's about the number of cammers Ford has to build and sell. Perhaps Ford could fit these into Lincolns instead of the MEL big block.
I think the problem is selling enough of these exotic engines to make it worthwhile for Ford to set up a proper production line with reasonable production costs to make it a worthwhile engine to fit into Ford cars available for sale to the public. Chrysler built about 11,000 Hemis between 1965 and 1971, so that's about the number of cammers Ford has to build and sell. Perhaps Ford could fit these into Lincolns instead of the MEL big block.
The Corvair's air-cooled engine would have been more difficult to tune for low emissions and fuel economy. The basic problem is that air-cooled cylinders expand and contract un-evenly, sometimes becoming pear-shaped in cross-section. That makes it difficult to get a precise seal on piston rings. It also means that the entire engine has to be built to looser tolerances to allow different components to expand and contract at different rates.
For example, my air-cooled, 1975 VW van always leaked oil, the same as most air-cooled airplane engines.
But fuel economy was not an issue until after the 1972 oil crisis. That oil crisis drove car manufacturers to switch to liquid-cooled engines which could be built far more precisely. e.g. VW switched from air-cooled to air-cooled with liquid-cooled heads to all liquid-cooled during the 1970s.
For example, my air-cooled, 1975 VW van always leaked oil, the same as most air-cooled airplane engines.
But fuel economy was not an issue until after the 1972 oil crisis. That oil crisis drove car manufacturers to switch to liquid-cooled engines which could be built far more precisely. e.g. VW switched from air-cooled to air-cooled with liquid-cooled heads to all liquid-cooled during the 1970s.
^ This is a legitimate point, but the point in reverse of that when it comes to the Corvair is that a rear-engined liquid-cooled car presents a major cooling challenge. If you put the radiator at the front, you get a system which has a lot of liquid moving around and quite possibly heats up the cabin to a considerable degree, but having the radiators at the back compromises cooling and only really works with very wide cars or requires huge air intakes.
Delta Force
Banned
I know it wouldn't be best for fuel economy or emissions, but what about a Wankel engine for a third or fourth generation Corvair? They are ideal for rear engine automobiles due to their compact size and low weight, allowing the Corvair to gain some of the benefits of both rear engine design (more cabin and cargo space) and a mid-engine layout (better weight distribution). General Motors had a major rotary engine program in the early 1970s, so it seems likely if the Corvair had survived the idea would have occurred eventually.
poor to average Fuel economy, Emissions and rotor seal life, plus, no lighter than the Vega I4 is what killed the GM effort
What got the Wankel rotary engine canned by most automakers was the problems of reliability and fuel economy. Rotaries have to be worked hard to make a car go, and even a small rotary like the Mazda 13B gets terrible fuel economy. The GM rotary's metallurgy problems were also a serious issue, and being that many American consumers are remarkably ignorant about routine maintenance on a vehicle, having an engine which could flake away metal from its rotor and from the engine casing around the exhaust port is a very, very big problem, and one which with 1970s technology I don't think is solvable. Worse still, the Vega RC2-206 rotary was a big sonuvabitch for a rotary engine, and while turbocharging might have made a seriously-fast machine, it was impractical with the technology available at the time.
Not really, no. The Fiero was meant as a sports car, the Corvair began life as a small car with many different designs, specifications and purposes. The whole point of the Corvair was to bust the Volkswagen Beetle one in the chops, which was never the case with the Fiero.
Driftless
Donor
My older brother sailed on the Great Lakes ore boats in the summers. He would leave whatever vehicle he owned at the time with my folks, for the several months he was serving on those ships.
The Spring of my junior year in high school, my brother called home to say he was coming by to drop off the car for the season, and specifically I could drive it. My dad heard him say that the car was a 1960 Corvette.... I about wet my pants over that possibility. A couple of days later, I saw that the car was NOT a Corvette, but rather a well worn 1960 Corvair. I was crushed.... For a while... However, that Corvair was a wonderful car. It was surprisingly nimble and just fun to drive.
Later, I read "Unsafe at Any Speed" and it left me with thoroughly mixed emotions. My experience with the Corvair had been all positive, but a friend had flipped her car, when cornering at a high speed (the rear live axle tucked under and over she went. No harm done to her, but the car was totalled, and several rows of corn got flattened.)
The Spring of my junior year in high school, my brother called home to say he was coming by to drop off the car for the season, and specifically I could drive it. My dad heard him say that the car was a 1960 Corvette.... I about wet my pants over that possibility. A couple of days later, I saw that the car was NOT a Corvette, but rather a well worn 1960 Corvair. I was crushed.... For a while... However, that Corvair was a wonderful car. It was surprisingly nimble and just fun to drive.
Later, I read "Unsafe at Any Speed" and it left me with thoroughly mixed emotions. My experience with the Corvair had been all positive, but a friend had flipped her car, when cornering at a high speed (the rear live axle tucked under and over she went. No harm done to her, but the car was totalled, and several rows of corn got flattened.)
Delta Force
Banned
A small car could have used a single rotor, or a smaller scale variant. Wikipedia compares the GM Rotary Engine to an unspecified 5.0 liter V-8, which a small car wouldn't be equipped with. Also, a smaller scale design would probably be easier to work the kinks out of.
What if it had been an engine option for the third generation for a sporty car version (assuming the Corvair continues to be a multi-application platform), perhaps becoming standard or a more prominent option on sporty models for the fourth and later generations?
I think the Corvair name could have lived on as a line of cars sharing common chassis, engine, and transmission technology, as a smaller complement to the Corvette, or as something of a purchasable demonstration vehicle for technology to be trialed on before being rolled out across General Motors.
It seems like something the Corvair could have evolved into if the name had continued on as a sports car design.
The Vega had a huge engine bay, dropping a SB chevy in there was a snap.
What that car, and the Corvair needed, was the Aluminum Buick V8 that GM unwisely sold to British Rover, and was too proud to buy completed engines back from Rover later on.
Indeed. Why didn't Triumph use that instead of the of developing the notoriously unreliable Stag V8? It could have fitted in the GT6, the TR6, the Dolomite...
The trouble is, rear-engined cars look efficient because you need a lightweight engine for them to handle at all well. That means, for a longitudinal engine (the simplest way, and GM need simplicity) aluminium, air-cooled, flat (lower CG and better air flow than V) and no more that six cylinders max to keep it short. It's not hard to beat the VW - the Corvair is basically a scaled-up Karmann Ghia - but hard to do fast and powerful. Porsche had been refining that for twenty years, and arguably wouldn't get it right (for drivers of average ability) for another twenty. This was GM's first try.
So, even if the Corvair was a good car, it had no outstanding qualities that justified the use of a layout so different from the rest of the line, one that had some well-known, er, quirks. It's notable that the later concept drawings look more and more like front-engined cars.
So, maybe if GM had taken an existing, efficient engine, and put it the conventional position, but in a body that had some idea of light weight and good use of space.
Indeed. Why didn't Triumph use that instead of the of developing the notoriously unreliable Stag V8? It could have fitted in the GT6, the TR6, the Dolomite...
Because the Triumph V8 was already in a late stage of development by the time British Leyland was formed and it would have been a waste of money to scrap it (given the amount of money spent developing the V8), that and Triumph having a NIH attitude when it came to using its rival's engine.
It might have worked though in a scenario where Triumph had cash and was still involved with Saab in further developing the Slant-4 from which the Triumph V8 and later the Saab V8 (with 32 valves and four camshafts) were derived from.
http://en.wikipedia.org/wiki/Saab_V8