Dune Buggies & Corvairs - A Potent Combination

  • Posted by aorange
  • October 10, 2012 11:17 PM BST
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CORVAIR ENGINES FOR DUNE BUGGIES Most dune-buggy builders use a shortened VW chasis with the VW front and rear suspension and a VW engine and transaxle. While a stock or modified VW engine is still the most popular, the prices for these engines and transaxles have zoomed on the used market, causing many buggy enthusiasts to consider Corvair power.

Corvair engines, especially older ones, will probably continue at more reasonable price because they must be adapted to fit the VW transaxle -and the Idea of adapting does not appeal to Mr. Average Man, regardless of how well engineered or how many such adaptations have been made to lead the way. However, if you are about to build a dune buggy and are still trying to decide between a Corvair and a VW, let's look at the differences to help you make up your mind.

Nine Corvair engine models range from the 140 cubic inch 80HP 1960 model through the 164 cubic inch 95, 110, and 140HP models which were offered in the 1969 models - and the '65 and 66 Corvair Spyders had turbosupercharged 180HP units (150 HP in the 145-cubic-inch 1963 and 164 cubic inch 1964 Spyders). None of these engines are especially better than the other except that the 1964 and later models are 1.7 times bigger in displacement than the largest VW available as of 1969 (1600cc, 96.6 cubic inches). On the other hand, only 1966 or later 1300, 1500 or 1600cc VW's should be considered because these are the "Vintage Years" according to a CAR LIFE article entitled, "VW Engines, Timepieces... or Timebombs?" in the January 1969 issue. So, your VW choices offer 78, 91, or 97 cubic inches.

Rebuilding costs for the two engines are similar, but the VW requires several "trick" modifications to get reliability for competition or off-road use, Hotrodding the VW to obtain 100 110HP (comparing advertised SAE HP ratings) costs about $850, according to expert VW tuners. You can get this much or more from a stock Corvair without spending a penny for modifications. In comparing costs for the two engines, you ought to consider that the Corvair requires the Crown adapter parts, and if you will be using a 68 or later non-swing-axle VW or Porsche trans¬axle, the costs of a reverse-rotation camshaft must also be included in the Corvair's column. And if you are starting with a 1963 or earlier Corvair, the reverse-rotation engine requires the straight-bladed blower fan. Weight difference between the two engines is about 75 pounds, and with the big tires that you will undoubtedly be running on the rear of your buggy, that extra weight will not even be noticable when comparing handling. This brings up a final point - the VW engine, even when modified, requires new 3rd and 4th gears to make these cogs usable with big tires. Add to this the fact that anything you do to the VW engine to raise its horsepower (except for the expensive process of replacement big-bore cylinders and a stroker crank) will narrow its usable RPM range, moving it upward on the scale so that low-RPM performance falls 'way off. By the time you have purchased one or two hop-up items for the VW you could have purchased a Corvair with twice the horse¬power - and with the adapters, clutch and flywheel, starter adapter, and even a reverse-rotation camshaft. Thus, it is hard to argue for the VW.

Seasoned off-road racers remove the cooling-air damper duct from the Corvair's underside, thereby decreasing oil temperarture about 20 F and reducing vulnerability of the engine to rock damage. Of course, this is not recommended for a street buggy for reasons detailed on page 73. The distributor is reasonably well sealed against dust so long as the vacuum-advance boot and point/cap dust shield are intact. Air intake should be through a flexible hose attached to an air cleaner just under the roll bar.

The TRI-PHASE construction-equipment-type air cleaner which spins the entering air to drop out dust seems to work best of all. If the FILTRON filters are used, these must be oiled. They can be used alone, or as a bootie over the paper-type air cleaners. Carburetors need throttle-shaft seals. Crown Manufacturing has a $7. 50 kit with O-rings, washers and springs to seal four carbs. O-rings are placed at each side of the carb base on the throttle shaft. A light spring between the lever and a flat washer holds the O-ring in contact with the carburetor for an effective seal.

Late-model vw transaxles (beginning in 68 with the busses and semi-automatics) with two U-joints per axle cannot be used in reverse rotation because the internal parts are designed for only one direction of rotation of the input shaft. Some stick-auto transaxles with the "tunnel-type" case can be reversed by flopping the ring gear. These are identifiable by the same-size bolt circles on each side of the differential, indicating that the ring gear can be installed from either side. Non-symmetrical cases with only one large bolt circle cannot be reversed with a flopped ring gear.

Corvair-engined buggyes need rear motor mounts, these can be suspended from an encircling tube or bumper around the back of the buggy. Such a structure can be tied to the chassis and roll bar and can support both the rear motor mount and the skid plate. If a VW transaxle is used then extra trans. mounts are also needed. Mid-engined buggies are easier to equip with engine/transaxle mountings, and with skid-plate protection for the engine.

CORVAIR SUSPENSION FOR BUGGIES

Corvair suspensions are now being used in some dune-buggy chassis. The very high rate of the stock Corvair springs (designed for the weight of a complete Corvair) is exactly the opposite of the suspension requirements for off-the-road fun and competition. A softly sprung, long-travel suspension is needed and this cannot be obtained with the stock Corvair springs. Although the soft rear springs offered by Crown manufacturing for its Corv-8 conversions can be adapted to buggies equipped with '65 and later Corvair rear suspensions, even these springs are too stiff for best off-road use. And, there are no commercially available springs soft enough for using the Corvair front suspensions for off-road use. You can use the Corvair suspension fore and aft for a street buggy, but specially made springs of about half the spring rate would be required for serious off-road use. One dune-buggy manufacturer who uses Corvair components modifies Chevelle springs by cutting off two coils, but admits that these are too stiff for off-road use. As VW chassis become harder to obtain, special springs will probably become available to meet the demand for Corvair-suspended buggies suitable for off-road operation. It should also be noted that the Corvair spindles make a much stronger front end than can be obtained with the VW components.

As of mid-69, a number of chassis builders were planning to utilize Corvair suspensions - both early and late types.

MID-ENGINE BUGGIES - the coming trend

The rearward position of the engine mounted behind the trans-axle in the usual dune buggy poses problems in serious off-road activity: the engine can hang up, perhaps leaving the rear wheels off of the ground - and more likely, causing severe damage to the engine and/or transaxle. While the rear mounting produces maximum cornering power with the right tires on shorter slalom courses (but makes it harder to drive), and the engine location aids in traction for some off-road situations, a mid-chassis location for the engine offers some advantages. First, the weight is better distributed, especially for high-speed events. There is less polar movement on long, fast courses - and less under steer on short courses. Secondly, the overhang is limited to that of the transaxle - less than half of that when the engine is in the rear. Thirdly, the engine is better protected from damage, gets less dust and is better protected from drowning out in water hazards.

As of mid-1969, only two or three buggy manufacturers had decided to market mid-engined buggies capable of handling Corvair power. One of these, Dearborn Automobile Company of Marblehead, Massachusetts, offers the Deserter GS (GS stands for "Giant Slalom"), which is pictured and described in the photos and captions. These pioneering firms are being joined by an ever-increasing number of individuals who are "scratch-building" buggies from the ground up. If you are planning to buy or build a buggy, observe the trend in formula-car racing, Detroit's idea cars, Crown's Corv-B, and new dune buggies such as the Deserter GS - think seriously about travelling the mid-engine route.

The Corvair engine can be used in its stock form (no reversing is required) by merely mounting it to a VW swing-axle transaxle which has been beefed up with Crown's special parts and using their engine-to-transmission adapter, clutch, flywheel, etc. The entire shifting mechanism (linkage, etc.) can be bought from Dearborn Automobile Company.

Some readers will wonder why the Corvair transaxle, with its beef, cannot be modified to turn backward - as can the VW swing-axle transaxles. The VW gears are straight cut and will operate in either direction. The Corvair hypoid gears are designed for one direction of rotation and cannot successfully operate in reverse rotation. The Corvair transaxle can be used if VW Transporter spur-gear housings are mounted at the outer ends of the axles to reverse the "backward" output. This set up allows normal rotation of the engine and transaxle in a mid-engine buggy. Careful adaption and sealing is required in grafting the VW closed-tube axle parts to the open-tube configuration of the Corvair axles.

Mid-engine cars are being forecast for introduction in 1970's and transaxles from some of these cars may open up the range of choice for the builder.






 

This article is an extract from the book "How to Hotrod Corvair Engines" by Bill Fisher (ISBN-10: 091265600X). For more great technical information about Corvair engines and conversions we recommend buying his book.

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