SOT: The truth about Corvair engines, Nothing but the facts and experience, please Options

[Dr Evil]

There has been lots of interest in the corvair power plant over the years as a possible source of cheap HP for many vehicles. There are used in experimental aviation, dune buggies, buses (such as mine), and in place of many other air cooled VW power plants. They are fairly cheap to buy and build, very easy to build and maintain, and plentiful with readily available parts from several suppliers.

The main divide in the corvair engine line took place in 1965 when the displacement of the engine was moved to 2.7L and was offered in a NA 110HP, NA140HP, turbo 150HP and turbo 180HP. The only differences in the long block between these engines are the nitrided crank found in all but the 110HP, and the heads: 110 had one single barrel on each head, the 140 had 2 with one acting as primary and one as secondary. The turbos had a single barrel blow through setup.

The heads are the major limiting factor in the design. They are not built in an intuitive way and rob much hp. The 140 head had bigger valves, but like its 2.0L TIV analog, would drop valve seats due to the limited amount of material between the seats in the head, and the inability of larger seats to shed heat as well as smaller seats. This can, and has been overcome by those who have been rebuilding these heads fro decades by making sure the crush tolerance on the seats are correct, and staking the seats in place.

Currently, you can get a set of rebuilt, 140hp larger valved heads, with new hardware and no core for about $1200 from Corvair Ranch in Gettysburg, PA. I bought a set that was rebuilt and had the plenums taken off for tri porting for $1500 shipped off of ebay from Starr Cooke in El Cajon, CA, another well known Corvair entity.

Modified with plenum removed for individual runners:


The above uses an adapter that allows the placement of Weber triples. My set came with this adapter.

Here is a head with a stock plenum, modified with bungs for FI. This is a 140 head as it has two carb bases on it:


Standard engine:


One of the cool things that many ACVW folks like is that the corvair engine has stock hydraulic lifters on it that use standard lifter, push rod, and rocker parts from Chevy. Easy and cheap to obtain.

Another great feature that I like over ACVW is the box design on the case. The top and bottom come off and allow for any maintenance. Swapping rods, bearings, what ever, is easy.

[jk76.914]

Coupola more thoughts... The only issue with reversing rotation was with the belt life. The alternator (generator through '64) is fixed in place, and doesn't swivel to tighten the belt. This ensures that the belt geometry is fixed on the tension side: crank pulley-to-alternator-to-fan. The moveable pulley that adjusts belt tension is on the slack side: fan-to-pulley-back to crank. This was the case from day 1, obviously, and this is what you lose with a reverse rotation. Other changes over the years- belt guards on the adjustment pulley and just as the belt exits the fan pulley prevent the belt from flipping over. These came along in '64, along with the magnesium fan. The new fan was probably the biggest contribution to belt life, and it's the only fan that can be reversed. The earlier steel fans had curved blades to bite into the air as the fan turned, and they wouldn't work in reverse. All Corvair owners carried an extra fan belt, along with a 9/16" wrench to change it on the side of the road, but with all the improvements along the way, I personally never had one fail me.

Also, another comment about valve train and push rods- many firms offered performance cams for Corvair in the '60's, and all were hydros. It was generally accepted that hydros were necessary in the air cooled Corvair, and all 1.7 million Corvairs built used them. The only exception was an aftermarket cam by Edelbrock, which was for solid tappets. Interestingly, theirs was the only kit with aluminum pushrods. The theory was that though the push rods don't heat up as much as the cast iron cylinders, the aluminum expands more per degree and somewhat equalizes things. Sound familiar?