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.

[McMark]

I understand the internals would be spinning opposite of their designed intent. But just as a mental exercise:

If you install a 911 transmission in a 914 (type 4, etc) you get 5 'reverse' gears.
If you then install a Corvair motor and spin that transmission backwards, don't you get 5 'forward' gears?

It's still running on the 'backs' of the gears, but wouldn't flipping the diff be counter productive?

[Dr Evil]

I understand the internals would be spinning opposite of their designed intent. But just as a mental exercise:

If you install a 911 transmission in a 914 (type 4, etc) you get 5 'reverse' gears.
If you then install a Corvair motor and spin that transmission backwards, don't you get 5 'forward' gears?

It's still running on the 'backs' of the gears, but wouldn't flipping the diff be counter productive?

(IMG:style_emoticons/default/headbang.gif)

You are focusing on the OUTPUT only. The helical cut gears would be spun so that their coasting side would then be the power-on side. Not good. You can switch the output of any differential by flipping the diff (if the design allows such), but the ring is being driven by the coast side of the pinion, because the INPUT shaft is spinning backwards of the tranny design no matter what side the diff is on.

[ChrisFoley]

You are focusing on the OUTPUT only. The helical cut gears would be spun so that their coasting side would then be the power-on side. Not good.

People (including me) set up close ratio boxes by installing gear sets in the "wrong" position all the time so that they run backwards. Yes, I know the thrust is in the wrong direction but I've never heard of any problems resulting from this.
Whats the difference if all 5 gears are spinning the "wrong" direction?

[Dr Evil]

You are focusing on the OUTPUT only. The helical cut gears would be spun so that their coasting side would then be the power-on side. Not good.

People (including me) set up close ratio boxes by installing gear sets in the "wrong" position all the time so that they run backwards. Yes, I know the thrust is in the wrong direction but I've never heard of any problems resulting from this.
Whats the difference if all 5 gears are spinning the "wrong" direction?

It mainly is an issue with the pinion/diff. I, too, flip gears for ratios often and that is not a problem, but if the diff/pinion is not turning in the correct orientation it would not be a pretty site. Also, you dont flip 1st. 1st gear is set up to only be down shifted into whilst turning in one direction due to its band and block configuration. Shifting from reverse to 1st real fast is one way you can try what it would be like to shift into first with the box being turned the wrong way. With first running backwards, you would be prone to popping out of gear as the band would not be reinforced by the internal mechanisms of the synchronization package.