140HP - PG Engine- timing question

[lonestranger]

I have a 65-66 140HP engine that was attached to PG. I believe these engine came from factory with "retarded" timing. My question is whether this was done with a "retarded" gear on the crank or "retarded" gear on the cam. I ask as I want to convert to "conventional" timing for use with my 4-spd.

If this is a dumb question - excuse me - I am old enough to forget a lot of things!!

[Jerry Whitt]

Looking at my 1965 Factory manual, did not find any listing about retarding the cam or crank gear.

Did note the initial ignition timing is listed at 18 degrees with a maximum of an additional 18 degrees at 2800 rpm and 22 more degrees with full vacuum advance at 14 inches of vacuum.

The only spec found related to cam gear and crank gear shows .002 up to .004 back lash.

Not sure where the "retarded" timing thought originated. Perhaps some one else has heard of this.

[joelsplace]

The 140 PG crank has a retarded gear.(I think 4 degrees) If it had A/C it has a different distributor gear to clock the distributor to clear the A/C belt.

[terribleted]

Best I know, 140 PG cars used a 4 degree retarded gearing on the crank to camshaft gear. 65 models used the same distributor for PG and stick cars. 66 and later 140 PG cars did not share the same distributor and the stick shift 140's.

[Jerry Whitt]

joelsplace and terribleted both indicate 4 degree retard, related to a crank gear. From which tech manual is the information obtained?

[lonestranger]

So the crank gear is the "retarded" gear! It figures, since the cam gear is easier to change and will be replaced when I change the cam - ( I am building a turbo motor) Thanks for the quick replies (even if it was not the one I was hoping for! )

[joelsplace]

You can buy an adjustable gear and make up the difference or use an offset key.
Jerry, I'm not sure where you can find it documented but the gears are visually different and it is common knowledge among Corvair people.

[lonestranger]

Do you mean use an adjustable gear or offset key on the mating cam gear?

[terribleted]

Why not just use a proper crankshaft and cam for the application? You say you are building a turbo engine. Any non powerglide 140 or turbo crank would suffice they are the same, they are nitrided which is the only difference between them and other late model cranks except the PG 140 ones. If you are building some one off 140 head turbo, I have no idea what would work best.

[joelsplace]

Sorry I left that helpful word out. Cam gear.

http://www.american-pi.com/corvair/html/specialty.html

[66vairguy]

The CORSA club tech manual has information and how to identify the "retarded" 140 PG only crank gear. Basically the books say the 140HP engine and the PG were not a great match and Chevrolet used an off the shelf milder cam and the crank gear was revised. This was done make the 140 with PG have more low end pull, yet it would still breathe at higher RPM. It was a compromise to work with the PG and will work with a 4 speed, but not optimally.

A competent machine shop can install a new "standard" crank gear. Clark's sells them. I've replaced the crank gears with new on both my 140HP rebuilds due to gear wear, both teeth and sealing area. I know Corvair folks are frugal, but when building a turbo engine it's best not to skimp. Also install a better crank gear woodruff key. The original keys have been documented to shear and the crank gear slowly slips causing all kinds of odd running issues since it's hard to identify.

I never could figure out why folks want to turbo 140 heads. Only advantage is wide open performance racing. Due to higher temperatures, and for daily street use, the smaller valve heads are more durable and it's possible, with a modern turbo, wastegate, ignition, and fuel management to get as much HP and torque as the transaxle can handle with the small valve heads - although it will cost $$$$$$$$.

The Corvair books have documented that the main restriction on a stock Corvair turbo engine is the carburetor (necessary because there is no boost limiting waste gate). The heads and exhaust are not the limiting factor for "reasonable" power increases.