Low Compresion on one side

[pjofcgbc]

Finally got around to doing a compression test on my new 1963 Corvair and I am afraid that I might have an issue. One the right side as you face the engine all three cylinders are testing around 150 PSI. On the left side the front cylinder is reading 0 PSI while the back is reading 30 PSI. any thoughts on most likely causes before I start tearing things down. Any help would be greatly appreciated.

[USAF_vair]

corvairs heads are known for dropped valve seats. if you feel like the compression check was done right, then only thing i would say you could try doing, is taking the valve cover off and have someone rotate the engine with a wrench while you look to make sure everything is in proper working order under the valve cover. could be as simple as a rocker problem. but dropped valve seats can happen at any time to any corvair engine unless properly rebuilt.

[pjofcgbc]

Thank you for your replay I will chevk into that. Hopefully I will have some time to do checks tomorrow.

[tboltkc]

When you pull the valve cover off, see if about the same amount of threads are showing on each adjusting nut. If someone messed up setting the valves (too tight) you will experience compression problems. You can try backing the adjustment off on the low cylinders and check compression again. If it comes up, readjust all the valves and check again.

[pjofcgbc]

ok...I got into the valve covers today and everything was working fine. I guess Will need to do the valve seats. is there anything else I should be looking for while I have things apart.

[USAF_vair]

well really only thing you can due is pull off that head and look at the valve seats. the only other thing you could do is see if some how the walls got washed of oil and you have sooo much blow-by past the piston rings on those cylinders. but either way the fix for both issues would be to take the head off. if the second issue is the reason why you lost compression then the engine needs to be completely rebuilt. at least a valve seat, one can have that head done.

if you find the valve seats are bad. there are a few corvair machinists that due great work with valve seats and i have had no issues with my performance corvairs with their work. but it will cost. both heads i want to say cost 2 grand.

[pjofcgbc]

thanks alot. I will hopefully get the heads off this week sometime.

[tboltkc]

ok...I got into the valve covers today and everything was working fine. I guess Will need to do the valve seats. is there anything else I should be looking for while I have things apart.

Did you loosen the rocker adjusting nuts and try again? Just because things look right doesn't mean the valves aren't too tight. I had a turbo engine that sat for a few years I wanted to install temporarily. I did a compression check and several were low. I loosened the nuts on the rockers and they all came up to acceptable level. Engine ran fine while still in the car.

[bbodie52]

If you haven't ever pulled a Corvair cylinder head before, you might benefit from reading the article I wrote on that same subject before you tackle that somewhat difficult job. The article is located in this same section of the Forum, and is titled Removing Corvair Cylinder Heads. There is another article I wrote in the same area titled NEW MECHANICS: Engine Rebuilding & Maintenance Tips that you may also find useful. If you remove the head(s) and find one or more dropped and broken valve seats, I read about a machine shop in Southern California that specializes in installing special deep valve seats in Corvair head that are more secure and are unlikely to ever fail again. I will try to locate the contact info for that shop and will post it here for your information. Good luck with the exploratory surgery on you Corvair!

[bbodie52]

HERE IS SOME INFO THAT I LOCATED ON THE WEB REGARDING CORVAIR VALVE SEATS, FOR WHAT IT'S WORTH...

Valve Seats.

The biggest durability issue with the Corvair head is dropped valve seats. It used to be that only 140s were a noted problem, but since all the heads are 30 or more years old, the problem has started to show up in small valve heads as well. There are a few ways to deal with the problem:

First, you can stake the seats. This involves using a staking tool which fits in the guide and has a little chisel shaped plunger, you go all the way around the seat and peen some aluminum over the seat. This technique has been debated a bit, but it's safe to say that it only really works on heads that haven't been overheated. When Corvairs were fairly new, or better yet if you started with a new pair of heads, this probably worked pretty well. But nowadays how can you be sure the heads haven't been overheated?

Method two is the preferred racer's technique - remove the old seats entirely and replace with a bigger, deeper seat. Expensive, but the best way to go. You can also fix a set of heads by welding then installing new seats, if you do this you should plan on doing all the seats, because the other ones are probably loose too.

Next is a method that involves somehow mechanically locking the seat in place, either by machining screw threads into the head and seat, or by machining the seat with a flange on the bottom, the seat would be installed then heliarced into place. Warren LeVeque offers the latter "sunken" seats as an option when he prepares heads.

Finally, Chuck Cromwell sent me this neat trick for installing set screws. He's had very good luck with this method, so I'm happy to put it up here. I will make two observations that may help you be successful. First, don't do this to a set of heads that have dropped a seat and you're trying to get by with replacing just one seat. Second, I'd suggest using a drill press to get the holes in straight, and perhaps practice on a junk head first.

Do this before you do a valve grind. With a 1/16th drill, drill a hole 1/4 inch deep into the aluminum right against the seat. Opposite that hole, drill another 1/16th hole 1/4 inch deep. That will be 2 holes 180 degrees from each other. Now drill both holes with a 1/8th drill, and finish with a 9/64ths drill, maintaining your 1/4 inch depth. Tap both holes with a 5/32nds (Note: a 10-32 should be the same size) bottom tap using plenty of oil on the tap. This will stop the aluminum from plugging the flutes. When you finish tapping the holes, flush them out with a good solvent such as brake cleaner, lacquer thinner, etc. Look in the holes and you will see threads in the side of the seats. Using (red) locktight on your screws, screw the screws down tight and let the locktite set up overnight. Then, using a dremel tool with the thinnest cut off blade, cut the screws off as close to the head as possible. Finally, use a grindstone in your dremel tool and grind the screws off flush with the head.

http://autoxer.skiblack.com/heads.html

MORE INFO...

http://www.corvaircorsa.com/4carbs.html

Over the years the 140 Corvair engine has picked up somewhat of a reputation for dropped valve seats. Corvair cylinder heads are aluminum, so the seats, which have to be of a harder material, are pressed in.

According the Bob Galli, of the Virtual 'Vairs (VV) Internet e-mail discussion group, using valve seats that are stepped on the outside diameter (OD) might be a sure cure for 140s. They were recommended to him by Corvair engine guru Richard Finch. A company that makes custom stepped valve seats is the Tucker Valve Seat Company. Contact information is shown below:

Tucker Valve Seat Company
Toll free; USA: 1-800-362-7321
Toll free; Canada: 1-800-367-7321
Web site: http://www.tuckervalveseat.com/

Another knowledgeable contributor to Virtual 'Vairs, Ed Corson of Corson's Classic Corvairs, believes a permanent fix for dropped valve seats involves taking your heads to a good aluminum head shop to have all the valve seats replaced with deep seats, and he points out that these same seats are used in Porsche heads and some VW heads.
Ed recommends the shop listed below, one which he's been doing business with for at least 23 years.

Fumio Fukaya Enterprises
4000 Alamo Street
Riverside, CA 92501
Tel: (909) 784-1251

NOTE: I tried a reverse lookup on the above phone number, but it produced nothing. However, a GOOGLE search for the above firm produced a result with the same address, but a different phone number area code, shown below:

Tel: (951) 784-1251

According to Ed, Fumio Fukaya arrived at California's Riverside Race Track about 30 years ago with a Japanese race team that raced a car with an all aluminum engine. When the team folded, he opened a shop in Riverside, where he would build/repair only aluminum head engines.

"He is so good and well known around the country and in racing circles," Ed told me, "that heads are sent to him for repair or remanufacture from all over the U.S. and Canada. I feel very fortunate to be located here where I was able to learn of him and get to know him. We have become very good friends and business acquaintances. I highly recommend him for Corvair heads. You can call him or send heads to him at the address and number listed, or if you would rather send them through me, contact me at Corson's Classic Corvairs."

Corson's Classic Corvairs
16953 Mockingbird Canyon Rd,
Riverside, CA 92504
Tel: (909) 780-7880

E-mail: EUGENE1938@aol.com

"A set of heads usually takes about 3 weeks to be completely redone with new deep seats and silicon/bronze valve guides. I recommend you disassemble the heads and clean them yourself, which will save you about $50.00. I also recommend that you not send him your valves, but replace them with new ones. After all if you are going to put that much effort into a set of heads you might just as well do it right."

[cnicol]

Blown head gaskets are also a possibility and as Travis suggested, try adjusting the valves before taking anything apart.

I recently repaired and engine with a similar problem and it was a simple matter of the last guy forgetting to torque the cylinder heads.

[pjofcgbc]

Thanks everyone. Life got in the way and I have not gotten back to the corvair. I was actually planning on adjusting the valves again before I began getting any deeper. Thanks so much for all the great insight on these issues. I am hoping to do some work this week and I will let you know what I find.

[pjofcgbc]

Thanks for all your help guys. On Saturday I was able to do a valve adjustment and the compression came up into normal range. Apparently the valves were adjusted too tight.