Corvair Forum

Hi all . I took her out for another spin unfortunately now seem's to be running lumpy on the number 4 cylinder side. There is also a loud tapping coming from the rocker cover on that side.
I haven't been able to remove this as of yet , hoping maybe a loose rocker not allowing a cylinder to function correctly.
There is a chuff chuff noise coming from carburetor
Thanks again from uk

Running on 5 and chuffing thru the intake,the valve is being held open. a loose rocker the valve would be closed all the time. Sounds more like the valve seat fell out.

Ooop compression test time

I didn't realise the valve seats were removable

Datsolow wrote: » Wed Aug 10, 2016 11:29 am
I didn't realise the valve seats were removable

The aluminum cylinder head material could not withstand the stress that must be endured by a valve seat. The steel valve seats are a press fit into the head and are normally not removed, unless severely damaged or if they loosen up over time. Dropping valve seats has become an increasingly common problem with Corvairs over time as they age — particularly in the 140 hp big valve heads. A qualified machine shop can replace a dropped valve seat, and special deep seats can be obtained and fitted to help prevent the problem from recurring.





The machine shop route with deep seats can be expensive, and if one has loosened there may be further problems in this area in the future with other valves unless a preemptive and expensive head rebuild with a complete set of deep seats is undertaken. A used replacement head may be less-expensive, but a replacement is still an aging used head and could also develop similar problems later. Most heads are about half a century old and have far-exceeded GM engineers' operational time and mileage expectations! Remember that the use of cast aluminum in cylinder heads was a fairly new technology in the 1960's, and the Corvair was marketed as an economy car with limited service life expectations.

Further discussion...


http://corvaircenter.com/phorum/read.ph ... 499,748649

Bob Helt wrote:Well the suggestions are all over the map. My opinion is to have the one chamber welded up and then install a new seat. Then put it back together and go.......

Sure you could drop another seat sometime...or maybe never. It's an unknown.
I'd say that the crank is undamaged and that the piston is OK to use as is.

FYI, in MO, staking will not help at all and could cause hot spots.

My shop used to use a small hammer and tap all around each seat. From the sounds then, it was possible to determine how well the seat was being retained. Maybe that would work for you too.

Hi thanks for the information , I took a look inside the rocker cover and the suspect cylinder (4) had a bent push rod ! I did the timing and still lumpy. (5)
Can I take head off whilst engine is still in the car?

If you are going to remove a cylinder head, you should review the shop manual and the procedures below to see what you are getting into. The heads are somewhat difficult to remove with the engine in the car, since you need to get the carburetor mount and manifold to clear the engine compartment perimeter frame. The process of detaching the peripheral items around the perimeter of the engine and partially lowering the rear of the engine to allow the engine head to clear the body when sliding it off of the cylinder barrels and studs can be a pain. When you add doing all of this while lying on your back under the car, getting dirt in your eyes and mouth, and repeatedly dragging yourself back out from under the car to grab another tool you forgot... well I think I prefer just pulling the entire powertrain and working on the engine heads when everything is clear of the car. There just isn't that much more work involved with pulling the powertrain out of the car first.

Others may disagree.

Having one or more experienced assistants with you to help with the project can make things go faster and safer.

Removing Corvair Cylinder Heads
viewtopic.php?f=225&t=4063

LM Corvair Engine Removal — Part 1 and 2

Hi , I've done a compression check and 1=zero2=75psi 3=45psi 4=75psi 5=45psi 6=50psi.
Doesn't look so great how the hell was it running and still runs.
What is a healthy engine meant to read also , where do I go from here?
Thanks Paul

Paul wrote:Hi , I've done a compression check and 1=zero2=75psi 3=45psi 4=75psi 5=45psi 6=50psi.
Doesn't look so great how the hell was it running and still runs.
What is a healthy engine meant to read also , where do I go from here?

Healthy cylinders should read 130 psi each, with a maximum variation of 20 psi between cylinders. Zero is a complete failure (hole in the piston, stuck valve, etc.) If the rest of your readings are accurately measured (following the procedures in the attached shop manual section) at cranking speed with the throttle wide open, etc., then you are looking at worn cylinders and rings, blown head gaskets, worn out or damaged valves, etc. A cylinder leak down test using an air compressor to pressurize each cylinder can help to determine the cause without disassembly, but an engine with such poor readings would certainly require disassembly and overhaul... or replacement with a serviceable engine.

Thanks for info , I've just found a machine shop to cut new seats n valves £350

Hi all, update on my sic vair ...... new compression test done.My older tester was useless....
Cylinders
1=165. 2=0
3=150. 4=145
5=165. 6=145
Obviously cylinder 2 is shot to bits .....and this side lower than right side . I'm hoping to just rebuild left 2-4-6 hoping it's valve issues.Any ideas would be good.
Cheers from U.K.

One post you say zero on number one then later you're saying number two????????? Watch this video & reset your valves then check the compression again. Fast forward to 20:00 min. & watch Dave use the book to set them. I just think it's better to check before you tear it down.

Hi thanks for the reply , my first post I used a busted tester. The second time a reliable tested one . The second set of results are correct. However I will check valve settings b4 anything drastic.

Hi put camera down through plug and there was an indent of half valve in the top of piston . I will add pic once this iPhone allows access to pictures [emoji30]


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Pics as promised any causes for the indent please reply
Cheers paul[emoji1058]


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Stuck valve. overadjusted valve. jammed lifter, dropped valve seat, broken valve spring (any of these might cause a bent or broken push rod as well).