Corvair Forum

Compression test went well. Low but even. All around 130 but the motor hasn't run in over 20 years. I did pre-oil as posted above, and I did do a wet check. Honestly, I was happy to hook up the battery and not let out any Magic Smoke! After all, being a Brit Bike guy, I keep extra bottles of Lucas Magic Smoke in the shop. Bottom line is, it cranked over as it should with no terrible noises.

I just put in an order to Clark's for all the "under gaskets". I want to adjust the valves cold before I do anything. May as well do the oil pan and tube rings at the same time.

I'll continue forward and get it fired. If it needs a rebuild, I'll know after a few heat cycles with fresh oil and some Marvel Mystery Oil in the mix. If that stuff brought my 1948 Royal Enfield Model J back to life, I'll try it again.

Messing with anything besides changing oil is a mistake before running it long enough to see what's up. People screw up the valve adjustment more often than not. It is very very easy to get wrong especially after replacing the o-rings.

joelsplace wrote: ↑Sat Mar 30, 2024 11:24 pm Messing with anything besides changing oil is a mistake before running it long enough to see what's up. People screw up the valve adjustment more often than not. It is very very easy to get wrong especially after replacing the o-rings.

Thank You. Wise words indeed. I got a call last week about a new club member with a Corvair that would not run well. The "mechanic" decided it needed a valve adjustment and now it runs WORSE. I said that a well maintained Corvair engine will run its lifetime WITHOUT EVER ADJUSTING THE VALVES! If the engine does not run well, then first fine out exactly what the problem is. If it is a valve problem, then usually it's failed component.

That is why they are called hydraulic lifters so they don't need to be adjusted. If when you start it up there is some valve noise let it run for a while and they will most likely quite down on the own.

Strange on checking the valves. Been building car and bike motors my whole life. I'll take the Corvair Guru's advise, finish assembly and just fire it with fresh oil first. Usually on something this old, I have zero trust in baseline adjustments. Too many other hands in its history.

2LZ wrote: ↑Sun Mar 31, 2024 9:47 am Strange on checking the valves. Been building car and bike motors my whole life. I'll take the Corvair Guru's advise, finish assembly and just fire it with fresh oil first. Usually on something this old, I have zero trust in baseline adjustments. Too many other hands in its history.

True you never know what "someone" did before you got the car. That is why I prime with the oil pump with a dummy shaft AND have someone rotate the engine to see if anything binds (spark plugs removed).

Even newly rebuilt engines that sit for awhile can occasionally experience valve clatter on start up due to a lifter that has leaked down when the engine stops with a valve open. Usually goes away in a few minutes at idle as Rex said.

66vairguy wrote: ↑Sun Mar 31, 2024 11:26 am

2LZ wrote: ↑Sun Mar 31, 2024 9:47 am Strange on checking the valves. Been building car and bike motors my whole life. I'll take the Corvair Guru's advise, finish assembly and just fire it with fresh oil first. Usually on something this old, I have zero trust in baseline adjustments. Too many other hands in its history.

True you never know what "someone" did before you got the car. That is why I prime with the oil pump with a dummy shaft AND have someone rotate the engine to see if anything binds (spark plugs removed).

Even newly rebuilt engines that sit for awhile can occasionally experience valve clatter on start up due to a lifter that has leaked down when the engine stops with a valve open. Usually goes away in a few minutes at idle as Rex said.

That's why my paranoia exists on old stuff. I decided to check the valves on my '68 BSA (clean and complete bike) before I fired it for the first time. The valves ended up being within spec.....but the valve lifter was installed totally incorrectly. Glad I checked. Would have really worked out on the exhaust rocker and leaked oil everywhere. Never know what you may find.

Tough situation when you don’t know the history of what has been done. Early in ownership of my current Corvair after sitting for a couple months I had lifter noise for a concerning amount of time but it went away after 15-20 minutes.

I would try to let it run for at least 20-30 minutes and see how it does. A lot of variables if the engine hasn’t been run in a while, especially carburetors.

In my opinion the first thing to do is figure out what you’re dealing with.

I guess it depends on what approach you want to take. You can be minimalist, changing the oil and cleaning the carbs, etc, to see how it sounds running, or go deep! It will take you longer and cost more in gaskets and seals, but you can better know what you have. For example, you can see how much sludge is behind the valve covers and check for broken valve springs and bent pushrods. I think most valve adjustments happen during hot adjustments.

To get back to what Joel said about "incorrect valve adjustments", the static valve adjustment is very easy to do incorrectly. I've read all kinds of comments about were to turn the engine to adjust a valve and how to deal with empty of full lifters.

Just me ----- but with all the different cam grinds I finally settled on a "no guess" procedure. I take off the fan/top engine cover (usually needs a new gasket and sealing) and OBSERVE when the lifter is on the lowest part of the cam lobe and THEN adjust the valve rocker nut. The "zero lash" adjustment is tricky since that should be when the lifter is fully extended and the lifter spring does not have much tension, especially if the lifter is not full of oil after sitting. Some lightly "wiggle" the pushrod up and down until play is gone, others "spin" the pushrod until it gets tight. I found the "wiggle" process is a better indicator of play. Once you have zero lash, then tighten down the rocker nut 1/2 TURN!!! NOTE: Over the years Corvair books have said only 1/4 turn to 1 FULL turn down from zero lash. The 1/4 turn after zero lash was SUPPOSEDLY to avoid lifter pump up at high RPM. I believed this incorrect logic until I learned lifter pump up is NOT a lifter problem, but due to inadequate valve spring tension to keep the valve drain from "floating" that allows the lifter to pump up trying to fill the "gap". This is why more aggressive cam profiles require higher tension valve springs, but of course this puts more strain on a flat tappet cam design. If the engine has all new valve train parts and you expect some "wear in" then one full turn from zero lash may be advised, but NOT for a valve train with some mileage on it.

So at 1/2 turn from zero lash you are in the ball park. Then once the engine is warmed up you can do a hot running engine adjustment. This requires BOTH sides to be hooked to a muffler so you can hear the valve clatter. SLOOWLY back off the rocker nut until you hear CLATTER, then SLOOOWLY turn down the nut until the clatter stops - or zero lash, then VERY SLOOOWLY turn the rocker nut down an additional 1/2 turn. DO THIS SLOWLY as the lifter has to "bleed down" to adjust so the valve is not held too far open while the lifter adjusts.

Just me --- other can comment on how they do it.

Thanks for the wise words gang. Much appreciated. I also saw on Davemotohead's cold adjust video he suggested a 1/2 turn after zero lash, as well. Looks like a basic SBC cold adjustment.

I'm fixing this thing up for our local car show in July. I have the Brit Bikes to "mark their spots" at the show. I want the Corvair to be a nice example of a driver. That said, this thing is so easy to work on, I'll probably fire it once I get the carbs done and see what I have.

I gotta tell ya, I've never had to take a torch to the main jets before the get them out. The secondary carbs are even worse than the primaries. I needed to "lightly tap" on the main jet yesterday with a manual impact driver, after torching, to pop it loose. It's soaking in the parts cleaner, as we speak. New jets on the way. I'm at 3000' elevation and drive between 500' and 5000', so I ordered the 49's for the secondaries.

Yes the main jets are often difficult to remove unlike other carburetors I've worked on. Per davemotohead I got a good manual impact driver, use the biggest blade that fits the slot - WAM and the jet comes loose. Much better than chewing up the jet with a plain screwdriver of even worse - having to drill it out.

I also learned to use aluminum anti-seize on the cluster screws. Sometimes the screws are broken off by folks trying to get them loose!!

Unlike some carburetors, the Corvair Rochester base is all aluminum, only the top is zinc alloy "pot" metal.

Jet sizes -- this is like asking "What oil to use" - LOTS of opinions. Bob Helt liked to run bigger (richer) jets. Before the PES (power enrichment circuit) was used on the bigger engine the EM engines used a richer jet due to a "lean" spot. With PES jet sizes were reduced.

Frankly the engines I've torn down with BIG jets were loaded with carbon, sometimes the piston rings were full of carbon sludge and stuck!! I run 65 carbs on my 140HP with #51 primary jets, and #48 secondary jets. Pulls strong and no pinging on hot days. Just me ----------

The #49 secondary jet size should be fine. If you open the secondaries often, then check the spark plug electrode color.

66vairguy wrote: ↑Mon Apr 01, 2024 10:20 am Yes the main jets are often difficult to remove unlike other carburetors I've worked on. Per davemotohead I got a good manual impact driver, use the biggest blade that fits the slot - WAM and the jet comes loose. Much better than chewing up the jet with a plain screwdriver of even worse - having to drill it out.

I also learned to use aluminum anti-seize on the cluster screws. Sometimes the screws are broken off by folks trying to get them loose!!

Unlike some carburetors, the Corvair Rochester base is all aluminum, only the top is zinc alloy "pot" metal.

Jet sizes -- this is like asking "What oil to use" - LOTS of opinions. Bob Helt liked to run bigger (richer) jets. Before the PES (power enrichment circuit) was used on the bigger engine the EM engines used a richer jet due to a "lean" spot. With PES jet sizes were reduced.

Frankly the engines I've torn down with BIG jets were loaded with carbon, sometimes the piston rings were full of carbon sludge and stuck!! I run 65 carbs on my 140HP with #51 primary jets, and #48 secondary jets. Pulls strong and no pinging on hot days. Just me ----------

The #49 secondary jet size should be fine. If you open the secondaries often, then check the spark plug electrode color.

Excellent info 66vairguy, thank you!
Good to hear my main jet issue isn't a one-off situation. Makes me feel better about it.
I've been scouring Bob Helt's book, and it's a wealth if great info and very easy to consume and digest. Poor thing lives on my workbench and is starting to look like dirty flannel, at this point.

Good day today, all things considered. Got the "ala Davemotohead" stacks done, including paint and PCV inlet fitting.
Plus, both secondary carbs are now done, minus new main jets. Should be here tomorrow to finalize the carbs. Odd that one secondary carb looked like it had been through a war....but the last one I did today (#4), looked like it had been replaced. It was actually pretty clean and the float bowl wasn't muddy.

Looks good!

County98 wrote: ↑Thu Apr 04, 2024 7:23 amLooks good!

Thanks! One other thing I forgot to mention is that BOTH secondary carbs had the floats adjusted down to zero and the needles were completely closed off. Once I replaced the needles and seats, it took a lot of tab bending to get then back into Bob Helt's specs in his book. I guess this was the easy trick to turn it into a 110???