cylinder head removal

[m37aswell]

It looks like I may have a burned valve on the #5 cylinder in one of my 1965 Corvairs. 0 psi on a compression check, I pulled the valve cover in the hopes of finding a broken rocker or something, but no such luck. I did spin the engine with the remote starter switch, and it looks like normal operation. Can I pull that right side cylinder head in car? Looks like I may have to lower the engine just a little. Wondering if it's a real pain or not so bad at all.

[flat6_musik]

Me personally, when my cylinder head screwed up, I looked at everything and thought "I think I'll regret doing the job in-car" so I yanked the motor. But mine's a turbo, a fair amount more annoying/complicated.

Are you sure yet that it's a valve and not a burned piston?

[66vairguy]

It looks like I may have a burned valve on the #5 cylinder in one of my 1965 Corvairs. 0 psi on a compression check, I pulled the valve cover in the hopes of finding a broken rocker or something, but no such luck. I did spin the engine with the remote starter switch, and it looks like normal operation. Can I pull that right side cylinder head in car? Looks like I may have to lower the engine just a little. Wondering if it's a real pain or not so bad at all.

It's been done, BUT in my mind it's a toss up as to if it's easier versus dropping the whole drive train. In my "younger" years I might tackle it, but now I just drop the whole drivetrain. If your very experienced with dismantling a Corvair engine then "in the car" wouldn't be that bad.

The other issue is these engines are OLD. I run into loose head studs and other "things" done by folks before me. Now I just pull the entire drive train (DO NOT PULL THE ENGINE OFF THE TRANSAXLE IN THE CAR). It allows me easier access and inspection. Just me.

BTW - A burned valve on #5 is often the cause of a torn fresh air heater hose from the top engine shroud to the heater box. It bleeds off air flow to the #5 cylinder part of the heat so it overheats. I always inspect and replace that hose (a real paint to install). Some just block off the outlet on the engine top shroud. Good luck.

[bbodie52]

» Sun Nov 20, 2022 10:23 am

It looks like I may have a burned valve on the #5 cylinder in one of my 1965 Corvairs...

65 Monza 110 auto

Number 5 cylinder is notorious for running hot and for resulting in damage to the valves or valve seat. This is especially true if the cold air upper sheet metal shroud connection hose is torn or missing. This can starve the #5 cooling fins for airflow — often resulting in loss of life in the number 5 cylinder. A loose/dropped valve seat is also a possibility.

» Wed Aug 10, 2016 1:32 pm
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.

Corvair Engine Heater Hose Connections

[66vairguy]

I looked into the #5 overheating issue. GM made a LOT of Corvairs and this issue never showed up until they were older.

What I found is that typically the fresh air hose is leaking OR the flapper in the heater box is leaking (rodents like to eat the rubber flap). The flap is also adjustable and the control cable can bind so the flap doesn't close.

If the hose is good, and the heater box fresh air flap seals --- there isn't a #5 overheating issue. The problem is folks usually don't find the "leaking fresh air" issue until AFTER the engine head is damaged by heat!!! So now most just block off the engine top shroud fresh air outlet. This precludes moderating the hot air from the heater box UNLESS you run the fan motor. Not a big deal if you remember.

[m37aswell]

I suppose it could be a burned piston. I did block off the shroud at the #5 cylinder a few months ago, I got this Corvair in March of 21. It's been a good running engine until a couple of weeks ago when it started acting as if it was running on only 5 cylinders. If I drop the head and find a burned valve, I can repair and reinstall and be back in the game, if it's a burned piston then I suppose I could go ahead and drop the engine. #1 cylinder is 145 psi, #2 is 160 psi, #3 is 130 psi, #4 is 165 psi, #5 is 0 psi, #6 is 145 psi. I did the Viton seal thing on the pushrod tubes etc. a couple of months ago. The rocker arm studs apparently are half of the clamping force on the head, I am wondering if the long bolts above are going to give some bit of trouble. It's up on my 4-post lift and it looks as if I can possibly pull the head off and down and out after removing carb and some shroud-work. The cylinder readings are uneven and not quite up to par but going through the whole engine would take much longer to get back on the road and cost much more. Not quite sure what to do just yet.

[66vairguy]

I suppose it could be a burned piston. I did block off the shroud at the #5 cylinder a few months ago, I got this Corvair in March of 21. It's been a good running engine until a couple of weeks ago when it started acting as if it was running on only 5 cylinders. If I drop the head and find a burned valve, I can repair and reinstall and be back in the game, if it's a burned piston then I suppose I could go ahead and drop the engine. #1 cylinder is 145 psi, #2 is 160 psi, #3 is 130 psi, #4 is 165 psi, #5 is 0 psi, #6 is 145 psi. I did the Viton seal thing on the pushrod tubes etc. a couple of months ago. The rocker arm studs apparently are half of the clamping force on the head, I am wondering if the long bolts above are going to give some bit of trouble. It's up on my 4-post lift and it looks as if I can possibly pull the head off and down and out after removing carb and some shroud-work. The cylinder readings are uneven and not quite up to par but going through the whole engine would take much longer to get back on the road and cost much more. Not quite sure what to do just yet.

If the piston is "holed" you'd know it --- since the the exhaust would be throwing out a LOT of blue smoke every time you opened the throttle under load --- BTDT decades ago with a poorly maintained company car.

If the car spent anytime in a "rustbelt" area, then yes getting the top nuts off the stud can be an issue. Even out West I sometimes have to "vise grip" the upper head stud so it won't turn while removing the nut. If the stud turns more than just a little and turns out, then you usually have to do a TimeSert (special length) and then die cut the head stud to remove the locking threads to get it back in the TimeSert -BTDT a few times. This is what I meant by "Old Engines". I'm not being negative, just what MIGHT happen. It could all go just fine - but it IS an old engine.

After my younger years patching up driver cars I finally got to the financial point were I could restore old cars for fun and do total engine rebuilds. You'll have to determine what works best for you.

[flat6_musik]

Maybe apply a bit of compressed air into the spark plug hole on #5 (with the piston @ top of the compression stroke, distributor rotor pointing at the #5 wire) and see where the air escapes from.....exhaust, crankcase or maybe even the intake. You shouldn't need to apply much air really.....to tip you off.

[aircooledairhead]

Many years ago I did this on a ‘66 Monza 110. I drove the right side up on a curb. I removed the long carb stud using two nuts with a lock washer between them. Tightened both nuts against the lock washer, then put a wrench on the top nut and removed the long stud.

I soaked the top head nuts in Liquid Wrench. While that worked, I pulled the valve cover, disconnected the vacuum balance tube, removed the plugs and wires, removed the bolts holding the top shroud to the head, removed the right shroud, then went after the head nuts. Using a vice grip on the studs, remove the top set of head nuts, then the rocker nuts, balls and rockers. Be careful to keep the rocker nuts, balls and rockers in the correct order.

If you can extract the shorter carb stud in the same way you removed the upper stud, it will make things much easier. Double check that nothing is still attached to the head and try to slide it off, making sure the cylinder jugs stay in place. If you can’t get the shorter carb stud off, you will have to support the engine and remove the locking nuts on the motor mount and lower the engine. That will give you the clearance to slide the head off.

If the issue is with the head, it will be apparent. If a piston is damaged, then you can remove the top shroud, crankcase cover and unbolt the connecting rod and remove the piston.

In my case, the piston had cracked and I was able to replace it with a good one I had already installed on a rod. I honed the cylinder and put it all back together. Be very careful torquing the head bolts, and, of course you will have to adjust the valves.

I seem to remember the bolt that the coil attaches to being a problem that may have necessitated removing the front lower shroud it passes through, but it was 47 years ago. You will also have to remove the bolts into the head on the shroud that the large heater hose attaches to.

Good luck!

[aircooledairhead]

If you remove the top shroud (turkey baster) it will allow you to get a vice grip on the studs so there is less chance of them coming out of the crankcase. Clamp the vice grip on the stud you are removing the head nut from and position the other end against an adjoining stud or a board you place on top of the cylinders. If a stud comes out, cleanly (no aluminum in the threads), you can reinsert it and use 2 head bolts and a washer to reinstall it. Tighten gently with a torque wrench and see if it holds torque of 25 ft. lbs.

When reassembling, there's a diversity of opinion on the torque to use, but many experienced Corvair folks stop at 30 ft. lbs. Some use 25, few brave souls go above 30 ft. lbs. On my son's 57 year old car I stopped at 30 ft. lbs.

If you will be removing the top shroud, you can save some time by unbolting the 2 carbs, the fuel pump bolt and separating the rubber fuel line above the driver side wheel (just before the shroud) from the metal line that goes to the fuel pump. This will allow you to lift the carbs, their connected lines, and the fuel pump off the engine as one assembly and save you the aggravation of disconnecting the fuel lines and re-tightening them. You will also have easier access to the carb studs facilitating their removal.

Again, good luck! I hope your issue is minor (a loose rocker if you are really lucky!) or easily repairable. Sorry if you are experienced at this and it has all been too much information!

[erco]

I've done it, removing a head is much easier & quicker than dropping the whole drivetrain. Nothing to lose. Worst case you remove the head and determine you need to drop the drivetrain later.

Who knows what wonderous things you may find inside?

[m37aswell]

Today I pulled off everything that looks like it needs to come off [in-car job] and that did expose the head nicely. Both carb studs have been removed. I removed the right-side shroud but not the big top fan shroud. I think I will leave the exhaust log on. I think I will try to remove the top stud nuts before removing the rocker arm studs etc. I hope the nuts will back off without taking the stud with it. If the stud backs out, can I double-nut it and screw it back in there? Anyway, I have been periodically hitting the top stud nuts with PB blaster and will let it sit overnight. I hope I can remove the head tomorrow without too much drama.

[erco]

I left my carbs studs in, so I had to loosen the rear engine mount to lower the engine to get my heads off. I will be curious to hear if you can get yours off leaving the engine in place. Hope you do and the fix is nothing serious.

[m37aswell]

Today I was successful in pulling off the right cylinder head in car without lowering the engine. All of the top stud nuts backed off nicely. However, all of the 3 jugs wanted to come off with the cylinder head as well. I did manage to push the 2 outside jugs back towards the block but the middle jug removed still stuck to the cylinder head. I then tapped it off ok. Just like I have been warned the exhaust valve seat on #5 has dislodged so now the hunt is on for a machine shop that can repair such a thing. Another problem is how I am going to get the jugs back over the pistons on which I should install new rings. I should remove the other 2 jugs to replace the steel shim gasket to mate the jugs back to the block. I wonder if I can get a ring compressor inside the 4 long studs so as to install the jug onto the piston, could be tricky if it's even possible. BTW I've always blocked off the fresh air port in the top shroud on all my 3 Corvairs.

[Dennis66]

So this brings up the question: What is the purpose of the "cold air" duct? How necessary is it? Would it hurt to just block it off? I do recall one of my Corvairs back in the day that had a factory block-off plate (don't remember which one, and it may have even been a "loose" engine that I acquired). Dennis

[66vairguy]

Today I was successful in pulling off the right cylinder head in car without lowering the engine. All of the top stud nuts backed off nicely. However, all of the 3 jugs wanted to come off with the cylinder head as well. I did manage to push the 2 outside jugs back towards the block but the middle jug removed still stuck to the cylinder head. I then tapped it off ok. Just like I have been warned the exhaust valve seat on #5 has dislodged so now the hunt is on for a machine shop that can repair such a thing. Another problem is how I am going to get the jugs back over the pistons on which I should install new rings. I should remove the other 2 jugs to replace the steel shim gasket to mate the jugs back to the block. I wonder if I can get a ring compressor inside the 4 long studs so as to install the jug onto the piston, could be tricky if it's even possible. BTW I've always blocked off the fresh air port in the top shroud on all my 3 Corvairs.

First --- why are you installing new piston rings on just one side of the engine? If the engine is that worn, then it needs a full rebuild. If compression was O.K. then don't change the piston rings. As for the cylinder that pulled all the way off ---- if it's a 65 long stroke engine the lower cylinder that came off will be notched in the bottom on each side to clear the crankshaft. 63 and earlier cylinders were NOT notched so you could compress the piston rings and install the piston via the BOTTOM of the cylinder over them. 64 and newer cylinders require the piston to be loaded (with ring compressor) into the TOP of the cylinder. However ---- I've heard some do manage to load the pistons via the bottom of the cylinder, BUT the issue is the ring may stick out a little and get damaged at the cylinder cutout notches. This means the ring ends MUST NOT BE NEAR the cylinder cutout notch and great care must be taken to make sure the rings don't catch on the cylinder cut-out. Keep in mind I've never tried to load pistons into the bottom of the cylinder.