140 engine rebuild

[66vairguy]

Good points about the cylinders and the lip that forms with time. Makes sense about potential interference with the rings. I'll leave up to my air cooled guy. If the lip can be removed with honing only perhaps the cylinders/pistons can be reused. Otherwise I'm looking at buying a $ kit.

How do you guys feel about Heli coils?
I have a guy recommending I pretty much heli coil everything to do with head mounting and possibly beyond.

I'm not a full time engine rebuilder, but I have dismantled a number of engines for parts. One had 88,000 miles on it and I was surprised NONE of the cylinders had a "ridge" in the top. Plenty of carbon, but no ridge. Just speculationg, but I suspect the opposed cylinder design provides plenty of cylinder lubrication, or maybe the Corvair cylinder material was quality. It's no secret the Olds, Buick, and Cadillac second generation thin wall blocks from the late 60's were superior in wear and strength to the Chevy big blocks.

Heli-coils are fine for most repairs EXCEPT spark plug holes and block head stud holes. Those two location require a special Time Sert!!! One issue with the head studs is the last three or four threads have a "shallow" valley to seal (and bind) in the aluminum case!!! If you don't cut the stud threads to standard depth then the will lock up in the Time Sert BEFORE they are all the way in and there is a good chance it will deform the Time Sert and cause it to come out next time you take the head nut off the stud --- I've seen it happen!!! A helicoil will expand to accept an uncut head stud, but there is a risk it will turn back out when you loosen the head nut next time. I've only had to do a couple pulled head studs. NO FUN! Those head studs are TOUGH!! I had to order a top quality thread die that tended to bind on the stud with cutting oil!!!! An old machinist buddy said to use STP oil additive. IT WORKED, but very slow going to get smooth threads. Fortunately only 3 - 4 threads have to be re-cut to the proper depth. It is strongly advised that when you install the head stud into the Time Sert you use permanent Loc-Tite. NOTE: on long stroke blocks do NOT screw the head stud in past the inner block surface or the rod could hit it.

If you pull a head stud insert out, then the block is JUNK (too expensive to weld up and machine). Just my experience.

[Dennis66]

How do you guys feel about Heli coils?
I have a guy recommending I pretty much heli coil everything to do with head mounting and possibly beyond.

Can he give you a good reason why these should be helicoiled? I'd be real gunshy about helicoiling cylinder studs. I believe the quality thread inserts we used to use were called "Keenserts". These had a special drill bit, tap, and install tool. after the insert was in, there were 4 pins sticking up. The install tool was used to drive these pins into the threads (threads were keyed on the steel insert, this locked the insert in. Dennis

[erco]

Over the last 40 years, I have put in IIRC 3 helicoils after studs pulled out of the case. Torquing down the heads is terrifying after you experience that.

Two are still fine. One helicoil pulled out years later, so I made an oversize threaded insert from a bolt per Finch in HTKYCA.

[SpiderMan]

I had five out of the six studs on the top of the 2/4/6 side unscrew. They did not "pull out" per se.
The fine pitch end that has the cap nuts are really rusty and in some cases you can't tell there's a thread. Attempts with my Snap-on thread chasing kit have not been successful. I suppose they can be replaced.
As far as I can tell the block end coarser thread did not bring any aluminum with it so perhaps new ones will hold.
Should they be superglued into the block?

[erco]

That's a lot of studs pulling out. Might be time to find a new block. Get a donor engine?

Seabirds $300-400 https://seabirdsgarage.com/corvair-parts/

[Dennis66]

You describe a pretty common problem. The top head nuts are exposed to all the ugly stuff on the roads and are often corroded. Personlly, if the case threads are good, I would just get replacement studs from Clark's and loctite them in (or whatever Clark's suggests. They sell acorn nuts to go over the regular head bolts to prevent future corrosion and thread damage.
Personally, I haven't ever experienced the corroded bolt problem. I have a feeling I'm about to as I just picked up a pair of engines and toe first one has some pretty gnarly looking head bolts on it. I'll try chasing first. Dennis

[66vairguy]

I had five out of the six studs on the top of the 2/4/6 side unscrew. They did not "pull out" per se.
The fine pitch end that has the cap nuts are really rusty and in some cases you can't tell there's a thread. Attempts with my Snap-on thread chasing kit have not been successful. I suppose they can be replaced.
As far as I can tell the block end coarser thread did not bring any aluminum with it so perhaps new ones will hold.
Should they be superglued into the block?

As stated "it is not an uncommon problem", especially back east. Most screw the studs back in with some pemanent Loc-Tite. If you are building an engine, some put a plastic PVC tube over the stud and use a washer and bolt to torque it to 30 FOOT POUNDS - NO MORE! If the stud does not pull out you are good to go. Typcially that is done before assembly the rotating mass into the block. BTW ONCE when assembling an engine the cases were clean and with NO sign of corrosion so I DID NOT TEST THE STUDS and of course ONE pulled out - grrrrr. Ignoring Murphy's law is not advised.

f you just pulled the heads, then don't bother testing the studs as you'll find out when you put the head on and if a stud pulls then off comes the head again. If you are lucky you can do an insert without pulling the cylinder.

The odds are you'll be fine, but be prepared for that sinking feeling when torquing the head nut and it just keeps turning. Assembling a Corvair engine is NOT boring!

[SpiderMan]

Of the five studs that turned out I was able to remove the nut on two of them and chase those fine threads on nut and stud just fine.
On three of them the thread protruding from the nut is so rusted they are toast. I'll need to buy three studs. I notice Clark's has oversized studs. I could buy those but on the other hand the coarse stud threads that screw into the block look great with no aluminum on them. So maybe the block threads are in good shape.
Great idea 66vairguy about using a tube over the stud with washer and nut to check if they will torque up proper.
Do the studs bottom out or must you measure their seated length and stop turning in when it is correct?

[66vairguy]

I do not know how far the studs can go in past the block inner surface. On the blocks I've had apart, I've never seen more than two threads protruding inside the block and typically it is one thread of less.

If your threads did not have any aluminum on them then I'd turn them in until they seat snug. Keep in mind the last 3 - 4 threads had a "shallow" valley for a standard thread pitch. They are NOT special threads. Typically a screw cutter turns a standard pitch and depth, then a finish tool determines the peak and valley shape. There are standards in the screw and die books. So GM did not finish the last 3-4 thread valleys so they bind in the block aluminum threads. Those threads on the head stud will bottom out in the existing block threads (if the are good) so you shouldn't turn in past were the factory screwed the head studs in. At least that is the theory.

I know it is a lot of work to pull the tin and fan/engine top cover, but it is how you can actually see the studs inside the block. If your fan bearing is not so good, this is the time to pull the cover and install a new bearing.

[SpiderMan]

I have pulled the top cover can see inside. I plan to pull the bottom and possibly split the block for an inspection anyway.

[SpiderMan]

Here's where I'm at. I removed the pistons today. All rings are mobile and there's very little carbon that I can see. I plan to replace the rings.
Everything looks good accept:
1. I found a rogue connecting rod sleeve bearing half lodged in the bottom of the block....WTF?
All connecting rod sleeve bearings are in place and accounted for.
Did a previous rebuilder drop it in there?
Did it come form the factory like that?
Fortunately It seems to have lodged itself in a safe place because it wasn't beat up in the least.
I'm stymied - Strange!
2. Check the gear damage. I wonder if I did that removing the oil pump housing?
Probably need to do something about that.

I've got a guy close by that fancies himself a boxer engine expert, as in Subaru engines. He's old enough to be good. I'm guessing 70+. He does nothing but rebuild Subaru engines. It seems the Subaru is the VT state car.
I'm having him hone the cylinders and judge their salvageability. I'm hoping boring is not necessary. He's also going to dip clean everything else for me.
It occurs to me I could measure the lifter travel easily at this point with an dial indicator gauge. Next is stripping the block. and inspecting measuring the crankshaft. The thing rotates wonderfully and there appears to be no end play.

[66vairguy]

I've never seen a badly worn distributor/oil pump drive gear. A few things come to mind.

High volume oil pump --- a complete waste of money and energy (they actually heat up the oil due to excess volume that continually goes through the pressure by-pass regulator. This issue was documented in a national car magazine evaluating aftermarket items. Of course this assumes the engine bearings are not badly worn.

The weak oil pressure regulator spring myth. Someone started saying the oil pump pressure regulator springs get weak (they don't, I tested over a dozen from old engine and NONE were out of spec.). So folks started to stretch them. This raises the oil pressure (not good for the oil pump or bearings). I ALWAYS run an oil pressure gauge on a rebuilt engine. I have NEVER stretched pressure regulator spring and the oil pressure was on the money. BTW I have taken apart end covers and found the oil pressure regulator piston JAMMED in place due to crud in the piston cup and spring. This will cause high oil pressure at higher RPM!

Dual bearing rebuilt distributors. Someone convinced Clark's two bearings are better vs. the stock one bearing and they started selling two bearing rebuilt distributors. After the forums reported two incidents of dual bearing distributor shafts WELDED in the end cover hole due to side thrust friction (plenty of oil). A few smart folks figured it out. The axis for the distributor shaft and the flange of the end cover the distributor sits against may not be a perfect right angle. This is normal manufacturing tolerances (nothing is perfect). The Corvair distributor shaft IS INTENDED TO HAVE A SHAFT WITH A LITTLE AXIAL PLAY to compensate for minor shaft alignment variations. When it is out of the engine a little shaft wiggle is NORMAL!! The hole in the end cover the distributor shaft fits in (to drive the oil pump) acts as a second lower bearing so the distributor shaft does not "wiggle" at the upper end were the cam and rotor fit with the distributor in the engine. If there is side to side play with the distributor in the engine, then the upper bearing is worn out. Before folks bad mouth the stock DELCO distributor, they actually had a better reputation for longevity compared to the units in Fords during the 60's.

[SpiderMan]

Good info 66vairguy. I’m not on to wonder far from stock in any case.
The bend in that first thread is pretty severe. I’m thinking I can bend it back or file it down.
Thoughts?

[erco]

Agreed, crazy wear on that bronze helical gear. What does the distributor gear look like?

Likely both candidates for replacement:

https://ssl.corvair.com/user-cgi/search.cgi?part=C1084R
https://ssl.corvair.com/user-cgi/search.cgi?part=C1366

[66vairguy]

Good info 66vairguy. I’m not on to wonder far from stock in any case.
The bend in that first thread is pretty severe. I’m thinking I can bend it back or file it down.
Thoughts?

I would junk that gear. They aren't that hard to find used and good. If nobody has one, then check with the Corvair Ranch or California Corvair. BTW the gears notch is somewhat random until around 1967 when the air pump belt made positioning the distributor so the vacuum advance cleared the belt, then all the gears had the notch in the same place relative to the gear teeth.

Definitely check the distributor gear and split pin. Also check the hole the distributor shaft fits into in the end cover. Make sure the distributor shaft is not bent and the shaft end play is not excursive.

[66vairguy]

Good points about the cylinders and the lip that forms with time. Makes sense about potential interference with the rings. I'll leave up to my air cooled guy. If the lip can be removed with honing only perhaps the cylinders/pistons can be reused. Otherwise I'm looking at buying a $ kit.

How do you guys feel about Heli coils?
I have a guy recommending I pretty much heli coil everything to do with head mounting and possibly beyond.

Not sure what your guy means. Bottom line --- ONLY use a heli-coil, Time-Sert, or Keen-Sert if needed. If you torque bolts then thread failure is not common. While head studs can pull out the threads, it really isn't that common. Studs turning out due to frozen rusty nuts is more common and usually just screwing the head studs back in works.

Here is an interesting comment on Time-Serts vs. Keen-Sert --- The TimeSert will have a thinner OD than the like size Keensert due to the locking stakes for one. When installed the TimeSert cold rolls into the material, it is not just a thread lock on the outside of the threads.

Peter Calhoun- Marketing Manager
Pace American, Inc.

NOTE: when FORD issued aluminum head spark plug thread repair kits to dealers they ONLY used Time-Sert and told the dealers ONLY Time-Sert was approved for repairs.

Personally I use heli-coils for most stripped thread repairs, BUT after reviewing many posts on spark plug thread and head stud repairs, AND reviewing the different inserts I decided the Time-Sert is a superior product for those applications - HOWEVER a Time-Sert is strong and you CANNOT screw in the original head stud unless you cut the "binding" thread valley to proper depth with a quality machine die. I've seen folks try and the head stud lock up in the insert at the first shallow thread so it isn't screwed in all the way. If you try to remove the stud it WILL rip out the Time Sert by screwing it out of the block. I've seen it done.

NEVER remove a head stud unless it's damaged. Years ago a buddy gave me a LM turbo block because someone TRIED to remove the head studs for shipping. I recall 3 or 4 heads studs were BROKEN OFF FLUSH AT THE BLOCK!!! If I ever find someone competent to remove the broken studs I'll fix it - way down on the list - LOL.

Why some head studs turn out and other break off if you try to turn them out is a mystery. It may be the way the studs are manufactured.