140 engine rebuild

[SpiderMan]

This is the engine I plan to drop into my "Considering this 66 Corsa".
The only detail I know about the engine is that it came out of a 66 Corsa with 84K miles on it, and that's it, unfortunately. I rolled the dice and decided to purchase it since it was quite cheap - $350.00
How far do I go is the question.
Initially, I don't plan to split the block. I will inspect and measure as best as can though.
I got the heads off and cleaned. It's encouraging as there are no dropped valve seats. (that's worth the purchase price). One exhaust outlet tube was decayed and it popped out easy. I'll get a used one.
Next I'll remove the top and bottom to check the crank and cam shaft.
Should the crank have issues, it's decision time, proceed or look for another candidate.
The cylinders have some wear. I've ordered a bore gauge set to check them out. I assume with that many miles it wouldn't be prudent not to replace them. A likely scenario is I'll buy a forged piston and cylinder set and a gasket/seal set.
Other things to look for?

[erco]

Splitting the block is no big deal IMO. Sounds like you're 95% there, just maybe 8 case bolts and 12 connecting rod nuts. Won't necessarily cost you anything more in gaskets or parts. Best case, you find everything is fine and you give her a thorough cleanout before reassembly. Worst case, you find something that would have stopped you somewhere down the road. If it's a new engine to you (unknown) then trust nothing.

Personally, I enjoy giving the once-over to all the parts. It's a man-machine bonding experience.

[Dennis66]

See my build for details on using it, but when you unbolt a rod (rods), inspect the bearing journal for scoring. If it's clean, get some plastigage (many parts people will have no idea what you are asking for), and check the oil clearance. If it's in spec and not scored, I would say you are good to go. Why new pistons? 84K isn't that high of mileage, even for a '60s car. When you pull the rings the ring grooves and overall insides of the engine should give some kind of idea of what maintenance has been like. Lots of sludge? I would say probably whole rebuild. Fairly clean? Maybe rings and rod bearings. Are you having valve seats put in? Dennis

[SpiderMan]

I'm debating valve seat replacement. I know it's a common issue. Reseating deeper is kind of expensive I imagine.
Ya, I'll crack it.

[erco]

Seems like restaking seats (at a minimum) at every opportunity might be a good idea, but I haven't heard of anyone doing or recommending it. If they loosen a tad each heat cycle, moving some metal to hold 'em in makes sense.

[66vairguy]

I'm debating valve seat replacement. I know it's a common issue. Reseating deeper is kind of expensive I imagine.
Ya, I'll crack it.

The small valve engines are less prone to valve seat drops, unless they are overheated. The 140's with the bigger valves, based on posts, are far more prone to a valve seat drop. A fellow in our club had a 140HP with PG, it had a good life and the mileage was around 50,000 miles and he dropped a valve seat! A surprise for a car that was never abused.

Staking the seats seem logical, but in reality valve seats that are staked still drop based on old posts. The greater seat diameter requires greater material contact between the seat and head. The seat and head are dissimilar materials with different expansion rates. No matter how "tight" you attempt to fit the seat in the head, repeated thermal cycles relax the tension between the seat and head. The only fix that has a history of working is "deep" (greater contact) seats. Keep in mind even they won't tolerate overheating the engine!

You can take your chances, but do you really want to take the engine apart again? Also if you get unlucky when a seat drops you can damage a piston and cause major damage to the head.

New valves, seats, springs, guides will set you back about $1,000.00 to $1,500.00 for two heads.

[Dennis66]

Often, seats that have been "staked" or "peened" as we used to call it will have some of the aluminum overlapping the edges of the seat. This would ten to keep them from popping back out. Now the down side: if the seats were loose, and they were staked, you need to make sure they are back in "square" to the valve guide. Just a little angle and the valve isn't going to seat properly. You can lap them, but while you have a good looking pattern, it still will not seal properly. My 102 heads had been staked. I lapped them, but when pressure checked, they still leaked. I invested about 200.00 in a Neway* valve seat cutter and an 11/32 pilot. The pilot is a taper fit so it goes into the guide TIGHT (my heads have new guides, but they make these pilots in oversizes so if there is a little slop in the valve guides, they will tighten up and be true. I haven't pressure checked my heads since the cutting, just been too busy with other projects around here. Maybe this coming weekend. Dennis
* There are cheap "Indian" made cutters available. After reading reviews, I wouldn't trust them. Won't take a chance on screwing up my heads and having to replace or spend BIG $$$$ to have new seats put in.

[66vairguy]

One thing not mentioned is what cam will be used. Over the years I've seen a number of posts about broken rockers, bent push rods, and "chirping" rocker balls or broken lifters after a new engine build. Finally a number of folks found a major cause ---- valve spring binding!!!

Today stock cam grinds are hard to find and most use the 260, 270, or 280 grinds (Otto numbers are 10, 20, or 30). ONLY the 260 or 10 cams work with stock valve springs and even then their lift is slightly greater than any of the stock Corvair cams. If you run a higher lift 270, 280 cam you must use competition valve springs to prevent spring binding.

The other issue is many use SBC (small block Chevy) V8 valve springs for higher spring tension (at Corvair spring height spec). I don't have the numbers handy, but i recall they are a bit taller fully compressed, but I could be wrong. Anybody with the numbers feel free to comment.

I know folks say the SBC spring tension is the same as Corvair, but the tension spec is for the V8 spring compressed spec. and the Corvair spec. is a lower height!!! When you compress the SBC spring to the Corvair spec. height the tension is greater.

[SpiderMan]

Good info on valve spring binding and valve seat staking etc.
I got my bore gauge set in the mail. I measured several spots in elevation and rotation. The cylinder bores measured 0.007" in diameter maximum greater than the published 3.437". At the most I measured 0.002 " tapering and negligible ovalization.
Do they warrant a re-bore?
Do they warrant just a honing and new rings or is that a different issue?
Or, do I just put it back together and do it at a later date when it gets worse?
Keep in mind I have no previous knowledge of the history of the engine.

[Dennis66]

At this point, what are your intentions for the car? 1-2 thousand mile a year hobby car? Occasional cruiser? Planning to go fast? Daily driver? First two categories, I'd say run a hone through them, a set of rings, and call it good (not sure about the heads though). If you're planning on cracking the secondaries a lot maybe the overbore, definitely head work. Dennis

[Wagon Master]

Dennis, would you cut the ridge out of 84,000 mile cylinders or just hone?

[Dennis66]

If they have ridges, they should be cut - ESPECIALLY on a Corvair engine. Reason: with a Corvair, you have no guarantee that the cylinder might not mount "just a few thousandths" lower than it was before. If this happens, your top rings could come into contact with the ridges causing broken rings / ring lands.
I have seen sometimes where what one thinks are cylinder ridges, but it was carbon buildup and "engine funk". It cleaned out with honing. I would at least run a hone through them first. If the ridge remains, A) find someone with bore measuring tools and check that, and B) if within spec, have the ridges cut out.
Two things to note here: Corvair cylinders, if bored, should be bored in a jig that simulates the clamping force of the cylinder head being torqued to the block. Educated, experienced folks say that there is some distortion caused by this and you want it that way for boring. This wouldn't apply so much to running a dingleberry or fine grit hone through them to deglaze. Second thing: bear in mind that there are different Corvair cylinders. 145 cylinders have the same bore, but thinner cylinder walls where the head gasket seats. You can use these with 164 heads, but they need to be shimmed. Also 145 cylinders would need to be notched at the bottoms for clearance of a 164 crank.
I have a set of 164 - 110 cylinders and pistons, but I haven't run a hone through them to see if they are worth anything yet. They do not have any ridge. Dennis

[66vairguy]

The 1964 models still used the thinner head gasket surface, but were notched for the longer stroke, basically a one year cylinder design.

The 1965 models had the wider head gasket surface, but the early 65 engines used the left over 64 cylinders with a ring (shim) installed around the top of the cylinder to fit the bigger head opening diameter. I've got one of those odd ball early 65 cylinders in my spares.

[Dennis66]

I have one of those cylinders too. When I rebuilt the Greenbrier engine about 10 years ago, this cylinder was "oddball". It almost looked sleeved. I thought "Who in the heck would sleeve a replaceable cylinder? We bought a used cylinder from Clark's. Until hearing about the shims on here, I always though it was shimmed. I use it when I need to support something. Dennis

[SpiderMan]

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.

[erco]

I've seen some mangled cylinders after botched amateur ridge reaming. It's easy to do, cheap reamers can leave a very rough surface. I thought I had a ridge but it turned out to just be carbon: viewtopic.php?p=125171

I would offer that for an economy re-ring job (assuming cylinders are in spec otherwise and reusing pistons & rods), it may be worth leaving the ridge, honing the cylinders, and adding a thicker or additional under-jug gasket to move the jugs and ridge away from the block in order to make sure the new piston rings don't hit the ridge. This would lower the CR slightly (depending on thickness added) but that's not necessarily a bad thing given today's low octane gas. Many people use thicker head gaskets to lower CR anyway, so this is just another way to achieve that. If you take the time to CC your heads and calculate actual CR, 10-20 thousandths of head gasket thickness makes a significant difference.