140 engine rebuild

[SpiderMan]

The heads on my 57 year old 140 do not have dropped seats. The heads on my other engine which is still in the car have two after dropped seats after an overheating event. The thermostat cooling gate on the right side was stuck closed and me being a newbie was clueless about how important that is.
So the new/old engine valve seats have survived this long which makes me think they will continue to survive without replacing the seats with deeper ones so long as I don't overheat the engine.
Maybe you guys know otherwise but I don't think every 140 engine drops its seats?
I plan to buy the 59000 tool, reline the guides, replace valve springs and possibly valves. I'll sell the tool afterward.
Should this all backfire on me I'll think about buying new heads.

[66vairguy]

The heads on my 57 year old 140 do not have dropped seats. The heads on my other engine which is still in the car have two after dropped seats after an overheating event. The thermostat cooling gate on the right side was stuck closed and me being a newbie was clueless about how important that is.
So the new/old engine valve seats have survived this long which makes me think they will continue to survive without replacing the seats with deeper ones so long as I don't overheat the engine.
Maybe you guys know otherwise but I don't think every 140 engine drops its seats?
I plan to buy the 59000 tool, reline the guides, replace valve springs and possibly valves. I'll sell the tool afterward.
Should this all backfire on me I'll think about buying new heads.

It is true nobody has solid number on how many 140's drop valve seats, but years of online chatter suggest it is greater than the small valve engines. A
fellow in our club has a very nice low mileage 140HP PG car the was well maintained and never abused, yet last year while taking the car out for a local spin it dropped a valve seat. I have never heard of, or read about a deep seat coming loose.

[erco]

The rare/discontinued Lyle 590000 tool is another option. There's one on Ebay at $400.00 and heading up in a bid war.

Looks like a tool set we'd all like to have!

[SpiderMan]

I'm concluding I fret too much about replacing valve guides and having them maintain concentricity with the seats.
Recall the theorem, if A = B and B = C, then A =C?
Assuming GM cut the seats after installing valve guides so they were concentric from the factory, and the guides they put in had the hole exactly down the center, then removing the guides and replacing with guides that have a hole down the center should maintain concentricity. Perhaps a little more valve lapping than usual will be required.
I have a path forward. I will buy the special punch and an appropriate reamer to finish the hole size should it shrink during install. That's not overly expensive and it's something I can do myself.
This engine supposedly has 80k miles on it and the seats haven't dropped yet so I'm taking my chances. Should it drop a seat later I'll address it later. At the moment I don't want to drop the 3K$ it would take to have deep seats installed in two heads.

[66vairguy]

I'm concluding I fret too much about replacing valve guides and having them maintain concentricity with the seats.
Recall the theorem, if A = B and B = C, then A =C?
Assuming GM cut the seats after installing valve guides so they were concentric from the factory, and the guides they put in had the hole exactly down the center, then removing the guides and replacing with guides that have a hole down the center should maintain concentricity. Perhaps a little more valve lapping than usual will be required.
I have a path forward. I will buy the special punch and an appropriate reamer to finish the hole size should it shrink during install. That's not overly expensive and it's something I can do myself.
This engine supposedly has 80k miles on it and the seats haven't dropped yet so I'm taking my chances. Should it drop a seat later I'll address it later. At the moment I don't want to drop the 3K$ it would take to have deep seats installed in two heads.

I have never confirmed it, but the Corvair books claim the valve guide holes ARE NOT EXACTLY DOWN THE CENTER of the guide. The articles I've read said GM had problems with the valve guides being exactly centered so they used a guide with an undersized bore. The machines cut the valve seats AND bore out the valve guides to be concentric all in one step.

[Dennis66]

The valve lapping doesn't take enough off to make up for off center. That's why I had to buy the guide and seat cutter. While my cutter works for the small valve heads, I don't think it has the range for 140 big valves. Dennis

[SpiderMan]

Damn! I was afraid of that.

[erco]

Agreed, you need a real valve job after any valve guide work. Lapping-only is a freshen-up for old valves that are otherwise serviceable, but nowhere as good as a real valve job.

[SpiderMan]

This could have done the job. As predicted, it's quite desirable.

[erco]

Have you looked for a machine shop that can install bronze liners? That method uses the original valve guide hole for reference, so it may be preferable to new guides if the holes are off-center, as been suggested here.

[SpiderMan]

Yes, with the knowledge you guys have imparted, the liner approach seems best.
Apparently, according to the MA Bay area Corsa guys, there are no machine shops in all of New England left that will machine Corvair heads.
I have an inquiry into the Corvair Ranch.
Alternately, I could have a precise steel drill guide made up by a machine shop that's shaped like the head of valve only longer. I'd figure a way to firmly clamp it in place in the seat and insert the appropriate end mill to machine the guides big enough to accept a liner. Some of these guide holes are quite ovalized and I'm afraid a conventional drill bit might follow the oval hole incorrectly.
Maybe there's some special bit for this I'm not aware of?

[erco]

Clark's Corvair is in Shelburne Falls, MA can they do it or recommend someone local?

[SpiderMan]

I asked Clark's about that. As time has passed there have been fewer and fewer machine shops willing to do Corvair headwork and now there are none on the East coast. They referred me to Corvair Ranch in CA.

[bbodie52]

The Corvair Ranch is not in California. It is on the east coast, in Gettysburg, Pennsylvania.

As shown below, and according to their web site, they do perform machine shop services...

https://corvairranch.com/machine-shop




Corvair Ranch

https://corvairranch.com/

email us at: findit@theranch.today

CORVAIR RANCH
1079 BON-OX ROAD
GETTYSBURG, PA 17325
US

(717) 624-2805

[SpiderMan]

My mistake. That's a little more convenient

[erco]

I asked Clark's about that. As time has passed there have been fewer and fewer machine shops willing to do Corvair headwork and now there are none on the East coast. They referred me to Corvair Ranch in CA.

That can't be right. Not near you, but someone in Florida recently posted about using a local shop. East-coastish anyway.