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Dropped valve seat - 140Hp
Posted by: MikeBuongiorno ()
Date: November 14, 2020 09:22PM

Hi all,

Two weeks ago I bought a restored, club-members 1965 Corsa with 1000mi since rebuild by a famous local corvair mechanic. Unfortunately, on this mornings jaunt (5th drive, <100mi since purchase) a horrible slapping/clanking sound came from the engine followed by increasing quantities of smoke from the exhaust. New to the corvair engine experience and reading some of the books I've recently gathered, it seems pretty clear I dropped a seat. Which is a pretty unfortunate turn of events indeed.

I've been working on a kelmark mid engine car for a long time and bought this second corvair as a "finished" driver. Now it seems I have two project corvairs. :-(

From what I've read in the books and on the forum the game is

1. Test compression to confirm / identify cylinder
2. Take the head off (remove drivetrain?) and hope the damage is not transmitted to bottom end / other cylinders
3. Send off to qualified corvair machinist or seek to acquire new heads

Am I on the right track?

Thank you,

Mike

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Re: Dropped valve seat - 140Hp
Posted by: RobertC ()
Date: November 14, 2020 09:32PM

Yes, except I never recall any smoke from any of the dropped valve seats that I have had.

“Condition” of the motor? Still has the stock pistons? I wonder if you lost the top of a piston?

I do not know what happens if the valve seat breaks into pieces.

You can remove heads from the engine without removal of the engine. Remove the stud for the carbs and droop the back of the engine a couple inches.

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Re: Dropped valve seat - 140Hp
Posted by: MikeBuongiorno ()
Date: November 14, 2020 09:34PM

Thank you. The motor was sold as "1000mi since rebuild."

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Re: Dropped valve seat - 140Hp
Posted by: RobertC ()
Date: November 14, 2020 09:40PM

MikeBuongiorno Wrote:
-------------------------------------------------------
> Thank you. The motor was sold as "1000mi since rebuild."


Yes, I understand. But, given the problem, something is not up to standard.

I should add, a valve seat in pieces, results in those pieces being distributed to the other two cylinders. But, I do not know if such conditions causes the motor to smoke.

Good luck.

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Re: Dropped valve seat - 140Hp
Posted by: joelsplace ()
Date: November 14, 2020 09:54PM

Dropped seats don't usually make the engine smoke but they could damage the cylinder or piston enough to do it.

Joel
Northlake, TX
5 Ultravans, 113 Corvairs and counting...

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Re: Dropped valve seat - 140Hp
Posted by: RobertC ()
Date: November 14, 2020 10:06PM

Well, 1000 miles since rebuild can mean many things.

You need a copy of the work order to see what was actually done.

You need more info than that . You néed the history of the motor.

Did it have a previous dropped valve seat? Were all the seats replaced in the head?



Edited 1 time(s). Last edit at 11/14/2020 10:07PM by RobertC.

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Re: Dropped valve seat - 140Hp
Posted by: MattNall ()
Date: November 14, 2020 10:20PM

1,000 miles on rebuild....that "Famous" engine rebuilder will fix it! get with the PO and contact that "Famous" rebuilder..

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Dropped valve seat - 140Hp
Posted by: RobertC ()
Date: November 15, 2020 12:48AM

MattNall Wrote:
-------------------------------------------------------
> that "Famous" engine rebuilder will fix it!

It is late and I am in a humorous mood.

You really think so???

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Re: Dropped valve seat - 140Hp
Posted by: dryenko ()
Date: November 15, 2020 04:55AM

If the heads were only cleaned and serviced , a valve seat can drop out at any time given the age of the heads nowadays.
Moreso if a lot of short cycle stop start cycles.
There is also no data given on the engine being run with no fan belt, etc.
If the engine was driven for any period after the noise was perceived, the damage will be extensive.
There is this tendency to "get home " which makes the problem much worse.
YOMV

Bob C aka Dryenko
Dobson, NC 27017

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Re: Dropped valve seat - 140Hp
Posted by: JimBrandberg ()
Date: November 15, 2020 05:36AM

Rebuilt can of course mean a variety of things.
The owner and how much he wants to spend is of course the factor in how far the project goes. People often don't want to put $1000-1500 or more of extra work in just the heads.
No matter how much or how little gets done it always seems to get advertised as rebuilt by so and so.
Even if you do everything you still have the uncertainty of 50 year old metal components with unknown past experiences.
I don't know who the famous local mechanic is or where this car is located.

I had one last year where an intake pushrod was bent and the valve was not opening. That one smoked as oil was sucked in and was fine with a new pushrod. A pushrod set free at the bottom of the lobe can certainly make a horrible slapping/clanking sound.
I'd pull the valve cover and have a peek before jumping to valve seat conclusions.
Of course there's other possibilities like a valve guide let loose or broken.

Can anyone hold a cylinder head in their hands and say that a valve seat or guide is about to separate from it's moorings due to aluminum that's lost it's temper? Maybe with a Rockwell Test. Perhaps the one paying the bill would like to have that done? Anyone? Bueller? Anyone? Sorry I stole the movie line from someone else on this forum. I LOLed the first time I saw it.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Dropped valve seat - 140Hp
Posted by: vairmech ()
Date: November 15, 2020 06:07AM

Since you know who built the engine contact that person to see if they remember what was done. If you think you are going to get a free engine repair, think again. Any warranty stops with the original owner, at least with me it does.

Start with a compression test, zero = probably a dropped valve seat. Any compression at all and it could be something else or could still be a dropped valve seat.
You say there was smoke from the exhaust, a Corsa 140 hp should have a dual exhaust so you know what side to start looking at!

If by chance it is a valve seat it could have shattered and that can cause piston problems especially since it sounds like you may have driven it some after the noise started. You should also have had a very substantial miss with a dropped valve seat.

Just like everyone else will tell you, if one seat drops how long before the next seat drops? Depending on what you find you may be going deeper into the engine than expected.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Dropped valve seat - 140Hp
Posted by: Backin66 ()
Date: November 15, 2020 06:16AM

A borescope is pretty easy to obtain nowadays. You may be able to confirm the problem. Try to get one with an angled mirror attachment so you can see 90°.

GeorgeW
66 Corsa
SE Ct

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Re: Dropped valve seat - 140Hp
Posted by: MikeBuongiorno ()
Date: November 15, 2020 07:22AM

Thank you all. Yes, I don't think the mechanic is on the hook, as frustrated as I am having just paid a premium for the vehicle. Unfortunate circumstances for me as I'm thinking that the "Desire to get home" even though it was less than a mile, may have really caused serious issues. Or I could just be going down the rabbit hole of youtube videos of extensive damage caused by shattered valve seats and cringing. One step at a time. I'll compression test then pull the valve cover and report back. -MIke

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Re: Dropped valve seat - 140Hp
Posted by: isucorvair ()
Date: November 15, 2020 07:49AM

1000 miles since rebuild.

That could mean it was rebuilt 20 years ago, and not driven much!


I dropped a seat on my 95hp in my 66 Monza. Took me about an hour to get everything disassembled, while still in the car, and head removed for analysis (after confirming with borescope).

I've got a new head on its way to me now... I'll clean stuff up while I wait, then slap it back together.

Eric P.
DeWitt, IA

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Re: Dropped valve seat - 140Hp
Posted by: RobertC ()
Date: November 15, 2020 10:34AM

MikeBuongiorno Wrote:
-------------------------------------------------------
> Unfortunate circumstances for me as I'm thinking that the "Desire to get home" even though it was less than a mile, may have really caused serious issues. -MIke

It is possible that the engine suffered no further damage.

Eric has a good point - how many years ago was the engine rebuilt?

Be nice to really know what was done when the engine was rebuilt, but given the circumstances that info may not be given.

Decades ago, had a club member who was into Concours. The engine was good enough to get off the trailer - did not smoke.

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Re: Dropped valve seat - 140Hp
Posted by: MikeBuongiorno ()
Date: November 15, 2020 02:31PM

Adventures in corvair motoring. First time, here we go.

1. Removed the plugs from the drivers side (suspect from which muffler smoke was coming from). And whoa! middle plug, picture below.
2. Compression tested the three plugs, all read zero. Suspect because I received the tester from the man who sold the corvair, I might be using it wrong, it might be bad.
3. Jacked up the car, removed the driver wheel, removed the muffler, removed the valve cover.
4. Oil looks clean, nothing obvious to my eye wrong here. Leave it to your trained eye to comment.
5. Not sure what to do next. Went to amazon and ordered a bore scope (thanks for the tip, $50, look forward to trying it out. Will also call the mechanic that did the work Monday. Car is in great shape, everything looks really clean and tidy. Work was performed 10yrs ago as previously mentioned. Car was always garaged and rarely driven.

Fingers crossed. What would you do next? Seems like pull the head and look down the barrels? Would continue down that path now, but likely will have to put it all back together and wait for new parts with car dissassmebled in the driveway. So, thinking call the mechanic, get the scope, and go from there. Thank you !

Attachments:

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Re: Dropped valve seat - 140Hp
Posted by: American Mel ()
Date: November 15, 2020 02:43PM

WHOA! Is correct! That picture is way too big to see anything. eye popping smiley
Maybe Matt can resize it for you.
After moving it around, I can see your sparkplug, and yes, SOMETHING was floating around in there and came between the piston and the plug.
Most likely valveseat pieces.
I would definitely make plans to pull that head.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza
Have had; '61 Monza coupe, 80hp, PG
'62 Monza Wagon, 4spd.
'63 Spyder,
'65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dually, approaching 400K
'03 Honda Del Sol
17'Terry

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Re: Dropped valve seat - 140Hp
Posted by: MattNall ()
Date: November 15, 2020 02:49PM

Looks like a low mile rebuild...too clean.

Yup, broken up seat on the tall spring. pull that head in the car if you are familiar with Vairs.... otherwise contact the builder..

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Dropped valve seat - 140Hp
Posted by: 63ConDan ()
Date: November 16, 2020 12:31PM

""1. Removed the plugs from the drivers side (suspect from which muffler smoke was coming from). And whoa! middle plug, picture below.
2. Compression tested the three plugs, all read zero. Suspect because I received the tester from the man who sold the corvair, I might be using it wrong, it might be bad.""

try compression test on the passengers side, if they also read Zero; tester may not work or it may being used incorrectly. this may help your cause to isolate the true issue.

Dan Central MN

1968 Convert

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Re: Dropped valve seat - 140Hp
Posted by: alphasud ()
Date: November 16, 2020 06:38PM

No need for any further diagnostic at this point. Yiur mission if you choose to take it is to remove the cylinder head. Then decide if you want to remove both heads and get them updated with deep seats. Hopefully the piston hasn’t been trashed but most likely has to require replacement. Or make plans with a shop to carry out the work. That’s a bummer!

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
1965 Corsa mid engine project
1973 Mercedes 280 project

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