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Identifying A Hack Job On A Head
Posted by: Max Roeder ()
Date: December 22, 2016 04:43AM

There has been some discussions concerning having valve seats replaced by "reputable" craftsmen of the trade. I just wanted to show you one pic of a seat replaced by one of the known craftsmen. After I received the heads back from being repaired I decided to look more closely at the work. I'll just show one seat since the remaining eleven were about the same. Note the seating face at 10:00 and at 4:00. There is about 25% difference in contact area. The valve depends on the seat contact to valve face to pull heat away from the valve. The difference in contact area will also contribute to valves not walking i.e., rotating properly to crush and expel carbon particles. And the worse case, a burnt valve!

If you are going to have heads done ask for specs and pics of past work. Ask how seats are replaced and secured into head. If I remember correctly Ray Sedman uses a .008" interference and liquid nitrogen into a 500F head. He doesn't peen the aluminum over the seat with a club!

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Re: Identifying A Hack Job On A Head
Posted by: v8vair ()
Date: December 22, 2016 05:17AM

This is the 2nd set of heads I've had done by a local racer.
All new seats and ported and flowed. The first set was .009 interference, the 2nd was .010. He said the heads really need to be re heat treated as they've become to soft.Mike

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Re: Identifying A Hack Job On A Head
Posted by: gnvair ()
Date: December 22, 2016 05:40AM

Mike have you found a place to re-heat treat the heads?

Lee J
Southern New Jersey near Philly.
1966 Corsa 180/4 speed
1969 Monza convertible 140/4 speed

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Re: Identifying A Hack Job On A Head
Posted by: Max Roeder ()
Date: December 22, 2016 06:04AM


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Re: Identifying A Hack Job On A Head
Posted by: Brizo ()
Date: December 22, 2016 09:54AM

I recently worked on a pair of highly modified 140 heads with all new seats. The seat replacement work was beautiful, but they were so intent on providing a "three angle" seat, (Corvair seats are too narrow for an effective 3-angle job, IMO) the resulting actual exhaust valve-to-seat contact area was only .020 wide. Far too narrow for good heat transfer on a street engine, IMO .

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

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Re: Identifying A Hack Job On A Head
Posted by: 66vairman ()
Date: December 22, 2016 11:09AM

I talked with a knowledgeable fellow about interference fits and no matter how tight you fit a valve seat, after a few engine runs the different expansion/contraction rates of the head vs. the seat metals will result in a specific interference fit regardless of how tight the seats were installed. Of course that doesn't justify a "sloppy" or loose interference fit seat install.

The best way to increase valve seat retention tension is to put in a seat with more contact area with the head - deep seats.

Peening, rollover, set screws are not recommended as they create hot spots, and of course a deeper seat (properly installed) has been demonstrated to be effective and reliable.

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Re: Identifying A Hack Job On A Head
Posted by: Wagon Master ()
Date: December 22, 2016 11:28AM

Are you saying a seat installed at .001 will be the same as one installed at .010 after after 50 heat cycles? They'll both settle in to .005? I'm not buying.

'64 Monza Coupe 140 4 speed
'61 700 Lakewood 95 4 speed
'69 Monza Convert. 140 Auto.

Been aircooled since 1973
Northwest Ohio

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Re: Identifying A Hack Job On A Head
Posted by: jjohnsonjo ()
Date: December 22, 2016 12:25PM

Somewhere I read that .005 is the magic number. Anything more than that will end up there.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

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Re: Identifying A Hack Job On A Head
Posted by: 66vairman ()
Date: December 22, 2016 06:26PM

Wagon Master Wrote:
-------------------------------------------------------
> Are you saying a seat installed at .001 will be
> the same as one installed at .010 after after 50
> heat cycles? They'll both settle in to .005? I'm
> not buying.

Of course not - J.O. summed it up well.

What I meant to say was - Expansion will reduce the initial interference fit if it exceeds what the head/seat expansion cycle tolerates, "that doesn't justify a "sloppy" or loose interference fit seat install."

So of course a seat installed with a 0.001 interference fit will NOT get tighter.

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Re: Identifying A Hack Job On A Head
Posted by: v8vair ()
Date: December 22, 2016 06:38PM

Im no expert but i believe once the heads get soft they expand at a much greater rate than the steel seats,requiring such a tight interference fit. When they are reheat treated you dont need as much. the various copper seats expand at close to the same as the aluminum which dot require but maybe 004 Mike

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Re: Identifying A Hack Job On A Head
Posted by: JimBrandberg ()
Date: December 23, 2016 04:38AM

I had a pair of race heads heat treated. A local guy did it on the side but doesn't anymore. At that time there was also a place I think called West Coast Heat Treating in California, former Corvair racer Jon Brakke used them. Expensive proposition as all parts must be removed and replaced. The heads also tend to move about a bit during the process so careful attention to guide and seat and head gasket surfaces is needed. I would say again, expensive proposition. It's a valid point that some heads have gone too soft for good valve seat and guide retention.
I went to a heat treating lab where they checked how soft the aluminum was by shooting a ball and checking the depth of the dent. It was somewhat inconclusive and I didn't want to waste too much of their time as they were doing it for free and they were not going to do any work for me in the long run. I think it's still the way to test if possible.
Heat treating old heads is a good thing but expensive and difficult. I wish someone would work through it so it wasn't a one time deal. I would be interested in hearing more on the subject, I know very little aside from having it done once more than 10 years ago.
Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Identifying A Hack Job On A Head
Posted by: v8vair ()
Date: December 23, 2016 05:55AM

Theres a local place here in Atlanta that say they can do it. I have not been there yet to talk. My head guy can tell right away by the way the aluminum cuts. Im going to heat treat my next set of heads. As soon as i recover from all the latest purchases ! Mike

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Re: Identifying A Hack Job On A Head
Posted by: LawrenceNZ ()
Date: December 23, 2016 08:44AM

Hello There, i agree with with Max Roeder about hack jobs been done on these heads as i to have a set on and engine that Michael Leveque built for me and i must say they are trash none of the valves seated when brake clean was poured down the ports and talk about seats been held in by beating them with a club mine were hit with a pick axe . In fact the complete engine is trash and is headed for the scrap dealer. I don't mined mentioning his name as i have spent over 5 figures with the guy and his reply in writing was i quote " YOU GOT WHAT YOU PAID FOR ".
This is a man that can not be trusted to do engine work or body work / paint as i received the car back in a shocking state.
Sorry for the rant but i am bitterly disappointed.

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Re: Identifying A Hack Job On A Head
Posted by: WCcorsa ()
Date: December 23, 2016 09:12AM

I'm always amazed how many "rebuilt" Corvair heads I see on eBay or Craigslist or at swap meets that really aren't rebuilt. Some being touted as such by self-proclaimed Corvair experts.

Used valves, stock seats, old guides and lack of machine work are commom.

When I look into the details of many of these for sale the vast majority are simply cleaned up heads (valve grind) with mostly used parts and staked seats.

I finally have come to the realization that most Corvair owners will simply not fork out the money it requires to properly rebuild cylinder heads (I'm not taking about you LawrenceNZ).

If one doesn't do the real work to properly rebuild a head then how can one expect to act like one?

Machine shop costs, parts costs and know-how cost money. Our cars are no different.

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Re: Identifying A Hack Job On A Head
Posted by: Wagon Master ()
Date: December 23, 2016 09:27AM

Max Roeder, Would you please PM me who did your head work so I can avoid the same disappointment and frustration?
Thanks.


'64 Monza Coupe 140 4 speed
'61 700 Lakewood 95 4 speed
'69 Monza Convert. 140 Auto.

Been aircooled since 1973
Northwest Ohio

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Re: Identifying A Hack Job On A Head
Posted by: Max Roeder ()
Date: December 23, 2016 04:29PM

PM sent

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Re: Identifying A Hack Job On A Head
Posted by: VairKing ()
Date: January 01, 2017 06:35AM

Lets keep the discussion continuing. I have a guy in the Kalamazoo MI area who says he can re-heat treat heads to whatever hardness I want...I wonder how hard do I want? Would be nice to test a NOS head to see how hard they were from the factory. (I do not have any NOS heads) I am not a metallurgist but I am guessing that like steel there is a balancing point between too soft/flexible and too hard/brittle.

_________________________________________
Ryan Counterman (Moderator)
1965 Corsa Kelmark V8 400 HP ///1965 Monza Sedan 110/PG /// Ultimate Corvair Hauler/// Don Eichstaedt's 1965 Corsa Racecar
West Michigan Corvair Club /// New Build! 1966 Corsa GTP Convertible Mid Engine 3.8L Supercharged!

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Re: Identifying A Hack Job On A Head
Posted by: jjohnsonjo ()
Date: January 01, 2017 09:05AM

[www.tuning.mbs.id.au]

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: Identifying A Hack Job On A Head
Date: May 16, 2017 07:43AM

Here is a good link to the page J.O. cited above:

www.mbs.id.au/tuning/Engine/alloy_head.htm


Dan Davis - Pierce County, WA ~ CORSA Western Director + Corvairs NW + North Cascades Corvairs + Corvanatics
1966 Corsa Turbo coupe ~ ~ 1966 140 Corsa ~ 65 Monza 140/4 'Vert Sierra Tan/Fawn (my current driver!!)
~ 1964 Monza 'Vert ~ 65 Monza 140/4 Evening Orchid w/ ivory/black int ~ 1962 Monza Wagon 102/4
1963 Rampside/Scamper ~ 1963 Red/Greenbrier ~ 1969 Ultra Van #468

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Re: Identifying A Hack Job On A Head
Posted by: mspeters ()
Date: May 16, 2017 09:19AM

Do we know what alloy vair heads are?

Too much press fit would cause the heads to relax back close to its yield strength due to the excessive hoop stresses. Think of the horizontal portion of a stress-strain curve...

Matt Peterson
Ada, MI
65 corsa vert 180hp

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