Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“Performance
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum The fastest message board... ever.
Corvair Center 
140 Heads comparison
Posted by: JerryM ()
Date: April 14, 2018 10:16AM

Do I understand correctly the only difference in any 140 head is external casting features for bolt size and accessory accommodation?

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: Wagon Master ()
Date: April 14, 2018 10:56AM

Smog 140's and I believe all smog heads have stainless steel exhaust stubs.

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

Been aircooled since 1973
Northwest Ohio

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: 66vairman ()
Date: April 14, 2018 11:00AM

JerryM Wrote:
-------------------------------------------------------
> Do I understand correctly the only difference in
> any 140 head is external casting features for bolt
> size and accessory accommodation?

AFAIK yes the modification was to mount the 1966 140HP A/C bracket. Later A.I.R pump brackets were mounted.

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: JerryM ()
Date: April 14, 2018 12:02PM

Wagon Master Wrote:
-------------------------------------------------------
> Smog 140's and I believe all smog heads have
> stainless steel exhaust stubs.


Got a tip from American Mel on that. Did a magnet test on my smog and non-smog engines and found smog 140's are stainless

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: john.jackson ()
Date: April 14, 2018 02:17PM

JerryM Wrote:
-------------------------------------------------------
> Wagon Master Wrote:
> --------------------------------------------------
> -----
> > Smog 140's and I believe all smog heads have
> > stainless steel exhaust stubs.
>
>
> Got a tip from American Mel on that. Did a magnet
> test on my smog and non-smog engines and found
> smog 140's are stainless

Stainless for the higher temps of sir injected into exhaust tubes. All A
I.R. engines

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: REM654DPG ()
Date: April 14, 2018 07:58PM

Jerry, another difference is in the castings that have six versus four valve cover bolt bosses. If you are planning on using aluminum valve covers with six bolts that will make a difference when choosing cores.

Regan Metcalf
Portland, OR

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: gnvair ()
Date: April 15, 2018 04:59AM

The 2 main casting numbers end in 728 (1965) and 570 (66-69). I have also seen service replacement heads ending in 864 that was stamped (these looked identical to the 570 castings). With each casting number were revisions. If you look at the heads you will see some additional numbers. For example 70A, 71A, 72A, 73A, etc on up to 80A or 81A.
These numbers seem to have some correlation to modifications engineering made to them. The later 570 castings with the higher numbers do not have the 2 center bolt castings for the 6 bolt valve covers.
Some of these castings also take into consideration the stainless tubes on the smog engines.
But back to the original question.....
GM reinforced the castings where the head studs go through on 3 of the 4 holes around each combustion chamber. If you look at a 728 casting you will see the upper head stud exposed at the rear of the right side head and front of the left side head. On the 570 castings the stud is encapsulated in aluminum via the reinforcements added. The earlier heads did not have much connecting the rocker box area to the combustion chamber area. Engineering must have felt strong enough about it to upgrade ALL of the castings on ALL of the heads starting in 1966 since it wasn't just 140's that got the upgrade.
Besides this, they increase the bolt thread side on the side fan shroud bolts from 1/4-20 to 3/8-16 as well as the bolt sizes at the ends of the heads.

Lee J

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: JimBrandberg ()
Date: April 15, 2018 06:39AM

I would guess that all 140 heads have similar combustion chamber volumes but I never really checked. CORSA Tech Guide has the volumes listed in a chart. Folks have been just swapping in whatever 140 head they have to repair a dropped valve seat for years, whether it's a good idea or not is debatable.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: JerryM ()
Date: April 15, 2018 10:38AM

gnvair Wrote:
-------------------------------------------------------
> But back to the original question.....
> GM reinforced the castings where the head studs go
> through on 3 of the 4 holes around each combustion
> chamber. If you look at a 728 casting you will see
> the upper head stud exposed at the rear of the
> right side head and front of the left side head.
> On the 570 castings the stud is encapsulated in
> aluminum via the reinforcements added. The earlier
> heads did not have much connecting the rocker box
> area to the combustion chamber area.

Very interesting! I've owned several 140 cars and parts in the last 40 years and never noticed this feature.

Attachments:

Options: ReplyQuote
Re: 140 Heads comparison
Posted by: Early Guy ()
Date: April 21, 2018 08:28PM

I have one NOS non magnetic stainless steel 140 exhaust tube part number stamped on flat relief area is 3910314 My 1970 GM parts book group 3.602 sleeve shows the same number for 65-66 and 68-69 at .002 oversize. they must have replaced the regular steel with stainless as service replacement parts.


Ray Johnson Villa Park IL 63 Spyder Conv. 140 EFI

Options: ReplyQuote


Sorry, only registered users may post in this forum.
This forum powered by Phorum.