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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 08:32AM

The PG Crank is retarded 4 degrees so it advances the cam 4 degrees, The last thing you want on a PG Motor is retarded cam timing. Yes I to enjoy playing with cam timing. That's why I have an adjustable gear smiling smiley Mike

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Re: Do I really need to degree the cam?
Posted by: Brizo ()
Date: October 14, 2019 10:23AM

Much of the confusion on this issue is because so many engines we deal with have chain drive cams that rotate the same direction as the crank, but the gear drive Corvair cam rotates the opposite direction. Plus, GM retarded the 140 PG cam by moving the teeth on the crank gear rather than the entire gear, keyway or timing marks.

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

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 10:51AM

Ok , I just put a crank and cam together, If you retard the Crank it advances the rotation of the cam.
Im not that sharp but why would GM retard the cam timing on a PG. All I can think of is maybe so it wont creep at Idle ?? With the tall 1.82 first gear you would want as much low end torque as possible and as a general rule advancing the cam gives better bottom end. Any thoughts.. Mike

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Re: Do I really need to degree the cam?
Posted by: davemotohead ()
Date: October 14, 2019 10:57AM

Mike, GM retarded the cam in PG 140's to make it come in Later in the RPM range and give the 140 PG more top end power because they found the cam ran out of gas when the secondary's kicked in making the engine run flat, retarding the cam moved the power band up and gave the 140 PG a little more life at higher RPM. I think this is explained in one of Bob Helts books.







1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca



Edited 2 time(s). Last edit at 10/14/2019 10:59AM by davemotohead.

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 11:01AM

Ok that sounds logical but im confused,Ive really never had a 140 run out of top end. So they retarded the crank to retard the cam timing ??, That's what im questioning. Mike

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Re: Do I really need to degree the cam?
Posted by: JimBrandberg ()
Date: October 14, 2019 11:18AM

It goes against what my natural inclination would be but advanced for better low RPM torque and retarded for better high RPM torque is the rule of thumb as I understand it. It was given to me as a rule of thumb from a general engine builder before I ever considered the Corvair 140 PG application.
Again that is my understanding and I would be glad to learn if I'm wrong.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Do I really need to degree the cam?
Posted by: American Mel ()
Date: October 14, 2019 12:20PM

I do not want to argue with someone much more knowledgeable about engines than I am, but my understanding was exactly opposite of what Moto says.
I thought the 104 PG engine was tuned to have the power come on sooner (@ lower RPMs), due to torque converter losses.
My RB 140 that was installed behind a PG really came alive later, closer to the top-end.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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, '62 Monza Wagon, '63 Spyder, '65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dualy, approaching 400K
17'Terry

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Re: Do I really need to degree the cam?
Posted by: RCSmith ()
Date: October 14, 2019 12:42PM

The 140pg engine used the small 95hp cam
so they had the bottom end torque, GM then
Retarded the cam to extend it’s RPM range.

Ray C. Smith
'66 Corsa


Bergen County ,NJ

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 01:39PM

Theres got to be some GM Literature out there about this ????

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Re: Do I really need to degree the cam?
Posted by: FL103Dave ()
Date: October 14, 2019 02:03PM

RCSmith Wrote:
-------------------------------------------------------
> The 140pg engine used the small 95hp cam
> so they had the bottom end torque, GM then
> Retarded the cam to extend it’s RPM range.


This was my understanding as well.

We used to run an autocross car with a 140 4spd and a 95 cam. Really dug in good out of the turns. Also, a fun car around town.

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 04:48PM

According to my parts book, 65,66 and later,the 889 cam was the replacement for 110,140,180 auto and manual. there are 4 cranks listed, one specifically for the 140 PG but another listed for with AIR ? confusing to me. Doesent list the Crank Gear separately in my 73 book

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Re: Do I really need to degree the cam?
Posted by: steve c goodman ()
Date: October 14, 2019 05:15PM

grp 0.728 gear crankshaft


64-9 all excpt 140/pg 3847972

65-69 140/pg 3885399

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC



Edited 1 time(s). Last edit at 10/14/2019 05:17PM by steve c goodman.

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Re: Do I really need to degree the cam?
Posted by: RCSmith ()
Date: October 14, 2019 05:22PM

I wonder if the AIR crank was due to the
special distributor gear used to reposition the
distributor?

Ray C. Smith
'66 Corsa


Bergen County ,NJ

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 14, 2019 05:53PM

I don't know what the differences are on the gears, But I do know that if you Retard the Crank Gear it advances the Cam. With out a 140 PG crank I cant tell you what basic cam timing is. That PG gear could advance or retard the timing. Im not sure how you tell the difference with degreing one ?? Interesting Mike

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Re: Do I really need to degree the cam?
Posted by: davemotohead ()
Date: October 14, 2019 08:03PM

smoking smiley







1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca

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Re: Do I really need to degree the cam?
Posted by: Wagon Master ()
Date: October 14, 2019 08:22PM

As I look at those crank hubs, rotating clockwise, if you're viewing the same tooth, the left one has the crank gear retarded in relation to the crank throws. Advancing the cam gear, correct?

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Re: Do I really need to degree the cam?
Posted by: cnicol ()
Date: October 14, 2019 09:38PM

v8vair Wrote:
-------------------------------------------------------
> According to my parts book, 65,66 and later,the 889 cam was the replacement for 110,140,180 auto and manual.

Craig replies:
I'm not sure where you're getting that from.

In the 1973 parts book, Group 0.519:

889 is listed for Corvair & FC (95hp) and Sp. H/Per (140) w/P.G.2nd Design

EXCEPT (meaning NOT): Hi-per (110), 4/1BC (140), Turbocharger (180)


304 is listed for Corvair & FC w/ H/per (110), Sp. H/Per (140 MT) , Turbocharged (180), 1965 1st design Sp H/Per (140) P.G., and 68-69 w/ H/Per (110)

Items in parenthesis are my clarifications. Some edits for clarity.



304 was originally 180 Turbo only but engineering concerns with the original 110/140 891 cam led GM engineers and the parts department to recommend the 304 for all 110/140/180 except 140PG.


Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts




Edited 1 time(s). Last edit at 10/14/2019 09:45PM by cnicol.

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Re: Do I really need to degree the cam?
Posted by: REM654DPG ()
Date: October 14, 2019 09:40PM

It’s the terminology that has us all confused. Mike is correct in that if you retard the crank then the cam is advanced. And Dave is correct in what GMs intent was in retarding the cam but the diagram and everything we’ve have always heard says the “crank” is retarded.

If I’m correct in my findings and no guarantees here - As far as I can tell with the gears I have, if you look at it from the opposite side and reverence the key slot to the gear tooth you can see which direction the crank is moved with each gear.

The first picture shows a standard gear and its key location in reference to the gear tooth. The third picture shows the 4 deg. gear and its key location rotated CCW from the standard gear. This means that the crank on a 4 deg retard gear is actually advanced or rotated forward in its rotation which would then “Retard” the “Cam”. So, the title in the diagram should really say “4 Degree Retard Camshaft”.

Regan Metcalf
Portland, OR

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Re: Do I really need to degree the cam?
Posted by: v8vair ()
Date: October 15, 2019 05:40AM

Yup, The Crank gear for the PG is actually advanced and in turn it retards the Cam. Ok my Peas sized brain has absorbed the info and understands, A Picture always helps. Now lets talk about some other mystery like Rocker arm ratio !!!!!

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Re: Do I really need to degree the cam?
Posted by: JimBrandberg ()
Date: October 15, 2019 09:18AM

If we always talk in terms of The Intake lobe centerline as measured at the crankshaft with a degree wheel we will be talking the same language.
When you talk in terms of advancing the crankshaft gear to retard the cam it becomes too much for me to cope with.
I made a little diagram on the cabinet for when I'm using an offset woodruff key on a cam gear.
I think it's correct but I'm open to correction.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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