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Corvairvan
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140...

Post by Corvairvan »

So hopefully soon after the paint shop straightens out what they did wrong, I will be pulling the 140 out of my 67. I bought her 5 years ago, with a fairly fresh rebuild. Only reason for pulling it is the clutch is slipping when hot and under hard acceleration.. That being said, what would be my best bang for the buck as far as a little more performance?? I was thinking doing a little hotter cam, maybe massaging the heads a little if there is such a thing?? Also keep in mind it is kinda tall geared, I assume 3.27??? Any suggestions are appreciated.....

erco
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Re: 140...

Post by erco »

The biggest single bang 4 buck on my 140 was swapping in 3.55 gears for my original 3.27. Easy swap, instant results.

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terribleted
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Re: 140...

Post by terribleted »

If it is a 3.27 the cheapest best way to get more spunk is switch the rear end to a 3.55, I would do this before I even thought about engine mods which are expensive for very small gains. First verify what gear it is the diff has marks on it that should tell you, but there are other ways as well.
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.
https://www.facebook.com/tedsautorestoration/

Located in Snellville, Georgia

erco
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Re: 140...

Post by erco »

In his book "How to Keep Your Corvair Alive", Richard Finch goes on a rant about how 14" wheels lug the engine, causing it to overheat and drop valve seats. But he never mentions the diff ratio, which is at least as important in that regard. Good book otherwise.

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bbodie52
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Re: 140...

Post by bbodie52 »

Left-Click the next two images to enlarge for better viewing...
Corvair Axle Ratios (From Clark's Corvair Parts Catalog, Page 389)
Corvair Axle Ratios (From Clark's Corvair Parts Catalog, Page 389)

Corvair Axle Ratios (Updated).jpg

These pictures of the right side of a late model differential may help. I enlarged the image and used computer photographic software to enhance the numbers, which are difficult to see...

Image
bbodie52 wrote:According to the Clark's catalog tech page, you should be able to locate a differential code stamped on the right (Passenger) side of the differential near where it bolts to the transmission. (Usually poorly stamped and hard to see).
joelsplace wrote:No, it is stamped into the rough casting vertically close to the parting line between the transmission and differential. Often too lightly stamped to read even with it out of the car.

I wouldn't be too quick with the idea of swapping camshafts. The stock 140 hp cam (also used in the 110 hp engine) isn't bad, and swapping the cam in a Corvair engine requires a complete engine tear-down with splitting the engine cases. It is not nearly as simple as changing the cam in a V8. Installing a poorly chosen cam in a Corvair can be a real pain!

If you want to know something about what works in the Corvair world, you might start with a reading assignment. This book contains a great deal of performance information about the Corvair. As a teenager I read the earlier version of this book in 1970 and found it to be very valuable and informative. It is a personal favorite, and here is a recent update...
:link: https://www.amazon.com/Performance-Corv ... +to+hotrod
Image


:chevy:
Attachments
CORSA Corvair Technical Guide 1+2 - Corvair Code Numbers.PDF
CORSA Corvair Technical Guide 1+2 - Corvair Code Numbers
(1.25 MiB) Downloaded 4 times
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

Corvairvan
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Re: 140...

Post by Corvairvan »

As always, you gentlemen speak volumes of logic and experience. I toyed with the idea of diff ratios, but was reluctant to do so. That is truly the most logical choice, as it does all ready have 14 inch wheels and tires.... Thanks guys!!

66vairguy
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Re: 140...

Post by 66vairguy »

erco wrote:
Thu Jul 02, 2020 9:31 pm
In his book "How to Keep Your Corvair Alive", Richard Finch goes on a rant about how 14" wheels lug the engine, causing it to overheat and drop valve seats. But he never mentions the diff ratio, which is at least as important in that regard. Good book otherwise.
Maybe many decades back 14" wheels were an issue, but what REALLY matters is the wheel and tire diameter/circumference. I've seen low profile 14" tires that were actually smaller in diameter/circumference than the stock 13". A fellow in our club went on a tour and EVERYBODY was passing him at first. When we made a stop he was complaining he had to go 82MPH to keep up with us. Well we were going 70MPH, but his itty bitty low profile tires made the his speedometer read fast, not to mention his engine was really high on RPM.

Yes 3.55 axle gears will allow faster acceleration. I've got 3.55 in one car and 3.27 in my other. the 3.55 is nice around town, but on the highway the 3.27 car is more pleasant at 70MPH. BTW a 205/70X14" tire the same (allowing for tolerances) as the old 7.00 X 13" tires as far as diameter/circumference, but it is a little wider for better handling. So a blanket statement the 14" wheels are too big is out of date and no longer valid.

I like Finch, but some of his observations are now out of date.

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Re: 140...

Post by terribleted »

66vairguy wrote:
Fri Jul 03, 2020 9:18 am
erco wrote:
Thu Jul 02, 2020 9:31 pm
In his book "How to Keep Your Corvair Alive", Richard Finch goes on a rant about how 14" wheels lug the engine, causing it to overheat and drop valve seats. But he never mentions the diff ratio, which is at least as important in that regard. Good book otherwise.
Yes 3.55 axle gears will allow faster acceleration. I've got 3.55 in one car and 3.27 in my other. the 3.55 is nice around town, but on the highway the 3.27 car is more pleasant at 70MPH. BTW a 205/70X14" tire the same (allowing for tolerances) as the old 7.00 X 13" tires as far as diameter/circumference, but it is a little wider for better handling. So a blanket statement the 14" wheels are too big is out of date and no longer valid.
Exactly how I feel about 3.55 vs 3.27 gears.
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.
https://www.facebook.com/tedsautorestoration/

Located in Snellville, Georgia

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