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Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: July 25, 2022 01:38PM

Hi kids!

This is related to my other post on fixing some issues on my 65 Corsa but I wanted to call attention to my valve trian combo.

The 140 in my Corsa is rebuilt with an Otto 20 cam and I reused the stock valve springs from the engine core. So far I have broken 3 valve springs (one a while ago and 2 more recently).

My original thinking was to blame the old fatigued springs so I bought new Clark's stock springs.

[ssl.corvair.com]

Now I am nervous that the root cause of the spring breakages was not fatigue but the the spring design.

If I keep the revs below 5500 (doesn't do much up there anyway) am I fooling myself by thinking the springs will be ok?

James
65 Corsa
SF Bay Area

Re: Otto 20 Cam and Stock Valve Springs
Posted by: vairmech ()
Date: July 25, 2022 03:31PM

Did you check the valve spring installed height? Do you know what the coil bind height is of either valve spring you are using/used?

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

Re: Otto 20 Cam and Stock Valve Springs
Posted by: 63turbo ()
Date: July 25, 2022 08:13PM

Theres a real good reason they tell you to run a different set of springs with a cam like that. It is really hard on the valve seats and guides when the springs are not able to control the valve. It doesnt matter if you are revving the heck out of it or not... a TB-20 needs way stouter springs than stock. Always remember, 50% of the reason for valve seats falling out is from poor valve control. Once valve float starts the forces on everything in the valve train are tripled!

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



Re: Otto 20 Cam and Stock Valve Springs
Posted by: Seth Emerson ()
Date: July 25, 2022 08:15PM

Many people have used the Isky springs. Good for 6000. Be sure to check installed height and verify no coil bind.

Seth Emerson

Check my new Performance Corvair Web site: [www.perfvair.com]

Located in lovely San Jose, California

Re: Otto 20 Cam and Stock Valve Springs
Posted by: JimBrandberg ()
Date: July 26, 2022 05:03AM

There was a thread here last year where Crower springs are listed, I think by Regan. They're a fair bit cheaper than Isky. I like Isky but they are spendy, the retainers are about as much as the springs which will not accept stock retainers.
I'm a little surprised by how many cams get awful close to coil bind.
Some Otto 20 cams these days are noisy. I would think lifter noise equates to shock on the valvetrain system. I'm not sure about the turbo versions. They may very well have corrected the pattern by now too. Original Otto cams were good and if they strayed from the original pattern they may very well have strayed back.
I'm always happy to hear cam news good and bad. It can be hard to know what to choose.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Re: Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: July 26, 2022 07:42AM

Uncle!

Do it once, do it right (or at least redo it right)

These are coming my way.

[ssl.corvair.com]

I hope my Amazon spring compressor can handle them.

James
65 Corsa
SF Bay Area

Re: Otto 20 Cam and Stock Valve Springs
Posted by: AlecCarlson ()
Date: July 26, 2022 07:46AM

I put the C1386XA springs in my '66 turbo along with an OT-20 cam. It's been running 2 years with no problems.

Alec
Dahlonega, GA
1965 Corsa Convertible Turbo 4-Speed
Restoration "In Progress"

Re: Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: July 29, 2022 08:29AM

Does anyone know what the installed height is for the Clark's C8619 performance springs? Nothing came in the box and I can't seem to find it on the website.

James
65 Corsa
SF Bay Area

Re: Otto 20 Cam and Stock Valve Springs
Posted by: texas yenko dude ()
Date: August 02, 2022 06:59AM

You need to check them with a pressure gauge , but most likely between 1.780---- 1.800

Texas YENKO Dude
YS-070
YS-199
YS-320
Southeast of Disorder


Re: Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: August 02, 2022 09:23AM

Update:

I installed them to the stock height. The heads were professionally rebuilt and to my pleasant surprise, all of the spring heights were still within the shop manual spec (1.625-1.688).

I'm not sure I could get them to 1.800". I did not check the shims underneath the springs but I am sure they were not much thicker than .03".

Thanks for all the feedback. Its making me think

James
65 Corsa
SF Bay Area

Re: Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: August 02, 2022 09:40AM

Edit to my update: I could get to 1.800" with different retainers. I hope that's not required with these springs.

James
65 Corsa
SF Bay Area

Re: Otto 20 Cam and Stock Valve Springs
Posted by: KenHenry ()
Date: August 02, 2022 10:19AM

Clark's should have the correct installed height for the springs. Maybe give them a call? The Isky 4005 springs I used have an installed height of 1.687/115#. I think you want something in the 100-115# range.

You can rig up something to measure the spring force with a bathroom scale and large C clamp. Note that the retainers typically provide a little more compression to the inner spring than the outer. Good luck! Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

Re: Otto 20 Cam and Stock Valve Springs
Posted by: KenHenry ()
Date: August 02, 2022 10:32AM

This link has some interesting reading on valve spring pressure:

[www.n56ml.com]

FWIW Mike's Corvair parts sells the Isky springs in sets of 12, as well as the special retainers needed... Ken

Ken Henry, Rochester, NY USA
1965 Corvair Corsa
140 hp, 4 speed

Re: Otto 20 Cam and Stock Valve Springs
Posted by: jamesolefjensen ()
Date: August 02, 2022 11:17AM

From Clark's Technical Service on the question of the installed height for their C8619 springs:

"The installed height should be the same as stock."

It didn't take them but a 1/2 hour to get back to me. I wish all auto parts stores had Clark's customer service.

I am moving on with the spring installed at the stock height. I have enough of a warm fuzzy.

James
65 Corsa
SF Bay Area

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