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Valve spring pressure?
Posted by: KenHenry ()
Date: June 21, 2022 12:11PM

I have a CA Corvairs 270 cam w 0.441" lift that runs great but just broke a valve spring. It was an intake valve so the valve stem seal was also destroyed in the process. These have the flat inner spring which I believe is the stock style...

I have a set of Isky 4005 springs/retainers ordered and am curious what height/pressure I should install them at? I see 115# at 1.687 mentioned in the Isky specs rising to 240# at 1.187", w/ coil bind at 0.960". Spring rate: 250#/inch. Does this sound reasonable or should I go for a little less pressure closed? This is a recently rebuilt EFI street 140hp that I do not push past 5500 rpm.

Thanks for any input! Ken

0E1EC9C7-3C96-49B7-9AEE-74ABCF68C435 by kenhenry_06268, on Flickr

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

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Re: Valve spring pressure?
Posted by: dryenko ()
Date: June 21, 2022 02:15PM

I have used these with good results on street engines with less installed pressure.
Good for rpm's past 5500 rpm.
I would suggest installed spring height of 1.700 -1.710 "
That should give you a run in spring pressure of around 100#.

Bob C aka Dryenko
Dobson, NC 27017

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Re: Valve spring pressure?
Posted by: vairmech ()
Date: June 21, 2022 05:03PM

Yup, what Bob says!

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Valve spring pressure?
Posted by: KenHenry ()
Date: June 21, 2022 05:05PM

Thanks Bob & Ken thumbs up

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

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Re: Valve spring pressure?
Posted by: 63turbo ()
Date: June 21, 2022 08:59PM

Mine is around 125# closed, I think its 270 open, I believe the lift is .460. Titanium valve spring retainers and 23000 miles on the new cam. The engine has seen 6500 rpm a few times. No issues!

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

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]



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Re: Valve spring pressure?
Posted by: JimBrandberg ()
Date: June 22, 2022 04:50AM

I was intrigued a while back when it was reported that unlike the Isky 270, the California Corvairs 270 is okay to run with stock valve springs.
I was hoping that California Corvairs cams might be a little more repeatable compared to some others that may vary. I'm wondering if you got an actual Cam Card with it and if it measured out the same.
I don't know the lift to coil bind numbers by heart to know about your .441.
I've got some sets of good stock valve springs I'd like to use.
Isky springs and retainers don't come cheap.
I wonder if you had a coil bind issue or if it was just one of those things that happen sometimes.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Valve spring pressure?
Posted by: KenHenry ()
Date: June 22, 2022 05:24AM

Thanks Kevin, Jim. Jim, the CC-270 has similar lift/duration/overlap to the Isky 270, but 4* advance built into the profile. I found it to be true to the cam card but 4* more advanced than advertised, possibly due to no fault of the cam. I considered retarding it w an offset key but was tired of spending money and reasoned extra low end might be nice thumbs up. Read all about it here:

[corvaircenter.com]

Given the same lift I would expect the two cans (Isky/CC) to call for similar springs. Ken

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



Edited 1 time(s). Last edit at 06/22/2022 05:25AM by KenHenry.

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Re: Valve spring pressure?
Posted by: Wagon Master ()
Date: June 22, 2022 05:55AM

Is the 7-8 degrees of advance that your seeing, in camshaft or crankshaft degrees?

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Re: Valve spring pressure?
Posted by: KenHenry ()
Date: June 22, 2022 05:56AM

Crankshaft degrees

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

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