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Clark's C785 timing check
Posted by: bwells ()
Date: June 07, 2019 12:51PM

Folks,

I am having trouble with a new 110hp build and getting it to idle properly. I have tried many things and finally decided to ensure I got my timing gears meshed properly. I just checked intake timing on #1 and got these numbers @ .050 lift:
opens@2 degrees BTDC and closes @ 32 degrees ABDC. Lobe lift looked like about.240
inch. This is a Clark's C785 cam, that I assume is close to the GM 304 cam.
Are these numbers in the ballpark to ensure I did not jump a tooth or use a bad gear or cam?
Thanks much,
Bill

Bill Wells
North Texas Corvair Assoc.
www.northtexascorvair.org
61 Ramp
65 Corsa

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Re: Clark's C785 timing check
Posted by: AlecCarlson ()
Date: June 07, 2019 03:52PM

The stock intake lift for a '65 110 engine is .3907. If you're only seeing .240 something is seriously wrong.

Click here: 1965 Chev Corvair Heritage Specs page 59 (I think)

Alec



Edited 1 time(s). Last edit at 06/07/2019 04:01PM by AlecCarlson.

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Re: Clark's C785 timing check
Posted by: 66vairman ()
Date: June 07, 2019 05:28PM

I recall the GM lift and degree numbers were absolute, based on drawings. Today most cams come use a 0.050 lift reference as it makes physically degreeing the cam more accurate.

Bill - you said the intake was opens@2 degrees BTDC and closes @ 32 degrees ABDC.

Bob Helt's book said the 304 cam (using a 0.050" ref.) was OPEN 3 BTDC to CLOSE 35 ATDC. So based on Bob Helt's data your numbers seem O.K.

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Re: Clark's C785 timing check
Posted by: jjohnsonjo ()
Date: June 07, 2019 06:00PM

AlecCarlson Wrote:
-------------------------------------------------------
> The stock intake lift for a '65 110 engine is .3907. If you're only seeing .240 something is seriously wrong.
>
> Click here: 1965 Chev Corvair Heritage Specs page 59 (I think)
>
> Alec


.240 is without the rocker arm in the measurement.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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Re: Clark's C785 timing check
Posted by: vairmech ()
Date: June 07, 2019 06:26PM

AlecCarlson Wrote:
-------------------------------------------------------
> The stock intake lift for a '65 110 engine is .3907. If you're only seeing .240 something is seriously wrong.
>
> Click here: 1965 Chev Corvair Heritage Specs page 59 (I think)
>
> Alec
>>>>>>>>>>>>>>>>>>>>>>>>>>

He said lobe lift, not valve lift, .240 X 1.57 = .376

I put the numbers in my Dyno program and the power seems down from what it should be.

After idle does the engine run really good? What are your compression numbers? Are they somewhat even?

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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