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Author Topic: Questions about "O" Rockers 3974290 for 69 Z/28  (Read 1159 times)
Bryan302
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« on: April 14, 2014, 01:06:43 AM »

I have decided to go with a "140" cam instead of the "346" cam.  I have everything NOS, including the 3927142 valve springs, retainers, valves, etc.  My question is..  Are the 3974290 "O" rockers arms good enough to be compatible with and intended to be used with the "140" cam?

If a person were to build a set of 3974290 rocker arms from the current sources of NOS parts, ebay, camaro shops, etc.  Would he still get the same "O" rocker out of the current 3974290 box?  Are they still made the same, heat treat, hardness, etc.  Do the new ones still have the "O" on them?

Does anyone know if the new replacement part number of 10089648 gets you an "O" rocker?  My dealer says that the 10089648 is a direct replacement for the 3974290, but I kinda doubt it!

What aftermarket brand such as Crane or Manley, with the part number, would replace the "O" rocker?

Please advise and suggest.

Thanks,
Bryan
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Bryan S.
1968 RS Z/28, 12E, PNT R2, TR 749
1969 Z/28 X33, 05A, PNT 52 52, TR 719, endura bumper
Kelley W King
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« Reply #1 on: April 14, 2014, 09:06:43 AM »

I think I read Jerry M,s Z turns 8600 rpm with stock rockers. You might want to contact him.
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69 Z28 RS Scuncio Hi Performance
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68Zproject
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« Reply #2 on: April 14, 2014, 09:43:38 AM »

http://www.camaros.org/forum/index.php?topic=6862.0
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BillOhio
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« Reply #3 on: April 14, 2014, 08:07:45 PM »

Bryan do you have stock retainers or the aluminum ones?
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1969 Z28, Burgandy, numbers matching, 12,900 miles
1967 Plymouth GTX Hemi, 4 speed, dana
1961 Chrysler 300G convertible
Bryan302
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« Reply #4 on: April 15, 2014, 02:26:11 AM »

Hi Bill,

I have the steel retainers, pn#14003974 for the 3927142 spring.  By the way, I noticed a notation under the listing of the 3927140 cam in Hooper's book, in the parts listing in the back.  It stated to use thrust bearing 3887871.  Do you know if this bearing is critical to the use of a 140 cam?  Exactly where is the bearing used, is it a type of cam bearing or like a cam button for the timing gear?  As you can tell, I never heard of it.  Thankful for any help!

Thanks,
Bryan
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Bryan S.
1968 RS Z/28, 12E, PNT R2, TR 749
1969 Z/28 X33, 05A, PNT 52 52, TR 719, endura bumper
jdv69z
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« Reply #5 on: April 15, 2014, 07:26:44 AM »

I would think it would be like a cam button, for thrust loads which would be from any for and aft movement of the cam and gear.
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Jimmy V.
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« Reply #6 on: April 15, 2014, 07:49:59 AM »

I'm not familiar with that part, or PN, either, but here's an old ebay listing with a photo.  I don't recognize the part, and it's identified as a part for a 454 Mercruiser-Quicksilver??  Could that be an error in Hooper's book?

http://www.ebay.com/itm/GM-GMC-3887871-CAMSHAFT-THRUST-BEARING-FOR-MERCRUISER-454-QUICKSILVER-23-49124-/181326780245?nma=true&si=kA4%252FKicFYZKSnm4atRU9XiLTZXU%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Bryan,  re the 140 cam.. back in the late 60's and early '70's, I knew a couple of folks who tried the 140 cam, and neither realized any benefit from it nor were they happy with it (in street cars, used heavily for street racing).   I suspect your experience would be the same or even worse for how I suspect you'll use your car.

How was Super Chevy Memphis?  Smiley

Gary
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
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Bryan302
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« Reply #7 on: April 15, 2014, 02:25:09 PM »

Hi Gary,

After seeing that picture of the part, I don't think it is a relative part of the 140 grouping.  There is not even a place I can think of, it could go, especially related to the timing gear.

Memphis was very good.  The Z parts were thin.  I saw five DZ carbs, six 472 intakes, a 68 BV rearend, three or four 403 bell housings, one each 668 and 456 pulley, one endura bumper, a nice set of guages, a pair of non drip valve covers, and a early set of 69 Z exhaust, and that was it.  For someone, that would have been something to dance about, I didn't find squat.  I did pick up a good 367 starter, but not my date.

Thanks for finding that part.  Maybe someone will know about it.

Thanks,
Bryan
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Bryan S.
1968 RS Z/28, 12E, PNT R2, TR 749
1969 Z/28 X33, 05A, PNT 52 52, TR 719, endura bumper
luv2sixty9
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« Reply #8 on: April 15, 2014, 03:46:24 PM »

Yes, the "O" Rockers can be used with the 140 Camshaft.
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1967 Z/28 Butternut Yellow
1969 Z/28 Rally Green
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JohnZ
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« Reply #9 on: April 16, 2014, 10:11:53 AM »

My question is..  Are the 3974290 "O" rockers arms good enough to be compatible with and intended to be used with the "140" cam?

If a person were to build a set of 3974290 rocker arms from the current sources of NOS parts, ebay, camaro shops, etc.  Would he still get the same "O" rocker out of the current 3974290 box?  Are they still made the same, heat treat, hardness, etc.  Do the new ones still have the "O" on them?

Does anyone know if the new replacement part number of 10089648 gets you an "O" rocker?  My dealer says that the 10089648 is a direct replacement for the 3974290, but I kinda doubt it!

What aftermarket brand such as Crane or Manley, with the part number, would replace the "O" rocker?

Please advise and suggest.

Thanks,
Bryan

GM hasn't manufactured the "o" rocker arm for decades - the only stamped rocker arm available from GM these days is the "guided" rocker with the "ribs" to keep it centered on the valve stem, and you can't use that rocker with solid lifters.
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