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Author Topic: 1.94 or 2.02 over the counter heads is there a???  (Read 5673 times)
opelitis1
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« on: April 30, 2008, 06:23:52 AM »

I have a non-matching set of over the counter hump heads numbered #3861492 dated K30 1 and 3973370 dated D23 0... Did these automatically come with 1.94s or 2.02s???  Is there a quick way to tell just by looking at them without measuring? How much distance is between the intake valve and exhaust valve of a 1.94 head vs distance between 2.02 intake valve and the exh. valve??? Both heads are press-in studs and I don't see any "factory grind relieving" in the combustion chambers.. Accessory bolt holes are already there...
Thanks!!! 
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jdv69z
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« Reply #1 on: April 30, 2008, 08:26:33 AM »

If the valves are practically touching each other they are 2.02's. If there is a gap, they are 1.94's

Jimmy V.
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Jimmy V.
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« Reply #2 on: April 30, 2008, 08:56:30 AM »

Pretty sure all 2.02's came with screw in studs for high performance applications too.
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1967 Camaro SS/RS 350
1966 Chevelle SS 396
1970 Chevelle SS 396
1967 GTO
69 Z11
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« Reply #3 on: April 30, 2008, 10:43:13 AM »

Pretty sure all 2.02's came with screw in studs for high performance applications too.

I think the first 2.02s with screw in studs started in 1969.  I know some of the early 2.02's were press in, they might have all been.

Edit:  Hmmm, after thinking about it, seems like some of the earlier 2.02s were screw in but didn't have the milled flat for the rocker stud.  The studs were screwed in, but you had to use two rocker arm nuts on the stud to turn them in and out.

Well, I guess that pretty well demonstrates how much I know about screw in rocker studs, so I guess I'll stop embarrassing myself now and let someone who really knows straighten this all out.

Thanks,
Hank Kimble
(you older guys will get the reference)

« Last Edit: April 30, 2008, 10:52:01 AM by 69 z11 » Logged

69 Z11
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Huggers at the Car Show
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« Reply #4 on: April 30, 2008, 11:58:36 AM »

You could be right, Hank. I was queuing off the cast date and his comment "accessories bolt holes are there". I'm not as familiar with the camel hump 2.02s of the 327, early 302 heads. The 461's I have are 1.94's with press in studs and it was going to cost A LOT to convert them to hardened seats, 2.02 valves and screw in studs. Shocked
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1967 Camaro SS/RS 350
1966 Chevelle SS 396
1970 Chevelle SS 396
1967 GTO
opelitis1
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« Reply #5 on: April 30, 2008, 12:21:14 PM »

Thanks gentlemen!!!  There is a gap and they are not close to touching each other.. I appreciate the help...   Gotta be the 1.95 ints.   Ted
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Blown 67 RS
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« Reply #6 on: April 30, 2008, 03:43:00 PM »

Are you sure that one head casting number isn't 3891 or 3991? 3861 is an odd number.

3973370 = 350 head with 1.72 intakes

All factory SBC heads were pressed-in studs prior to 1970.
If they had accessory holes it was after 1968. (Except some truck heads with larger holes)
Heads with 2.02 intake valve made between 1964 and 1970 had press in studs.

http://www.chevytech.com/3c10o12.html

http://www.chevy-camaro.com/chevy-camaro-chevy-head-codes.asp?group=1
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69 Z11
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« Reply #7 on: April 30, 2008, 05:43:01 PM »

All factory SBC heads were pressed-in studs prior to 1970.

Didn't the 69 Z/28 heads had guide plates that were attached with screw in studs?
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69 Z11
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« Reply #8 on: April 30, 2008, 06:41:16 PM »

Didn't the 69 Z/28 heads had guide plates that were attached with screw in studs?

Never mind, just checked my MacNeish book, 69 Z/28 heads were press in without guides.
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69 Z11
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opelitis1
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« Reply #9 on: May 01, 2008, 05:50:44 AM »

I will go down and check the numbers again since I am re-doing my inventory listings..
Blown 67 RS is correct in that the casting number is in fact 3991492 with casting date of K30 1... 64cc Straight plugs - press-in studs - accessory holes - and in the middle of the head there is a GM 56 - not sure what that means...  They originally came with 2.02s
The other head is 3973370 also 64cc with casting date of D23 0 straight plugs - press-ins - accessory bolt holes... Did a Google on these two numbers and apparently they were both over-the-counter heads with the straight plug configuration..  3370s originally came with 1.94s...
Spacings between the valves on the 2 heads are similar and are not close to touching..
Believe both to be 1.94s and not 2.02s...
Have corrected my listing according to show 3991492 instead of 3861492
Thanks again!!!   Ted
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JohnZ
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« Reply #10 on: May 01, 2008, 10:27:29 AM »

Factory screw-in studs and guide plates on heads with 2.02's started in 1970.
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'69 Z/28
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« Reply #11 on: May 01, 2008, 02:14:06 PM »

Factory screw-in studs and guide plates on heads with 2.02's started in 1970.

Thanks John.  I always screw this up (pun intended) because my 69 Z had screw in studs and plates.  I know now that heads were either modified or weren't the original heads.
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69 Z11
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Adz28
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« Reply #12 on: May 01, 2008, 04:00:51 PM »

3991492 with casting date of K30 1... 64cc Straight plugs - press-in studs - accessory holes - and in the middle of the head there is a GM 56 - not sure what that means...  They originally came with 2.02s

Just trying to confirm... Did all the 3991492 heads after 1970 come with 2.02s? Also, what were the performance differences between these service replacements and the stock 302 heads? Any improvement?
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68Zproject
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« Reply #13 on: May 01, 2008, 07:09:59 PM »

According to Colvin, these heads are similar to the 68 and 69 302 heads.  They had a part # of 3927187 or 3927186 until 10/9/70 and all 3991492's should have 2.02s.  There were some changes in the combustion chamber from the 3917291s along with the accessory bolt holes being added.  It doesn't say if they were an improvement or not. Take that for what it's worth, he does have some inaccuracies.
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68Z28
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« Reply #14 on: May 02, 2008, 10:53:33 AM »

Thanks for the reference.
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