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  1. #1
    dapper
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    Default corvette cyl. heads "power pack" from 1960-67

    hello, i am looking for info on a cyl.head for corvette 60-67 called a power pack head. supposedly the corvettes in the late 50's and early 60's came with aluminun heads, which either warped or cracked, so a service bulletin went out to replace the aluminun heads with these power pack heads. what i want to do is get a copy of that service bulletin or info on the intake valve size, was it 1.72" dia. or was there a option to go up to a 1.94" dia intake valve. i know this is problaly very technical but i need this info quick! any helpers out there thanks dapper

  2. #2
    Administrator Tom Bryant's Avatar
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    1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)

    Default power pack heads

    Dapper,
    Welcome to the forum. I'll try to give you the short version of the aluminum head story so I don't end up rambling. Both of the '60 FI engines were to have aluminum heads with 1.94" intake valves and higher hp ratings. They were advertised and even people ordered cars thinking they were getting the heads. Never happened. They cracked between the valve seats and some even cracked during initial torquing. The '59 FI engines rated at 250 and 290 hp were carried over to '60 and the "Advertised Maximun Engine Performance" chart was revised in June 1960 to show this. There were only a few engines built at Flint with aluminum heads and they were sent to Warren Tech Center for testing.

    There were no Corvettes delivered with aluminum heads by the St. Louis plant. The rumors of cars being recalled because of aluminum heads cracking are false and just rumors. Since there were no heads delivered there were none to recall so there is no service bullitin relating to this subject. This is varified by a letter from Joe Pike (Chevrolet Asst National Sales Promotion Mgr. and later Corvette News editor, from where most of us knew Joe) dated August 1961 stating that "There were no 1960 or 1961 Corvettes produced with aluminum cylinder heads." The letter further states the use of the '59 engines in the '60 FI car and the new 315 hp engine in the '61. This '61 engine had an iron version of the aluminum head with the double hump marking on the end.

    You will see some of the alum heads in private hands as they were cast by Chevrolet and other sources including Alcoa in the mid '60s for use in an Indy engine project. All seem to have the '59 casting dates that were in the molds. I don't feel that these heads would be good for anything except a display novelty. They would crack if you tried to use them and they wouldn't be correct on a restoration.

    But you asked about Power Pack heads, didn't you? In the passenger cars the 265 and 283 inch engine were standard with low compression heads and a 2bbl carb. When given the higher compression heads, 9.5 on the 283, a 4bbl and dual exhaust they were called Power Pack. They were listed as such in the advertising also. The Power Pack 283 was available thru '66 in passenger cars. It was used in the Corvette through '61 but not called Power Pack since it was the base engine and not an option as in the other Chevrolet lines.

    These Power Pack heads were also used on the 250 hp 327 " engine available through '64 in Corvettes and Chevrolets. They carried 1.72 inch intake valves and 1.50 inch exhausts and were marked with a small pyrimid on the end. All '60 engines used the power Pack head 3774692. '61 Corvettes also used casting number 3774692 on 230, 245 and 270 hp engines. The '61 275 and 315 hp FI engines used casting number 3782461 with the 1.94s.

    The '62 to '65 327/250hp used Power Pack head casting number 3795896. The '62 through '64 higher hp 327 engines used either a 1.94 or a 2.02 intake valve head depending on the hp rating.

    I hope this is what you needed to know. If I can be of further assistance let me know.

    Tom
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry

  3. #3
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    1957 Rowley Craft Speed Boat

    Default

    Hello,

    I have a 1957 Rowley Craft boat with a 1967 #3892657 block and #3795896 "power pack" (stamped August 29, year- 3) heads.

    So, I looked these up but I'm a little confused... So, is this a 327?

    Thanks

  4. #4

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    '67 Marina Blue Convertible

    Default

    Quote Originally Posted by barkerco View Post
    Hello,

    I have a 1957 Rowley Craft boat with a 1967 #3892657 block and #3795896 "power pack" (stamped August 29, year- 3) heads.

    So, I looked these up but I'm a little confused... So, is this a 327?

    Thanks
    Almost all 657 blocks were 327's, and the 896 heads were used in many base-level car and truck 327 applications from '62-'67; those heads used the "small" (1.72" intake/1.5" exhaust) valves, and produced a 10.5:1 compression ratio with standard pistons.

    John
    '67 Convertible

  5. #5
    Administrator Tom Bryant's Avatar
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    Default

    Welcome to the CAC barkerco. It's good to know that some of these old threads are still helping new members. Is your boat something like this?



    Thanks for the input John.
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry

  6. #6
    MMM

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    '63 Coupe, '72 Convert, '02 Z06

    Default

    I could be wrong, but I believe the 1965 250hp, 327 Corvette engine used 461 heads with 1.94 intake valves. I do not have a quick reference to check on this, but I swear I read it once upon a time.

    Mike

  7. #7
    Administrator Tom Bryant's Avatar
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    Default

    You are correct. The last year of the 250 horse 327, 1965, did use the 461 castings. As far as I can see the only difference between the 250 and the 300 for that year only was the intake and carb. The 250 had the WCFB and the 300 had the AFB.

    Tom

  8. #8

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    Default

    Quote Originally Posted by Tom Bryant View Post
    You are correct. The last year of the 250 horse 327, 1965, did use the 461 castings. As far as I can see the only difference between the 250 and the 300 for that year only was the intake and carb. The 250 had the WCFB and the 300 had the AFB.

    Tom
    Tom -

    The 300hp (with manual transmission) also got 2-1/2"-outlet exhaust manifolds in '65; all 250hp applications and the 300hp with Powerglide got 2"-outlet manifolds.

    John
    '67 Convertible

  9. #9
    Administrator Tom Bryant's Avatar
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    Default

    Thanks John. I wonder what the real difference in output was between the two.
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry

  10. #10
    Member vettefinderjim's Avatar
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    Back in 1964, a good friend drag raced his 1963 Bel Air, 2 door with the 327/250hp and a 4 speed. He was in G/S as I remember, because the car was rated at 250hp. He ran very close to the more powerfull 327/300hp Chevies time and mph wise, so that old WCFB carb at 450cfm was the only hold back on horsepower. But not that much.
    enjoying the hobby since 1969

    http://www.vettefinderjim.com

  11. #11
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    1957 Rowley Craft Speed Boat

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    Quote Originally Posted by Tom Bryant View Post
    Welcome to the CAC barkerco. It's good to know that some of these old threads are still helping new members. Is your boat something like this?



    Thanks for the input John.
    Yep, that's the boat I purchased! There were only 26 of these boats made in Stockton, CA. Cor-ten steel hull, looks similar to Chris-Craft runabout.

    Bad news, water in oil. Pressurized cooling system with shop air and can hear leak under intake manifold, pulled off and found 2" small crack in water jacket on intake side on #3. Also cylinder pitted on #1 (assume from water being drained back from exhaust cooling), has water line around it. Motor runs great though...

    Luckily, friend has a 67' 327 block that I can use...

    Thanks all for info!!!

  12. #12
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    Quote Originally Posted by Tom Bryant View Post

    You will see some of the alum heads in private hands as they were cast by Chevrolet and other sources including Alcoa in the mid '60s for use in an Indy engine project. All seem to have the '59 casting dates that were in the molds.

    Tom, just found this information you posted eons ago. This is the first I've read of these heads, all '59 dated, being produced in the '60s. When in the '60s were they made? How did you learn this fact?

    Here is an example of one such head:



    Jim

  13. #13
    Administrator Tom Bryant's Avatar
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    Default

    Hi Jim,

    I barely remember writing that. I'll have to see if I can find that info again and get back with you.

    Tom

  14. #14
    Administrator Tom Bryant's Avatar
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    I've been searching but I haven't found the exact source yet. I would bet that it was in the Restorer. Seems to me there was an in depth article on these heads at one time. I'll keep looking.

    Tom

  15. #15
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    Thanks for looking, Tom. Maybe I can trick someone with one of the new searchable Restorer CDs to see what they could uncover.

    Jim

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