350 - Team Camaro Tech
Engine General Engine Discussion.

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  • 2 Post By Garfields Maro
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post #1 of 10 (permalink) Old Jan 20th, 20, 12:27 PM Thread Starter
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danny
 
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350

Does anyone know anything about double hump heads? Just trying to learn a bit on them. I have a 68 350 With them on.
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post #2 of 10 (permalink) Old Jan 20th, 20, 01:32 PM
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Brian
 
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Re: 350

These heads appeared on 327 and 350 cubic inch engines across most of the 1960s (beginning in 1962). Although there are some variations, they generally have small chambers for the high-octane unleaded fuel readily available at the time, smaller intake ports and valves that measured either 1.94 for the intake and 1.50 for the exhaust or 2.02 and 1.60 respectively.

69 Hugger Orange 396 M20 3:31
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post #3 of 10 (permalink) Old Jan 20th, 20, 03:27 PM
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Dave
 
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Re: 350

They were designed in 1956 for the Fuel Injected 283 horse 283 and the 1962 360 horse 327 engine. They are old and crusty and will not offer any more horsepower today than they made back in 1962 with a solid 30-30 cam and mechanical fuel injection.

All power comes from the cylinder head. If you want modern SBC power of 500 to 600 hp then you will have to have a modern computer designed head and cam design. Old heads won't get you there.

If those humps are important to you buy an AFR or Trick Flow head and ask them to CNC mill those humps into the aluminum head ends for you. Sand blast the ends to give a sand cast look and paint them Chevy Orange.

Easy as pi to get 500 horse out of heads with humps on them.

Big Dave
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post #4 of 10 (permalink) Old Jan 20th, 20, 08:54 PM
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Garth
 
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Re: 350

I'm thinkin Dave is referring to "Power Pack" heads that originated in the mid-late 50's. Double hump were a little later and I'm not sure what the differences were ?

As mentioned, they had smaller combustion chambers (higher compression) and larger valves than standard heads of the time. Compression was increased from 8.75 to 10:1 on a 68 327 and 10.25:1 on the 350. 327 L30 and 350 L48 used the same heads.

Not everyone needs 500hp to enjoy the cruise. 350-400hp isn't difficult to attain using these old Chevy heads.
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  • '68 RS, AA, 749, L30, M(uncie)20 (originally a 3spd), 15yr backburner resto........
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post #5 of 10 (permalink) Old Jan 21st, 20, 01:06 PM
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Rufas
 
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Re: 350

Double hump heads were called "F I heads", "Power Pak heads" had a triangle above the base rectangle, very different heads.
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post #6 of 10 (permalink) Old Jan 21st, 20, 01:52 PM
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Re: 350

Quote:
Originally Posted by Larger Dave View Post
T

If those humps are important to you buy an AFR or Trick Flow head and ask them to CNC mill those humps into the aluminum head ends for you.

Big Dave
TF makes a "double hump" head if OP wants a more modern head

https://www.summitracing.com/parts/tfs-30210003
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post #7 of 10 (permalink) Old Jan 21st, 20, 04:49 PM
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alex
 
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Re: 350

WELL Danny HERES MY TWO CENTS. I AGREE WITH DAVE RAY GARTH AND BRIAN NOT EVERYONE NEEDS THE HIGH DOLLAR STUFF TO MAKE SOME POWER AND HAVE FUN WITH THE CAR ESPECIALLY IF THERE ARE BUDGETARY CONSTRANTS. ALTHOUGH BIG DAVE IS RIGHT THE POWER IS IN THE HEADS HE TENDS TO GET A BIT TOO TECHNICAL FOR A SIMPLE QUESTION AND NOT EVERY ONE HAS DEEP POCKETS GOD BLESS HIM IF HE DOES. WE RAIDED THE BONE YARDS IN OUR YOUTH TO GRAB THOSE HEADS. THEY WERE MOSTLY WITH THE 1.94 INTAKE BUT WITH A NICE CAM INTAKE AND HEADERS THEY WILL MAKE DECENT POWER TO ABOUT 5500. ITS ALL IN THE COMBINATION OF COMPRESSION AND THE VALVE EVENTS, SOME CAMS ARE BETTER THAN OTHERS . THE ISKY 270 MEGA IS A GOOD ONE HOWARDS MAKES A NICE ONE AND U D HAROLDS 276/286 IS ALSOA GOODONE. SOME OF THE NUMBERS TO LOOK FOR ARE 461 /462 /993 / 186 OF COURSE THIS DEPENDS ON THE YEAR AND HOW THE ACCESSORIES BOLT UP. HOPE THIS HELPS YOU OUT,BUT IF YOUR GONNA SPEND MONEY ABSOLUTELY BUY AFR THEY ARE THE BEST OUT OF THE BOX AND DONT GO CRAZY ON RUNNER SIZE. AL
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post #8 of 10 (permalink) Old Jan 21st, 20, 05:26 PM
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I have a 302 in my car. When I built my engine my head's needed alot of work. They are the 69 double humps with 202 intake valves and the accessorie holes. I had a set of Edelbrock preformer heads. Not RPM heads, the earlier ones. I put the Edelbrock heads on. The engine ran great. Last winter I had all the exhaust seats replaced along with guides and valves. Put them back on my 302. I couldn't believe how much of a difference the aftermarket heads made in performance. When the smoke cleared I had more money in the original heads than I would in a decent set of aftermarket heads. I wanted the original look and that's the only reason I switched. If you have to buy the heads and then get a machine shop to rebuild them, might as well get a good set of aftermarket heads. A matched set of heads and camshaft will make power. It is what it is.

X-77 keith
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018
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post #9 of 10 (permalink) Old Jan 21st, 20, 07:10 PM
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Re: 350

I also have a 302 with double hump heads. Had them cut to 2.02, 1.60 valves, all machine work and port matched to Victor Jr intake, runs well but if I recall work on the heads was about $800 in 1985. You can buy aftermarket either Cast Iron or Aluminum today that will perform better for less. Really don't know what $800 in 1985 equates to in 2020. I have a set of Aluminum heads in my closet to tone down the compression on my 302 but that will be another thread when I start to get motivated.

68 302 M20 - 85 IROC Z
The older I get the faster I was.
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post #10 of 10 (permalink) Old Jan 21st, 20, 08:07 PM
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Yeah, I have about ba grand in the double humps now. Stainless valves, new exhaust seats, springs, retainers, studs and guide plates. All to look more original. I am thinking about running the 302 for another season , ND next winter putting a 409 small block I have in the corner of the shop in it. Then just beat the snot out of it. Car shows are ok, but might try autocross.

X-77 keith
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018
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