I have a buddy that has a 327 with factory double hump heads on it out of a late 60's suburban. Now I've heard of double hump heads and I actually was the one that noticed they were double hump heads. (obviously the double hump casted into the head)
i was wondering if these would be an upgrade from the factory 350 heads in my 79 Camaro Rally Sport. I can get them really cheap. And if anyone could elaborate on what stands out in Double hump heads compared to other factory heads please feel free to contribute your knowledge.

 

If you can get them cheap I would buy them in a second check out the casting number there are different versions. They are a closed chamber 64cc head which offers a higher compression and supierior burn characteristics performance wise than your open chamber 76cc heads and more than likely flow better.

 

what is the risk of burning up my pistons by switching to these heads, If any? I have a mild street cam, headers, edelbrock intake, edelbrock carb, Pretty sure stock internals. i will check out the casting number. One more question will my headers still bolt up to the double hump heads?

 

your headers should still hook-up,i would make sure that all the other threaded holes thats supposed to be are there.powersteering mount,alt.mount and anything else that bolts up to the head.some castings dont have the holes and you have to drill them.if you switch to this head i would run nothing but 93 octane and if you still here a little knocking i would throw a bottle of octane booster in the tank.other than that you will notice the h.p. gains.

 

This was a real popular upgrade in the 70's and 80's as there wasn't much else around to choose from. Works very well. Might have to increase the octane on the fuel you run and or have the distributor recurved. They would be a good upgrade for the smogger heads you probably have now...

Take a look at the plugs on the double hump heads. There were two types, angled plug and straight plug. The angled plugs had the plug tips angled towards the exhaust valve. They were the most desirable. The straight ones went straight in.

If these are the old style head, then they will not have accessory mounting holed on the front of the head.These heads came in a 1.94 or a 2.02 intake valve arrangement. I can tell you that unless these heads have been re worked, you can count on having to replace the exhaust seats. As the name implies, unleaded fuel has no lead in it. In the early years designers relied on the lead to lubricate the exhaust valve seat. To solve this problem when un-leaded fuel came around, designers had the exhaust seats hardened (usually by laser). So if these are the old style heads, and haven’t been rebuilt then the exhaust sets are probably hammered into the heads. I've seen them with the valve almost .1-.3 inches sunk into the head....

So what I'm getting at here is that these heads can get pretty expensive to fix. If they are worn badly then you could be looking at a Lot of cash to get them usable. For example

If you do have to rebuild them, then consider the following. When the folks came in with small block heads most time they needed newvalves and usually they were the small valves..I recommended that they upgrade the intake valve to the next size.The cost difference was like 50 cents a valve...most that were gone far enough to need valves, also would need intake seats. So why cut the old seat out and put an insert in, when all you need to do is put in a large valve and open up the pocket a little.(The seat and install would run $8 a hole) I charges $1 to cut pockets for bigger valves... The same applies to the exhaust. If you are going to have to buy valves and hardened seats anyway, then move up to the 1.6 exhaust valve...
Chances are your guides will be shot to hell as well.
The good thing about these heads is that they are a heavier casting head.

So my advise is to find a good shop and go ask them what it would cost you to rebuild those heads, worst case,

I think you'll find it less expensive to just buy a set from Summitracing.com the last time I looked, a castiron set, 67CC chambers, 2.02 intake 1.5 exhaust was like $650 a set fully assembled and ready to go....

If you want to invest in the old set of double humps, then they will be a better head than what originally came on your 79.
I'm not saying that these heads are junk, if uncracked there still desirable casting for the right folks, but, I’ve gone through this drill many times with folks..sometimes it just doesn’t pay to rebuild the old stuff

Hope this helps
Good luck
Greg

 

The other thing to check is the casting numbers and the date codes, I have a set of 186 number double hump heads that are dated 1969, same heads as used on a 302 69 Z/28, a Z restorer may be interested, I was offered $750 for my set, a buddy said he thinks they are worth more like $1200-$1500. Year One may have the info on their web site, seems like I saw it on one of the big supplier sites.

 

"The old days of looking for a set of "double hump" heads are history".
John Lingenfelter

 

I have a set of double hump heads from a 1971 corvette. they are 202 fuely heads that they call them on my camaro they came off my 327 that was in a 68 nova I had ..so yes i would get them.

 

If you want the heads for a restoral project, then get them. Otherwise the heads on the market noware a whole lot better.

 

the double hump heads are great for restoration like pete said , but the L31 Vortec heads can be bought new for about $260 ea. and flow ALOT better that the double humps (even with 2.02's and 1.60's). the L31 heads do require a different intake manifold because they only use 4 intake bolts per side (the old ones had 6 and were at a verydifferent angle) i built a 383 about 5 yrs ago using off the shielf vortec heads with Comp. Cams LS1 valve springs and the engine made 441hp and was still very street friendly.... my $.02