I have an 84 camaro with a 305 LG4. it has what my dad tells me to be doublehump heads. My 2 questions are:
1. What is so special about them?
2. Would these work on a 350, with a mild build?

I have included two pictures....
Thanks in advance.

 

Ummm....

where to begin.....????....

Oh, right...

THOSE ARE NOT DOUBLE HUMP HEADS. If they are stock LG4 heads from a 305, they are not bad at all if you mod them for a street car. Bigger valves, good valve job, some port and bowl work, and they work very well on a 305 and are a nice addition to a street 350 as well.

Double hump heads actually look more like a letter B with the flat side down and humps facing up. You don't have that. Guys around here like sofakingdom will probably tell you that if you did have them, you should sell them to someone who restores cars and leave performance to something built in the last 25 years; use the extra money to buy beer. I tend to agree.

I honestly would rather have your heads for a mild street build on a 350 than the old double hump heads from the 1960's-1970 that don't have accessory bolt holes on them like yours do.

 

Thanks for the info, also, what would all that cost to do? Is it worth modding these, or getting other ones?

 

305 heads on a 350 will make WAY too much compression. Something like
11-ish to 1...

They have a small chamber thus raising compression on a 350.

11:1 might work with an Alum head because they can
take more heat without detonation.
An iron headed 11:1 compression 350 would be bad without
race gas & even then...

Summit sells thier own vortec iron head for around 300bucks (each)
They got standard iron ones for about the same price.

Sure beats searching for a good set of heads and then paying
a few hundred bucks getting them milled and a valve job.

 

A man after my own heart!

But yes, he's right; the heads that came on the 305s aren't double-humps. So your dad is a little over-enthusiastic on that point.

Those usually come with 416 casting; 58cc, 1.84"/1.5" valves. Not real good in stock trim. But with 1.94"/1.6" valves (350 size) installed in them, and port work to match, they can be OK. If you can do ALOT of the work yourself, especially the porting part, they can make a decent junkyard buildup.

As far as compression, that depends on the 350 and the pistons that are in it. If it already has good compression, then yeah, the 305 heads will make it too high. On the other hand, if the 350 is like most stock 350s from the early 70s on up, it has like 8.2:1 compression with the heads that are there; and swapping the 305 heads on one of those can bump it up to mid 9s. Not too bad, especially if a little more cam is also involved.

Here's a set of double-hump heads, showing the "Dolly Parton" casting mark.

 

Some cheap vortecs will give better performance and make up for the price at the machine shop.

 

Except for the new intake he'd need, and whatever other parts (SA rockers, or guideplates, pushrods, etc).

I ported 416 heads on my 350, with some chamber work, decking the block and flattops ended up with 10:1 CR on the nose. With a decent cam that works pretty good.

 

Vortecs would be better, even after machine work, BUT he would still need a different intake manifold (different bolt pattern and port layout), new valve covers and hardware, probably pushrods as well.

In the end it would be more expensive, but it might be worth the extra money too.