double hump heads on a 78 engine

[sk8er32283]

I have an opportunity to buy some double hump heads #461 for about 400 bucks. Here is the info in the ad.

I took these heads on trade. They
have been rebuilt with 2.02/1.60 stainless valves, double valve springs, machined for screw in studs. They have not been run, I do not know specs on springs, was told they have hardened seats but it is tuff to tell without removing a couple of valves. They are casting 461 and should be 64cc chambers. I do not know who did the rebuild.

First question is will they work on a 78 350 engine and will it up the performance a lot or just a bit. Second question is that a good price for those heads. Any suggestions are welcome. I don't know much about heads except that theyear have a smaller chamber that will up the compression ratio a bit and help in the horsepower department. Thanks guys.

[bigmac73]

that is a lot of unknowns , especially since with todays after market aluminum heads the Double humps are dinosaurs and obsolete to most guys.

but they should work fine on a 78 , do they have the accessory bracket bolt holes??
I think pre 69 or 67 or so had no holes for brackets

[Ft.ValloniaStreaker]

I put a set on my '78 Z28 back in the day, and I"ll tell you it won't make a race engine out of it alone, but they'll be an improvement. Their old school and that's where it's at for a lot of guys. Like bigmac says do they have enough holes for your mounting brackets and AC?

[sk8er32283]

I dont have A/c so no worry there. I can't tell in the pictures if there are any mounting holes. If I don't have A/c do I even need to worry about that. Based on what is in the ad. Here are the pictures he has. What do you think these heads would be worth given all the unknowns. The guys took them on trade and is asking 400 but I bet if I could come with ammo about the heads I could talk him down a bit.

[70CHEVYBB]

The intake valves do not look stainless.

[leftybass209]

I'd do a couple quick checks for compatibility and quality of the heads. First, check what the compression ratio is for a 78 and what CC chamber heads it uses. This will give you the correct information to find out what compression ratio you will have with your new heads. Then, I'd run those heads down to a machine shop and have them leak tested and checked for hardened seats to be sure. It probably won't cost very much, versus installing them blind and finding out you have a problem.

[Coley]

Be careful here...the '461's did not have the front accessory mount taps so you will need a '60's style alternator mount bracket that goes off the water pump, intake, etc. Trucks and cars since 1970 almost all used the accessory mount taps for various brackets.
They are a good head and will add some power and compression to your engine.
My two bits.
Coley

[Mike C]

Good advice above. You said your engine was a 78 but not what vehicle it's in. If it's a 69 or newer with a long water pump and passenger side alternator, you are asking for lots of other problems.

Once again, if your vehicle uses a long water pump, you would be better off buying brand new Vortec heads and intake IMO.

[Five O]

461 heads will perform like a vortec head. Looks like the spring pockets have been cut to fit the bigger springs. The springs might be too much for your cam. Are they drilled for 3/8 or 7/16 studs? Do you have the rockers for them? Do they have a home porting job hiding in there? Any cracks? You've got a few questions to ask

[special-K]

i think the price is right and they are good heads. You'll just need the early alternator brackets and either the early exhaust manifolds (left side at least) or if you have headers you need the mount offered for early trucks w/headers. My question is what about the rest of the engine. As with any hi-performance engine components, you need the rest of the equation to get great results. They want to be with the right cam and higher compression pistons would be even better. It can go on from there. If you just want to go with better heads on a stock engine, you'd do better with 1.94s IMO

[mechanicalman]

Originally Posted by leftybass209

i'd do a couple quick checks for compatibility and quality of the heads. First, check what the compression ratio is for a 78 and what cc chamber heads it uses. This will give you the correct information to find out what compression ratio you will have with your new heads. Then, i'd run those heads down to a machine shop and have them leak tested and checked for hardened seats to be sure. It probably won't cost very much, versus installing them blind and finding out you have a problem.

x2

[mechanicalman]

Those 461 casting quench heads can have as small as 62cc chamber un-milled. And you may have a set that has been milled a ways, look at how far the intake valve extends past the border of the chamber. 2.02 valve will do that but not that far unless milled.
Also, if milled more than about .035 you run into intake manifold fitment issues.

And your 78 350 must have dish pistons or your compression will be too high.

[GRX]

Agree with all the above. You may be pushing your compression envelope with pump gas. And how is the bottom end? If your cylinders and rings are worn you are opening a can of worms bolting on a new tight set of heads.

[frankslagoon]

I've worked with these and the old angle plug heads a lot in the day. 2.02 really needs some rpm to keep the air comin in. I don't know about the rest of your motor. the 1.94 run way better until you really get crankin. my 2 cents. but that's a good price if they are as advertised.

[mechanicalman]

Originally Posted by frankslagoon

I've worked with these and the old angle plug heads a lot in the day. 2.02 really needs some rpm to keep the air comin in. I don't know about the rest of your motor. the 1.94 run way better until you really get crankin. my 2 cents. but that's a good price if they are as advertised.

X2. If it's a stock/stock engine 1.94 way better.

[mechanicalman]

Originally Posted by sk8er32283

First question is will they work on a 78 350 engine and will it up the performance a lot or just a bit. Thanks guys.

OK I'd rather see you get a set of these if you are stock or close to stock:

http://www.aeroheadracing.com/chevy.html

If you have dish pistons get the 65cc version or if you have flat-top get the 76cc version. 1.94/1.5" valves. Or have them make a custom set 1.94/1.6" valves for maybe $25.00 or so extra just don't get the 2.02 unless you are very high RPM cam, headers, low rear gear, etc.

[GRX]

Originally Posted by frankslagoon

I've worked with these and the old angle plug heads a lot in the day. 2.02 really needs some rpm to keep the air comin in. I don't know about the rest of your motor. the 1.94 run way better until you really get crankin. my 2 cents. but that's a good price if they are as advertised.

x3.

[mmiddle]

X4. 461s are pre bolt holes and the .202s are really more than a typical STRONG truck engine needs or wants. You will be miles ahead finding a newer set of vortec heads if you are after a great performing truck engine. 400 bucks is about top end unless you find some Vette or Camaro nut that needs that date code... Then sky is the limit on price, however the screw-in studs lower the price to some.
As Special-K said... there are a lot of unknowns about your engine and these heads. Personally, unless I had a flip lined up I would stay away from them.

[sk8er32283]

Big thanks to all that replied. It looks like I would be in way over my head with these. If anyone is interested in these they are for sale in east idaho 9th craigslist. Thanks again for saving me some bucks.