Differences Between 291, 461 and 462 Heads [Archive] - Chevelle Tech

: Differences Between 291, 461 and 462 Heads


Lionel-n-Chevelles
Jun 27th, 10, 10:52 AM
Hi Guys,
I am building a 383 for my 55 Chevy Nomad. I want to keep it looking old school and am starting with a 1970 4 Bolt Main Block (3970010). I am using an Eagle Forged Rotating Assembly.
What are the differences between the 291, 461 and 462 Castings? Which set of heads will work best? I was thinking of using a Comp Cams Magnum 270 Cam and Lifter Set.
The car will be street driven and will have a Vintage A/C System.
I have a modified 200 4R and a 1957 Olds Super 88 Posi with a 3.64 gear.
Any suggestions, advice and information is greatly appreciated.
Thank You.

70-SS454
Jun 27th, 10, 11:09 AM
I'd personally use Votec Heads that were drilled for the early valve covers and intake...

Tom Mobley
Jun 27th, 10, 12:24 PM
Tory,

All those heads are small chamber, does your 383 kit have dished or flattop pistons? You know, right, that those 60's heads are obsolete as far as ports and making power go?

If you're going to use a non-roller cam be sure to understand the stuff in the oil topics at the top of Perf and engine sections. Any error on the oil type will result in a flat cam.

Highway Star
Jun 27th, 10, 12:47 PM
Tory,

Old school engine? Cool. That thing sounds like it will definitely go for sure.

I found this looking for some good info to post for you regarding old school chevy heads...


This is from a waaaay old thread that google found for me. It is actually from TC...

A good post:

I got to tell you this: Iīve measured most of these camel hump heads (#186, #291, #461, #461x...) intake ports myself last winter, and they really were all the same. ALL OF THOSE CASTINGS MEASURED 165cc, INCLUDING THAT #461x.

I located tens of pairs of these old camel hump heads just by accident from a wrecking yard, and I was wery eager to return there again and measure them to find a superior head for few dollars. You can imagine my disappointment when I finally got to measure the intake ports, and they all were the same! Really! The intake port from a #461x is just as small (approx. 165cc) as from a #291, for example.

I had read from Hot Rodding magazines that there are some superior big intake port camel hump and fuelie heads cast by GM, and I thought they were either #461x, #292 or both. So now I know the superior head definetely is not the #461x...

On the latest Chevy High Performance Magazine there are quite many SB Chevy heads measured (both the intake ports and combustion chambers), and they even flowed them on a flowbench. Itīs a VERY good article! One camel hump head was there, namely the #492. Their measurement did not end up as big as mine, I think they got 159cc, but Iīm not sure. Gotta check that article again. Anyway my measurements are from stock heads, not ported, so what could be the difference between the magazineīs and my measurements? My measurements may be off by 1-2cc, but no more.

That wrecking yard I visited has got various types of those camel hump heads lying around. Ported, stock, with valve seats installed and without, small and big valves, screw and pressed studs, complete and bare, some cracked, some not... They cost less than $300 a pair. That may sound like cheap, but I wouldnīt install any of those heads straight without first checking (and maybe machining and fixing) them.

And to answer Bryans question: the main difference (in my opinion) between a #462 and a #461 (x or not) is the combustion chamber size. The #462 has got the normal approx. 64cc chamber and the #461(x) has got a bit smaller one with approx. 60,5cc. Just as Scooter said. So with the same pistons you get more compression (=power or problems...;) with the #461(x) heads.

Bryan, you said youīve got #292 heads there. PLEASE VERIFY THE INTAKE PORTS OF THOSE AND THE #461(x). Put an intake valve in itīs place in both heads and check which headīs intake port will swallow more water. By doing that you could end this never-ending debate about mystery GM SB heads! Please do that and try to be accurate. No accurate cc number is necessary, just the fact whether they are the same size or not.

I mean you could do me a BIG favor. Iīve been searching those "mystery" big port heads for some five years every time I went to a swap meet or wrecking yard, and Iīve already given up because I thought the best ones were the #461x castings. But what if the #292 is the one? You would send me on a mission again by telling me that #292 intake port is clearly bigger. I donīt care how much bigger, just the fact would put me on the road again..... ;)

Million thanks already.

Discussion here (http://www.chevelles.com/forums/archive/index.php/t-79036.html)


I'd be looking for the most runner volume you can get with that stroker.

Lionel-n-Chevelles
Jun 27th, 10, 1:22 PM
Tory,

All those heads are small chamber, does your 383 kit have dished or flattop pistons? You know, right, that those 60's heads are obsolete as far as ports and making power go?

If you're going to use a non-roller cam be sure to understand the stuff in the oil topics at the top of Perf and engine sections. Any error on the oil type will result in a flat cam.
Hi Tom,
The pistons are dished. Which Roller Cam is comparable to a Comp Magnum 270 Hydraulic Cam?
Thank You for your help.

Lionel-n-Chevelles
Jun 27th, 10, 1:27 PM
Hi Jake,
Thank You for the post. It was very helpful.

Highway Star
Jun 27th, 10, 1:48 PM
Comp makes a retro-fit hyd roller 270 magnum, but I don't know if you can get it on a billet core.

Wolfplace
Jun 27th, 10, 2:12 PM
Tory,

Old school engine? Cool. That thing sounds like it will definitely go for sure.

I found this looking for some good info to post for you regarding old school chevy heads...


This is from a waaaay old thread that google found for me. It is actually from TC...

A good post:



Discussion here (http://www.chevelles.com/forums/archive/index.php/t-79036.html)


I'd be looking for the most runner volume you can get with that stroker.


Pretty good info except the part about the 461x
They were in fact 170-175cc not 162-165 which is what I have measured the other heads at & they are pretty rare
There are heads with an "X" on them that are not 461x heads & this is where people get confused
The "desirable" X head will have the casting number as 461X
Others will have 461 with an X divorced from the actual 461 casting number

Be advised all of these heads do not have hardened ex seats & which can be an issue with todays fuels unless you use an additive especially if you are going to drive this hard, haul a load or put a lot of miles on it.

For what you are doing the differences between the heads except for chamber sizes as noted are not worth mentioning
Just realize that you can most likely build a brand new set of the "Street Replacement" aftermarket heads for less money which will have many advantages & be reasonably hard to detect except for the "purists" once installed ;)

Id's
http://www.fastnuf.com/Headguide.html

VORTECPRO
Jun 27th, 10, 8:00 PM
Hi Guys,
I am building a 383 for my 55 Chevy Nomad. I want to keep it looking old school and am starting with a 1970 4 Bolt Main Block (3970010). I am using an Eagle Forged Rotating Assembly.
What are the differences between the 291, 461 and 462 Castings? Which set of heads will work best? I was thinking of using a Comp Cams Magnum 270 Cam and Lifter Set.
The car will be street driven and will have a Vintage A/C System.
I have a modified 200 4R and a 1957 Olds Super 88 Posi with a 3.64 gear.
Any suggestions, advice and information is greatly appreciated.
Thank You.The combustion chamber. Use the 291s, there better.

Lionel-n-Chevelles
Jun 27th, 10, 10:49 PM
The combustion chamber. Use the 291s, there better.
Hi Mark,
Thank You Very Much.
What are the sizes of the Combustion Chambers for 291, 461 and 462 Heads? I have a set of each and will use one of the sets on the 383.

zombie1969
Jun 27th, 10, 11:40 PM
I cant help you with what the cc of the heads are but if you get a piece of plexie glass/some vasoline and a syringe that has cc readings you can check yourself easly.

Highway Star
Jun 28th, 10, 11:44 AM
Pretty good info except the part about the 461x
They were in fact 170-175cc not 162-165 which is what I have measured the other heads at & they are pretty rare
There are heads with an "X" on them that are not 461x heads & this is where people get confused
The "desirable" X head will have the casting number as 461X
Others will have 461 with an X divorced from the actual 461 casting number

Be advised all of these heads do not have hardened ex seats & which can be an issue with todays fuels unless you use an additive especially if you are going to drive this hard, haul a load or put a lot of miles on it.

For what you are doing the differences between the heads except for chamber sizes as noted are not worth mentioning
Just realize that you can most likely build a brand new set of the "Street Replacement" aftermarket heads for less money which will have many advantages & be reasonably hard to detect except for the "purists" once installed ;)

Id's
http://www.fastnuf.com/Headguide.html


I remember reading somewhere that the 461X wasn't really a production head, more like a "bowtie" racing head. I have read that they had much bigger runners, closer to 175. Seems that there is a lot of conflicting info out there. Even your link, Mike had a bad piece of info in it...claiming that the 624 smogger head is actually a 305 head with 1.84/1.50 valves.

Tom Mobley
Jun 28th, 10, 2:47 PM
the old info was that the 461X was bigger, but there's no X on the casting number, it's xisible through a water jacket hole in the deck. I remember seeing pics of this back in the early 80s but I've never seen a head like that.

Lionel-n-Chevelles
Jun 29th, 10, 11:05 AM
3782461X 60-63, Larger intake runners, 172/64cc port
3782461 327, 64-66 Double humpers or Camel hump 161/62cc port
3767462 327, 62-67, 161/65cc ports
3917291 302, 327, 350, camel hump, 161/65cc ports


Courtesy of:

http://www.kendrick-auto.com/chevrolet_head_casting_number_re.htm

Are the 462 and 291 Castings Identical?
I know that the 291s have a provision for the Temperature Sending Unit. Does the 462 Casting have the same provision?

Murdog
Jun 29th, 10, 11:56 AM
the only difference between the 461 and 462 is more meat in the valve spring area on 462, which allows machining for oversize valve springs...not familiar with the 291...try to find a set of 492's...angle plugs, best of the camelhumps...

sixt9er
Jun 29th, 10, 2:05 PM
All of the research that I done, led me to believe that the "461X" heads were used on the Corvettes with fuel injection. This is what I gathered from info researched on the old school double-hump heads. The 461 and 462 were slightly different, as mentioned above a few times. My first "budget" 350 had a set of home-ported 462's on it and it made decent power and a gang of torque. If torque is the OP main objective, the intake runner sizes of the 461, 462, 291, and 461X should make great torque due to the high-velocity ports that these heads offer. If all out HP is desired, then there are better choices for the 383 than these heads and the camshaft that you have chosen.
Usually, builders that do 383's are looking for tire-frying torque output. The 270 cam should work good with those heads. Keep in mind that for what-ever reason, small combustion chambers (461, 462, 291, 186 and 492 heads) tend to work more efficiently with a dished piston, as far as flame travel is concerned.
Good luck with the build...

spodrbik
Jun 29th, 10, 2:35 PM
I'm currently running the 462 heads with the magnum 280 cam with 4.56 gears in a 10 bolt rear end and a turbo 400 trans. I cleaned up the ports which are 64cc and matched the intake runners to the intake. It's a 283 with a holley 650 dbl/pump carb. This engine runs very strong in a 72 chevelle with 275/60/15 tires and tears them up without any problem. The heads are good heads for this motor, but for a 383 they will work ok it just depends on what you want.

Scott:thumbsup:

DZAUTO
Jun 29th, 10, 3:06 PM
There is no question that the 461-291 heads from the 60s hi-perf engines were old school. BUUUUUUUUUUUUUUUT, with careful re-work, they can, and will, make very good heads!!!!
USUALLY, there is plenty of metal to permit opening up the intake runners several cc's, and the REALLY good old time head gurus can shape them to be very efficient for serious performance.
For a street-performance engine, simply cleaning up the bowls, opening the seats up for 2.02/1.6 valves (on heads that were originally 1.94/1.5), and cleaning up and matching the intake runners/ports will go a long way to make these "old school" heads into good performance heads.
All of the above, WITHOUT doing a full blown port and polish, can be done at a fairly reasonable price and the results will be respectable.
I have a SB400 in my 56 Vette with 462 heads that have had a few "tricks" performed on them to produce an appearance of a REAL early head that performs well.
I carefully ground off the double humps and re-shaped a pyramid symbol on the ends to make them look like 57 power-pac heads. Then, I had extra bosses welded, drilled and tapped to permit installing early valve covers with the staggered bolt pattern.
This really produces an old school look! :D
ANY head, 69-later or aftermarket, will have threaded holes and flat machined surfaces on the ends of the heads which will be a dead giveaway that they are NOT early heads.

http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/headpyramid1.jpg

http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/9fincover.jpg

http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/dualholes.jpg

AZCamino
Jun 29th, 10, 4:51 PM
Are the 462 and 291 Castings Identical?
I know that the 291s have a provision for the Temperature Sending Unit. Does the 462 Casting have the same provision?

The 291 heads were 1968 only. That was the first year that the temperature sensor was located in the head. 1969 still had double humps but added the drilled holes and flat mounting surfaces for the 69 and later brackets.

Prior to 1968 the temperature sensor was in the intake manifold, so the heads did not have that feature like in 68 and later.

The 461X heads did not have the big valves. The 2.02 intake and 1.60 exhuast valves were first used in the 1964 model year and the head casting was apparently revised to accomodate the bigger valves.

Per Chevrolet by the Numbers, QUOTE After "G" of 1963, a "64" is cast above the casting numbers to differentiate between the early '461x casting and the '461 casting. UNQUOTE G = July.

Apparently, just removing the Xs wasn't considered to be sufficient to differentiate the revised 461s. The Xs aren't that visible, so the '64' was added.

Remember that the '461X heads were used in 1961, 1962 and 1963 with valve sizes 1.94/1.50 only. The revised 461 heads were available starting in 1964 models with either 1.94/1.50 or 2.02/1.60 valves, depending on application.

The later 461 or 462 heads would be my choice for a nostalgic look and high performance. Either buy a set with the bigger valves or add them. The 291s would be OK but would have the tell tale plugs for the temp sensor.

Also, here is a link to a photo at Super Chevy that shows the X on a 461X head. The heads on my 62 fuely look the same as this photo.
http://image.superchevy.com/f/technical/engines_drivetrain/cams_heads_valvetrain/8909930+w200/sucp_0712_15_z+1962_chevrolet_corvette+fuelie_engi ne_rebuild.jpg
__________________

DZAUTO
Jun 30th, 10, 11:31 AM
Here's closer pictures of the X. This is a 63 casting.
http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/100_1101.jpg

http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/100_1100.jpg

Also, not mentioned, but since we're on the subject, heads that originally had the 1.94/1.5 valves had an as-cast combustion chamber. But when the factory machined the castings for the larger 2.02/1.6 valves, they machined a relief adjacent to the intake valve. If you have 1.94 heads upgraded to 2.02, almost any good, knowledgeable machine shop will know how to machine this relief next to the intake valve.
You can see the differences below.
http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/100_1103.jpg

http://i65.photobucket.com/albums/h219/DZAUTO/Driveline/100_1102.jpg