1963 Cylinder Heads

[Stuart F.]

Have been told by one reliable source that only 360 hp engines (F.I.) use the 461-X heads (62 &63), and that my 340 hp engine has regular 461 heads (which have never been off my engine to verify). Another NCRS member owning a 63 Z06 advised that the - X heads were used on the 340 hp and even the 300 hp engines. Could someone clear this up for me. It has been written that the - X heads are rare and therefore valuable, and that they show flow numbers on a test machine equal to the latest cast Vortex heads. Comments please.

[Duke W.]

Re: 1963 Cylinder Heads

Oh really! Who's your reliable "source"?

Current thinking is that all 461s cast for the '61 to '63 model year engines are of the "X" variety. The list of engines includes 283/275, 315 HP and 327/300, 340, 360 HP. For sure the OE heads on my '63 340 HP are 461X, and all 461X heads were built with the 1.94/1.5" valve set.

From '64 to '66 the 461 castings were non-X and port inlet volume dropped from about 172 to 160 cc, but SHP versions got the 2.02/1.6" valves. This 160cc port volume was maintained on all later "big port" Gen I heads, including those with the larger 76cc chambers.

Does the OE 461X with 1.94/1.5" valve flow better than the OE 461 non-X with the 2.02/1.6" valves? I don't know because I have never seen data for these two configurations that was taken by the same source, but I suspect they are in the same ball park. Typical OE flow numbers for all "big port" heads are about 200/140 CFM at 0.5" lift, 28" H20 depression regardless of valve size.

I have seen flow numbers on various "massaged" 461X, 461, 462 and later big port heads, as high as 235/190 CFM at 0.5" lift, 28" H2O depression and by massaged I just mean pocket porting/port matching/chamber relieving and good multiangle valve seats with a top cut off the valves to eliminate the unused portion of the seating surface - no "porting" of the interior.

Valve size is not a determining factor as I have seen the 1.94/1.5" valve set flow about the same as the 2.02/1.6" set. The key to flow is getting the seat to bowl blending right, not valve size.

With these flow numbers, a LT-1 cam and all OE valvetrain, cast iron exhaust manifolds, and the OE SHP manifold and carb a 327 will make 325-340 net HP at 6500 with usable revs to 7200. In this configuration the inlet manifold is the limiting factor, not the heads

I believe the above flow numbers are better than off-the-shelf Vortecs but the Vortecs can probably be massaged to higher numbers. It's debatable if higher flow will produce more power up to 7000 on a 327. Above that, maybe. How high do you want to rev?

The same applies to most aftermarket heads of no more than 190cc port volume.

These vintage heads don't take a back seat to "modern" heads of reasonable port size for a carbureted road engine, but it takes some work to get them to maximum flow potential because the high chromium iron makes the material very tough. Well into the seventies I recall stories that some sprint car engine guys preferred them to even the new GM offroad heads because they believed the 461X castings were more durable, and a "seasoned" set of 461s was often the starting point for a sprint car engine.

I don't think 461X heads are particularly rare - A lot of 327/300s with 461X heads were built because it was a popular engine option in '62-'63 passenger cars. Few are really interested in 461X heads, today, so they are nearly forgotten, but they are out there in the dusty recesses of garages. I have an acquintance who recently picked up a used set for $125. They appeared to be untouched OE - just taken off an OE engine and set aside. If you find any they will probably have casting dates that correspond with '61 to '63 model year useage.

Duke

[Joe C.]

Re: 1963 Cylinder Heads

Have been told by one reliable source that only 360 hp engines (F.I.) use the 461-X heads (62 &63), and that my 340 hp engine has regular 461 heads (which have never been off my engine to verify). Another NCRS member owning a 63 Z06 advised that the - X heads were used on the 340 hp and even the 300 hp engines. Could someone clear this up for me. It has been written that the - X heads are rare and therefore valuable, and that they show flow numbers on a test machine equal to the latest cast Vortex heads. Comments please.

Welcome Stuart, and thanks for the interesting post. As Duke said, the "X" heads were used for many applications in from 1961 - 1963, even trucks! I'm not certain if anybody knows, for sure, why they were used in certain applications, and not exclusively for the SHP engines. I would guess that they would have been preferred for use with the L76, as well as the L84, since they were essentially the same engine except for the inlet manifold and carburetion.

I suspect that the "X" head, with its larger intake port was used with the "Duntov" cam, because that cam did not have enough overlap to erode low/midrange torque. The larger intake port would provide more horsepower with a slightly higher power peak, but at the expense of low/midrange. The 3736097 (Duntov) cam, with its relatively mild 228/230 durations and low lift (.395/.401), had enough low/midrange to spare, but benefited from the boost in peak power. In 1964, the SHP engines were equipped with the much "bigger" 3849346 cam, AKA the "30-30". With its long 254/254 durations and relatively high lift (.485/.485), it produced less low/midrange torque than the earlier SHP engines, but prodigious peak power. This engine can be characterized as "peaky", and needed the C/R transmission in order to keep the RPM's in the sweet spot. The higher lift cam also would benefit from larger valves. Because of these characteristics, it is my guess that Duntov ordered his engine team to abandon the idea of a larger intake port, in favor of larger valves, to supply the hungry engine for more charge at high RPM. It turns out, that in stock form, the "large valve" heads flow only marginally better than the "small valve" heads (standard, or "X" version). Interestingly, if an uninformed machinist decided to upgrade to large 2.02/1.6 valves (easily done) without modifying the combustion chamber, the resulting product would actually flow LESS than the 1.94/1.5 valved versions.

These heads, (with the 2.02/1.6 valves) in either 160 or 170cc form, are both flow limited by the location of the pushrods, which constrict the port runners. The limit @ 28" is around 250/190cfm @ .6" lift int/exh cfm. 1.94/1.5 valved versions will flow correspondingly less because flow will peak at lower valve lift of about .5".

Optimized Vortec heads will flow about 270/210cfm @ .5" lift, @ 28". Flow is limited by valve size (1.94/1.5) and valve lifts higher than .5" will show little flow advantage.

Joe

[Stuart F.]

Re: 1963 Cylinder Heads

I was also told by the fellow NCRS member with the 63 Z06 that you could tell the 461-X heads from the outside (without removal to check for number) by looking/feeling for bumps/protrusions in the casting above the exhaust manifolds at the lower valve cover screw locations (?). The 461-X heads were said to bo flat/smooth in these areas. Can anyone verify this.? I have not been to a show lately to check for myself.

[Timothy B.]

Re: 1963 Cylinder Heads

Stuart,
You are correct about the lower valve cover bolt hole protrusions. Not sure they are completely flat, I will have to go look and refresh my memory.

[Ray C.]

Re: 1963 Cylinder Heads

461 head with a casting date of 1966. Look under the mounting screw and you can see a bump .

Please note my error! The bumb is not on the early 461 X head but on a 461 1966 head. The April 1961 461X head did not have this bump! I have a set of 1960 (October-November) 461X heads but they are at machine shop and I can not check them at this time.

"Thanks for catching my error Joe"

Ray

[Joe C.]

Re: 1963 Cylinder Heads

I was also told by the fellow NCRS member with the 63 Z06 that you could tell the 461-X heads from the outside (without removal to check for number) by looking/feeling for bumps/protrusions in the casting above the exhaust manifolds at the lower valve cover screw locations (?). The 461-X heads were said to bo flat/smooth in these areas. Can anyone verify this.? I have not been to a show lately to check for myself.

Yes, there was quite a detailed thread discussing this subject, on another website a few months ago. I have verified this on a set of 461 (non - "X") heads that I have, dated Feb '63. They DO have the semicircular extensions for the VC bolt bosses. Other contributors to that thread also confirmed both "X" and "plain" configurations as being as you have heard; the "X" versions being flat, but with a very small longitudinal bar-like reinforcement about 1 1/2" long, beneath the VC bolt bosses.
Despite what some believe, there WERE both versions of the 461 head produced, at least in 1963. Possibly, and although I have never seen one, the two versions may have been produced in '61 - '62 also.

Joe

[Joe C.]

Re: 1963 Cylinder Heads

461 X head with a casting date of April 1961. Look under the mounting screw and you can see the bump referred to in an earlier post.

Ray

Ray,

That's what is referred to as "flat". You'll notice a bar shaped reinforcement under the bolt bosses.

The "Plain" versios have a very pronounced semicircular boss, protruding from the head casting. The boss itself, protrudes from the non X head about 1/4".

Joe

[William C.]

Re: 1963 Cylinder Heads

Hate to disagree, but I have never seen a 461 head from the '61-62 era that was not an "X" head, and that involves looking at hundreds if not thousands over the last 35 years or so...

[Ray C.]

Re: 1963 Cylinder Heads

Please note correction on my previous post!

Ray

[William C.]

Re: 1963 Cylinder Heads

For a clear view of the rocker cover boss difference photo attached.

[Clem Z.]

Re: 1963 Cylinder Heads

the "X" heads were in great demand by super stock drag racers because of the larger intake port volume BUT after NHRA allowed any head to be ported to a specific CC volume the demand for "X" heads went away. the "X" is in the water jacket only seen with the head off the engine

[William C.]

Re: 1963 Cylinder Heads

In addition, some of the circle trackers who had to use "stock" engines used up quite a few on high-priced "Budget" engines.

[Stuart F.]

Re: 1963 Cylinder Heads

Thank you all for a very interesting thread. I have learned a lot. One thing being; I will NOT rework my heads with hardened valve seats, nor drop the engine compression ratio with thick gaskets, etc. It is all still original (never apart) so, when the time comes, I think I will go crate engine and set this one aside. Thanks again. It's a thoroughbred now, why make it a gelding?