461x heads

[Richard P.]

What is the difference in the 3782461 heads and the ones of the same number withe the X cast in them. Are the same casting? Thanks

[Donald A.]

Re: 461x heads

I've read they are the same. Perhaps an expert could explain the "X"

[Jack H.]

Re: 461x heads

There are differences as back in the day the 461X heads were sought after by the racers in factory stock racing classes. I don't know the details, maybe runner size and/or combustion chamber size, etc...but in any case the 461X heads have always been the most desired of camel humps and maybe all of the oldschool SB heads.

[Dino L.]

Re: 461x heads

X on early 62 heads were small valve heads

[Duke W.]

Re: 461x heads

"461X" heads were used on '61 275 and 315 HP engines and '62-'63 300, 340, and 360 HP engines. The were
replaced by (non-X) "461" heads for the '64 model year. It has been said that the 461X is simply a cast iron version of the ill-fated aluminum head from 1960.

Both have chamber volumes as originally machined in the 60-61 cc range. Later heads beginning with 462s eliminated the small quench zone on the spark plug side of the chamber which increased chamber size to about 62 cc with the standard valve size.

The primary difference is the 461X heads have slightly larger as-cast inlet port volume - 170-172cc versus 160-165 (depending on source) cc for the 461 non-X and later "big port" heads. It's not clear to me why port volume was reduced, but it may have been to provide more core position tolerance (This is often referred to as "core shift", but it's really just the tolerance of core placement within the mold, which is essentially the same as tolerance for machined surfaces, but more tolerance is required for a mold core than a precison machined surface such as a crankshaft journal.)

Some race engine builders going back to the sixties/seventies preferred starting with a set of 461X heads, supposedly because the cast iron had a higher nickel content than later heads, which made the material tougher and the head less likely to crack in racing service.

I know from my own experience pocket porting my '63 461X heads that the material is very tough and I spent many hours grinding with a compressed air-powered rotary file.

BTW, it's recommended by experienced hands NOT to increase valve size from 1.94/1.5" to 2.02/1.6" on 461X heads as the seats may not have enough material to reliably accept the larger valves. You can break into the water jacket or end up with too thin a section that will eventually crack.

The best flowing set of massaged heads I have in my library of flow tests is a set of very well massaged 461s (non X) with the standard valve size, and all are just pocket ported/port matched with and without mulitiangle valve seats. None are fully (race) ported from manifold interface to valve seat.

Duke

[Tom P.]

Re: 461x heads

Duke's answer is the best! The 461X heads were 61-63, and as he mentioned, the "plain" 461 heads were introduced in the 64 model, and then replaced in 66 with the 462 heads. EXTERNALLY, they ALL look the same and have the same double hump symbol on each end.The 461X heads ONLY had 1.94/1.5 valves----------------------the 461Xs NEVER had the 2.02/1.6 valves. BUT, the 461 and 462 heads were machined with both 1.94-2.02/1.5-1.6 valves.Duke advises against having 461X heads opened up for the larger 2.02/1.6 valves. I've had it done on a few with ZERO issues (fingers crossed-------------yes, it's probably a roll of the dice). BUT, regardless, if ANY head that was produced with 1.94/1.5 valves is opened up to 2.02/1.6 valves, the chamber wall around the head of the intake valve needs to be machined/relieved as it was done on ALLLLLLLLLL factory 2.02 heads.Below is one of my 461X heads BEFORE and AFTER they were opened for 2.02/1.6 valves and the relieving that was done on the chamber wall around the intake valve (as done by the factory).

[Stuart F.]

Re: 461x heads

I thought, or was once told and shown, 461-x heads had a small machined pad (build up) of cast material just outside of the valve cover screw hole. The fellow who showed that to me had a 63 Z-06 coupe (all original with papers). I was distraught because my original 63 (never apart) L-76 did not have that, so I assumed mine didn't have them. Is that for real or am I dreaming?

Stu Fox

[Duke W.]

Re: 461x heads

I'm not sure what you mean, but if your '63 has "correct" date code heads, they have to be 461X. The "X" is under the water outlet, and I think it can be seen with a mirror if the inlet manifold is removed.

Duke

[Timothy B.]

Re: 461x heads

I thought, or was once told and shown, 461-x heads had a small machined pad (build up) of cast material just outside of the valve cover screw hole. The fellow who showed that to me had a 63 Z-06 coupe (all original with papers). I was distraught because my original 63 (never apart) L-76 did not have that, so I assumed mine didn't have them. Is that for real or am I dreaming?

Stu Fox

Stu,

Look at your heads where the outside holes are for the valve cover bolts. The X heads do NOT have the half circle material built up like the non 461 heads. That's a way to tell without removing a head to see the X in the casting.

[Stuart F.]

Re: 461x heads

Thanks Tim and Duke. I guess I was confused at the time. I recall some previous threads about this so I'll go looking again. It's not often that I get that confused.

Stu Fox

[Tom P.]

Re: 461x heads

??????????Sorry, I'm still confused on this half circle thing???????I just went out and pulled 461X, 461, 462 heads and I just do not see anything resembling a half circle.

[Timothy B.]

Re: 461x heads

??????????Sorry, I'm still confused on this half circle thing???????I just went out and pulled 461X, 461, 462 heads and I just do not see anything resembling a half circle.

Tom,

Half circle may not be the correct term to describe what I am talking about. The casting area around the outside valve cover holes does not protrude out like the later 461 non X heads. If you look side by side you will notice the difference.

[Stuart F.]

Re: 461x heads

What I was referring to was more like a rectangular boss of cast material just outside of the valve cover screw hole. I went looking in the archives for the thread where a post showed a good photo of it, but could not find it. Oh well, it's not that important. As for checking my heads with a mirror, well, my intake manifold has never been off and in 51 years I never had a reason to take it off so I'll probably have to go on faith for the rest of my years with this car.

Stu Fox