461, 461X, and 462 heads
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461, 461X, and 462 heads
I decided to start a new thread to supplement the "C2 FI heads" thread of the last couple of days and expand the discussion. The difference between the 461 and 461X heads and their origin has always been somewhat mysterious to me as is the use of the "X" suffix.
From the prior thread it was established that the 461X heads have slightly more port volume - about 175 versus 160 cc for the 461s with the extra volume being in the bowl above the valve pocket. I'll take that on faith!
There has been some disagreement on the use of these heads. Interestingly, the NCRS spec guide does not distinguish between 461 and 461X during the time frame that they were used.
In 1960 Chevrolet planned to equip both "low horse" (mild hydraulic cam) and "high horse" (Duntov cam) FI engines with aluminum heads, and they were advertised as 275 and 315 HP, but problems forced cancellation of the aluminum head at the eleventh hour, and there is some controversy if any aluminum head Corvettes were shipped from St. Louis - probably not. According to the NCRS Spec Guide both '60 FI engines were carryover from '59, so the real ratings were 250 and 290 despite any literature that advertised them as 275 and 315 HP.
In '61 a "big valve" iron head showed up on both FI engines and the original advertised ratings with the ill-fated aluminum heads were advertised for these 1961 iron head engines. These iron heads apparently had the same valve and port configuration as the ill-fated aluminum heads. The increase in power for both FI engines is also partially attributed to an increase in compression ratio from 9.5 to 11:1.
First question: Were these 1961 1.94"/1.5" irons heads casting number 3782461 or 3782461X.
Stepping back to Briggs Cunninghams 1960 Le Mans effort, use of the aluminum head was planned, but the reliability issue forced a decision to use iron heads. Did they use early 461 or 461X castings or were they the older heads? Considering that the cars were prepped in in the May/June time frame it seems feasible that early 461 or 461x castings could have been available.
I'm going to skip 1962 for now.
My '63 SHP (L-76 340 HP) engine has the original heads and they are 461X castings, and to the best of my knowledge ALL '63 SHP/FI engines received 461X heads while the 300 HP engine received 461 heads.
As far as I know the same utilization applies to '64 300 HP and SHP and FI engines, however the valve seats on the 461X heads for SHP and FI engines were ground for 2.02"/1.6" valves.
No change for '65 EXCEPT the 461s were also used for the base 250HP engine, though the power rating was not changed. From 62-64 this engine had 3795896 head castings with 1.72"/1.5" valves.
Second question: Which came first - 461 or 461X, if the answer is 461X, when did the 461s show up, or vice versa.
Right now I go on the assumption that '62 engine head utilization is the same as my understanding for '63. (Is this correct?)
Third question: Why did Chevrolet use the "X" suffix rather than assigning a different part number. If the bowl volume of the 461X heads is larger, a different port core would have been required, and you would think these castings would have received their own unique seven digit number.
I'm not sure of the head untilization on '66 engines, but I assume 461s on the now base 300 HP engine and 461X on the L-79 350 HP engine.
For '67 the casting number was changed to 3890462 and was used on both 300 and 350 HP engines. What's the difference between this casting and 3782461 and 3782461X?
As far as I know there is no visual way to distinguish these castings on the car with the valve covers in place because the casting number and casting date are under the valve covers and they have no distinguishing external features. All are "double hump" with no accessory holes at the front.
The head used on '61 FI engines became known as the "fuel injection head" because it was unique to the FI engines that year, however, the utilization of this head was extended to SHP 327 engines in later years, and beginning in '64 they were machined for larger valves. Beginning in '67 and continuing into the seventies, different casting numbers were used with what is apparently the same port and valve configuration, but the term "fuel injection heads" is often applied (or, perhaps, misapplied) to these later heads.
End of this story as all new castings came on line for '68 and I believe they all had accessory pads/holes on the front face for accessory bracket mounting, which makes them visually distiguishable from earlier heads.
Discussion? Comments?
Duke
[Modified by SWCDuke, 11:50 PM 1/25/2003]
From the prior thread it was established that the 461X heads have slightly more port volume - about 175 versus 160 cc for the 461s with the extra volume being in the bowl above the valve pocket. I'll take that on faith!
There has been some disagreement on the use of these heads. Interestingly, the NCRS spec guide does not distinguish between 461 and 461X during the time frame that they were used.
In 1960 Chevrolet planned to equip both "low horse" (mild hydraulic cam) and "high horse" (Duntov cam) FI engines with aluminum heads, and they were advertised as 275 and 315 HP, but problems forced cancellation of the aluminum head at the eleventh hour, and there is some controversy if any aluminum head Corvettes were shipped from St. Louis - probably not. According to the NCRS Spec Guide both '60 FI engines were carryover from '59, so the real ratings were 250 and 290 despite any literature that advertised them as 275 and 315 HP.
In '61 a "big valve" iron head showed up on both FI engines and the original advertised ratings with the ill-fated aluminum heads were advertised for these 1961 iron head engines. These iron heads apparently had the same valve and port configuration as the ill-fated aluminum heads. The increase in power for both FI engines is also partially attributed to an increase in compression ratio from 9.5 to 11:1.
First question: Were these 1961 1.94"/1.5" irons heads casting number 3782461 or 3782461X.
Stepping back to Briggs Cunninghams 1960 Le Mans effort, use of the aluminum head was planned, but the reliability issue forced a decision to use iron heads. Did they use early 461 or 461X castings or were they the older heads? Considering that the cars were prepped in in the May/June time frame it seems feasible that early 461 or 461x castings could have been available.
I'm going to skip 1962 for now.
My '63 SHP (L-76 340 HP) engine has the original heads and they are 461X castings, and to the best of my knowledge ALL '63 SHP/FI engines received 461X heads while the 300 HP engine received 461 heads.
As far as I know the same utilization applies to '64 300 HP and SHP and FI engines, however the valve seats on the 461X heads for SHP and FI engines were ground for 2.02"/1.6" valves.
No change for '65 EXCEPT the 461s were also used for the base 250HP engine, though the power rating was not changed. From 62-64 this engine had 3795896 head castings with 1.72"/1.5" valves.
Second question: Which came first - 461 or 461X, if the answer is 461X, when did the 461s show up, or vice versa.
Right now I go on the assumption that '62 engine head utilization is the same as my understanding for '63. (Is this correct?)
Third question: Why did Chevrolet use the "X" suffix rather than assigning a different part number. If the bowl volume of the 461X heads is larger, a different port core would have been required, and you would think these castings would have received their own unique seven digit number.
I'm not sure of the head untilization on '66 engines, but I assume 461s on the now base 300 HP engine and 461X on the L-79 350 HP engine.
For '67 the casting number was changed to 3890462 and was used on both 300 and 350 HP engines. What's the difference between this casting and 3782461 and 3782461X?
As far as I know there is no visual way to distinguish these castings on the car with the valve covers in place because the casting number and casting date are under the valve covers and they have no distinguishing external features. All are "double hump" with no accessory holes at the front.
The head used on '61 FI engines became known as the "fuel injection head" because it was unique to the FI engines that year, however, the utilization of this head was extended to SHP 327 engines in later years, and beginning in '64 they were machined for larger valves. Beginning in '67 and continuing into the seventies, different casting numbers were used with what is apparently the same port and valve configuration, but the term "fuel injection heads" is often applied (or, perhaps, misapplied) to these later heads.
End of this story as all new castings came on line for '68 and I believe they all had accessory pads/holes on the front face for accessory bracket mounting, which makes them visually distiguishable from earlier heads.
Discussion? Comments?
Duke
[Modified by SWCDuke, 11:50 PM 1/25/2003]
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Re: 461, 461X, and 462 heads (SWCDuke)
I can't seem to find the previous thread you refer to (link?) so forgive me if this is old stuff.
Lafontaine's "Chevrolet Small-Bock V-8 ID Guide" says about the 461X:
"The 461X was introduced for special high-performance applications and got a 175cc intake runner... The 461X castings have been most valuable in class racing...where no porting is allowed."
Sounds to me like it was supplied for race car applications. It does not appear in his tables of applications to cars and trucks.
Lafontaine's "Chevrolet Small-Bock V-8 ID Guide" says about the 461X:
"The 461X was introduced for special high-performance applications and got a 175cc intake runner... The 461X castings have been most valuable in class racing...where no porting is allowed."
Sounds to me like it was supplied for race car applications. It does not appear in his tables of applications to cars and trucks.
#3
Melting Slicks
Re: 461, 461X, and 462 heads (SWCDuke)
Duke, the heads on my 62 FI car are 461X's, and I believe they are the original heads, since both have the same casting date and they are about 3 weeks prior to the car's build date. As far as I know, the 62 and 63 engines were identical except for changes in the FI intake plenum for the #375 FI.
#4
Re: 461, 461X, and 462 heads (SWCDuke)
Since we're just chattin' here and not stating anything as absolute fact, I'm gonna say what is an opinion based on a very shakey memory. My 63 340 HP & 360HP cars have the original heads and I'm pretty sure they're X's. I haven't looked at the heads on the 62 fuelie I just bought, except to compare the casting dates to the original block and be comfortable that they're original as represented. This'll be an easy thing to verify Monday. As far as different intake port volume on the X heads, this is new information for me. I won't state this as fact or strong opinion, but an old Nascar racer who was much along the lines of Smokey in terms of smarts, told me years ago that the X pertained to the thickness of the casting in certain areas, which made the head more suitable for modification and if we weren't planning on cutting on the ports, for our use the 461 and 461X were exactly the same. In all these years I've never heard that the two had different intake volume until this forum today. I won't argue that point any farther without measuring them, but I've got 461's, 461X's & 462's on the shelf if I haven't used em on something already. I'm sure that I've got X's that aren't on an engine, just not so sure about the other 2.
One other thing that intrigues me about this discussion is the suggestion that not only 61, but 60 Corvettes as well may have come factory equipped with double hump heads. I've always thought that the two humps originated with the 327's in 62. I've seen heads in the past that had 2 triangles, similar to the single one on the old powerpack 283 heads, and also another with two straight lines or bars, much like small stumps sticking up. I always thought these were the early fuelie or SHP heads. My 270 horse 59 has the original heads also, but I have no idea what the marking on the end looks like. I plan on looking at those Monday also.
One other thing that intrigues me about this discussion is the suggestion that not only 61, but 60 Corvettes as well may have come factory equipped with double hump heads. I've always thought that the two humps originated with the 327's in 62. I've seen heads in the past that had 2 triangles, similar to the single one on the old powerpack 283 heads, and also another with two straight lines or bars, much like small stumps sticking up. I always thought these were the early fuelie or SHP heads. My 270 horse 59 has the original heads also, but I have no idea what the marking on the end looks like. I plan on looking at those Monday also.
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Re: 461, 461X, and 462 heads (SWCDuke)
For '67 the casting number was changed to 3890462 and was used on both 300 and 350 HP engines. What's the difference between this casting and 461 and 461X?
Duke
Duke
#7
Melting Slicks
Re: 461, 461X, and 462 heads (SWCDuke)
Regarding '66 heads, the 461's were used into March of '66, when production switched to the 462 for both 300 and 350HP engines. My '66 Coupe - FO329, serial# 18479 is an example of the early usage of the 3890462 heads, both cast on C246, on an L-79 engine. Who knows why they changed the casting number?
Not sure if the 461X was used in '66.
Not sure if the 461X was used in '66.
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Re: 461, 461X, and 462 heads (Solidlifters)
Good discussion, guys. Keep it comin'. Maybe we'll be able to get to the bottom of these issues.
Duke
Duke
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Re: 461, 461X, and 462 heads (gary6696)
Lafontaine's "Chevrolet Small-Bock V-8 ID Guide" says about the 461X:
"The 461X was introduced for special high-performance applications and got a 175cc intake runner... The 461X castings have been most valuable in class racing...where no porting is allowed."
Sounds to me like it was supplied for race car applications. It does not appear in his tables of applications to cars and trucks.
"The 461X was introduced for special high-performance applications and got a 175cc intake runner... The 461X castings have been most valuable in class racing...where no porting is allowed."
Sounds to me like it was supplied for race car applications. It does not appear in his tables of applications to cars and trucks.
Chevrolet apparently regrouped and transferred the port configuration and larger inlet valves from the aluminum head to an iron casting and these became the 461 or 461X heads.
My hunch now is that this first big port cast iron head was a 461X, but I still don't understand the reason for the "X" suffix.
That leaves a question of when the 461 first showed up - the '62 300 HP engine, perhaps.
Duke
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Re: 461, 461X, and 462 heads (SWCDuke)
"That leaves a question of when the 461 first showed up - the '62 300 HP engine, perhaps."
LaFontaine says 461s were used 62-69.
He also says the 462s with the long # 3767462 had no bolt holes, and were used 62-67. There are other long number ending in 462 but he has a "-" in the bolt holes column.
LaFontaine says 461s were used 62-69.
He also says the 462s with the long # 3767462 had no bolt holes, and were used 62-67. There are other long number ending in 462 but he has a "-" in the bolt holes column.
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Re: 461, 461X, and 462 heads (gary6696)
go to http://nhra.com/tech_specs/engine/index.html to see what heads were used on what HP engines. they also give port volumes :chevy
#13
Re: 461, 461X, and 462 heads (SWCDuke)
I'm not familiar with LaFontaine, but the other numbers books that I've run across have so many errors they're virtually worthless for authenticity purposes although maybe somewhat useful for identifying some junkyard or swap meet parts in a pinch. The worst of the worst was the numbers crap that many of the major car books used to publish by a certain freelance writer from North of the border. We used to have contests to see who could find the most errors in his "statements of facts". I think the record was 6 in one article. Fortunately, he regressed into publishing time saving tips, and I think the magazines finally quit buying his work.
The NCRS reference manual which I have is the first edition and may have been updated since, but it shows the 461 heads as first available on 61's with fuel injection engines only.
The NCRS reference manual which I have is the first edition and may have been updated since, but it shows the 461 heads as first available on 61's with fuel injection engines only.
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Re: 461, 461X, and 462 heads (gary6696)
That leaves a question of when the 461 first showed up - the '62 300 HP engine, perhaps.
Duke
Duke
My '67 300hp has 462's (as did all '67 327's), double-hump with no accessory holes. My references indicate that '68 327's used 3917291 and 292 heads (both valve sizes, hole added for temp sensor when it moved from the intake manifold), then switched again to 3927186 and 187 (accessory holes added, 2.02 valves only) in 1969 on 350's.
#15
Re: 461, 461X, and 462 heads (JohnZ)
When the C-Econo guys were paying half a years wages for a set of 461X heads we tried to figure out exactly what they were supposed to have been on. The best thing that we could come up with is that the castings were used as they became available. There was no special purpose like only solid lifter motors etc. We found them on 300HP and just about anything that used the 1.94 head. I am begining to think it was a short run because eveyone that I have left ( 5 ) are Oct 61 castings. It may be just a coincidence I don't know does anyone have some later or earlier casting dates.
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Re: 461, 461X, and 462 heads (JohnZ)
Lots of conflicting information.
In summary here's what I distill out as most likely:
1. 3782461X first used and unique to the 275 and 315HP FI engines in '61.
2. Beginning in 1962, "461X" heads are used on SHP and FI engines (340 and 360 HP). This same year the 3782461 (no "X") shows up on 300 HP medium performance engine; 461 has slighly smaller port volume (160 vs. 175cc), which is more compatible with the lower operating speed range of medium performance engines.
3. Similar untilization carries through to mid '66 (461X on 340, 350, 360, 365, and 375 HP engines, 461 on 300 HP engine) with the addition of the 250 HP engine to the 461 (no "X") utilization list in 1965, but power rating does not change.
4. Beginning in mid '66 and carrying through to '67 the 3890462 casting replaces both 461 and 461X and is used on both 300 and 350 HP engines. The 462 casting has the "large" 175 cc ports. Externally the 462 is characterized with the double humps and no pads/holes on the front surface for accessory mounting making them visually indistinguishable from the 461 or 461X on the car (unless the valve covers are removed to expose the casting part number and date.)
Does anyone know why Chevrolet added an "X" to the seven digit part number to distinguish between the two castings rather than assigning a unique seven digit part numbers to each (JohnZ?)?
Any more comments?
Duke
[Modified by SWCDuke, 10:22 AM 1/27/2003]
In summary here's what I distill out as most likely:
1. 3782461X first used and unique to the 275 and 315HP FI engines in '61.
2. Beginning in 1962, "461X" heads are used on SHP and FI engines (340 and 360 HP). This same year the 3782461 (no "X") shows up on 300 HP medium performance engine; 461 has slighly smaller port volume (160 vs. 175cc), which is more compatible with the lower operating speed range of medium performance engines.
3. Similar untilization carries through to mid '66 (461X on 340, 350, 360, 365, and 375 HP engines, 461 on 300 HP engine) with the addition of the 250 HP engine to the 461 (no "X") utilization list in 1965, but power rating does not change.
4. Beginning in mid '66 and carrying through to '67 the 3890462 casting replaces both 461 and 461X and is used on both 300 and 350 HP engines. The 462 casting has the "large" 175 cc ports. Externally the 462 is characterized with the double humps and no pads/holes on the front surface for accessory mounting making them visually indistinguishable from the 461 or 461X on the car (unless the valve covers are removed to expose the casting part number and date.)
Does anyone know why Chevrolet added an "X" to the seven digit part number to distinguish between the two castings rather than assigning a unique seven digit part numbers to each (JohnZ?)?
Any more comments?
Duke
[Modified by SWCDuke, 10:22 AM 1/27/2003]
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Re: 461, 461X, and 462 heads (SWCDuke)
duke the X is not in the casting number is located in the water jacket that must be seen from the bottom of the head thru a water passage :chevy
#19
Re: 461, 461X, and 462 heads (SWCDuke)
Okay, there's a wrinkle or two in the summary: First of all, I have NO firsthand knowledge of 61's, so I'm not going to bore you guys with speculation.
As far as 62's & 63's, I believe the 300hp, 340hp and 360hp all got the same heads. There were no 2.02 valves until 64. I believe that these were all the same, meaning the 300 horse got the X heads also, because the set listed below came from a 63 Impala junkyard engine and they were very close in casting date to the 300 horse block assy they were on, suggesting that they were the originals. It doesn't seem logical that someone would've gotten a special set of "X" heads that just happened to be within days of the block, then left the cast iron intake and exhaust manifolds in place.
In looking at my head stash this morning, I found a set of Jan 63 heads on the shelf with the X. I fount a set of early 65 461 heads and a set of early 66 (L 22 65) heads that were 462's. I've never seen 63 heads without the X, but haven't spent loads of time looking to be honest. I've never had occasion to search for 64 or newer heads, although I do seem to have accumulated 2 sets from who knows where.
I'm still skeptical that the intake volume is different between the 461 and 461X head. I've just never heard any such rumor until this week on this board. If it proves true, it'll just be something else I've been wrong about for 35+ years.
There's one other thing that I mentioned briefly before, but no one has commented on.............one of the humps being ground partially off on one end of the heads. I've seen numerous heads with this cut on the hump and have never heard a plausible explanation.
[Modified by Solidlifters, 8:12 PM 1/27/2003]
As far as 62's & 63's, I believe the 300hp, 340hp and 360hp all got the same heads. There were no 2.02 valves until 64. I believe that these were all the same, meaning the 300 horse got the X heads also, because the set listed below came from a 63 Impala junkyard engine and they were very close in casting date to the 300 horse block assy they were on, suggesting that they were the originals. It doesn't seem logical that someone would've gotten a special set of "X" heads that just happened to be within days of the block, then left the cast iron intake and exhaust manifolds in place.
In looking at my head stash this morning, I found a set of Jan 63 heads on the shelf with the X. I fount a set of early 65 461 heads and a set of early 66 (L 22 65) heads that were 462's. I've never seen 63 heads without the X, but haven't spent loads of time looking to be honest. I've never had occasion to search for 64 or newer heads, although I do seem to have accumulated 2 sets from who knows where.
I'm still skeptical that the intake volume is different between the 461 and 461X head. I've just never heard any such rumor until this week on this board. If it proves true, it'll just be something else I've been wrong about for 35+ years.
There's one other thing that I mentioned briefly before, but no one has commented on.............one of the humps being ground partially off on one end of the heads. I've seen numerous heads with this cut on the hump and have never heard a plausible explanation.
[Modified by Solidlifters, 8:12 PM 1/27/2003]
#20
Re: 461, 461X, and 462 heads (clem zahrobsky)
Clem brings up another very valid point. I wonder if the fact that the X is under the head isn't confusing to a lot of people who expect to see it on the end of the number and therefore assume the heads aren't X's. While it can be seen with the intake off with a mirror, just pulling a valve cover is useless in this search. I may stand corrected on this as the discussion continues, but I have never thought that they cast X and non X heads in the same time frames.