bowtyebob

A few months ago I asked if anyone on this forum knew the actual differences between 461 and 462 cylinder heads. There was a lot of discussion, opinions, and a lot of information, both published and unpublished, about the differences; everything from combustion chamber volume, quench and squish areas, and runner and port volume. I suspected that a lot of this information might simply be legend, rumor, or myth passed on down from a knowledgeable source or sources.
It so happens that I currently have two sets of freshly rebuilt cylinders heads. One set are 3782461 castings and the others are 8890462s from an all original L79. Both with 2.02/160 valves and both trued with a .010 cut.
Interestingly enough, both sets have the number 462 cast on the underside of one intake runner and both sets have the number 461 cast and visible inside the water jacket opening adjacent to that runner.
To verify the differences between these heads I compared the combustion chamber volumes of both. You guessed it. There was NO difference in combustion chamber volume with both at just slightly more than 62CCs by my measurement which might be slightly off. The shape of the combustion chambers and their squish/quench areas is absolutely identical.
The same was true of the intake and exhaust runners/ports. There was NO difference in either volume or shape between the 461s and the 462s.
There is no information like the real deal hands-on deal.
I am sure that the controversy will continue and that there will be "more informed" sources and downright disbelievers, however at least one of us now knows the answer.
I wanted to post the photos of both, but my membership level doesn't seem to allow that.

62Jeff

Here's your original thread...
http://forums.corvetteforum.com/c1-a...different.html

You can't upload attachments with your membership level, but you can upload your photos for free to a Photobucket album, or more generically, to www.tinypic.com. Once uploaded, just copy/paste the text that starts with [IMG] and ends with [/IMG]

MiguelsC2

What method of measurement did you use? I hope more than visual?

bowtyebob

Thanks. I will give that a try.

bowtyebob

The 'visual' part was a close look-see. When I couldn't see any apparent difference, I went to my 'haven't used in years' clear 3/8 lexan 'plates' and the vile marked in 1/10 CC increments. Pretty simple procedure. Fasten the plate to the head, then put the tip of the vile into the hole in the plate, open the valve and see how much light mineral oil it take to fill the combustion chamber The same for the intake and exhaust ports/runners; first a visual inspection then an actual measurement using different plates made for each. It took some time to find the old bolts and washers that I used long ago ...and, of course I forgot at first to use some wheel bearing grease to make a good seal. It's been awhile since I did that stuff.

bowtyebob

The pics. Thanks for the tip.

The 461 - http://i39.tinypic.com/2zxw2ad.jpg[/IMG]
http://i43.tinypic.com/2bcxg0.jpg[/IMG]
http://i40.tinypic.com/2yv6oih.jpg[/IMG]

The 462 - http://i39.tinypic.com/11sf3uw.jpg[/IMG]
http://i39.tinypic.com/14xpda8.jpg[/IMG]
http://i44.tinypic.com/2qntchz.jpg[/IMG]

62Jeff

Fixed it for ya!

MikeM

Regardless of the casting # confusion, those combustion chambers are typical of 462 heads.

Vipermike

This is off topic but the combustion chamber on the intake valve side on both of those heads needs to be unshrouded to get any additional performance out of the 2.02 valves that were added.

bowtyebob

Mike,
You are undoubtedly correct, although I'm not certain about the "any additional performance". There may be some, maybe not, although probably no harm done. Both sets of these heads came to me with 2.02/160s and so were simply rebuilt with the same size valves and a three angle valve job. To tell the truth, I believed(past tense)that L79s came with those valves. Fact is that I have seen many of these 461s and 462s over the years, most with the 1.94/1.50 and many with the 2.02/160 combination. I saw so many 462's with 'unshrouded' 2.02s that I simply assumed that was the way they were originally. As you may know there is a lot of rumor, legend, and myth concerning these 'double hump' /'fuelie' heads ...and what some of us 'remember' to be fact, well ...just ain't always so. An example of a potentially flawed memory is where I could swear that I have seen 'untouched' 462s with unshrouded 2.02 intakes. Have I been ....mistaken all this time? It seems possible if not likely.

JohnZ

All Saginaw-cast/Flint-machined/assembled 461, 462, and 291 heads with 2.02/1.6 valves from the factory had the unshrouding cut made in the chamber adjacent to the intake valve. Adding 2.02/1.6 valves to 1.94/1.5 heads was a popular modification, but not all shops made the unshrouding cut, or even had the correct 1.37" cutter.

bowtyebob

Thanks for that information, John.
You referenced Saginaw-cast/Flint-machined/assembled heads. I had assumed (first three letters of ASSume?) that all of those heads were of the Saginaw/Flint combination. Were there others?
These 462s that I have now have a 'w' stamped on the front face adjacent to the 'double hump'. Would you happen to know it's significance?

JohnZ

Production heads didn't have anything stamped on the front/rear surfaces - the "W" is probably a rebuilder's identifier.

Tonawanda also cast/assembled 461 and 462 heads, but only in the 1.94/1.5 valve sizes; Tonawanda castings are easy to spot - they didn't machine the surface of the "double-hump" casting symbols on the ends of the heads perpendicular to the deck surface like Flint did - they just left them "as-cast". Photos below show the difference.

bowtyebob

Yes. I have noticed the machined and as cast differences before, but did not know why. Thanks for that.
Bob