Mk II vs Mk III detail differences?

[numboltz]

http://www.hotrod.com/articles/mickey-t ... -stingray/

Always interested in reading about the first canted valve engines, and have often seen that
Chevy made many changes' all apparently in the cheaper direction, between 1963 and 1965.
Anyone know, in detail, what the changes were?

[Ratu]

Mk III was a place holder, a lable reserved for a potential engine. Packard had a V-8 line and when that company failed there was a proposal for GM to purchase the production line and designs etc from the Packard liquidator. GM were seeking a new V-8 big block at the time and Packard's V-8 was set on 5" centres which meant plenty of room to grow in future. Further, it appears there was a V-12 variant of the V-8 which could be manufactured on many of the same tools. In the end the Mk III project never progressed much further than investigations and analysis work (possibly some testing). It was not taken much further and instead it was decided to modify the MII, developing it into the Mk IV.

Smokey Yunick commented favourably on the Mk II design and expressed his admiration for its lead designer on several occasions. He mentioned to me that the Mk IV was "productionised" in an unsympathetic manner and that some of the good aspects of the original design were discarded. He was dismissive of the early versions of the Mk IV. It does appear he had a point, as it took a while to sort out the Mk IV BBC and make it work reliably for high performance application. I recall him saying that during the transition the valve centres were altered some and that the port shapes were changed. There were other amendments but I can't recall all of them. I regret not asking a few more questions and writing it all down, but he sure was a prickly personality, sometimes impatient and fast to annoy. He could close a conversation down quite quickly and make a person feel unwelcome real fast!

It would be interesting to revisit the two engines, put them side by side and go through the details and analyse the differences.

[Newold1]

Thanks for the magazine article and its pics. I long ago tossed mine but I remember those pictures very well. I always loved two early developments in those Mark IV's. One was the interesting little bump in the upper left corner of the exhaust port and the oval shape of the exhaust port. Somehow those two developments got lost in the original production Mark IV's and only appeared as improvements in later years through testing and performance version aluminum heads. The other early great part in the pictures for me were those great cast iron header manifolds. The Corvettes received a later variant exhaust manifold but it was not as good as these early racing offerings.

I always understood that the two iterations of the Mark versions were really not both Mark engines. One was the modified 409 (427) W engine named the Z11 and the HD-427 Mark III engine described in that article that appeared at the 63 Daytona race. There have been some releases of info and pics on some prototype developments but I have always heard that none of those made in into GM Racing programs or production. IE: the overhead cam 427, etc.

[ProPower engines]

having never seen the original block and valve train lay out that was some fancy push rod guide plate engineering.

[numboltz]

Interesting that in spite of multiple statements in the articles of the day stating it was entirely a racing
engine, the cylinder heads have heat crossovers in their castings and it appears that the intakes
have those provisions, too.

Other trivia I have seen includes the fact that they used the same basic rod forging as the 409, with
the pin hole moved a small amount. I would assume that the block went down the same line as the
409s did, even though the decks were at a different angle. With the cranks being interchangeable,
the rods similar and the bore spacing the same I wonder just how much detail difference there was
in the basic block castings? Be fascinating to compare the two blocks.

Finally, I have read that Chevy was forced to sell 2 engines to Ford to prove the engines were
available in the market place and thus NASCAR legal. Apparently late in the season Junior
Johnson was plumb out of engines and by some form of shenanigans was able to acquire one
of the two from Holman & Moody. I suspect the other one is the grandfather of the 385 series not
too mention the Cleveland family.

There must be at least one patent for the canted valve idea, but so far I haven't found it.

[PackardV8]

The late, great Francis L Preve for 33 years was the historian at GM Power Train Tonawanda Plant and was an avid drag racer at Lancaster Speedway. He told me he always felt it was a mistake when they chose to abandon the MKII block and go with the new MKIV design.

FWIW, the MKIII option had some adherents. Being able to buy the complete and brand new Packard V8 design and production line had many cost-saving advantages and the bean counters were all for taking it on. However, engineers don't get many chances at a new clean-sheet design, so they played the "Not up to GM standards and will have the reputation of being from a failed car company to boot." By selling wolf tickets, the Engineering Department won out over the Accounting Department.

[F-BIRD'88]

Racing at Lancaster is an adventure.

[Schurkey]

Reviving an old thread!

Checking to see if this post makes it through.

Awhile back, just before my stroke, I re-read Smokeys 3 book series and took some notes.

He didn't actually directly compare both Engines but made several comments throughout.

If the thread continues I'll post the notes I made back then for discussion.

If not, I'll start a new thread.

Thanks
Randy

I, for one, am happy to have this thread revived. Please continue.

I've also got the 3-book set, but I never went so far as to take notes. I do remember that Smokey acted as though the designer of the Mystery Engine and the Mk IV more-or-less "gave up" and transferred to Germany. I'm not sure that's fair or kind--but of course I wasn't there to watch any of it.

[Kevin Johnson]

...
There must be at least one patent for the canted valve idea, but so far I haven't found it.

https://patents.google.com/patent/US3276438A

Dick Keinath cited: https://patents.google.com/patent/US2769434A

Witzky did not claim the canted valve arrangement as unique rather the rocker arm mounting.

[ProPower engines]

After seeing the valve train layout and how the push rod guides were made inline is it possible they used a 409 block
with the canted valve head.
Never had thought about it till now or had two side by side but some guys did run a 409 block and used the at the time new 454 crank in them. While the Z11 is said to have used a 6.135 long rod the 396-454 did also but the 409 block with the canted valve head would explain how the 396 and 427 heads came to be.

Is it possible that GM had the later 396 BBC on the drawing board and had some stuff made at that time and they adapted
the canted valve 396 heads to the larger bore 409 block?

Back then the back doors of the car manufactures had cool parts leaving to be run in nascar this may have been one
of those times when someone said hey why not try this and kick ass in february.

[SchmidtMotorWorks]

I would like to know how the head bolt and intake port design decisions were made.

It is probably the most slapped together mess in all of that era of engine design, but people figured out how to make power with them.

[PackardV8]

Yes, but remember in the first few years, they had a reputation as hand grenades. I even knew small dealerships who wouldn't sell the high-performance versions. They knew they'd be getting too many problems.

[Schurkey]

Recently I bought a book containing a Dick Keinath interview, lots of info from the man himself.

What book? Link?

[Schurkey]

http://www.alexgabbard.com/fast-chevys.html

Thanks
Randy

So I go to the Amazon web site for that book, thinking it sounds interesting and maybe one I should buy.
https://www.amazon.com/Fast-Chevys-Alex ... ef=sr_1_1?

Amazon tells me I bought it in 2012.

That's when I went down to my library and found it parked on a shelf.

Senility approaches.

[ole4]

I bought the fast chevy book $4.95 on amazon used. What a great read so far! Thanks for posting that.