Chevy 427 Mystery Motor

[jbedit]

Anybody see the article on the Chevy 427 Mystery Motors over at http://www.hotrodenginetech.com
I never knew they made them in three different sizes. Always thought they were all 427's. Does anyone
have one of these motors? I'd love to see more pictures.

[BrazilianZ28Camaro]

Waaay cool!

Cast headers and all...

[DaveMcLain]

That article was cool. It looks like in the pictures that the lifters are in straight lines as in the 409 engine on the block shown.

[af2]

That article was cool. It looks like in the pictures that the lifters are in straight lines as in the 409 engine on the block shown.

NO they are not.

[DaveMcLain]

That article was cool. It looks like in the pictures that the lifters are in straight lines as in the 409 engine on the block shown.

NO they are not.

Look at picture 25, don't they look like they are set up just like 409? Different valve order so the cam would be different. I wonder if they used the same oil pump as a small block too?

[axegrinder]

I think the engine would have been a bigger success if it had beefier guide plates.

[Schurkey]

Smokey Yunick tells the story that the '65 Mark IV was a cheapened, bastardized version of the "proper" Mystery Motor; and that Dick Keinath was so disappointed in it that it essentially "broke" him. Ended up in Europe working for GM of Germany (???)

Is Keinath still alive? I'd love to hear his side of the story.

Interesting that a "developed for NASCAR" engine block would have two-bolt mains.

[fdicrasto]

Actually, Dave is correct in observing the lifter bores are inline in the early mystery motor,partly the problem with valve train reliability they did encounter. They corrected that with redesigning lifter bore geometry via canting them to better align the pushrod,rocker arm and valve angles. It was definitely a 90 degree deck block but with some carried over 409 design influences. The Z-11 was the true early 409 rehash with killer power for its day. The mystery motor of course was the mother of the mark IV. Factory engine development in those days was a progressive conservative evolution,not much blank sheet stuff like you see now. Phil D.

[DaveMcLain]

It's interesting when they show the heads how they clearly have a provision to provide exhaust heat to the intake and carburetor. I would say that indicates how close this design must have been to actual production. It seems strange then that the actual design of the cylinder heads was altered as much as it was. Were the ports redsigned/head bolts removed changes the result of getting the valvetrain to work more effectively?

This is interesting stuff.

[Pontiac_Puller]

Does anyone reproduce those manifolds? They'd be great for my class.

[jbedit]

There's an out of print book Fast Chevys by Alex Gabbard still available used on amazon. In it Kenaith describes how he did the ports to help equalize airflow with unequal length runners. In particular he describes the short port as being best. He doesn't specify directly about what production issues caused the revisions for the Mark IV design, but it is very interesting reading straight from the original designer. Used books range from five bucks to fifteen or twenty.

[RAS]

There was never any money appropriated for this engine. It was built under the table so to speak. GM was financially/legally out of racing in 63. The head bolt layout was and still is the God aweful design part of this engine. Finally fixed in the last redo 496" motor. That plus twisting the valve centers sunk the exhaust valve and created some of the worst combustion chambers in automotive history. The original bathtub chamber was hopeless. Then throw in two different intake ports and a heavy valve train. With time and money it could have been way better. Richard

[Schurkey]

The head bolt layout was and still is the God aweful design part of this engine. Finally fixed in the last redo 496" motor.

Ever laid an 8100 head gasket on top of a 454 head gasket? The head bolt holes all line up except three, and those three are only about 1/2 the diameter of the hole different.

[dfree383]

There was never any money appropriated for this engine. It was built under the table so to speak. GM was financially/legally out of racing in 63. The head bolt layout was and still is the God aweful design part of this engine. Finally fixed in the last redo 496" motor. That plus twisting the valve centers sunk the exhaust valve and created some of the worst combustion chambers in automotive history. The original bathtub chamber was hopeless. Then throw in two different intake ports and a heavy valve train. With time and money it could have been way better. Richard

Kinda sounds like your wanting a 460 ford?

[Pontiac_Puller]

The head bolt layout was and still is the God aweful design part of this engine. Finally fixed in the last redo 496" motor.

Ever laid an 8100 head gasket on top of a 454 head gasket? The head bolt holes all line up except three, and those three are only about 1/2 the diameter of the hole different.

The 8100 layout makes each bore have the exact same bolt pattern, whereas the older Mark IV, Gen V or Gen VI is slightly different from bore to bore. The 8100 also uses all the bolt holes, even the two holes that the former pattern skips.

This is what it takes to put Mark IV heads on a Gen VII block. It's tough, but doable. They also start out as a 9mm thread, but can be drilled to 3/8" and re-tapped to the traditional 7/16 coarse, like what you see here. It's tough material btw, the same stuff they make bowtie blocks out of. I wore out a high quality tap on each bank, and used a third in reverse order just to make sure I got everything.





I love 8100s. Seriously a well designed motor. Here's a pic of the crank, note the added center counter weights, and bull nosed profile.