[PunchT37]

When I read this;

“We can’t keep pushing a 3.580” crank and 6.200 to beyond 1,000 hp,” Weber says. “We need to add some displacement. So we add a 4” crank with a 2.100 GM rod journal. That’s about as much as we can stretch and still be able to get the packaging correct. I like the 4” with the 2.100 because it has overlap between the rod journal and the main. That overlap is what transmits all the power from the engine. When you fail or flex a crank it’s because there isn’t enough overlap. The last journal transmits every bit of power and shock from every cylinder. The overlap between a rod journal size and a main size becomes really important.”

Rest of article here;

http://www.enginebuildermag.com/2017...l-hemi-engine/

[JLMounce]

Pretty cool article, was worth the read.

[Tom Vaught]

Agree, a well written artical with a lot of good points on building a engine correctly.

Many excellent race engines use Skirted Blocks (for a reason).
Wish someone made a PROPER piece for a Traditional Factory Engine.
You might get another 500 HP out of the basic 67 400 2-Bolt GOOD Casting if you had the ability to add that feature on a production block. Marty's engine might have lasted 5 years or more (vs 3 years under boost) if he had that capability at the time.

Tom V.

[Singleton]

Journal overlap. Probably why Pontiac engineers went with the 3.25 main journals with the longer 4" stroke.

[johnta1]

That's correct.

Surprised they didn't explain that better.
(not that the writer explained much)

The magazine has a better article on the journal overlap I believe somewhere.

[PunchT37]

Originally Posted by Singleton

Journal overlap. Probably why Pontiac engineers went with the 3.25 main journals with the longer 4" stroke.

It also allowed them to use a cheaper cast crank at those strokes.

[PunchT37]

Buick went through this also;

They went 3.25 mains on a 3.90 stroke...











Rest of SAE booklet;

http://www.v8buick.com/index.php?thr...t-scan.218560/

[dataway]

Am I correct in assuming the overlap they are talking about is the overlap between the OD of the main journal and the "inside" edge of the rod journal?

[Tom Vaught]

Originally Posted by dataway

Am I correct in assuming the overlap they are talking about is the overlap between the OD of the main journal and the "inside" edge of the rod journal?

Correct.

Tom V.

[Half-Inch Stud]

PMD OHC-6 has/is a skirted block, and revs to7500 with stock parts.

Too bad the OHC cam tower bore spacing differs from the V8.

stroke-up has been done. How about a bore out, or A pair of OHC-6s


Hmmmm? Aftermarket PMD V8 with PMD Cam tower design stretched for OHC V8?

[johnta1]

Am I correct in assuming the overlap they are talking about is the overlap between the OD of the main journal and the "inside" edge of the rod journal?

Crank Journal Calc