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#1
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I Thought About Pontiac
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/ |
#2
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Pretty cool article, was worth the read.
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-Jason 1969 Pontiac Firebird |
#3
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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.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#4
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Journal overlap. Probably why Pontiac engineers went with the 3.25 main journals with the longer 4" stroke.
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66 GTO, 495, M22, Strange S-60 w/4.10 Sold new at Royal Pontiac. 70 Formula |
#5
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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.
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#6
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It also allowed them to use a cheaper cast crank at those strokes.
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#7
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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/ Last edited by PunchT37; 06-01-2017 at 12:08 PM. |
#8
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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?
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#9
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Quote:
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#10
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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? Last edited by Half-Inch Stud; 06-01-2017 at 07:46 PM. |
#11
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Quote:
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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