CLASS RACER FORUM - View Single Post

Adger Smith · 09-25-2010, 08:38 PM

Paul wrote:
On the small-journal versus large-journal.
The 67' blocks were 2-bolt mains, and utilized connecting rods with 5/16" bolts.
Also pistons with pressed-in pins.
The theory is the 4-bolt mains and larger-journal cranks are stronger.

This one can be debated until eternity.
I say:
Yes, Paul it can be debated, but as an engine builder that lived and work through that era of cars/engines I can say with authority it is a theory that is true. One major change that came about with the large journals is the overlap of the main and rod journals increased in the crankshaft. It was so much stronger it reduced flex and you could reduce bearing clearances. The small journal cranks and 2" rods with 11/32, not 5/16, rod bolts you had so much flex in the crank and rod distortion you had to have insane bearing clearances. Since that time period the improvements in metallurgy have also improved the strength of both factory and aftermarket race parts. Wow, no more co-plated rods for floating pins!!! (remember them?)

09-25-2010, 08:38 PM	#41
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Can you settle an argument? Paul wrote: On the small-journal versus large-journal. The 67' blocks were 2-bolt mains, and utilized connecting rods with 5/16" bolts. Also pistons with pressed-in pins. The theory is the 4-bolt mains and larger-journal cranks are stronger. This one can be debated until eternity. I say: Yes, Paul it can be debated, but as an engine builder that lived and work through that era of cars/engines I can say with authority it is a theory that is true. One major change that came about with the large journals is the overlap of the main and rod journals increased in the crankshaft. It was so much stronger it reduced flex and you could reduce bearing clearances. The small journal cranks and 2" rods with 11/32, not 5/16, rod bolts you had so much flex in the crank and rod distortion you had to have insane bearing clearances. Since that time period the improvements in metallurgy have also improved the strength of both factory and aftermarket race parts. Wow, no more co-plated rods for floating pins!!! (remember them?) __________________ Adger Smith (Former SS)