Don Terrill’s Speed-Talk

If it only takes 1500 psi to crack these Rods in there thickest section, then how strong can these production Rods be?

It says "1500 pounds" not 1500 psi. That 1500 pounds may be concentrated on an area way smaller than a square inch.

Not to mention the design is likely favorable to the cracking process and, I would imagine, they use a tool designed to fracture the cap correctly.

Doesn’t the area matter also, probably less than square inch?

ptuomov wrote: ↑Mon Dec 02, 2019 8:25 am Doesn’t the area matter also, probably less than square inch?

Day late and dollar short on my part, point was made above...

rod being strong where they crack the cap, does not dictate rod strength as most would view it.

Rods are designed to be strongest longitudinally in tension and compression. In operation, there should never be any forces exerted perpendicularly, so strength in that axis is moot.

lefty o wrote: ↑Mon Dec 02, 2019 11:22 am rod being strong where they crack the cap, does not dictate rod strength as most would view it.

^^This guy gets it. It's a manufacturing operation, not a strength test. A few years ago, cracked cap rods were popular.

Rick! wrote: ↑Mon Dec 02, 2019 1:54 pm

lefty o wrote: ↑Mon Dec 02, 2019 11:22 am rod being strong where they crack the cap, does not dictate rod strength as most would view it.

^^This guy gets it. It's a manufacturing operation, not a strength test. A few years ago, cracked cap rods were popular.

packardV8 explained it better though.

The 306 in my mustang let go a couple weeks ago. Mexican block, Boss 302 crank, Boss 302 rods, Probe pistons... spun 7000 rpm over and over and over again on the street and at the track. At the track, it was always running off a 200 hp plate. Ran 6.26 @ 109 and 9.87 @ 135 with a toploader 4-speed, 4.33 rear and 28x9 tire.

Anyway, after tearing it down, it was a rod bolt that let go. No lack of oil, journal looks like it could be re-used, no spun bearings... just a rod splayed open like a rod bolt broke. Tore everything associated with the rear two cylinders all to pieces. What impressed me, was the adjoining rod! It got MANGLED... but never let go! It even took a HARD hit to a stress riser next to the bolt, and still stayed together. It's kind of ironic that 50 year old Ford parts were super heros... and the failure rested with a 3/8 ARP Wave-lock rod bolt. It was the standard black series, and had been in the engine around 15 years. I ran it for about 8 years, and refreshed it about 7-8 years ago. Oh well, engine owes me nothing! Just VERY impressed with those old Ford rods from 50 years ago!!!

Oh well... Finally time to put the 363 together.

Have you ever "cut" glass? You scrape a line on it, and smack it. The scored line is a tremendous stress-riser, the glass breaks at the scored area.

Note the text that goes with the photo:

...the rods are cracked on a pre-scored line...

Schurkey wrote: ↑Mon Dec 02, 2019 4:14 pm Have you ever "cut" glass? You scrape a line on it, and smack it. The scored line is a tremendous stress-riser, the glass breaks at the scored area.

Note the text that goes with the photo:

...the rods are cracked on a pre-scored line...

just don't ad any extra pre-scored lines and you are GTG

digger wrote: ↑Mon Dec 02, 2019 4:20 pmJust don't ad any extra pre-scored lines and you are GTG

Thus the admonition--back when people did such things--to always grind/sand/polish the rod beams lengthwise instead of crossways.

L31 powdered rods. Look how they shattered like glass! JUNK!

These are either early production or development PM rods for the Cadillac Northstar, sorry I don't remember which, it was 30 years ago... One pulled off the line just after the initial cold pressing, other pulled after the last hot forging.