Fragged my 455 at Cordova this weekend. Checked Oil pressure with a portable gauge before racing and it was great. 4 passes later the engine was cranking slow. Thought the starter or battery cable got fried. When I pulled a plug and turned it over with a breaker bar it was a horrifying feeling. Slower than dirt, with a 3 ft breaker bar. After the motor cooled it wouldn't turn at all.
I tore it down and even with all the caps off the mains and rods it STILL wouldn't turn.
Turns out the #3 rod bearings slipped underneath one another and welded themselves together. Then welded the #4s to it as well. I just had 1 solid 1.5'' ring welded around and to the crank. It was a total loss. Rods, crank, everything... JUNK. The block seems ok but you can't eyeball machinist tolerances.
It was running 14.6 in the 1/4 with a stock g headed motor, th350 and 7.5 3.08s Shifting at 5100. Oh well, At least it wasn't my 350.

Weirdest thing ever. No knocks, noises, rpm fluctuations, nothing. Ran strong every pass till it started cooling down.

Going back to 307 power this winter

 

#3 and 6 rod oil feeds come out at the wrong angle. At some rpm vs. oil pressure, the oil doesn't flow out. For at least 35 years people have chamferred the oil holes heavily and run a trough about 1/8" wide and deep in the direction of rotation at those journals. Run heavy wire through the oil feed holes and you will see what I mean, and what direction to run the troughs.

 

I put another big block in. It's a wimpy 72 motor though. I'm gonna have to do a decent amount of work on the heads to make it un-slow.
The 307 only had 75 psi compression in the # 6 cylinder, so It's in the junk pile now too.

 

You know the same thing happened to the 455 in my '76 Regency, except I wasn't racing it. Those big blocks seem to go without warning, even though they go forever, and ever, and ever....

 

Not in my garage! NO MORE 307S! Did you pick up that 69 455? Now thats something we can work with!

 

OUCH!
That is a painful story indeed... Do the 350's have any known weaknesses like that??
What might have happened if you hadn't shut it down??

Hope you get it running again, only better than before!

 

Ouch that hurts even from here in Bothell. Crazy that there was no warning. Do you have an oil guage at the dash as well and what was the reading during the cool down between passes

 

No he didnt. now he does

 

Shift this one at 4500 RPM.

Norm

 

Agreed. I don't know what cam you were running, but a basically stock 455 is all done before 5100.

My stock 69 442 400/325 auto/3.23 ran best left in drive 14.5 at 96 shifting at about 4700rpm.

 

Does this problem exist for 425 crankshafts as well? How about 330/350 cranks?

 

My first good car was a 66 Chev Impala SS 2 door hardtop with a 283 and the bullet proof two speed glide tranny. I was running it on the highway about 70 mph and stepped on it . When it hit 90 everything just stopped. It was like the motor shut it self off and I ended up coasting to a stop on the side of the road. turned out that one of the crank bearings slipped in behind the other and jammed up to stop the motor dead in it's tracks.Ended up that was only damage and just had to turn the crank and get new bearings. Then I sold it and put in a stock 325 horse 327.

 

Yeah, that's pretty much what happened to me as well. Except there was no saving that crank.