Why do we keep throwing rods? (Page 5 of 6)

From:  http://www.classicinlines.com/buildasix.asp in regard to building the Ford 200...

Connecting Rods: The next item to cover in the short block, is the connecting rods. Most sixes came with forged steel connecting rods, with the exception of those produced from 1973 thru 1981. During those years Ford used a variety of materials, from cast steel, to cast iron, to nodular iron. In 1982, they switched back to forged steel rods once again. As such, the rod bolts are the weakest point in the bottom end, and they should always be replaced when rebuilding a motor. We recommend using ARP small block Ford (V8) rod bolts, for increased safety and strength, however they need to be installed by your machine shop as a small modification is required for fitment.

Shot Peening: While not required for the average street motor, shot peening is an option used to increase the fatigue life of a stock connecting rod. By compressing the surface layer of the connecting rod, the likely-hood of failure from fatigue, stress cracks, and/or corrosion is greatly reduced. Another common practice is to eliminate stress risers by de-burring the rods and grinding all edges to a smooth radius prior to shot peening.

Shows what they know (BTW I have been all over their site and forums as we built and raced this, just not recently). The motor we just blew up had the best factory rods, and the ARP rod bolts, and it blew the quickest of any of them. The one that threw a rod at Sears Point (and tossed the cam through the block) was a 1977-80 motor with as far as I know stock bolts in it (lasted 4 race weekends), and not sure which type of Ford rods it had. The one motor that destroyed a piston and kept the rods intact was also a 1979 vintage bottom end with stock rod bolts, though I will say I know for sure that motor had cheap hypereutectic pistons in it, which I think are lighter than any of the other options.

The rod end likely has to be drilled a little or machined a little to accommodate the ?bigger? bolt or the bigger head or nut.

Well I finally got the engine out and have made a humble opinion.

From what it looks like, the bottom of the piston broke first at the oil ring / wrist pin line. The energy from the break threw the piston up, impacted the head, and made a impression of the combustion chamber in the top of the piston. As I find the piston, it is wedged at 30deg. To its normal plane.   The rod ripped out the last cam segment, cancelling valve movement and avoiding damage to the valves (I think) although the piston was down about an inch on the high side and 1.5 on the low side. I believe it stopped due to being wedged without a skirt.

The rod swung around the rod journal at 4,000 rpm about 5" long with the wrist pin attached while the car was traveling forward.  It really went bad when the car, after going off track, and in gear,  staeted going backwards. I think the reverse action now forced this rod backwards and bent it in the arch you have seen.  At some point tossing or just breaking off the cap.

I cannot guess at what then wedged on only 1 side of the engine and the crank just came around and beat about a 1/8th inch deep notch at the oil port. Im not going to be able to buff that out

Block, crank, pan, cam shaft, 1 piston, and rod...destroyed, FUBAR!

Would love some input on what you see.
I will figure how to download pictures tomorrow!

Excluding any mechanical damage after the fact, what is the condition of the rod journal and bearing shell (once straightened out)?

It has to be piston failure then. I was using the silvo-lite hypruretic (sp) flat top pistons. The flat top design was only available from a group of 4 for fords 4cyl 2.0 or 2.3.  It has the same wrist pin, piston deck to cl wrist pin length. As the 200 engine family.

In order to attach pictures you need to host them somewhere else. Facebook works, but then people need to be logged into a facebook account in order to see them (or so I've been told)

If you right mouse click the picture you can then "copy image location" in the pop up and get https://scontent-a-lax.xx.fbcdn.net/hph … e=54A5EB8A

Click the "img" button above and stick that link between the (img) tags that pop in

There is my problem ( pictures ). Im working from the tablet and phone and away from the computer with a mouse and right cliker.

So to note the pictures no scalding of the cylinder walls. 1 kiss of the intake in #5 piston. Must have been adjusted a bit to tight.  That wasnt the problem. ( could have been).

Who makes a better piston and rod combo?  If I could find one, maybe I would stick with this motor.  Not feeling it right now

The top edge of the piston looks like it rocked over far enough to drag on the cylinder wall.  That would be from a broken piston skirt on the opposite side.  Why the skirt failed is the ?  Seized wrist pin would be the first thing I'd look at...assuming piston to wall clearance was close to correct.

Remember everyone, we ran this motor all day at Sears Point in the spring with no motor issues, but plenty of other little issues. Still we did manage to finish 44th out of more than 150, so we weren't pussy footing around. I would think if it was a major piston clearance mismatch to the size of the bore we would have noticed it in those 300 laps we ran. Also, since we basically had a less than zero residual after blowing up in practice, we had the block bored and bought new pistons in the overbore size. Anyway, more pictures.

Ok, no question it was a piston failure.   I now see that the mark on top of the piston is from it hitting the head surface after detaching from the bottom.  It looks like the piston split radially at the oil ring groove.  The bottom of the piston is clean, so it wasnt too hot.  Examine the wrist pin bore area on whats left of the piston.  Are there any signs of gaulding?  If the pin was too tight, it would show up there.  Otherwise, it looks like the piston pin pulled out under tension.  everything else was from having a loose connecting rod flying around in the crankcase. 
Why...who knows, but I'd use a different brand next time.