429 Rod Failure: Why is it ALWAYS #6

Hi, thanks for input on my SCJ build, but here is a new question:

I have three 429 engines on the table all have one thing in common: They all have had catastrophic rod failure. #6 always seems to let go first, followed by nr. 1 or 2. By case here is what I have found:

1. 1970 D0VE-A, two bolt main CJ with 2YABC crank, CJ rods, ARP bolts and L2404F60 pistons. Melling 84 oil pump, ARP oil drive shaft. Shaft broke because of a broken lifter plunger clip getting loose. Got sucked up in the pump which seized up. Engine ran for about 20 minutes, but seized up. Upon disassembly two rods were frozen; nr 1 and 6. Rod nr. 6 was blackened, blued and burned from heat, while all others were light grey and showing no sign of overheating. Crank is fine and bearings are not severely damaged.

2. 1970 DOVE -A block, std. D0OE 4V rods. I built this engine many years ago. First it was used with a C-6 in a heavy car with no problems. Later installed in a ´71 Mach 1 4-speed. Always had oil pressure in the 60 - 80 lbs range. (C9AZ-6600-A oil pump) During a drag race a rod broke at the 90° cut on rod for original square head rod bolts. It was rod #6. Cylinder shattered, block was junked.

3. Current build: 1971 SCJ with original D0OE football head bolts. All rods are matching, numerically except rods nr. 1 and nr 6. Both have been replaced. Additionally I see that cylinder nr. 6 has a sleeve in it. This engine was originally built for ´71 Drag Pack Mustang w. 3.91 gears and 4 speed. It shows signs of serious abuse in racing or street stomping. Took the original L2366F pistons out. They don´t have a scratch on them and the engine is not severely worn in any sense. Again, rod nr. 6 takes the kick. Rods nr. 1 and nr 6 have been replaced, others are original to the engine going by the numerical markings on them.

Question: Has aynone here noticed this? Any particular reason why nr. 6 seems to be at the greatest risk? This is hardly a coincidence ......

gcj

The only rod bearing failure I've ever had was on #2. It chewed ip the side of #6 rod in the process though. I think this was a combination of my own mistakes, not necessarily design flaw of the engine. Cheap oil pan, thick oil, methanol.

About 2 races before this happened. I made a test pass off the trailer before I realized I hadn't changed the oil. It was bad milky. I have always wondered if that one pass washed out that rod bearing? I never had any warning signs of metal in oil. It just seemingly chewed a rod bearing to nothing in one pass.

My experience is that 4&8 show oil starvation signs first as they are the last to see oil.

I don't have any direct experience of this, but on the Cleveland forum people have just become aware why a pair of rod bearings always fail on 351C with stock cranks at 8000rpm. It's because the factory crank drillings are not clocked correctly so two of the rod bearings do not receive oil pressure right before maximum load. This is not an issue on stroker cranks as they are all drilled the same as Chevys which are correct (damn!). Maybe the 429 is similar? You'd need to draw it out to figure if that is the case.

Stated in the most general terms, it seems that there may be an oiing issue with the #2 rod journal on the 385 crank, affecting #6 and #2 connecting rod bearings. IF this is the case, then that must point to an issue with the delivery of oil from the main oil gallery, to the main bearing and on through the delivery to the #2 arm on the crank.

The evidence is clear upon disassembly as with my 474 that failed after a plunger spring on lifter at #8 cylinder popped out fell into the oil pan and got sucked up into the pump where is lodged between the gears and seized up.

Again, someone else on this forum must have had a similar experience. I have three engines with clear evidence of this issue.

Anyone?

Better rods won’t hurt the situation.

Might try 3/4 or even full grove main bearings too

Found the link to the 351C bearing issue explanation on Youtube. It's apparently #2 & #7 on a Cleveland. Fully grooved main bearings are a fix. Presentation is a bit dry but worth paying attention all the way through.

https://www.youtube.com/watch?v=q3T_A1EV-C0

pretty sure you meant fully grooved main bearings...

Isnt #7 the last bearing to receive oil ? I spun a #7 in a new build several years ago .My fix was to restrict oil at the crossover .And it worked on tear down all my rod bearings look good .Whenever I prime my engine you cant tell any difference in the amount of oil from the pushrods my lifters have held up as well (SFT) . Maybe a bigger oil pan or more oil in the pan you currently have .And this lifter clip issue wiped your oil pump out that is another story .Possibly check your rod main clearances and write them down for future reference the next time you build another engine .But from what little I know #7 rod bearing is the last in line for oil it feeds from #4 main .It is hard to find 3/4 groove main bearing and fully grooved are impossible to find now .Kind of funny though years ago when I could get fully grooved main bearings I had no rod bearing problems ..Doug

Hi:

The three engines I listed in my initial post all have one thing in common: #6 Rod / rod bearing was the first to freeze up / break:
Eng 1: 1970 D0VE CL77 bearings .020, 460 Crank, FORD SVO pump, ARP shaft broke. #6 piston pin first to freeze up. #2 followed. Froze up. No breakage.
Eng 2: 1970 D0VE. Federal Mogul bearings .010us CJ oil pump w. 65 - 75 lbs pressure: #6 rod broke at the widest part of the rod. 4V-rods, broached.
Eng. 3: 1970 D0VE SCJ. Rebuit this engine summer ´21. Runs A1, engine was obviously used for racing. #6 cyl has sleeve. Telltale.

The failures occurred for different reasons, but the outcome is always similar:  Rods on the 2nd arm of the crank seem to fail first.

Now, my question to the forum is this: Someone here must have seen something of this sort in the past. So it stands to reason to ask what the reason is. The biggest hint I have seen is the color of the rods in the 1st case where the front rods #1,2 & 6 were blued up and had obviously suffered heat damage.

gcj wrote:Hi:

The three engines I listed in my initial post all have one thing in common: #6 Rod / rod bearing was the first to freeze up / break:
Eng  1:  1970 D0VE CL77 bearings .020, 460 Crank, FORD SVO pump, ARP shaft broke. #6 piston pin first to freeze up. #2 followed. Froze up. No breakage.
Eng  2: 1970 D0VE. Federal Mogul bearings .010us CJ oil pump w. 65 - 75 lbs pressure: #6 rod broke at the widest part of the rod. 4V-rods, broached.
Eng. 3: 1970 D0VE SCJ. Rebuit this engine summer ´21. Runs A1, engine was obviously used for racing. #6 cyl has sleeve. Telltale.

The failures occurred for different reasons, but the outcome is always similar:  Rods on the 2nd arm of the crank seem to fail first.

Now, my question to the forum is this: Someone here must have seen something of this sort in the past. So it stands to reason to ask what the reason is. The biggest hint I have seen is the color of the rods in the 1st case where the front rods #1,2 & 6 were blued up and had obviously suffered heat damage.

I'm guessing these problems were all with factory rods?

Hi Mark:

Yes, all these engines had Ford rods, D0OE: #1 & #3 had CJ rods w. ARP bolts. #2 had D0OE "Square" head bolts.

Let´s stay on course with this issue: The rods or bearings failed because of an outside or secondary problem. The rods are a result, symptom if you will of that pre-existing condition. The rods are not the cause, but the result of something else that went wrong first.

My question once again is: What is the cause? To me it seems to be an oiling issue. I know there are people on this forum who have built hundreds of these engines with horsepower figures up to the nine hundred range with excellent reliability.

There is talk of priority oiling mods, dry sumps etc. Maybe this problem was addressed with the introduction of the Motorsport / SVO block and the Eliminator / IDT blocks. Some have installed bronze sleeves in the RH lifter galley etc in order to facilitate increased oil pressure to the mains and rods.

So, what has all of this shown in respect to longevity and durability of this (otherwise) great engine? The last one I built is a ´71 SCJ that has a few battle scars as previously stated. The block was std. 4.36" bore with a sleeve at #6 cyl. That tells a story. NO other damage visible, but the LH cylinder head has been replaced with a service part w. a casting date from the mid ´70´s. (D0OE-R)

Someone here must have seen this a long time ago and addressed it, but how and what did they find?

I lost a rod from seizure due to lack of oil control. Yes it was #2 or #6. It happened years ago where I wondered why the end of the line for oiling being #4 and #8 should be starved before others. This was on a D9 block with solid roller lifters and nothing done to the lifter bores for oil control. Definitely the cause for the mistake but still why #2 or #6? My thoughts on this is that during low oil pressure where #1 and #5 is first to be fed there will be scavenging from the fact that the crankshaft itself is a pump where the oil holes in the crank are drilled to the rod journal center line. During rotation there will be a centrifugal effect to draw oil from the main at crank center line. This is more substantial with higher rpm.

gcj wrote:Hi Mark:

Yes, all these engines had Ford rods, D0OE: #1 & #3 had CJ rods w. ARP bolts. #2 had D0OE "Square" head bolts.

Let´s stay on course with this issue: The rods or bearings failed because of an outside or secondary problem. The rods are a result, symptom if you will of that pre-existing condition. The rods are not the cause, but the result of something else that went wrong first.

My question once again is: What is the cause? To me it seems to be an oiling issue. I know there are people on this forum who have built hundreds of these engines with horsepower figures up to the nine hundred range with excellent reliability.

There is talk of priority oiling mods, dry sumps etc. Maybe this problem was addressed with the introduction of the Motorsport / SVO block and the Eliminator / IDT blocks. Some have installed bronze sleeves in the RH lifter galley etc in order to facilitate increased oil pressure to the mains and rods.

So, what has all of this shown in respect to longevity and durability of this (otherwise) great engine? The last one I built is a ´71 SCJ that has a few battle scars as previously stated. The block was std. 4.36" bore with a sleeve at #6 cyl. That tells a story. NO other damage visible, but the LH cylinder head has been replaced with a service part w. a casting date from the mid ´70´s. (D0OE-R)

Someone here must have seen this a long time ago and addressed it, but how and what did they find?

The 466 in my Mustang has been in the car since 2004 and the oil pan hasn't been off since then but i'm using Eagle H-Beam Stock length rods as was my buddy may he RIP and also my cousin with 466 cubic inch engines and have never had those problems!!FWIW my engine has a Solid Roller cam and my cousins engine had a Solid Roller Cam but my buddies was a Solid Flat Tappet Cam!!