I keep seeing alot of posts here about the connecting rod strength in the Lightning engine. The factory rods are pretty strong they would have to be to survive the ford durability tests. Now it's not the best rod on the market but for most of the modifications that people make to these trucks I don't think the rods would be the weak link. My question is why is the general perception that I hear is the rods are prone to break at a moments notice? Is it just because some of the tuners have broken rods? I am just curious if there is any hard evidence of what caused a rod failure? Were any of the people who broke a rod doing any data logging on the run so they know for sure it was not detonation or a over rev condition? Just trying to find an answer for my own curosity.

John..

 

I also have been wondering what on the rods are letting go? The bolts, the cap, wrist pin or are they breaking in the beam area? I don’t remembering anyone saying for sure where exactly what on the connecting rods are letting go ? Anyone that has broken rods what to enlighten us on where the weakest link is?

 

I've heard the whole rod just sucks for our application. They're to long and not strong enough to withstand the pressure placed on the long stroke, and only 1 has to give.

I've also heard of stock Lightnings blowing engines, so it's not just modded ones.

But anyway you look at it, if your going to put any type of forced induction on an engine you should beef up the internals, only if it's for additional reliability. Most stock motors (all cars) can handle around 6lbs of boost reliably with a good tune, over that it would be very wise to build up the internals.

 

Thats a good question....for the most part I take care of my stuff, I know whats going on inside my engine and pretty much had the notion that connecting rods were something that "other" peaple broke and that it wasn't going to happen to me.

So much for that theory......I broke #5 rod in mine and it took the center right out of it. It seemed to shatter like a piece of glass, little tiny pieces of metal (if thats what you want to call it) everywhere. The big end was still connected to the crank and the crank actually looks good. The small end was still connected to the piston and it came to rest up inside the cylinder. There were 3 holes in the block and the oil pressure went to zero imediately. But I was still able to drive it almost 5 miles back to home. When I pulled it apart the bearings looked like new. Only the center cam bearings on each side of the heads looked like they were getting a little warm but I am going to polish and reuse the cams in a different set of heads.

For what it is worth.....yes it detonated...but for a very brief moment. My truck was making a lot of power, I suspect at that moment it was making 11 second horsepower, boost was at around 14lbs. (boost would jump to 15+, and then back down to 14lbs) Except for ported heads, it will go back to the same state of tune it was in with a much stronger bottom end.
Dale

 

Thanks for the replys. Bad as L do you know at what RPM the engine was at when the rod let go? At least there are some clues as to what happened with your engine. Detonation can break any makers rods not just the factory ones. Granted some aftermarket rods can take more abuse before they fail than factory rods can.

captainoblivious, yes I have read the same types of things. That is why I started this discussion so that we may learn the reason behind the failure. Even on a stock truck what were the factors in the failure is what I am intrested in. And yes almost any engine can safely be supercharged to a degree. But the Lightning engine was subjected to design changes for a supercharged application.

Good discussion lets hear from any others that have broken rods.

John..

 

A friend of mine went to buy his first L. Brand new black 02 with 7 miles showing. Put a rod through the block on the test drive. They made it about 200ft out of the dealship.

 

First don't put to much faith into Ford's testing and standards. Look how many plugs fly out of the 5.4L heads on both N/A engines and the lightnings engines.

Next, take a look at the cobra's. For years guys have been throwing S/C on cobras, with a low boost and a good tune they're fine. But there are alot of ones that have blown due to the added stress of a blower. Now the 03' cobras are coming out and they have S/C on them and forged internals. Why - because Ford sees L engines throwing rods, and they know about cobra engines breaking due to S/C's on them. Same thing with Saleen, they are now starting to make the 281-e, with forged internals, and most likely for the same reason.

Now one of the reasons the rods break is because we have a really long stroke on our engines. If rods aren't strong enough they are more likely to break under long stroke applications such as ours. 1 little weakness or fualt when the rod is made and it drastically increases the chance of it breaking.

Someone correct me if I'm wrong, but we have the same rods as the regular 5.4's do right?

I'm sure someone more knowledgable will pop in and correct anything I got wrong.


Oh and one last thing, there are a bunch of broken engines out there b/c people pushed the truck to hard and ignored any warning signs like detonation, shuddering, etc. Whether they admit it or not, it happens.

 

Good observations, The length of the rod is a factor in the breaking. Plus the fact that most people racing the truck are going beyond the factory redline to make more power. The reason I started this post was reading everyones comments about the new blowers for the trucks. I don't think the stock internals would have much of a problem with added boost given you are conservative with the tune and Rod/Piston speeds. Running a higher boost level is not the root problem in the failure of Rods. That is why I was asking if anyone was data logging the truck when a rod broke. And as for the rod's between the N/A and S/C 5.4 they are different. Rods and pistons are changed for our application.

John..

 

JL suggested to set my redline at 5,600. I assume stock absolute redline is 5,500?