That picture of a bent rod shows that it failed in compression and buckled. IMO, most likely due to detonation, but also could be due to overboosting or too advanced timing (both of which generally lead to detonation) That was not due to excessive RPM, which would have caused a failure in tension, making the rod stretch or break.Horsepower is an imprecise measure of rod strength. Manley cites approximate HP in the catalog image, but caveats that with some of the other variables.
For our engines, being significantly undersquare, rpm may be more of a limiting factor than hp. For such a long stroke design, the 6,500 rpm redline is remarkable and generates insane piston speeds.
The stock rods seem to handle 800 hp ok. We've seen enough Whipples and TTs with stock bottom ends. But while 800 hp at under 6,500 rpm may be ok, far less hp may result in rod failure at over 6,500 rpm.
Boost is another tricky variable. Keep in mind that our stock blowers use 80 hp at full boost. A big Whipple will need well over 100 hp. So, a big Whipple motor needs to make well over 900 hp to put 800 to the output shaft and 7xx to the wheels.
The GT500 websites are full of broken and bent rod photos.
View attachment 37761
BTW, that's an I-beam, but I can't say for sure that it came from a 5.4 GT500.
And, who's to say the rod was too weak for the hp? Maybe the tune was to blame. Or over-revving. Ford was comfortable enough to put the same (or similar) rods in the 5.8 and put a factory warranty on 662 hp.
Pete is absolutely correct. The bent rod is definitely a compression failure as stated. Failure analysis to the trained eye can tell you a significant amount of information about the failure mechanism.That picture of a bent rod shows that it failed in compression and buckled. IMO, most likely due to detonation, but also could be due to overboosting or too advanced timing (both of which generally lead to detonation) That was not due to excessive RPM, which would have caused a failure in tension, making the rod stretch or break.
Being a technical person, I thought you might enjoy the papers in this SAE book.:thumbsupLast week, I picked up the SAE book on the FT and GT40--great book, can't put it down! (it is a bit pricey at $90 for a paperback)
I asked a similar question in the tire topic too. Over there it was about how the great amount of work on the Goodyears influenced the decision to use the same tire on the GT500
Here the question is similar. How much info sharing was done between the two teams on superchargers? The FGT used a different one, but underneath the engines were quite similar (yeah, I know, but at least for displacement and probably similar heat generation). Were design considerations on the FGT then leverged into the GT500?
Leveraging the FGT work, especially powertrain was SVT's intent, but I do not have first hand knowledge of the level of transfer to the GT500. I was not involved on the project and did not keep tabs on it. Mark McGowan may know.
With an appreciative nod of recognition to our esteemed Team Member mostly associated with our GT’s suspension, Scott says he does not have first hand knowledge on the engine development topic to adequately answer the specific FGT/GT500 engine architecture program carryovers. Although I was not on the Team, my interests lie in this arena and I have over the past 10 years talked to a number of Ford engine development members and will try my best to address some of twobjshelbys questions regarding parallels between the two engine programs.Glad its a help. 10-4 on water injection. I am sorry, I don't have the detail intake temp data for you.
I won't say that detonation CAN'T cause valve failures, but my experience is that it tends to put holes in the pistons, breaks rings and lands, and hammers the bottom end (rods and crank and bearings). Valve failures usually occur when the cam wears down, opens up the valve clearance, which causes the valve to slam into the seat instead of being "gently" lowered onto the seat by the closing ramp profile of the cam (I lost a Porsche 914 engine that way). Also, very worn valve guides will cause the valve to hit the seat at an angle instead of flat on all around its face, which can lead to valve seat recession, the valves not closing completely, and burned valves. However, I've seen some engines with really worn valve guides that still ran okay.I have seen detonation cause valve train components (springs, retainers and valves) to fail and pieces of valve dropping into the cylinder, preventing full stroke to TDC and bending a rod.
Not saying that is what happened in the picture tho.
Cylinder heads and crankshaft are the same, according to this article: http://web.archive.org/web/20080222195547/http://www.windingroad.com/features-page/ford-engines/Also I wish I had more detail beyond my memory, but didn't the ~2011+ GT500, finally use a head that was very close to the GT heads?