Some good news for those seeking super strong 4.6 connecting rods because as of now, thanks to Manley, there are some new off the shelf choices avalable for steel 4.6 rods. It used to be that the Manley's pro series rods made from 300M tool steel were a custom order part, but now Manley is making 300M 4.6 pro series rods avalable as an "off the self" part. It look s like the "standard weight" Pro series rods can hadle the same amount of power with the only diffrence being that the 300M rods at 650 grams are slighty lighter than the 680 gram standard weight pro series rods. I suspect that the 300M rods will also be more expensive than the standard wieght versions.
I first became aware of the 300M rods when 5.0 mustang magazine did a article on 2300HP 4.6 modular motor and I was impressed at how the Pro series I beam rods made from the 300M material survied multiple passes at 2300HP and 8000+ RPM. http://www.mustangandfords.com/how-to/engine/m5lp-0906-mercury-cougar-cobra-hybrid/
I tend to go overkill with my car as wittnesed by Viper T56, oversize Brembo brakes, etc so as soon I start my engine build for my mostly street driven Cobra, I'll go overkill with the engine parts as well so the rod of choice will be the standard weight 680 gram pro series rod with the oversize 7/16 bolts.
You right in that running the standard weight or the 300M rod would proboly be overkill a mostly street driven car but that's what I want. Years ago when the original 5 speed gave out on my 01 Cobra, I bought a Viper T56 because I did not want to have any more worries at all about durability and I'm going to use that same approach for the engine. Yeah, 7/16 is the same size bolt that Manley uses for their Ford powerstroke diesel rods so no worries about durability there and besides that, my car is a heavy 2001 Cobra convertible with a Vortech T trim blower so I figure why no just spend some extra money on some good rods and be done with it. I will also spend a little extra for tool steel pins on Manley's platinum pistons. The way I see it , I'm buying peice of mind by going over kill.
I think you are talking about the 300M rods and the standard weight rods with a "heavier beam for forced induction applications" should priced less than the 300M versions. All I care about is the durability and I suspect that the only advantage with the 300M vs. the standard weight rod is that the 300M rod is lighter.
Well the new standard manley rod was there heavy duty version which just came out at the beginning of the year. That being said there are a lot of cars out there with over 1000hp running them without a problem...so everything most ppl have now are their lightweight versions. Just because Manley's retail is $2200 doesn't mean we will pay that.
I just spoke with Manley and the suggested retail price for the 300M rods is $2200 while the standard weight rods go for $1500. Finally, Manley stated that the 300M was the rod that can handle the most power.
"The Manley rod is a serious piece. The original I beam rods lasted reliably up until around 1300 hp. Thus the 300 M rods were designed. There are many other options, Oliver probably being the best, the problem is the wait time. As far as weight is concerned, heavy seems to keep getting mentioned. Just what does that mean and being relative to what? The 4.6 300 M rods are around 650 grams give or take a few. If you look at a comparable Oliver or any other manufacturers rods they simply are heavier. The normal Manley I beam rod is 600 grams. We have reliably made over 1700 hp with the Manley rod and to date have never, ever bent one, broke one , or damaged one. We ran over the weekend in Las Vegas testing with the Pro Stock guys for Pomona. 10 passes between 6.79 and 6.73. Best pass was 6.731 @210.96 The best Pro Stock that I saw was Greg Anderson @ 6.82 @ 203.5 10 passes, 10.7 to 1 compression, 40 psi boost and 9200 rpm shifts, I'd call the Manley rod a good piece for the money. John Mihovetz."
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