Manley 5.4L rods

[DJOHAGIN]

Has anyone investigated using a 5.4L rod in a 460 build? I was looking at this rod:

http://www.summitracing.com/parts/MAN-14319-8/

It weights 628 grams and is "rated" at 800 hp. That is around 185 grams lighter than the "typical" 6.605-6.7 rod for a 460. I'm planning on a off-set crank and custom piston, so the odd sizes for the rod and pin diameters and width are not a problem.

My primary question would the power rating of the rod go way down because of having to use a heavier piston than the "typical" 5.4L piston?

I'm exploring different ways of getting a lightweight rotating assembly, when I came across this rod. I've been thinking about aluminum rods before this, but don't know exactly how long they would last for a street engine. I like to use the engine for deacceleration, and I know that puts a lot of stress on the rods.

Thank you for any help or suggestions,

Dave

[jc10000rpm]

the manley rod is .050 narrower than typical BBC rods (like the 6.7 mostly used in BBF builds) that is the difference in weight your seeing

the horespower rating is affected by piston weight and rod angle, longer stroke........... wider angle

IMO the scat "pro comp" rod (about $300.00 per set) would be a good value along the lines your thinking, however, it is heavier see specs below

Manufacturer: Scat
Mfg part #: 2-ICR6700-7/16



Description:
• NEW Forged High Tensile 4340 Chromoly Steel
• 7/16" ARP/Scat 8740 Cap Screw
• Lightweight "I" Beam construction
• Each forging is x-rayed, sonic tested & magnafluxed
• Shot peened to stress relieve surfaces
• Packaged in weight matched sets ± 1 grams
• Big block rated to 800 HP

[iadr]

I'm waiting on a prepaid set from the local place I hope to do my dynoing.

In my case I am using them (Manley 5.4 rods in the I-beam configuration) in a Mercruiser 4 Cyl, 460 based motor.

... Thought they'd give me a major offset grind (2.5 to 2.086) since I have no aftermarket crank selection... and also a streetable compression height.
Low weight was an appeal, too

[DaveMcLain]

You will certainly end up with a small light wrist pin if you use the Mod rod.

[iadr]

yeah- .866" !!

looks tiny, but the import tuners are running 800-1000 hp through 4 of pins that diameter.
I'm sure they are petty thick walled, but no one upsizes, even to .927. Running 650-750 hp through 8 will not be an issue, unless they are spec'ed wrong. (not that you suggested it would, Dave.)

[DJOHAGIN]

Originally Posted by jc10000rpm

the manley rod is .050 narrower than typical BBC rods (like the 6.7 mostly used in BBF builds) that is the difference in weight your seeing

the horespower rating is affected by piston weight and rod angle, longer stroke........... wider angle

IMO the scat "pro comp" rod (about $300.00 per set) would be a good value along the lines your thinking, however, it is heavier see specs below

Manufacturer: Scat
Mfg part #: 2-ICR6700-7/16



Description:
• NEW Forged High Tensile 4340 Chromoly Steel
• 7/16" ARP/Scat 8740 Cap Screw
• Lightweight "I" Beam construction
• Each forging is x-rayed, sonic tested & magnafluxed
• Shot peened to stress relieve surfaces
• Packaged in weight matched sets ± 1 grams
• Big block rated to 800 HP

I looked at that rod, but it is the same weight as BBC 6.7 rod, or is it misquoted?

Originally Posted by DaveMcLain

You will certainly end up with a small light wrist pin if you use the Mod rod.

Dave, don't you have to increase the wall thickness when going to a smaller diameter pin, so the weight stays about the same?

Thanks,

Dave

[DaveMcLain]

I'd have to look at the weights to know for sure but a year or two ago I built a 4.6 Ford for a twin turbo application. That engine had a Manley rod and a piston from Diamond. It seems that while the piston pin was rather "heavy duty" it still ended up quite light. The length was quite short too.