Stock LA rods

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Dart_br

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What is the power limit that stock LA rods can handle? No theory, only facts please! I refer to stock small forging, not the "big ones" 340 4bbl rods.
 
With good aftermarket bolts over 500hp, will depend on piston weight and rpm too but had a set in a 340 that was 500+ on nitrous that spun 6700 for years.
 
I was thinking what is harder to rod handle, high rpm's or big angles in big-arms stroker cranks... Any guess?
 
A lot depends on rpm and piston weight as well. I've heard of people using early 318 and 273 rods for the lighter weight, but I don't know about their life expectancy. Eagle and Scat I-beams are similar but each of those use a different forging material, which may also be different from OEM.
 
Come to think of it....in 20 years of wrenching, and 30 years of living in a Mechanic Family..8 years stuffing boost on 4 stroke engines turning 9,000 rpm...I have NEVER seen a rod that broke because it was WEAK.

Lack of oil, piston to valve contact, hydrolock, detonation, sure....seen 1000's of bent/broke rods.....never was the rod bent/broke because the material was subpar.

Edumacate me also ohhhh wise ones...:prayer:...how much power will a 1977 smogger stock 318 rod take before it lets go?
 
The last 360 I had used stock 360 rods w/ARP bolts. I ground the "knots" off each end and polished the beams. That motor went through the lights at 7K for several hundred passes and saw street miles also. Ran 11.50's in a 3200LB Duster. Not sure what kind of power it made but they held up fine for years. For the money I would use the SCAT I beams. I have used the SIR's but the scats wheren't out yet. H beams are also nice but heavy.
 
I have stock rods in my midly built 318 with a stock steel crank and have spun mine at 7,000rpm and going to continue to use them when i tear it down for better heads balance it and a larger cam. If that helps any lol
 
Prine said:
Edumacate me also ohhhh wise ones...:prayer:...how much power will a 1977 smogger stock 318 rod take before it lets go?
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That's the point!

I build a lot of 4 cyl turbocharged, and YES, i ever had a lot of failures on stock rods. No oil issues, valve, clearances, and they FAIL. Even on hi-prep N/A. But mopars are new to me, and that is the reason im asking this. Good to know from you, a person with REAL experiences, exactly what im looking for.
Here in BR is very complicated to get parts for v8, they are expensive and hard to find, due to this, the old stock rods became an option for me. I have a set of magnuns and a set of 318 LA rods, and in my opinion, looking closely in the construction details, is hard to determine wich one is the strongest.
 
bignick said:
The last 360 I had used stock 360 rods w/ARP bolts. I ground the "knots" off each end and polished the beams. That motor went through the lights at 7K for several hundred passes and saw street miles also. Ran 11.50's in a 3200LB Duster. Not sure what kind of power it made but they held up fine for years. For the money I would use the SCAT I beams. I have used the SIR's but the scats wheren't out yet. H beams are also nice but heavy.
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The books and the experience itself make me see that the bolts sometimes are as or more important than the rod that will be used.
 
I know you're looking for real world experience, but you need to find someone that has broken stock rods and under what conditions they broke under. I have run these to 6500/7000 N/A and never lost one. Probably lucky, but it is what it is. In a stroker situation, the piston will take more abuse, due to speed, then the rod, imo. If your really concerned about this with what your planning, i'd just go aftermarket and be done with it....By the way, did you get your crank squared away while you were in Florida?
 
To the OP, there is not set hp/tq number where the rods fail becuase there are a gazillion variables. Stock rods are great for a nice street driven mopar, hell my brother has a 381rwhp 360 with factory cast crank and rods (76' pieces) and he's got 42,000 miles on that setup! But his msd pills cut spark at 5700rpms so its not screaming and thats the key...

Only a few people have mentioned RPM's...stock rods are plenty stout up to about 450hp, but once you spin them past 6000rpm's or so on a regular basis, you begin to walk the tight rope (same story with a cast crank). If you're bulding a high revving screamer, go forged for piece of mind and longevity
 
Broke a stock 340/360 rod several years ago, snapped on the beam, cause heavy *** TRW pistons at about 7000 rpm....engine had been together for about 7 yrs.

stock 360 cast crank was fine.......
 
I had a 360 that I sprayed with a 180 shot for about 8 years with stock crank and stock rods...BUT, I had very light JE pistons and ARP rod bolts on those rods. I think if you are asking the question "what can these rods take", then it is time to upgrade. When I built my stroker I didn't want to find out if the stock rods could take the abuse of a longer stroke, so I went with Scat I-beams which are 4340 steel (and of course, a very light piston).
 
OldmanRick said:
I know you're looking for real world experience, but you need to find someone that has broken stock rods and under what conditions they broke under. I have run these to 6500/7000 N/A and never lost one. Probably lucky, but it is what it is. In a stroker situation, the piston will take more abuse, due to speed, then the rod, imo. If your really concerned about this with what your planning, i'd just go aftermarket and be done with it....By the way, did you get your crank squared away while you were in Florida?
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I call Dan but couldn't find him, in the last minute, after several calls to summit they delivered the crank. My wife don't know, but the parts was the purpose of the travel. She still thinks that was seaworld and disney world =)
 
flyfish said:
I had a 360 that I sprayed with a 180 shot for about 8 years with stock crank and stock rods...BUT, I had very light JE pistons and ARP rod bolts on those rods. I think if you are asking the question "what can these rods take", then it is time to upgrade. When I built my stroker I didn't want to find out if the stock rods could take the abuse of a longer stroke, so I went with Scat I-beams which are 4340 steel (and of course, a very light piston).
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This is the kind of experience that i am looking for. My engine will be a mild stroker, to be upgraded in the future, so i think the stock rods will handle my goals, e when i get bigger heads and cam, will be the time to upgrade the rods also.
 
"I think if you are asking the question "what can these rods take", then it is time to upgrade."

This is the best piece of advice. If you're nervous - upgrade.
 
Buy eagle SIR rods or Scat well worth money and not much more than reconditioning stock rods with new bolts
 
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