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#1
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What do you consider the horsepower limit for OEM 383/400 rods?
I'm new to big-block Mopars (had smallblocks before) and I'm currently aquiring parts for my 400. The engine will be fairly "mild" by today's standards of power. I've been told that the combo that I am planning could be good for 375-400rwhp. This will be in a car that will basically be a nice-day and weekend car that might see a few passes at the dragstrip in the summer just to see what it will do. Will the stock rods be OK to this point? This is one area that I could save quite a bit of money to spend elsewhere on the engine.
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#2
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Mopar had some of the best OEM rods. Youll be fine. Use a new set of rod bolts, ARP or Pioneer and forget about them.
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#3
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#4
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Is it really horsepower that breaks rods? I mean, the reason they break is propably not because the enormous cylinder pressure compresses them flat? I believe it's more rpm&stroke, than horsepower related thing, the weight of the reciprocating assembly and the legnth of the stroke (speed and accelration rates at certain rpm) has a big role in this. Light pistons, light pins, and the rod can handle a lot more "power" = rpm. But the B-engine factory rods are strong designs. Of course you propably do not know how bad they have been abused in the past and how much life they have left, but with good quality bolts they are capable of handling some enormous stresses. we had a budget 400, cast crank, stock rods with ARP bolts and TRW 2266F "tank pistons", 1100 grams with pin. Never dynoed this engine, but I believe it made over 500 crank hp. The '73 valiant, although a light car, run 10.6/128 mph with it and the engine was turned to 7500 rpm, on pump gas & with factory head castings. Those short stroke B's really like to wind!
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#5
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A 375-400HP engine is almost "stock". Driven as a street cruzer, with occasional blasts on the drag strip----you stock rods will work just fine.
As has been said before, use good bolts, have them resized, etc. We had an oval track BB(452) with about 600-625HP(pretty serious) and stock rods worked well up to 7200-7400 RPM for about 1200 laps. Then the big ends began to "egg shape". I have never seen a BB rod break---but I have seen them used too long and "egg shape". Just try to keep the piston/pin weight as low as possible. |
#6
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Does Horsepower break rods?
I wish I still had the article, ( maybe I do if I looked hard enough ) but 10 to 15 years ago I think it was, Dick Landy did some articles on engines. Everyone knows that weight and rpms will break rods but Landy showed that horsepower will to if I remember correctly.
Not too often do you catch an engine BEFORE the rod breaks. I beleive he showed an engine pulled from a dyno that had ( I think ) 6 pack rods and light pistons putting out big hp using some heads his shop did. Someone noticed something not right and shut it down and it was torn down. Several of the rods were badly bent but not broken. This was a rare thing because most often we don't have the dyno telling us when something gos wrong and we end up with a lot of scrap. I think this engine wasn't turning big rpms when it happen. It was about then that he also stated that a stock RB block is only good to about 800 to 850 HP. Then it starts cracking the towers under the crank. Okay, I'm getting old and forgetful but some things stand out. Anyone else remember the articles I'm talking about? He built an BB and put it in a 50 something Desoto if memory servers. Just thinking out loud. Maybe too much. |
#7
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#8
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Yes......
Have the rods resized, magnifluxed and new ARP bolts and they shold hold 500 to 550 HP. ( Flywheel )
I'm using my stock 340 rods (rebuilt) with Ross 514 gram pistons and this equals going to a much stronger rod with a stock piston. Rod has to handle less stress. |
#9
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For what you are doing the stock rods will be fine. I use stock rods in my 400 and turn it 7000rpm and it makes around 560hp. If I had more cam in it I would turn it 7500.
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