How much HP is too much for a set of stock crank and rods in a 402 big block? I'm building up the short block and the engine will end up producing about 500HP and 530 ft-lbs with 10.6:1 compression. I'm trying to spend my money wisely and would like to use the equipment that is already paid for, but would like to avoid a costly rebuild. Some of the parts magazines recommend a forged crank for anything over 450HP, but I didn't know if anyone out there had safely (no broken crank) run 500 HP on a stock crank. The engine is going in the '70 chevelle and will be a weekend street machine/ limited usage vehicle. Any and all opinions/ help is appreciated. Thanks.

Patrick Bellene

Patrick , I'm presently building a 454 : 2-bolt, cast crank and truck rods. I'm expecting 600 plus hp. I'm told that a 2-bolt with a stud kit and cast crank are good up to 600 or more. We'll find out soon because this will also get a 150 shot of NO2.

I have a friend running a stock cast crank and rods in a 502 that made 625 hp and 640 ft-lbs of torque. He has turned it to about 6800, but generally shifts at 6300-6500 rpm. As it is a street car first, it doesn't get as much abuse as a single purpose drag/race car. I would make sure you put a good bolt in the rod and the lighter the pistons the better.

Plenty of guys run cast cranks in 454's well into the 500HP range. A 3.76" stroke is even more forgiving. If your crank has a "N" prefix, it is nodular iron and very strong. My 402 motor has studded mains, a nod crank .010/.010 and stock rods w/ ARP bolts. Have had it to 6200 - 6300 and plenty of full throttle (3000 rpm converter) launches. No problems or worries here.

The real killer of bottum ends is not having it built with correct clearances and detonation. Detonation will just hammer a crank to death. Build it with good pistons, balance it and run it.

Which 402 do you have? A lot of them had forged cranks from the factory. The rods are the weak link even with a cast crank and should be upgraded even with just a bolt change. I went into the 10s with a 70 402. It was a 2bolt block with aftermarket rods and pistons and a forged factory crank. Had absolutely no problems with the setup.

Stock crank/rods are fine for what you want to do..as Mike pointed out,upgrading rod bolts is a wise idea too..either ARP or Pioneer replacements will work fine.

The N/A 468 in this 3100.lbs camaro has been running a stock cast crank and rods (and a 2 bolt main...) for over 10 years and is still running strong. The motor has been freshened a few times but still runs the same crank and rods. It's run a best of 6.2x at our 1/8th mile track.
http://www.chevelles.com/showroom/Purs/J.jpg

i as well have ran the cr@p out of a stock bottom end......i am a budget man .i build stuff cheap as one can.....i pound the cr@p out of them and i just keep going. have i broke a crank or rods..nope not yet....one of the engines i built was a 396 two bolt main, stock cast crank 30/40 ground (125 dollar regrind kit with bearings), stock rods , stock bolts everywhere from a 70 c-10 truck, this sucker went 7200 rpms on an unbalanced bottom end.....it ran in the tens (just a few times) on 175 hp nitrous shot.....this engine ran for 5 years before i tore it down and went threw it again....i did how ever...have alittle more money and bought arp studs and rod bolts..and balanced it....lol for a smaller hp motor.what was i thinking...lol

other bbc 396 i have built i just used what ever came with the engine, stock everything, and built it from there...most ran from 14's to 12's range and no problems......

i would say though clearences are key.....must be right on "within" spec.....

the bottom ends have appeared to be very strong in the bbc engines.....i think they would do for any street driven car(my idea is high tens and slower).....new bolts tho seem to be a good investment. maybe to me more a feel good factor....as i seem not to worried about blowing anything in the bottom ends...even stock.......maybe one day i will blow a crank or rod out the block and really have wished i would have bought them.....

jmo.

thought i would add as well.....my 468 has a cast crank, 10/10, with factory rods which have been lighten and polished on the sides i did intall arp rod bolts and stud the bottom end, this is with 13.5 to 1 comp.....it did have 14.9 to 1 when it ran 126 mph down the 1/4....i may find the limits with this motor...but only this year will tell.......

I had a factory steel crank, factory truck rods(bushed), factory TRW's and a 2bolt main(no studs). Ran it to 7300 throught the traps. No problems on the rebuilds either.

I forgot to mention that it was a 427.

Rob

A buddy of mine ran a two-bolt 454 (.030 over- 460) with a cast crank, 3/8 rods with ARP bolts, Heavy 12.5 to 1 TRW domed pistons (comp ratio was less because of open chamber heads)with a two-stage nitrous setup and never had a problem. Ran in the low 10's on juice and 11's N/A.

Thanks for the responses guys. I looked up the cost of studded ARP mains, and they're only about $50, which I think is pretty cheap insureance. My next question is why are studs better that regular main bolts? They are both using the same thread in the block? The only visual difference I see is that you have a set of fine threads to bolt on to, perhaps you get better torque retention, any ideas?

The builder that built my 505 has just torn down my old .030 over 454, said bearings were fine,crank,cam,rods and pistons looked great, going to hone it and put it back together for my son. The heads had Milodon stainless valves with a single face valve job, going to clean them up and do a 3 angle valve job and install new springs and it should be running mid 11's in my sons Olds. He did say that the valve springs varied as much as 30% which isnt too shabby after 600+ passes and several street miles in the last 5.5 years.

hi.i had in 461 bbc two bolt cast crank.crank was very carefully prepped and i had 6.535 c&a rods and light venolia pistons.the engine ran 10.14/137 with 1.54 60 ft.my car weighed 3300 lbs and i rewwed the engine constantly over 7000 and later sold it to a super comp car where it still lives and breathes.it`s gone flat out 8.70/165.the crank was polished and shotpeened and was turned 0.010 under.rods can`t handle that kind of abuse,the original old ones even with 7/16 bolts,i think.

Originally posted by Patrick Bellene:
My next question is why are studs better that regular main bolts?Just guessing here....the studs use all of the threads in the block, where the bolt obviously should not bottom out(assuming blind threads), leaving a thread or two unused. Using all of the threads would make for a more stronger (as my nephew would say) connection. Again, just a guess.

It's several things. As was mentioned, full engagement of threads in the block is assured, the finer threads of the nut on the stud make for a more-accurate, more similar torque reading from nut to nut, and the fastener is stretched properly. I also prefer both ends of the fastener being threaded, as opposed to reliance on a bolt shoulder when dealing with a main bearing cap or cylinder head, but that's just me. The higher quality of the fastener material is the biggest deal, but we all know ARP makes bolts, too.

Besides...studs are cool.

Scott Parkhurst~!