What caused this damage

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Stunning.

A lot of the comments already posted seem to cover the bases. I would also humbly suggest that perhaps the tuning was bad. The limited knowledge I have of big block blower motors is that a lean condition is death. You need lots of fuel and unrestricted exhaust. Perhaps the damage was started by overheated pistons. Can you see any burning or uniform cylinder wall scuffing? Just guesses

As far as stock mopar forged stuff, it's very good. I hope this doesn't reduce your opinion of factory parts. This is obviously extreme duty though and not a time to use stock components. You have to wonder how well it was tuned and what kind of fuel delivery it had if they put parts like that in it.

I agree with seeing the bearing copper. unlikely it got that pattern from starvation, you'd expect to see galling or tearing or even spinning on just 900 miles with a condition like that. Hard to believe they'd take a worn engine and throw a blower on it.

Someone could have even put a real low grade fuel in it and knocked it to death. The pistons could have been fitted too close. It could even have had a tapered bore job if it was machined incorrectly. There are so many places it can go wrong

I think there's an important backstory here we don't know about

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Vincent "hit" home with his post, since there could have been some other factors that may have caused this end result. Ignition timing and fuel mixture/fuel grade are paramount in a "boosted" engine, but so are the factors of a EXCELLENT cooling system and a WELL THOUGHT OUT oiling system also. Horsepower makes heat and heat has to be CONTROLLED to create maximum HORSEPOWER/TORQUE. But, you must first start with a ROCK SOLID foundation to build the HORSEPOWER on!!

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Having run a blown small block street/strip since 1985 I'll put in my 2 cents. Mine is a 340 so not everything applies. Stock block was used over 20 years, no failure. Upgraded to a R-3 block a few years ago. The result is less blow by,the breathers never drip a drip now. Original stock crank, rods were from the Chrysler Trans Am program. Venolia forged piston( 5/64 moly rings). I have beat on this thing to 7000 rpm a long time. Carb's were very rich a one time,not now. Stock jetted Carter Comp 750's, A?F is still 11.8-1 at wot. Timing is the key. Destroyed 2 sets of pistons before I figured that out. Only30 degress total lead. Same pistons since 1991. I run 12 PSI. Car runs [Email]11.0@123[/Email] 3875lbs in street trim.
Doug

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Classic example of what works and what doesn't. Just remember thought RB bottom ends ARE sturdy for most forms of competition, but emmense loads of torque/hp can play havoc with them. RB crank rod assemblies being both larger in stroke and rod length, exhibit more stress loading than it's B engine counterpart. B engine bottom ends are blessed (like the 340) with smaller circumferenced
cranks (less stress and rod loading). The 340 main webs are a bit thicker than the B/RB's main webs (even though the mains are nearly encased inside the B/RB motor). Bobweight and balancing, plays a big role too. The more mass to spin, the more power it soaks up. RB assemblies are heavy (in standard form) to begin with. Although VERY strong, they are high-torque, moderate hp/rpm pieces, with a some exceptions due to engine options.
Again it boils back to building a SOLID foundation
(a properly machined, clearanced and balanced block assembly), with a proper selection of power-producing parts/equipment, up top. By the way, Trans-Am engine pieces are kinda rare these days and were of the "improved" versions of the 340 hi-po production pieces. A much different forging than 340 Magnum pieces, they were made to take high stress loading at 8K, maybe higher in rpm. 3875lbs, not bad! Shed 300-500lbs and do some tuning, 10-teens are easy!

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The crank was checked and grinded 0.010 , they did not use any balancer on the crank, why i dont know but i will get one, what do you think about these parts

1. 440 -73 motorhome block that i have
2. Crank , will any of these brands do the job, eagle scat or k1
3. Rods same brand with 0.99 pins
4. Pistons 8.5:1 ross je venolia or wiseco
5. Aluminium or steel main caps and does they need to be cross bolted, will aluminium caps make the block last longer and what is best for street driving.
6. Does it need a girdle

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Suggestions to your questions (BUT DO research BEFORE you DECIDE!):

Q#1 - OK, but have it inspected and machined , if needed.

Q#2 - Aftermarket, yes, maybe better deal with a COMPLETE rotating assembly. Your choice of manufacturer.

Q#3 and #4 OK, but again your choice after reseach.

Q#5 - Steel, you'll want strength. If you are looking for "crossbolted caps", a new "crossbolted
type" block would be better alternative than converting your existing block to the "crossbolted cap" design.

Q#6 - Wouldn't hurt, especially at the hp level you're shooting for. Good alternative to the "crossbolt" caps/block scenario. Just have a good increased-capacity (8qt at least!) baffled oilpan, 1/2" pickup tube (modify block mount for tube) and hi-volume oil pump.

Food for Thought!!

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The crank was checked and grinded 0.010 , they did not use any balancer on the crank, why i dont know but i will get one, what do you think about these parts

1. 440 -73 motorhome block that i have
2. Crank , will any of these brands do the job, eagle scat or k1
3. Rods same brand with 0.99 pins
4. Pistons 8.5:1 ross je venolia or wiseco
5. Aluminium or steel main caps and does they need to be cross bolted, will aluminium caps make the block last longer and what is best for street driving.
6. Does it need a girdle

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The crank was checked and grinded 0.010 , they did not use any balancer on the crank, why i dont know but i will get one, what do you think about these parts

1. 440 -73 motorhome block that i have
2. Crank , will any of these brands do the job, eagle scat or k1
3. Rods same brand with 0.99 pins
4. Pistons 8.5:1 ross je venolia or wiseco
5. Aluminium or steel main caps and does they need to be cross bolted, will aluminium caps make the block last longer and what is best for street driving.
6. Does it need a girdle

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Do not drill the block for cross bolts Your weakening it by doing that I would choose aluminum main caps with good main studs and aluminum rods for your driving desires As far as the static(mechanical) compressionratio you might want to start with 9.0 to 9.5 to one and then limit the boost as well as use a intercooler or water and meth.alcholol injection

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We have two of them in our garage. This is the engine bay of a 1970 Chrysler New Yorker 4 D sedan


Iseriously doubpt that the reason for the breakage is the pistons or rods themselves. Shouldn't be at that power level. We have a 440 with a 6-71 that makes about the same power and it has been together for almost 30 years, but will be gone through this winter. We also broke a 400 with H-profile rods and a supercharger last summer, a rod broke. But that was because a cylinder wall cracked, water got on the piston and since it doesn't compress too well something has to give up... Although propably not the reason in this case, I would check the cylinder walls of that cylinder carefully just to be sure. Detonation might be one reason, but I would assume you should rather see it as gap walk first. And of course the pistons you have are tanks, but unless you wind it very high, I think it shouldn't be a major problem.

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The crank was checked and grinded 0.010 , they did not use any balancer on the crank, why i dont know but i will get one, what do you think about these parts

1. 440 -73 motorhome block that i have
2. Crank , will any of these brands do the job, eagle scat or k1
3. Rods same brand with 0.99 pins
4. Pistons 8.5:1 ross je venolia or wiseco
5. Aluminium or steel main caps and does they need to be cross bolted, will aluminium caps make the block last longer and what is best for street driving.
6. Does it need a girdle

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We have two of them in our garage. This is the engine bay of a 1970 Chrysler New Yorker 4 D sedan


Iseriously doubpt that the reason for the breakage is the pistons or rods themselves. Shouldn't be at that power level. We have a 440 with a 6-71 that makes about the same power and it has been together for almost 30 years, but will be gone through this winter. We also broke a 400 with H-profile rods and a supercharger last summer, a rod broke. But that was because a cylinder wall cracked, water got on the piston and since it doesn't compress too well something has to give up... Although propably not the reason in this case, I would check the cylinder walls of that cylinder carefully just to be sure. Detonation might be one reason, but I would assume you should rather see it as gap walk first. And of course the pistons you have are tanks, but unless you wind it very high, I think it shouldn't be a major problem.

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