Eagle Crank rated up to 400hp?

**JaycenK** · 12-11-2009, 01:43 PM

Hello, I have a problem. Had my machine guy buy me a rotating 383 kit for an LT1. Bascialy the botom end of the motor is all together and I just found out through Eagle's web site that the cast crank that was in the kit he got is only rated up to 400hp. I told him before he bought it I wanted to make around 500 flywheel and 400 to the ground.

My question: is it going to break if I end up making 500 flywheel hp? I don't know how these ratings work but I don't feel real good right now because my entire top end is a big question mark now. I know the rods are good to 500 and it has a forged piston in it. Let me know were I stand with this. It is going to be a street car but I don't want doubts every time I step on it weather I am going to flush 2300 dollars worth of work to the block and parts.

**JaycenK** · 12-12-2009, 03:37 PM

**c5z28** · 12-12-2009, 03:50 PM

Call eagle with the part number and ask them.

**azfrc** · 12-14-2009, 09:28 AM

You didn't specify cast steel or nodular iron, but if its a stock cast crank,
I wouldn't do it, although I do know guys who regularly spin cast cranks up past 6500 rpm. At 400hp I'd say you're pretty safe. At 500hp I'd say it's a crap shoot. Buying a forged 4340 rotating assembly gives you peace of mind where you don't have to worry about it. It's really rpm and not HP that kill an engine.

**Hi-Po** · 12-14-2009, 12:17 PM

Any word from Eagle on this? They would be the one to ask.

**JaycenK** · 12-16-2009, 09:27 PM

I put a call into them today but did not get a response yet. I have a list of questions I am going to ask them.
Found on thier site the crank is rated to 400hp. In another section it says 500hp. It's a cast 3.75 crank. I will let you all know what they say. I know there is a lot of bad press out thier on them with this crank but I can't figure out why so many builders use them if the suck that bad. It seems just about all lt1 rebuilders use Eagle & scat cranks for thier rebuilds, stroke kits, and whatever else. I have seen a lot of pics of broken cranks but never an answer as to why they broke, or what they were doing when they broke, or what kind of power they were making.

**408WS6** · 12-16-2009, 10:05 PM

It surprises me that they would even put a hp rating to their crank. And every Eagle crank that I have ever heard of was forged 4340, so it's probably good for the numbers your looking for. But even then there are no guarantees. I had a forged eagle crank and it blew up on me (no kidding). Its hard to say whether it was the cranks fault, or something else, but I went with a Scat crank this time around. So far, no problems, knock on wood.

**JaycenK** · 12-17-2009, 07:20 AM

Just got off the phone with Jimmy at eagle. Jimmy claims yes they have failures but alot of it is nos related. He claims the cast crank is good to 500 hp and up to 7000 rpms.
He also said failures arise on non NOS or boost engines because bearings are not sized right and people use stock weighted flex plates. This is what he harped on, on an internally balanced motor BOTH the flex and the balancer MUST be neutral. From the factory an LT1 uses a weighted flex plate or a weighted flywheel, but the balancer is neutral. He claims this is the root of most failures because it causes the thrust main to overheat the cap, bearing, and the journal. Another problem is people put the rods in backwards and the rods actually ride on each other. They fit and spin ok but it causes the rod to over heat the bearing, rod cap, and journal. This is why most cranks break at the rod journal next to the counter weight. The blue colored rods was the result of the failure to install them the right way and not damage caused after the crank broke. As far as casting defects, it's part of the game I guess. He admitted that yes they have failures but from the sound of it so do scat, stock, and other aftermarket. A chance you take with cast. I wish my machinist would have gone with forged internals but I don't have the money to fix it right now so I guess I have to chance it. I will still have the motor that’s in it now as a fall back. And if it happens I am just going to buy a short block and pray it wont take out my heads in the process.
To many builders use eagle to have that many problems. I am going to guess that most of the failures are from doing to much with too little. Others I am sure are just flat out casting defects. Some time there is just no way to know if one has a casting defect or not. Hope that helps some others as well. CHECK EVERYTHING.

**408WS6** · 12-17-2009, 05:08 PM

Originally Posted by JaycenK

Just got off the phone with Jimmy at eagle. Jimmy claims yes they have failures but alot of it is nos related. He claims the cast crank is good to 500 hp and up to 7000 rpms.
He also said failures arise on non NOS or boost engines because bearings are not sized right and people use stock weighted flex plates. This is what he harped on, on an internally balanced motor BOTH the flex and the balancer MUST be neutral. From the factory an LT1 uses a weighted flex plate or a weighted flywheel, but the balancer is neutral. He claims this is the root of most failures because it causes the thrust main to overheat the cap, bearing, and the journal. Another problem is people put the rods in backwards and the rods actually ride on each other. They fit and spin ok but it causes the rod to over heat the bearing, rod cap, and journal. This is why most cranks break at the rod journal next to the counter weight. The blue colored rods was the result of the failure to install them the right way and not damage caused after the crank broke. As far as casting defects, it's part of the game I guess. He admitted that yes they have failures but from the sound of it so do scat, stock, and other aftermarket. A chance you take with cast. I wish my machinist would have gone with forged internals but I don't have the money to fix it right now so I guess I have to chance it. I will still have the motor that’s in it now as a fall back. And if it happens I am just going to buy a short block and pray it wont take out my heads in the process.
To many builders use eagle to have that many problems. I am going to guess that most of the failures are from doing to much with too little. Others I am sure are just flat out casting defects. Some time there is just no way to know if one has a casting defect or not. Hope that helps some others as well. CHECK EVERYTHING.

Well, my engine was a non-nos engine. And it was the rod bearing, not the main bearing that failed. But to be fair to Eagle, it probably wasn't the Eagle crank that failed, but I suspect (and other expert opinions suspect) that the bearing clearance was not right and not properly checked. He is right in that you MUST check EVERYTHING. The one thing you don't check will likely be the thing that fails. Murphy's law.

I went with a new engine builder this time around, and so far has worked out very well. I won't name the other engine builder that built my other POS, but might in a pm if anyone really wants to know...