Forged crank machining

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nitrojunkee

nitrojunkee

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Looks like I may need to go down to .030 on the rod journals, on my factory forged 440 crank to get the stroke equalized. Going on the low side of .010 on the mains for the little bit of extra oil cushion. I was hoping to only have to go .020 on the rods, but we'll see. Any problem in going that far down, does anyone know? The machinist said they do it all the time, and it's a very reputable shop. This motor won't see over 7000-7200rpm and a max of 12lbs of boost.

Thoughts?
 
7200 rpm and 12lbs boost, I'd be looking at something aftermarket but that's just me.
 
Dcuda69 said:
7200 rpm and 12lbs boost, I'd be looking at something aftermarket but that's just me.
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Well, keep in mind, I'm at 6000' here. So I'll be down on power quite a bit from what you're probably thinking. We lose 80-100hp up here. This motor will probably only make 500-550hp here.

Also, I did have the crank mag'd and there were no issues.
 
moper said:
12psi? Blower or turbo?
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Procharger D1SC, blow through CSU carb. When I said 12lbs, that would be the max. My goal is to keep boost to 8-10lbs though. And also, I'm trying to spec out a solid roller that will take advantage of the flow at .600 on the RPM heads, without getting too crazy. Like I said, I don't want to spin the motor passed 7200. My machinist says these factory forged 440 crankshafts will take a lot more abuse than you think. But, I thought I'd see what you guys think as well.

He's in the process of align honing the mains now, with the ARP studs I brought him, and decking the block. Then I told him to let me know what the final deck height is so I can order pistons from Diamond, for zero deck. I'm going with Scat H-beams. Obviously I'm in the beginning stages of the build.
 
this is a pretty serious build. thats alot of rpm for a 440. that compounded with boost. I would consider an aftermarket crank mandatory. That and a pair of top shelf rods and a stud girdle.
 
Aside from whatever power adder you're talking about, on a N/A build with a forged crank, .100 under wouldn't hurt a thing. Taking into consideration your build I tend to agree to go aftermarket.
 
a new crank has not seen 1000's of miles and continued abuse. Newer HIGH quality forged cranks are going to be built from materials that are designed for the end users intended use. If he is planning on making 500+ hp NA. then stuffing 10+ lbs of boost to it then why even chance it. that is not a stock build. so why use stock parts?
 
younggun2.0 said:
a new crank has not seen 1000's of miles and continued abuse. Newer HIGH quality forged cranks are going to be built from materials that are designed for the end users intended use. If he is planning on making 500+ hp NA. then stuffing 10+ lbs of boost to it then why even chance it. that is not a stock build. so why use stock parts?
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This ^^^^^. Everything has a life span. As I said, in a N/A build, .100 under and you'd never know the difference. But the fact that the crank is an original forging, decades old, you don't know what it's been through, plus you're talking about going .030 on an engine with a very high power output. If ever you were trying to find the crank's failure point, that would be it. It's your money. Run it if you want to. You can get a nice crank for around 700 bucks. I would hate to see that engine destroyed because you didn't spend an additional 700. What have you got in it? 5 times that? More? Think about what you're doin. Even if you have to wait to save the money, it's worth it.
 
younggun2.0 said:
a new crank has not seen 1000's of miles and continued abuse. Newer HIGH quality forged cranks are going to be built from materials that are designed for the end users intended use. If he is planning on making 500+ hp NA. then stuffing 10+ lbs of boost to it then why even chance it. that is not a stock build. so why use stock parts?
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It won't make 500+ horsepower naturally aspirated up at this altitude though. The entire combo might make 500-550hp with 10lbs of boost. And I'm using a stock '77 440 block that has been mag'd and sonic checked. The crankshaft was mag'd as well and looked fine. The thing I'm mostly concerned about is going .030 on the rod journals to get stroke equalization.
 
nitrojunkee said:
It won't make 500+ horsepower naturally aspirated up at this altitude though. The entire combo might make 500-550hp with 10lbs of boost. And I'm using a stock '77 440 block that has been mag'd and sonic checked. The crankshaft was mag'd as well and looked fine. The thing I'm mostly concerned about is going .030 on the rod journals to get stroke equalization.
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your already putting lip stick on a pig. if your dead set on running a stock crank i would get one that does not require that level of machining. in fact it would be cheaper to get a crank that is alot closer to specs. and not have to pay for the machine work.


I think you need to concentrate more on "Is this the right crank" than "Will this crank come apart"
 
RustyRatRod said:
This ^^^^^. Everything has a life span. As I said, in a N/A build, .100 under and you'd never know the difference. But the fact that the crank is an original forging, decades old, you don't know what it's been through, plus you're talking about going .030 on an engine with a very high power output. If ever you were trying to find the crank's failure point, that would be it. It's your money. Run it if you want to. You can get a nice crank for around 700 bucks. I would hate to see that engine destroyed because you didn't spend an additional 700. What have you got in it? 5 times that? More? Think about what you're doin. Even if you have to wait to save the money, it's worth it.
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Who sells a nice crankshaft for $700? 440source? No thanks. Even a Scat is more than a grand, and that's about as low on the manufacturer pole as I'd go. You guys keep saying "very high horsepower", but I don't think you realize just how much power we lose at 6000' above sea level. As I said, this combo MAY make 550hp on 10lbs of boost, but probably more like 500-525. You wouldn't trust a factory forging that has been mag'd to 500hp? This isn't a roots or screw blower, It's centrifugal and low boost.

Maybe I'm completely wrong in my thinking, and need to go back to the drawing board.
 
younggun2.0 said:
your already putting lip stick on a pig. if your dead set on running a stock crank i would get one that does not require that level of machining. in fact it would be cheaper to get a crank that is alot closer to specs. and not have to pay for the machine work.


I think you need to concentrate more on "Is this the right crank" than "Will this crank come apart"
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I don't know, maybe so. I appreciate the input, for sure! Guess I need to really think about it some more, before I get any deeper in.
 
nitrojunkee said:
Who sells a nice crankshaft for $700? 440source? No thanks. Even a Scat is more than a grand, and that's about as low on the manufacturer pole as I'd go. You guys keep saying "very high horsepower", but I don't think you realize just how much power we lose at 6000' above sea level. As I said, this combo MAY make 550hp on 10lbs of boost, but probably more like 500-525. You wouldn't trust a factory forging that has been mag'd to 500hp? This isn't a roots or screw blower, It's centrifugal and low boost.

Maybe I'm completely wrong in my thinking, and need to go back to the drawing board.
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this answered that.


your already putting lip stick on a pig. if your dead set on running a stock crank i would get one that does not require that level of machining. in fact it would be cheaper to get a crank that is alot closer to specs. and not have to pay for the machine work.

we are only telling you what we recommend. in the end its your build. sounds like you already have your mind made up and your looking for validation. It could last forever. it could blow up on the dyno. wont know till you throw it together and run it.
 
Build the thing. You could get an aftermarket crank, girdle etc, and have way more money wrapped up in overkill too. Opinions are just that.. so too all these aftermarket crank advocates, show me a picture of a broken factory forged 440 crank.
 
72BBSwinger said:
Build the thing. You could get an aftermarket crank, girdle etc, and have way more money wrapped up in overkill too. Opinions are just that.. so too all these aftermarket crank advocates, show me a picture of a broken factory forged 440 crank.
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Thanks! That was originally my thinking. I won't put a girdle on it, I never thought I needed that. I've never seen a factory forged 440 crank break at the power level I'm looking at either. And I was asking for opinions, but mostly about the degree of machining on the rod journals. I'm not sure about possibly having to go .030. Even if the machinist says not to sweat it. That was my biggest concern....

I hope nobody takes any of my posts the wrong way, I'm totally open to listening to what anyone has to say, about anything. I don't know everything, and don't claim to! I value what anyone says, and will always take it into some kind of consideration! ;)
 
Makes a little more sense now. Your original post just said 7200 AND 12lbs boost. Now it sounds like the goal is 550hp....you shouldn't have to spin it to 7200 for that(especially with boost) and I don't know if Eddy RPM heads would support that any how? You should be fine...just sounds strange to use aftermarket rods/pistons/ heads,etc with a stock crank cut .030" but it'll probably work. Good luck and post back when it's together!!
 
Dcuda69 said:
Makes a little more sense now. Your original post just said 7200 AND 12lbs boost. Now it sounds like the goal is 550hp....you shouldn't have to spin it to 7200 for that(especially with boost) and I don't know if Eddy RPM heads would support that any how? You should be fine...just sounds strange to use aftermarket rods/pistons/ heads,etc with a stock crank cut .030" but it'll probably work. Good luck and post back when it's together!!
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Thanks man! I will be going from 2.14" to 2.19" intake valves on the RPM heads, and doing my own bowl work. Hopefully they'll flow a little over 300cfm @ .600 that way. We'll see what happens. I contemplated doing a build thread, but maybe I won't now lol. I'll definitely post up a vid or something when I get it put together and shoved in.
 
0.030 undersize bearings don't hold up well at high rpm or so i have read in the past, but if you're going this route why not use 2.200" (chev) size rod ends .You could even offset grind the crank and pick up 30 cid
 
I'm all about truned factory cranks - within thier limits. I have one on the shelf that's .020/.030. But to hang a belt driven supercharger on one and then rev it to 7K? I wouldn't use a factory crank for that if it was new... Buy an aftermarket. They are designed for more power, made of a better material, and have no time on them as noted above. No need to consider bearing speed or loads... You're asking too much.
 
I`ll take that old American forged crank over all these chinese cranks all day long. I have seen main caps,rods & blocks fail but in the 35 year I`ve been racing BB mopars I have never seen a broken 440 crank. I`m not saying to put a 440 crank is a Indy block or a K1 but if your running a factory block your crank is not going to be your weak link. Anything under 650hp I like them old cranks
 
So after thinking on it overnight, doing a little more research, and talking it over with a buddy. I decided to order a K1 4.150" stroke crank, with the Chevy 2.200" rod pins. I found a decent deal on one, and decided to pull the trigger. I'll gain a little more cubic inch, and have some piece of mind at the same time. Probably won't have to spin the motor as hard either. Honestly, if I was going to leave it naturally aspirated, I wouldn't have thought twice about it. But like Moper said, having the extra stress of a belt driven blower hanging off the side of it, really got me thinking. And I could have tossed it together and never had an issue. But for what I'll have wrapped up in this build cash wise, the extra $800 or so really isn't a big deal.

I seriously appreciate everyone's input on this! I took everyone's opinions into consideration, and it helped cement my decision. I can post up a build thread after I get a little further along, if anyone is interested?

Thanks again!
 
To me anyway its not so much who is machineing the crank as it is who forged the crank my Machinest is a great machinest I`ll put him up against anyone. So is there any cracks out there that are forged in the USA thats the question that makes me crazy. My Machinest says only the most expensive of the Callies or other high end cranks are forged in the USA. I do all my own work on my cars and truck and I`m so sick of junk chinese parts I can`t stand it
 
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