Resurface Crankshaft or Replace it?

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Mazda Mazdaspeed Protege
Hi Guys,I'm rebuilding my engine with forged parts right now.
Took it to the machine shop to have head work,cylinders bored,and balanced.
The machinist shows me some troubling surface scratches on the crankshaft and lets me know he would have to take .10 off to use it,then tells me i'll also need .25mm over main and rod bearings.
He is charging a modest $110 for the grind btw.
Would it be better to start looking for a used crank or will a mild grind be ok?
I found a few places that sell the clevite bearing sets .25 over for about the same price as the grind.
Any help from some of you guys with any experience on this matter would be much appreciated.
 
Hi Guys,I'm rebuilding my engine with forged parts right now.
Took it to the machine shop to have head work,cylinders bored,and balanced.
The machinist shows me some troubling surface scratches on the crankshaft and lets me know he would have to take .10 off to use it,then tells me i'll also need .25mm over main and rod bearings.
He is charging a modest $110 for the grind btw.
Would it be better to start looking for a used crank or will a mild grind be ok?
I found a few places that sell the clevite bearing sets .25 over for about the same price as the grind.
Any help from some of you guys with any experience on this matter would be much appreciated.

First of all, guess what, you already have a used crankshaft- why go purchase another one? Secondly, you're taking this component to a man who specializes, he shows you scarring and recommends it to be machined- why are you questioning him?
Thirdly, you will be required to install undersized bearings when the crankshaft is machined- it's not one or the other, it's both.

Is he cutting the mains, rods or both?

You'll be hard pressed to find a like new OEM MSP crank. I stumbled across one that had been sitting on a Mazda dealerships shelf in middle Tennessee and got a hell of a deal on it, but that's not going to happen again. Also purchased a brand new OEM "Probe" crank from a Ford dealer out of Florida. I'd have no issue machining the crankshaft.
 
First of all, guess what, you already have a used crankshaft- why go purchase another one? Secondly, you're taking this component to a man who specializes, he shows you scarring and recommends it to be machined- why are you questioning him?
Thirdly, you will be required to install undersized bearings when the crankshaft is machined- it's not one or the other, it's both.

Is he cutting the mains, rods or both?

You'll be hard pressed to find a like new OEM MSP crank. I stumbled across one that had been sitting on a Mazda dealerships shelf in middle Tennessee and got a hell of a deal on it, but that's not going to happen again. Also purchased a brand new OEM "Probe" crank from a Ford dealer out of Florida. I'd have no issue machining the crankshaft.
I saw replace the crank. Look on the Mazda parts pages on facebook. Mazda protege parts MPP for short. Also protege parts for sale. There you can tell everyone what you are looking for and even request pic and measurements.
Also address the faulty FS oil system.

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Thanks,i defiantly wasn't questioning the specialist just worried that taking it down might also take off any special coating from the factory if it had one vs getting a crank that didn't need machining.
My other concern was would "thinning" it albeit only .10 inches could weaken the cranks integrity in a prepped engine that when balanced would be redlining significantly higher than factory.
He did ask me to get new main and rod bearings because the oem i already he couldn't use had so i'm guessing he will need to do both the mains and rods.

I do have my oil pump out to DocB as we speak for his oil treatment combined w/ the AWR oil pan.
 
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Thanks,i defiantly wasn't questioning the specialist just worried that taking it down might also take off any special coating from the factory if it had one vs getting a crank that didn't need machining.
My other concern was would "thinning" it albeit only .10 inches could weaken the cranks integrity in a prepped engine that when balanced would be redlining significantly higher than factory.
He did ask me to get new main and rod bearings because the oem i already he couldn't use had so i'm guessing he will need to do both the mains and rods.

I do have my oil pump out to DocB as we speak for his oil treatment combined w/ the AWR oil pan.
There are no coatings or changes to worry about taking down a crank. You only change the rotational mass if they shave weight off the counter weights.
Make sure to have your block alignment alignment honed. And normally the shop will balance your crank with the pistons. My shop went the extra mile and balanced with the balancer and the flywheel and clutch. Now you have a perfect balanced assembly.

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Thanks,i defiantly wasn't questioning the specialist just worried that taking it down might also take off any special coating from the factory if it had one vs getting a crank that didn't need machining.
My other concern was would "thinning" it albeit only .10 inches could weaken the cranks integrity in a prepped engine that when balanced would be redlining significantly higher than factory.
He did ask me to get new main and rod bearings because the oem i already he couldn't use had so i'm guessing he will need to do both the mains and rods.

I do have my oil pump out to DocB as we speak for his oil treatment combined w/ the AWR oil pan.

It's not .10, i'ts .010. That's a quarter of a millimeter to give you an idea. Balancing the rotating assembly will decrease the likelihood of a failure whether the crank is turned or not. I can tell you that practically any engine builder will recommend components to be machined before install. Additionally, having the rotating assembly balanced will likely require drilling and refill with mallory. So at the end of the day, you're still taking material away from the crankshaft.
 
You only change the rotational mass if they shave weight off the counter weights.
That is insanely and wildly incorrect- you're adding different (lighter weight) rods and pistons- so both your rotating and reciprocating weight are going to change...
 
That is insanely and wildly incorrect- you're adding different (lighter weight) rods and pistons- so both your rotating and reciprocating weight are going to change...
I'm just saying that taking 1000 is not going to make a big change

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Good to know.
The machinist did ask for all the new rods & pistons,pressure plate,flywheel,and harmonic balancer so looks like he is taking good care of my baby.
I did choose this guy over the general auto zone machine shop based off his experience.
 
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