Crankshaft__important

PolkCounty_TSI · Jan 25, 2005

Hey guys, today i was talking to some mechanics and we were talking about a engine rebuilds.
They said that you wont get 50, 000 miles on a rebuilt motor, and this is why.
They said that when people rebuild a engine they usally get the crankshaft turned and micropolished and the cylinders honed. They said when you do that , generally the pistons are over sized and the crankshaft is undersize.(because when you have the crankshaft turned, you make it smaller.) When this happens the crankshaft is lieable to break and thats what mostly happens to rebulit motors because the pistsons are making more compression and its to much compression for the crank (because where dose all the force go to?.... the crankshaft)..
They said if you want to get alot of miles on a rebuilt motor having oversized pistons, then buy a standerd crankshaft or and oversized crankshaft. Which buying a oversized crankshaft
and pistons will be like buying a stroker kit.. So anyways basically to some it off , they said that our crankshaft will break, so can anybody out there can tell me if this is true or not because i definently want to get alot of miles out of my motor..

RoasT BeeF · Jan 25, 2005

Sounds like some shadetree mechanics. Ask them how you put oversized pistons in a honed block.

And the chances of the crank breaking are slim to none. Yes it has happend but simply saying that just because you get the crank turned means it will break is outrageous.

Cesar · Jan 25, 2005

The proper way to cut a crankshaft is to have a radius grind. A radius grind involves a concave surface on a main/rod journal, making the center point of the journal the lowest, thereby allowing more clearnace for the oil between the bearing. Mind you, this is not really something that is easily measured. A micrometer is required.

As far as a crank breaking from too much power being forced onto it, is unlikely in my opinion. A vast majority of import crankshafts are forged and heat treated and should not be ground in the first place.

A rebuild motor is able to go the distance if the proper procedures are followed and the proper components are used.

PolkCounty_TSI · Jan 25, 2005

well i dont know if these mechanics worked on imports but they tolded me that all these guys that think they know alot about these motors really dont... he said take it to a pro .. i was about to call the guy a dumba**

DSMnewbi · Jan 25, 2005

Don't listen to those mechanics and don't let them get within 10 ft. of your car.. Those are the types that will put a dab of oil on your head/block and tell you that you need a whole new engine.

PolkCounty_TSI · Jan 25, 2005

DSMnewbi said:
Don't listen to those mechanics and don't let them get within 10 ft. of your car.. Those are the types that will put a dab of oil on your head/block and tell you that you need a whole new engine.

yeah really man, nah i wont let them touch my car. Like my friend said "These cars aint honda's" but thanks for the comments.

defrag010 · Jan 25, 2005

sounds like that guy thinks rebuilt motors won't last past 50k cause he never has built one that lasted that long.. :laugh:

I worked at an engine remanufacturing plant, and we've only had about one in every 20 of our rebuilt motors come back in less than 100k miles. One customer bought one of our 256 AMC motors for his jeep, and the last time he came by, his jeep had 200something thousand on his odometer. If I remember right, his motor was turned .010 on the mains and .020 on the rods.

PolkCounty_TSI · Jan 25, 2005

yeah i have confidence in my motor.

Defiant · Jan 26, 2005

PolkCounty_TSI said:
Hey guys, today i was talking to some mechanics

The evidence at hand tends to make that an incorrect classification.

and we were talking about a engine rebuilds.

Pity I couldn't have been there.

They said that you wont get 50, 000 miles on a rebuilt motor, and this is why.
They said that when people rebuild a engine they usally get the crankshaft turned and micropolished and the cylinders honed. They said when you do that , generally the pistons are over sized and the crankshaft is undersize.(because when you have the crankshaft turned, you make it smaller.) When this happens the crankshaft is lieable to break and thats what mostly happens to rebulit motors because the pistsons are making more compression and its to much compression for the crank (because where dose all the force go to?.... the crankshaft)..

Engines aren't built that close to the edge. Polishing a crank won't remove enough meat to suddenly make it fragile, and a .010" cleanup bore on a block won't release dozens of extra horsepower.

They said if you want to get alot of miles on a rebuilt motor having oversized pistons, then buy a standerd crankshaft or and oversized crankshaft. Which buying a oversized crankshaft
and pistons will be like buying a stroker kit.. So anyways basically to some it off , they said that our crankshaft will break, so can anybody out there can tell me if this is true or not because i definently want to get alot of miles out of my motor..

Back in the olden days, there was no such thing as childguard caps on aspirin bottles. Consequently, semi-tool-using apes as stupid as these beings you wrongly refer to as being "mechanics" would wolf down enough asprin at age three to die, and the gene pool would remain much more pure. The overall intellectual level of even the most backward backwaters of society -yes, even in Florida- was slowly on the rise. Then, some sonofabitch lawyer thought of yet another way to get more money, and pointed out we were losing idiots to poisoning, and sued someone to grab some easy payoffs. In typically knee-jerking reaction to a siphoning off of profits, the manufacturers came up with childguards.
And now, we have "mechanics" like this.

Ain't progress grand.

Oh, nice thread title, too.

I won't ask if any of those monkey's sisters were your grammar teachers.

PSI TSI · Jan 26, 2005

Ive learned over the years , That most Mechanics think they know everything about cars. In reality they only know asmuch as they have experience with . I have freinds that are certified techs. They act like they know everything. But when you talk about performance they are stupid. Its just like anything else though you dont talk to a Proctologist if you have a sore throat do you. If you want to talk rebuilds a engine builder would be the guy to believe not some morron mechanic with his head up his ass.

2-0turbo · Jan 26, 2005

Defiant said:
Back in the olden days, there was no such thing as childguard caps on aspirin bottles. Consequently, semi-tool-using apes as stupid as these beings you wrongly refer to as being "mechanics" would wolf down enough asprin at age three to die, and the gene pool would remain much more pure. The overall intellectual level of even the most backward backwaters of society -yes, even in Florida- was slowly on the rise. Then, some sonofabitch lawyer thought of yet another way to get more money, and pointed out we were losing idiots to poisoning, and sued someone to grab some easy payoffs. In typically knee-jerking reaction to a siphoning off of profits, the manufacturers came up with childguards.
And now, we have "mechanics" like this.

Well put. You write quite well.

DV8 · Jan 26, 2005

Defiant said:
The evidence at hand tends to make that an incorrect classification.
Pity I couldn't have been there.
Engines aren't built that close to the edge. Polishing a crank won't remove enough meat to suddenly make it fragile, and a .010" cleanup bore on a block won't release dozens of extra horsepower.
Back in the olden days, there was no such thing as childguard caps on aspirin bottles. Consequently, semi-tool-using apes as stupid as these beings you wrongly refer to as being "mechanics" would wolf down enough asprin at age three to die, and the gene pool would remain much more pure. The overall intellectual level of even the most backward backwaters of society -yes, even in Florida- was slowly on the rise. Then, some sonofabitch lawyer thought of yet another way to get more money, and pointed out we were losing idiots to poisoning, and sued someone to grab some easy payoffs. In typically knee-jerking reaction to a siphoning off of profits, the manufacturers came up with childguards.
And now, we have "mechanics" like this.

Ain't progress grand.

Oh, nice thread title, too.

Agreed

braap · Jan 26, 2005

9 times out of 10, the only difference between you and the average repair technician ("mechanic") is the fact that he gets paid to work on your car. Buy a factory service manual, a decent set of hand tools, find a trusted automotive machine shop in your area and have a blast repairing/rebuilding/anything... yourself! If you've got half a brain and any common sense at all you can figure out anything on these cars.

pinknuggit · Jan 27, 2005

defrag010 said:
sounds like that guy thinks rebuilt motors won't last past 50k cause he never has built one that lasted that long.. :laugh:

I worked at an engine remanufacturing plant, and we've only had about one in every 20 of our rebuilt motors come back in less than 100k miles. One customer bought one of our 256 AMC motors for his jeep, and the last time he came by, his jeep had 200something thousand on his odometer. If I remember right, his motor was turned .010 on the mains and .020 on the rods.

Damn dude, are you my evil twin or something? That sounds exactly like what I would have said... Sounds exactly like where I used to work too!

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