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Crankshaft included in rebuilt
I know this is on me but if my engine was rebuilt (full rebuild w/ added HP), would I not assume the crankshaft would have been included? After my 3.2 was rebuilt, the mechanic mentioned the crankshaft lost a part because of the increase in power and now had to be replaced.
Would a 25k+ rebuild typically not include a new crankshaft or at least a repolish? |
Always depends on what has been agreed upon.
I've seen people call overhauls 'full rebuild' without opening the bottom cases. You mention more hp, what has been done to the engine? 25k is a lot of money but again, depends on what has been done as standard parts + labor costs can become a hefty sum quite fast. To me, a full overhaul would indeed logically include a detailed check or rework of the crankshaft but if they figured it might have been still 'good enough' it could have been put in again as is to save cost. Also, what part of the crankshaft has been lost? |
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Replacing a crank isn't typical for rebuilds as they are generally durable and have gotten expensive. A typical rebuild might include a thorough cleaning and a polish, which are simple procedures. If yours has failed in some way, then it would need more attention, and of course repairs or replacement would be part of a proper rebuild. Depending on the nature of the failure, it may be repairable. Hard to say without knowing how it failed. A common type of damage is a journal being damaged - a fixable problem in most cases.
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A good working crank isn’t usually replaced during a rebuild. It’s not generally a consumable part. Like it was said, clean and polishing is the norm. If something is wrong, that’s a different story. Same can be said of other main parts like heads, case, cam towers, etc. Getting another 20 + hp out of an engine won’t damage a crank.
how was it messed with? |
I've never had to replace a crankshaft yet. My machinists actually comment on how durable the Porsche cranks are, compared to the other engines they perform work on.
They always check mine for cracks, straightness etc and always perform a micro polish. I have seen cranks that have had a rod bearing fail and that can spoil a journal. |
I always have the cranks inspected, measured, magnafluxed and micro-polished.....I've only had to replace one, to date.
regards,al |
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To answer your question, a new crank is not a standard replacement part during a basic overhaul. The rod and crank configuration is one of the weak links in the 3.2/3.3 engine design. They wanted to make the rod journal larger but given the oil pump proximity, the big end rod dimension was limited. That limitation forced the designer to use a 9mm rod bolt instead of the much stronger 10mm bolt used in most Porsche flat six engines. Smaller bolt with compromised yield strength. We always use a rod upgrade or at least ARP bolts. Getting back to the horse concern, the 9mm rods bolt has limitations based on rpm not so much horse power. If the horse power increase was produced by revving the engine above *7400 or so, that may cause a failure. Without really knowing more than "lost a part" I can't comment on the true cause of the failure but experience tells me you're looking at a connecting rod failure. Causes: low quality rod bearings, rod journal in spec but out of round, rod out of spec, rod accidentally assembled wrong (number to number mis-match....people are human) Lastly oil contamination. Oil lines, oil cooler, oil tank all collect junk while cars sit around waiting for the new engine. |
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Needing a brand new crankshaft or to be replaced with a used crankshaft would significantly make the cost of an engine rebuild much higher, wouldn’t it. Good luck rebuilding your engine and have a good time with your car after the rebuild. |
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