What should "rebuilt" mean?
07-18-2001, 10:51 PM
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What should "rebuilt" mean?
Dear Friends,
Please educate me on the proper definition of
1) a Rebuilt engine,
2) a Rebuilt transmission,
3) Why is it necessary, and
4) Why do I see ads with rebuilt engines and transmission when they have so low miles?
Many thanks.
GeorgeMa
83 SC Targa
Please educate me on the proper definition of
1) a Rebuilt engine,
2) a Rebuilt transmission,
3) Why is it necessary, and
4) Why do I see ads with rebuilt engines and transmission when they have so low miles?
Many thanks.
GeorgeMa
83 SC Targa
07-19-2001, 04:26 AM
#2
RL Technical Advisor
Hi George:
You have asked some great questions. I think I'd like to respond with something I posted some time ago on this subject which is near & dear to me. This addresses the engine aspect of your inquiry but I think you'll get the point,...
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"Rebuilt" - Reconditioned"…………What do they mean?
To a car owner, these words have different meanings for each individual, and nobody seems to know exactly what their expectations should be. The word "rebuilt" is often bandied about when a car is up for sale. I would like to offer some advice and the benefit of some professional experience in this field.
"Rebuilt" can be used to describe a whole range of conditions that range from "like-new" to "simply cleaner." One must carefully decide what constitutes truly "rebuilt."
There are some parts should never be rebuilt and others that can be reconditioned to extend their lifespan. For example, pistons can't be rebuilt any more than sparkplugs can be. If a piston is worn enough for the piston-to-cylinder wall clearance to be at or near tolerance or the ring-land grooves are found to be too wide for new rings, its best to replace the pistons with new parts.
Brake calipers, alternators, starters and the like can have some internal parts replaced to make them function again without spending the money for an entire new unit. For those folks who are on a strict budget (and who isn't?), this may be an acceptable short-term solution until a more permanent repair can be made. Certain fuel-injection parts can be changed without incurring large labor costs, and their performance can be monitored easily in case the rebuilt/reconditioned part doesn't last very long. Other items are penny-wise and pound-foolish to rebuild if they are labor-intensive to change/repair or have dire consequences if they fail at an inconvenient time or place.
A good example might be installing a used or rebuilt fuel pump. The folly of using a rebuilt fuel pump becomes obvious when you are stranded 200 miles from a replacement. The same can be said of using a rebuilt clutch that fails when you are far away from a shop that can install a new one. Some items simply shouldn't be rebuilt when you are using your car at or near its limit on the track or street. Wheel bearings, brake parts, and some suspension parts fall into this category.
The single most expensive part of any Porsche is its engine. Everyone has his or her own expectation of how long a "rebuilt" engine should last before needing to be disassembled once again, and a "rebuilt" engine can last anywhere from 5,000 to 200,000 miles depending upon what new parts were used in the rebuild and who performed it.
For a street engine, we feel that a proper rebuild should last as long or even longer than the original OEM powerplant. To this end, certain parts cannot be reused if the owner expects the rebuilt engine to perform as new and be as durable as the original engine. Considering the normal labor charged by dealers, independent shops or high-performance specialists, this is a reasonable expectation. Our shop charges 32-45 hours of time to disassemble, clean, rebuild, and reassemble an entire engine. (The variation exists between naturally aspirated and turbocharged engines.) This figure doesn't vary much, since it takes the same amount of time to measure, install and set up everything regardless of whether it's a '70s 2.2 or a late-'80s 3.6. If a "rebuild" can cost as little as $4,000 or as much as $12,000 with the labor to do this job properly, then the difference lies in the cost of the parts that were used during this job-in the case of Porsches generally a function of whether the parts were new or reconditioned, OEM or cheap substitutes.
Repairing an otherwise fine engine is a different thing altogether. For instance, many 3.2 and 3.6 litre engines simply need new valve guides to reach their potential lifespan and to that end, a top overhaul may be all that is necessary. It would be irresponsible for the shop not to also inspect and replace any worn valves and check the valve springs for proper seat pressures. Nikasil cylinders last a very long time, and in some cases, a simple ring replacement will ensure that the engine has good compression until major overhaul time if the pistons are still serviceable.
It's important to realize that when it's time to rebuild the engine "as new", using "recycled" or worn parts is not economical or prudent if you wish to achieve the maximum engine life and restore the original performance to the car. There are no shortcuts, whatsoever.
An honest-to-God rebuilt engine should have new internals to perform as such and last as long. Here are just a few of the parts that I would replace with new-not "reconditioned"--ones:
Pistons, rings & cylinders
Valves (as needed)
Valve springs
Valve guides & seals
Cam chains and ramps
Chain sprockets and idlers
Intermediate gears (as needed)
Chain tensioners
All engine bearings
New rod bolts and pin bushings
This doesn't include machine work and other operations to ensure that the engine is in as-new condition or any modifications made to increase performance.
So when you select a shop to rebuild the engine in your Porsche, here are some things to think about:
1) Labor is a small part of the total cost of a proper rebuild. If the overall cost looks too good to be true, then something is wrong. New OEM Porsche parts are not cheap. You get what you pay for.
2) Ask the shop whether they use new or reconditioned parts. What parts ARE new? What machine work do they do? You must have full confidence in the shop that performs the work for you, and whether or not the owners are nice guys is immaterial. They must be competent and honest.
3) Get references from previous customers. Porsche ownership is an extended family, and there are some great resources out there through the PCA, so use them. The National Tech Committee is just one of them at your disposal. Talk to people who KNOW engines, not just another person who may not know any more than you do about this subject. This takes legwork and diligence. Remember, its your money that's at stake!
4) Nobody likes to be without their "baby" for any longer than necessary, but be wary of anyone who promises short turnaround times. It _takes_time_to do this entire job properly and these engines are not as simple to do as an American V-8. Porsche ownership comes at a premium, and you expect appropriate levels of engineering and execution. Don't be in a hurry. If you need cardiac-bypass surgery, is time the most important criterion or is it having the job done correctly?
Just one person's opinion about this.
You have asked some great questions. I think I'd like to respond with something I posted some time ago on this subject which is near & dear to me. This addresses the engine aspect of your inquiry but I think you'll get the point,...
----------------------------------------
"Rebuilt" - Reconditioned"…………What do they mean?
To a car owner, these words have different meanings for each individual, and nobody seems to know exactly what their expectations should be. The word "rebuilt" is often bandied about when a car is up for sale. I would like to offer some advice and the benefit of some professional experience in this field.
"Rebuilt" can be used to describe a whole range of conditions that range from "like-new" to "simply cleaner." One must carefully decide what constitutes truly "rebuilt."
There are some parts should never be rebuilt and others that can be reconditioned to extend their lifespan. For example, pistons can't be rebuilt any more than sparkplugs can be. If a piston is worn enough for the piston-to-cylinder wall clearance to be at or near tolerance or the ring-land grooves are found to be too wide for new rings, its best to replace the pistons with new parts.
Brake calipers, alternators, starters and the like can have some internal parts replaced to make them function again without spending the money for an entire new unit. For those folks who are on a strict budget (and who isn't?), this may be an acceptable short-term solution until a more permanent repair can be made. Certain fuel-injection parts can be changed without incurring large labor costs, and their performance can be monitored easily in case the rebuilt/reconditioned part doesn't last very long. Other items are penny-wise and pound-foolish to rebuild if they are labor-intensive to change/repair or have dire consequences if they fail at an inconvenient time or place.
A good example might be installing a used or rebuilt fuel pump. The folly of using a rebuilt fuel pump becomes obvious when you are stranded 200 miles from a replacement. The same can be said of using a rebuilt clutch that fails when you are far away from a shop that can install a new one. Some items simply shouldn't be rebuilt when you are using your car at or near its limit on the track or street. Wheel bearings, brake parts, and some suspension parts fall into this category.
The single most expensive part of any Porsche is its engine. Everyone has his or her own expectation of how long a "rebuilt" engine should last before needing to be disassembled once again, and a "rebuilt" engine can last anywhere from 5,000 to 200,000 miles depending upon what new parts were used in the rebuild and who performed it.
For a street engine, we feel that a proper rebuild should last as long or even longer than the original OEM powerplant. To this end, certain parts cannot be reused if the owner expects the rebuilt engine to perform as new and be as durable as the original engine. Considering the normal labor charged by dealers, independent shops or high-performance specialists, this is a reasonable expectation. Our shop charges 32-45 hours of time to disassemble, clean, rebuild, and reassemble an entire engine. (The variation exists between naturally aspirated and turbocharged engines.) This figure doesn't vary much, since it takes the same amount of time to measure, install and set up everything regardless of whether it's a '70s 2.2 or a late-'80s 3.6. If a "rebuild" can cost as little as $4,000 or as much as $12,000 with the labor to do this job properly, then the difference lies in the cost of the parts that were used during this job-in the case of Porsches generally a function of whether the parts were new or reconditioned, OEM or cheap substitutes.
Repairing an otherwise fine engine is a different thing altogether. For instance, many 3.2 and 3.6 litre engines simply need new valve guides to reach their potential lifespan and to that end, a top overhaul may be all that is necessary. It would be irresponsible for the shop not to also inspect and replace any worn valves and check the valve springs for proper seat pressures. Nikasil cylinders last a very long time, and in some cases, a simple ring replacement will ensure that the engine has good compression until major overhaul time if the pistons are still serviceable.
It's important to realize that when it's time to rebuild the engine "as new", using "recycled" or worn parts is not economical or prudent if you wish to achieve the maximum engine life and restore the original performance to the car. There are no shortcuts, whatsoever.
An honest-to-God rebuilt engine should have new internals to perform as such and last as long. Here are just a few of the parts that I would replace with new-not "reconditioned"--ones:
Pistons, rings & cylinders
Valves (as needed)
Valve springs
Valve guides & seals
Cam chains and ramps
Chain sprockets and idlers
Intermediate gears (as needed)
Chain tensioners
All engine bearings
New rod bolts and pin bushings
This doesn't include machine work and other operations to ensure that the engine is in as-new condition or any modifications made to increase performance.
So when you select a shop to rebuild the engine in your Porsche, here are some things to think about:
1) Labor is a small part of the total cost of a proper rebuild. If the overall cost looks too good to be true, then something is wrong. New OEM Porsche parts are not cheap. You get what you pay for.
2) Ask the shop whether they use new or reconditioned parts. What parts ARE new? What machine work do they do? You must have full confidence in the shop that performs the work for you, and whether or not the owners are nice guys is immaterial. They must be competent and honest.
3) Get references from previous customers. Porsche ownership is an extended family, and there are some great resources out there through the PCA, so use them. The National Tech Committee is just one of them at your disposal. Talk to people who KNOW engines, not just another person who may not know any more than you do about this subject. This takes legwork and diligence. Remember, its your money that's at stake!
4) Nobody likes to be without their "baby" for any longer than necessary, but be wary of anyone who promises short turnaround times. It _takes_time_to do this entire job properly and these engines are not as simple to do as an American V-8. Porsche ownership comes at a premium, and you expect appropriate levels of engineering and execution. Don't be in a hurry. If you need cardiac-bypass surgery, is time the most important criterion or is it having the job done correctly?
Just one person's opinion about this.