align bore a 72T

[47silver]

my son's 72T stock motor has about 85000 miles on it, we have the car completely apart to get painted and not sure what to do with the motor.
do 2.4Liters motors normally need align bored?
The motor turns over nicely though we never heard it run,, the previous owner believes it could use a valve job, if we tear it down that far then thinking may as well put new bearings and have machine work done.

[69BahamaYellow]

I had a 71T that I replaced the main bearings in, and the case needed to be line honed to correct distortion of the magnesium after years of heat cycling. The guy who did the honing said this was a problem with magnesium cases.

Before the case honing, I checked the crankshaft, and it did not require machining, so I decided to just have it polished and replace the main bearings with new ones in standard size, but when I torqued the bolts to spec on the case halves, the crankshaft seized up, that's when I knew I needed to have the bearing journals honed in the case.

[Steve@Rennsport]

Originally Posted by 47silver

my son's 72T stock motor has about 85000 miles on it, we have the car completely apart to get painted and not sure what to do with the motor.
do 2.4Liters motors normally need align bored?

Yes, if the case is opened up.

The motor turns over nicely though we never heard it run,, the previous owner believes it could use a valve job, if we tear it down that far then thinking may as well put new bearings and have machine work done.

Do a leakdown test to see if the rings/pistons are passing air. If not, Just do a valve job, fix the oil leaks and enjoy yourself.

[cgarr]

^this, check it out, get it running if some basic checks seem fine then go from there.

[47silver]

great thank you all for the responses...

[cmcfaul]

align boring is not always needed. I suspect most who say it needs to be done are the ones that get paid to do it. Also, you sure that car has 85,000 miles on it? Calling BS on under 2,000 miles per year. More realistically the speedo had turned over several times. Do the math even at just 5,000 miles per year.

Chris

[47silver]

thanks for the information, we will take it apart and see where it stands.. some suggest putting it back with new bearings and seeing how the crank spins. is that something we could or should do?

the previous owner bought the car in 1988, put it in storage in 1991. he said that he mileage was 82000 and i think it is accurate. (the speedometer even works) he lives overseas and we communicate about the car and other things a few times a month on skype and I do not have any reason to doubt him.

Also when we disassembled the car for painting we took note of bushings, wheel bearings and wear items and did not notice anything that would indicate a high mileage car, i think it had the original clutch and flywheel and brake rotors.
The interior items like turn signal stalk and steering wheel are in great shape so in my opinion the mileage is correct.
the mfi spins and with power applied has pressure but probably a good idea to get it rebuilt.

[Walt Fricke]

It is possible to check the case to see if all the bearing webs are the right dimensions, and concentric as well. While doing this, check the cylinder spigot surfaces for distance from the crank centerline. Not every machine shop is set up to do this.

If the webs aren't within spec, you want to use a machine shop which will shave a little bit off the parting surfaces until the widest of the webs is now just within spec as to edge to edge width. Then the case is line bored back to standard.

You absolutely do not want to use oversize bearings, which is what you will end up needing to do if the case, as is, is line bored. Even worse if they also bore oversized the #8. #8 is normally reused as is (much less stress on it). Look up the cost of an oversize #8.

Maybe the T cases are less apt to distort? But checking through careful measuring is really critical - I don't think you can tell if something is too large by relying on how the motor feels spinning the crank.

[cgarr]

Just remember if the case halves are shaved its not only boring the mains, you need to do the intermediate shaft and rear main seal. there is a limit to what can be done, you have cover plates, oil breather, IS cover etc that still have to fit.

[47silver]

did porsche align bore every racing motor that they disassembled? seems like that would say this is really idiotic..

[m42racer]

Originally Posted by cmcfaul

align boring is not always needed. I suspect most who say it needs to be done are the ones that get paid to do it. Also, you sure that car has 85,000 miles on it? Calling BS on under 2,000 miles per year. More realistically the speedo had turned over several times. Do the math even at just 5,000 miles per year.

Chris

And the ones who say it doesn't usually know what about engines????

Listen to the experts who know, not the internet.

Steve gave you solid advice.

For free!!!!