[AT] 39 Farmall A coming along.....

[Doug Tallman]

There are pros and cons to plastigage. They claim it can become 
distorted and give incorrect readings. If its been layed  flat too long 
or had weight on top of it in storage it may be off to start with and 
not even be noticeable. Another thing to watch out for that the opposite 
side such as a rod is tight against the crank before you tighten the cap 
with the plastigage. For instance, if you put it on a rod cap and then 
use the cap and nuts to draw the piston down the bore to the crank, the 
reading will be off because you had 0 clearance when you were pulling 
the rod with the cap. There's no substitute for inside and outside mikes 
to check actual clearance and it would be a good time to teach that too. 
Most of the bearings are marked on the back for std or undersize. A 
thought on getting the piston out. Not sure if this would be feasible to 
do at the school or not and it also depends where the piston is. If you 
can get an inch or 1 1/2 in of kerosene on top of the piston light it 
and let it burn. You'll need a paper wick to keep it going. After the 
kero has burnt out your chances of getting the piston out will be a lot 
better. Sometimes it takes a few tries but I've never had it fail. Good 
luck!! Doug T

Rupert wrote:
> 	Plasticgaging the bearings is a must do in my books. Check them all as 
> it is possible that an off size bearing got in the box.
> 	Don't forget to check the piston ring end gap too when it comes time to 
> install the pistons.
>
> Rupert
>
> On 3/10/2010 5:13 PM, charliehill wrote:
>   
>> Al,  I'm no pro on the subject but when you put the crank assembly back
>> together you need to plastigage the bearings to make sure you have the right
>> amount of bearing crush.   Some of the others can tell you from more hands
>> on perspective than I can.  Steve W. comes to mind.  There are others for
>> sure.
>>
>> Charlie
>> ----- Original Message -----
>> From: "Al Jones"<farmallsupera at earthlink.net>
>> To: "Antique tractor email discussion group"<at at lists.antique-tractor.com>
>> Sent: Wednesday, March 10, 2010 7:01 PM
>> Subject: Re: [AT] 39 Farmall A coming along.....
>>
>>
>>     
>>> I was wondering if plastigauge would be needed to double-check stuff when
>>> it
>>> goes back together.  I gotta get a copy of Spencer's engine overhaul
>>> book.......
>>>
>>> You are correct, this is sort of a side project.  I have about 5 students
>>> that are really eating it up.  Before it is over I intend for all 24
>>> students to have played some role in it.  Basically when they are finished
>>> with what I am actually grading them on, (basic electricity--they have a
>>> test on the unit Friday) they can work on the tractor.  They are all
>>> fairly
>>> proficient with hands-on type stuff so it works well to keep them busy.
>>>
>>> A lot of people don't realize it but career-technical education (formerly
>>> vocational) classes in NC public schools have an end of course test just
>>> like the "academic" subjects.  We have to make sure the students get the
>>> core curriculum (in other words, what they will be tested on) first.  I
>>> will
>>> keep my opinions on how the system is run, at least in NC, to myself.
>>>
>>> Al
>>>
>>>
>>>