motor rebuild: how to proceed

just a quick review:
i have a 95 m-ed which i got at 26K w/ a 6# jr/sc. it started to smoke
sometime after 100k and i pulled the drive train at 112k. had the
tranny rebuild, blower rebuilt and i stripped the motor to a short block
and had a machine shop bore, deck, balance and assemble the short block.
i installed everything and apperently got a lean condition which i
could not diagnose in a timely manner, in addition, due to circumstances
i was forced to drive the car until the pistons melted...literally.

i now have the motor out and down to a short block again and i was
hoping to minimize the cost of a re-rebuild so i was thinking that i
would disassemble the crank and pistons and have the block rebored to
..75 over and attempt to balance the new rods/pistons my self since the
crank was balanced previously.

reading about balancing, the basics seem doable but the part about
measuring each end of the rods seems a bit more than i would be able to
do without "special" tools/balances.

so, after a bit thought, i wonder if it would be better if i just bring
the short block to the shop and have them bore/balance/assemble it. the
bore/clean/piston kit will be ~$500 and maybe another $400 for balance
and (dis)assemble. therefore, my questions is: is balancing the
rods/pistons easily doable at a home shop or would it be better to cough
up the money to have the shop do it?

as far as the lean condition, i am not sure exactly what caused it as
the car ran well for > 80k miles but here are my thoughts:
1) i ask ask moss motors what they suggest at this point since the only
after market engine control is a knock sensor. perhaps a AFPR, (and new
fuel pump) and/or a piggyback ECU are called for.
2)i will check the EGR or just replace it.
3) there seemed to be 2 marks on the crank pulley so i will determine
which is the correct one.

any thoughts beyond these?

peter > wrote:

> so, after a bit thought, i wonder if it would be better if i just
> bring the short block to the shop and have them
> bore/balance/assemble it. the bore/clean/piston kit will be ~$500
> and maybe another $400 for balance and (dis)assemble. therefore,
> my questions is: is balancing the rods/pistons easily doable at a
> home shop or would it be better to cough up the money to have the
> shop do it?

I think you'd be better off paying. Balancing requires a fairly
accurate scale and the knowledge of how to create setups to weigh
rod ends, pistons, etc. and where to remove metal to make them
balance w/o reducing strenght, although I'll bet you can find
something on the web if you Google for it......

> as far as the lean condition, i am not sure exactly what caused it
> as the car ran well for 80k miles but here are my thoughts:
> 1) i ask ask moss motors what they suggest at this point since the
> only after market engine control is a knock sensor. perhaps a
> AFPR, (and new fuel pump) and/or a piggyback ECU are called for.
> 2)i will check the EGR or just replace it.
> 3) there seemed to be 2 marks on the crank pulley so i will
> determine which is the correct one.

Do number 1, ask 'em. Do number 3, that's essential!

Then, maybe you shouldn't worry about it. Drive the car and check
spark plugs often to see it it's still lean, if it is, that's the time
to do your trouble shooting. You just might be spending time fixing a
problem that the rebuild took care of such as an air leak in the intake
system or ?????



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1.8L engines don't have a lost ot spare when it comes to cylinder wall
thickness.
I assume that the last rebuild involved some amount of overbore as a start.
I don't know how much total overbore a particular block can support, but
have been told that the maximum displacement is about 2.0L.

"peter" > wrote in message
...
> just a quick review:
> i have a 95 m-ed which i got at 26K w/ a 6# jr/sc. it started to smoke
> sometime after 100k and i pulled the drive train at 112k. had the tranny
> rebuild, blower rebuilt and i stripped the motor to a short block and had
> a machine shop bore, deck, balance and assemble the short block. i
> installed everything and apperently got a lean condition which i could not
> diagnose in a timely manner, in addition, due to circumstances i was
> forced to drive the car until the pistons melted...literally.
>
> i now have the motor out and down to a short block again and i was hoping
> to minimize the cost of a re-rebuild so i was thinking that i would
> disassemble the crank and pistons and have the block rebored to .75 over
> and attempt to balance the new rods/pistons my self since the crank was
> balanced previously.
>
> reading about balancing, the basics seem doable but the part about
> measuring each end of the rods seems a bit more than i would be able to do
> without "special" tools/balances.
>
> so, after a bit thought, i wonder if it would be better if i just bring
> the short block to the shop and have them bore/balance/assemble it. the
> bore/clean/piston kit will be ~$500 and maybe another $400 for balance and
> (dis)assemble. therefore, my questions is: is balancing the rods/pistons
> easily doable at a home shop or would it be better to cough up the money
> to have the shop do it?
>
> as far as the lean condition, i am not sure exactly what caused it as the
> car ran well for > 80k miles but here are my thoughts:
> 1) i ask ask moss motors what they suggest at this point since the only
> after market engine control is a knock sensor. perhaps a AFPR, (and new
> fuel pump) and/or a piggyback ECU are called for.
> 2)i will check the EGR or just replace it.
> 3) there seemed to be 2 marks on the crank pulley so i will determine
> which is the correct one.
>
> any thoughts beyond these?

Chuck wrote:
> 1.8L engines don't have a lost ot spare when it comes to cylinder wall
> thickness.
> I assume that the last rebuild involved some amount of overbore as a start.
> I don't know how much total overbore a particular block can support, but
> have been told that the maximum displacement is about 2.0L.

the block is at 0.50mm over now. i am told it can go to 1.00 so i will
go for 0.75mm pistons with low compression like 8.8.

i do have a spare jy motor but this block has been decked and completely
cleaned inside and out so i would like to use it rather that paying for
that work to be done again.

btw, the short block weighs only 410# or so my bathroom scale says...my
back otoh, says it is more

thanks.
peter

XS11E wrote:
> peter > wrote:
>
>> so, after a bit thought, i wonder if it would be better if i just
>> bring the short block to the shop and have them
>> bore/balance/assemble it. the bore/clean/piston kit will be ~$500
>> and maybe another $400 for balance and (dis)assemble. therefore,
>> my questions is: is balancing the rods/pistons easily doable at a
>> home shop or would it be better to cough up the money to have the
>> shop do it?
>
> I think you'd be better off paying.
being "frugal", i am willing to try almost anythingbut i realize when it
is time to pry open the wallet so i will drop off the block off today.

is the reassemble of the short block difficult? i know there are
measurements to made and can follow the factory manual, but if it isvery
difficult, perhaps the shop should do it/

? Balancing requires a fairly
> accurate scale and the knowledge of how to create setups to weigh
> rod ends,
the rod ends are what stopped me from just going this at home so thanks
fo verifing this point.

pistons, etc. and where to remove metal to make them
> balance w/o reducing strenght, although I'll bet you can find
> something on the web if you Google for it......
i did, then came here for knowledgeable advice.

>
>> as far as the lean condition, i am not sure exactly what caused it
>> as the car ran well for 80k miles but here are my thoughts:
>> 1) i ask ask moss motors what they suggest at this point since the
>> only after market engine control is a knock sensor. perhaps a
>> AFPR, (and new fuel pump) and/or a piggyback ECU are called for.
>> 2)i will check the EGR or just replace it.
>> 3) there seemed to be 2 marks on the crank pulley so i will
>> determine which is the correct one.
>
> Do number 1, ask 'em. Do number 3, that's essential!
>
> Then, maybe you shouldn't worry about it. Drive the car and check
> spark plugs often to see it it's still lean, if it is, that's the time
> to do your trouble shooting. You just might be spending time fixing a
> problem that the rebuild took care of such as an air leak in the intake
> system or ?????

hmmm, the early jr/sc had virually no after market fuel/engine control.
i understand they do now...on this point, does anyone prefer either
the flyingMiata or the moss ecu better than the other?

thanks,
peter

"peter" > wrote in message
...
> XS11E wrote:
>> peter > wrote:
>>
>>> so, after a bit thought, i wonder if it would be better if i just
>>> bring the short block to the shop and have them
>>> bore/balance/assemble it. the bore/clean/piston kit will be ~$500
>>> and maybe another $400 for balance and (dis)assemble. therefore,
>>> my questions is: is balancing the rods/pistons easily doable at a
>>> home shop or would it be better to cough up the money to have the
>>> shop do it?
>>
>> I think you'd be better off paying.
> being "frugal", i am willing to try almost anythingbut i realize when it
> is time to pry open the wallet so i will drop off the block off today.
>
> is the reassemble of the short block difficult? i know there are
> measurements to made and can follow the factory manual, but if it isvery
> difficult, perhaps the shop should do it/
>
> ? Balancing requires a fairly
>> accurate scale and the knowledge of how to create setups to weigh
>> rod ends,
> the rod ends are what stopped me from just going this at home so thanks fo
> verifing this point.
>
> pistons, etc. and where to remove metal to make them
>> balance w/o reducing strenght, although I'll bet you can find
>> something on the web if you Google for it......
> i did, then came here for knowledgeable advice.
>
>>
>>> as far as the lean condition, i am not sure exactly what caused it
>>> as the car ran well for 80k miles but here are my thoughts:
>>> 1) i ask ask moss motors what they suggest at this point since the
>>> only after market engine control is a knock sensor. perhaps a
>>> AFPR, (and new fuel pump) and/or a piggyback ECU are called for.
>>> 2)i will check the EGR or just replace it.
>>> 3) there seemed to be 2 marks on the crank pulley so i will
>>> determine which is the correct one.
>>
>> Do number 1, ask 'em. Do number 3, that's essential!
>>
>> Then, maybe you shouldn't worry about it. Drive the car and check spark
>> plugs often to see it it's still lean, if it is, that's the time to do
>> your trouble shooting. You just might be spending time fixing a problem
>> that the rebuild took care of such as an air leak in the intake system or
>> ?????
>
> hmmm, the early jr/sc had virually no after market fuel/engine control. i
> understand they do now...on this point, does anyone prefer either the
> flyingMiata or the moss ecu better than the other?
>
> thanks,
> peter

There's no need to have the stock parts "balanced" since it's done
acceptably from the factory.
I think a piggy-back from Bipes will keep your timing in order.
http://www.crosslake.net/~dbipes/BipesACU/index.htm

peter > wrote:

> is the reassemble of the short block difficult? i know there are
> measurements to made and can follow the factory manual, but if it
> is very difficult, perhaps the shop should do it/

If you're careful and don't get in a hurry, you can do it. Make sure
you have all the necessary tools such as torque wrench(s), etc.

If you get in a hurry, you'll mess up for sure, at least I always do.
:-(




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i was hoping i could winnow the crank, rods and rods from my motor and
reuse them...alas they are damaged. i will determine if i can use them
or if i will use the jy motor i have