Engine Rebuild - Cylinder Bore Wear

Started by onenastyviper, June 22, 2022, 19:46

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onenastyviper

Hi, I've recently taken my spare 1zz engine apart (history unknown but looks clean) for checking and found that all the bores appear to be larger than the 79.013mm limit in the Toyota service manual.

I've checked and rechecked my bore gauge (Draper 02753) and feel it is reasonably accurate but my cylinder bores were typically measuring between 79.01 & 79.07

Should I worry?

Carolyn

Quote from: onenastyviper on June 22, 2022, 19:46Hi, I've recently taken my spare 1zz engine apart (history unknown but looks clean) for checking and found that all the bores appear to be larger than the 79.013mm limit in the Toyota service manual.

I've checked and rechecked my bore gauge (Draper 02753) and feel it is reasonably accurate but my cylinder bores were typically measuring between 79.01 & 79.07

Should I worry?

79.01, no problem. 79.07... very borderline.  If you have ordered piston rings, I suggest you pop a new one in the bores, halfway down, using a piston to set it level, and measure the ring end gap.  That will tell the story.
Perry Byrnes Memorial Award 2016, 2018.  Love this club. 
https://www.mr2roc.org/forum/index.php?topic=63866.0

onenastyviper

Thanks Carolyn.

This was already an engine from a breaker so I am loathed to gamble several hundred pounds to be in the same situation again buying another 2nd hand engine.

If it is the case that my block is out of spec, are my options limited to either a rebore or a new block?

shnazzle

Quote from: onenastyviper on June 23, 2022, 11:58Thanks Carolyn.

This was already an engine from a breaker so I am loathed to gamble several hundred pounds to be in the same situation again buying another 2nd hand engine.

If it is the case that my block is out of spec, are my options limited to either a rebore or a new block?

Bore it out to 79.5 with some aftermarket pistons and rings :) Sorted. And more capacity
...neutiquam erro.

onenastyviper

Quote from: shnazzle on June 23, 2022, 12:10Bore it out to 79.5 with some aftermarket pistons and rings :) Sorted. And more capacity

Sounds like I need to break open the piggy-bank  8)

Carolyn

Quote from: onenastyviper on June 23, 2022, 11:58Thanks Carolyn.

This was already an engine from a breaker so I am loathed to gamble several hundred pounds to be in the same situation again buying another 2nd hand engine.

If it is the case that my block is out of spec, are my options limited to either a rebore or a new block?


These engines are not designed to be rebored,  It can be done BUT.

By the time you've bought four oversized pistons, rings, paid the machine shop, and bought all the other bits you'll need to do a decent rebuild job, you might just get another used 1ZZ, open it up and see what gives.  It doesn't have to come from an MR2.

But, I bet, your block will be fine.
Perry Byrnes Memorial Award 2016, 2018.  Love this club. 
https://www.mr2roc.org/forum/index.php?topic=63866.0

Call the midlife!

I'd wager there are more people who've rebuilt engines WITHOUT checking the bores and have probably got similar wear as yours.
It's one of those conundrums isn't it? If you'd not checked them and carried on it would probably not be a problem.
60% of the time it works everytime...

onenastyviper

I've contacted a local engine shop just to get an indicative price for a rebore and hone (costs nothing to ask).

Next on the list: source good OEM rings to perform the check that Carolyn kindly suggested.
-> Any recommendations?


onenastyviper

Quote from: Call the midlife! on June 23, 2022, 19:05I'd wager there are more people who've rebuilt engines WITHOUT checking the bores and have probably got similar wear as yours.
It's one of those conundrums isn't it? If you'd not checked them and carried on it would probably not be a problem.

I have a degree in "Procrastination" with a minor in "Overthinking"  :))

Carolyn

#9
Quote from: onenastyviper on June 24, 2022, 10:06I've contacted a local engine shop just to get an indicative price for a rebore and hone (costs nothing to ask).

Next on the list: source good OEM rings to perform the check that Carolyn kindly suggested.
-> Any recommendations?



I've used these with good results

https://www.ebay.co.uk/itm/192561585471?hash=item2cd5909d3f:g:3IEAAOSwvGZZxKjP

EDIT:  I'm sure I  got mine from a UK supplier.  I noticed this ad has a big shipping charge!  Any set that sells for around 30 -40 quid will be fine.
Perry Byrnes Memorial Award 2016, 2018.  Love this club. 
https://www.mr2roc.org/forum/index.php?topic=63866.0

onenastyviper

Quote from: Carolyn on June 24, 2022, 10:14I've used these with good results

https://www.ebay.co.uk/itm/192561585471?hash=item2cd5909d3f:g:3IEAAOSwvGZZxKjP

EDIT:  I'm sure I  got mine from a UK supplier.  I noticed this ad has a big shipping charge!  Any set that sells for around 30 -40 quid will be fine.

Thanks Carolyn. Just ordered some from Autodoc, together with a complete rebuild gasket kit...  :o

AJRFulton


paulj

Reading this out of academic interest as it is well beyond any spannering i might do myself....

One question though - on the link that @Carolyn posted it looks like you can order the rings oversized.  How does that work?  Is it a solution for a block with worn bores, or have i missed the point!  Of interest only if anyone has a moment spare to post a reply.
Today
2000 x reg pfl - blue - as original no mods
In the late 1980's
1982 x reg Toyota Corolla Liftback Coupe (also blue)
1978 s reg Mitsubishi Celeste Coupe (yellow)

Call the midlife!

Quote from: paulj on June 28, 2022, 20:18Reading this out of academic interest as it is well beyond any spannering i might do myself....

One question though - on the link that @Carolyn posted it looks like you can order the rings oversized.  How does that work?  Is it a solution for a block with worn bores, or have i missed the point!  Of interest only if anyone has a moment spare to post a reply.
Oversized means you can take the ends down to fit your bores, if you've had them bored out and/or sleeved. You file bare minimums off the ends and keep test fitting them in the bores until they meet the specs you're looking for.
You CAN use them for worn bores if the standard ones are out of spec but it's pushing the limits of the tolerances and we're talking parts of mm.
60% of the time it works everytime...

onenastyviper

Quote from: Call the midlife! on June 28, 2022, 21:52Oversized means you can take the ends down to fit your bores, if you've had them bored out and/or sleeved. You file bare minimums off the ends and keep test fitting them in the bores until they meet the specs you're looking for.
You CAN use them for worn bores if the standard ones are out of spec but it's pushing the limits of the tolerances and we're talking parts of mm.

...and if you don't file enough or incorrectly then the ring ends touch as they expand with cylinder heat and bad things can happen  :o

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