Maximum bore size with stock pistons

Zans

Zans

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hello,
i'm doing a rebuild on my 1.8t APY and would like to know the maximum bore on which stock pistons can be used. I read in the workshop manual that for standard 80.95 mm pistons the bore must be 81.01mm, and for a repair oversize it's 81.45 mm piston and 81.51mm bore.

After 200000km the bore won't be 81.01mm anymore (i haven't measured yet) so according to the manual I need to rebore my block to 81.51mm if it's bigger than 81.01mm? but i don't want to spend a fortune on new over sized pistons or aftermarket ones.

So my question is what would practically be the maximum bore (less than 81.51mm) for stock pistons with not pre gaped rings?

Thank you
 
Max bore will be 81.01mm... thats what the specs suggest, thats what it needs to be...

If you have wear then you will need to rebore to the next suitable oversize measurement... bear in mind that bores tend to wear oval so depending on how worn your bores are you might need to go up another size to ensure straight bores...

You can over bore to suit 82.5mm pistons on the standard head gasket but tbh there is not much to gain between 81.5 or 82.5mm pistons...

Also bear in mind that its not just the bores that wear... the pistons will have worn too so its not a simple case of open the bore a little to reuse the original pistons...

Put simply... if the bores are worn enough that blow by is an issue, running a hone down the bore and fitting new rings won't fix the problem... if anything it will make it worse and the pistons will slap about

<tuffty/>
 
<tuffty/> said:
Max bore will be 81.01mm... thats what the specs suggest, thats what it needs to be...

If you have wear then you will need to rebore to the next suitable oversize measurement... bear in mind that bores tend to wear oval so depending on how worn your bores are you might need to go up another size to ensure straight bores...

You can over bore to suit 82.5mm pistons on the standard head gasket but tbh there is not much to gain between 81.5 or 82.5mm pistons...

Also bear in mind that its not just the bores that wear... the pistons will have worn too so its not a simple case of open the bore a little to reuse the original pistons...

Put simply... if the bores are worn enough that blow by is an issue, running a hone down the bore and fitting new rings won't fix the problem... if anything it will make it worse and the pistons will slap about

<tuffty/>
Click to expand...
Okay thanks!
 
<tuffty/> said:
Max bore will be 81.01mm... thats what the specs suggest, thats what it needs to be...

If you have wear then you will need to rebore to the next suitable oversize measurement... bear in mind that bores tend to wear oval so depending on how worn your bores are you might need to go up another size to ensure straight bores...

You can over bore to suit 82.5mm pistons on the standard head gasket but tbh there is not much to gain between 81.5 or 82.5mm pistons...

Also bear in mind that its not just the bores that wear... the pistons will have worn too so its not a simple case of open the bore a little to reuse the original pistons...

Put simply... if the bores are worn enough that blow by is an issue, running a hone down the bore and fitting new rings won't fix the problem... if anything it will make it worse and the pistons will slap about

<tuffty/>
Click to expand...
Are cylinder sleeves an option for the 1.8t?
 
<tuffty/> said:
Afraid not...

<tuffty/>
Click to expand...
Did they make the 1.8t in an aluminium block? this way i could buy new sleeves for it and be done with it...

The problem is that there was a lot of dust in the engine and it took a lot of material off the bores, highest measurement was 81.36 mm so boring the engine block isn't an option where i live and i'd like to keep the stock pistons because they're in good shape
 
Zans said:
And the early longitudinal 058 as well?
Click to expand...
Yes although the 058 block is different mechanically to the 06A and not something thats easily fitted...

Assuming the reason you are asking these questions is due to your engine being worn I would basically look for another transverse 1.8t engine and look to use that in some form as without boring your current block and fitting over sized pistons its scrap anyway...

You can take an engine from a K03 turbo'd A3 or golf (AUM) or even one from a Seat or Skoda and swap pistons and rods if you feel you need to do it this way at all but bear in mind that any engine of any age is subject to wear so a light hone and new rings won't guarantee that you will have a good engine out of it

If budget is your problem here then tbh the best bet is to source another engine but weigh that up against the price of new pistons and a rebore first

<tuffty/>
 
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<tuffty/> said:
Yes although the 058 block is different mechanically to the 06A and not something thats easily fitted...

Assuming the reason you are asking these questions is due to your engine being worn I would basically look for another transverse 1.8t engine and look to use that in some form as without boring your current block and fitting over sized pistons its scrap anyway...

You can take an engine from a K03 turbo'd A3 or golf (AUM) or even one from a Seat or Skoda and swap pistons and rods if you feel you need to do it this way at all but bear in mind that any engine of any age is subject to wear so a light hone and new rings won't guarantee that you will have a good engine out of it

If budget is your problem here then tbh the best bet is to source another engine but weigh that up against the price of new pistons and a rebore first

<tuffty/>
Click to expand...
That sums up my problem pretty well!
Thanks for the advice! i'll go to a junkyard with a bore gauge and see if i can find something not so worn out
 
Question out of topic....
Did VW make a manual timing belt tensioner or i need to buy the aftermarket ones? I asked yesterday at a local parts shop and they only got the hydraulic ones
 
There isn't one made directly for the 1.8t but you can adapt the old valver ones or use the ones fitted to an 06B inline based engine (A6 etc)

I don't know the part numbers but I have used both setups myself on my own engine before

<tuffty/>
 
<tuffty/> said:
There isn't one made directly for the 1.8t but you can adapt the old valver ones or use the ones fitted to an 06B inline based engine (A6 etc)

I don't know the part numbers but I have used both setups myself on my own engine before

<tuffty/>
Click to expand...
Okay thanks!
 
<tuffty/> said:
There isn't one made directly for the 1.8t but you can adapt the old valver ones or use the ones fitted to an 06B inline based engine (A6 etc)

I don't know the part numbers but I have used both setups myself on my own engine before

<tuffty/>
Click to expand...
Do the manual tensioner pulleys tend to go bad with time or it's fine if i buy a used one from the junkyard?
 
Zans said:
Do the manual tensioner pulleys tend to go bad with time or it's fine if i buy a used one from the junkyard?
Click to expand...
Like most things pulleys wear out... its still a pulley with a bearing like the standard 1.8t one so same principles apply.... if replacing a critical item like a cam belt you normally change the pulleys too...

<tuffty/>
 
<tuffty/> said:
Like most things pulleys wear out... its still a pulley with a bearing like the standard 1.8t one so same principles apply.... if replacing a critical item like a cam belt you normally change the pulleys too...

<tuffty/>
Click to expand...
Alright then i'll try to find a part number for that and ask at the shop
 
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<tuffty/> said:
This is where I used the valver tensioner...
https://www.audi-sport.net/xf/threads/my-minor-modding-thread.76389/page-58#post-1997536

You have to pack it away from the head as the mounting is closer to the head than 06A applications... I used an Integrated Engineering spacer as I had one available but I suspect you could use some suitably large washers...

...and the 06B version...
https://www.audi-sport.net/xf/threads/my-minor-modding-thread.76389/page-68#post-2218146

<tuffty/>
Click to expand...
Thanks! i'll try find something suitable for my car
 
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