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Scratched bores

starboard147

starboard147

New member
Not a new subject from me, I'm afraid, but I'm looking for a good 2nd hand block to rebuild my turbo engine - mine has scratches on all the bores and I can't source oversize pistons [:(]. Failing that, I guess an S2 crank would allow me to go oversize with stroker pistons... Can anyone help or point me in the right direction??

Paul
 
Bad news Paul [&o]

Who have you tried for oversize pistons? I know when I needed some they were completely unobtainable and Mahle were not supposed to be doing a run for 18 months. However 6 months into my engine build they suddenly started popping up [:mad:]
 
For what it's worth I know someone who bought 100.5 mm turbo pistons from Porsche 18 months ago for about ... €2k [&:]
 
Fen if Paul dosent want it can you send me some details, as I am also have scratched bores and have been putting off ripping the engine out.
 
Scratches are down to turbo retaining nut and washer coming off, and removing all the compressor vanes, which subsequently went through the engine. Interestingly, it still made good power without smoking afterwards, however oil consumption was pants (300 miles/ltr!!).

Bought 2nd hand engine off e-bay, stripped back to short block, rebuilt top end, new turbo, clutch, oil seals & gaskets, water pump and rollers, and installed in the car earlier this year. No 4 had slight scratching however it made comparable power with other turbos at the dyno day last week. So, thanks Fen, but no, my plan was to try and get the original engine back up and running. Tom, please be my guest...

Thanks for the info about oversize pistons. I have tried Bert and Ski (Rennlist) to no avail. Not yet tried OPC or US suppliers (I see that LR are advertising Mahle oversize pistons - what's the diff between 4032 and 2618 forgings?) however 2000 euros is probably a bit steep. If that was the price on offer, I would try for an S2 crank and oversize strokers... which, if noboby knows of a block, is looking like the way I'll be going!!!
 
ORIGINAL: starboard147
I would try for an S2 crank and oversize strokers... which, if noboby knows of a block, is looking like the way I'll be going!!!
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I believe there is a problem with rod block/clearance when fitting the S2 crank in the turbo block with the original rods so would need to budget for a set of aftermarket rods (eg Carillo) on top of it ; slippery slope ? No Sir, not one bit ...[;)]

Also why not try to source a 2.7 engine and simply have the pistons machined to lower the CR ? Our colleagues in Germany all do that when they build a 3.0, and that may prove the less cost ineffective way to both upgrade and replace a damaged turbo engine.
 
No problem Paul, just thought I'd ask. I did send you a mail yesterday Tom, so if you didn't get it let me know.
 
ORIGINAL: TTM

I believe there is a problem with rod block/clearance when fitting the S2 crank in the turbo block with the original rods so would need to budget for a set of aftermarket rods (eg Carillo) on top of it ; slippery slope ? No Sir, not one bit ...[;)]

Also why not try to source a 2.7 engine and simply have the pistons machined to lower the CR ? Our colleagues in Germany all do that when they build a 3.0, and that may prove the less cost ineffective way to both upgrade and replace a damaged turbo engine.
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How do they get the 3.0 capacity with the 2.7 engine ?, I'm not looking for an engine but in the unllikely event that a bargain 2.7 turns up I could store it away for a rainy day.
 
The 2.7 engine is effectively the 3.0 bore with the 2.5 stroke. Stroking a 2.5 with the 3.0 crank gives 2.8 litres approximately. Of course it isn't just a case of swapping the crank across.
 
ORIGINAL: Fen

The 2.7 engine is effectively the 3.0 bore with the 2.5 stroke. Stroking a 2.5 with the 3.0 crank gives 2.8 litres approximately. Of course it isn't just a case of swapping the crank across.
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Yes that's as I thought, the S2/968 use the 2.7 block , is it good engineering practice to machine the 2.7 pistons to lower the comp ratio though ?.
 
ORIGINAL: pauly


Yes that's as I thought, the S2/968 use the 2.7 block , is it good engineering practice to machine the 2.7 pistons to lower the comp ratio though ?.
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I'd be more concerned about using the 2.7 N/A pistons in a 3.0L turbocharged engine. However if there are many cars modified this way in Germany it could be a proven method for those on a budget?

2.7 blocks are pretty rare. They were only made in 1989 so there are not many around - the beauty is the 2.7 head has the largest valves in the series and it bolts straight on to the larger bored block. It's what my engine started out as [:)]
 
I don't know if the S2/S3 use the 2.7 block as such. They definitely use the same bore as the 2.7, but there might well be some differences.
 
The only difference between 2.7/S2/968 blocks I am aware of is the oil squirters in the 968 block.
Though not the block itself the 968 crankshaft seems to weigh less than the other two. Mine at least weighs 25.0 kg while several other 2.7/S2 crankshaft weighed in the 27.5 kg area.
The girdle on the 968 features three studs on which the oil pump is attached while on 944 girdle the oil pump is attached with bolts only. Two of the three studs that attach the seat of the tensioner are longer on 968 than on 944 (hydraulic vs spring-loaded tensioner).

ORIGINAL: 944 man
They do: 1989> blocks say 2.7 on them.
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Mmmmm ... are you sure it's on the block itself or rather on the water pump ?
 
ORIGINAL: nick_968

I have a complete 968 engine (remove from my 968) and also a brand new 104mm (3.0 968) bare block.....
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Weren't you thinking about going 16v on your turbo conversion ?.
 
ORIGINAL: nick_968

I have a complete 968 engine (remove from my 968) and also a brand new 104mm (3.0 968) bare block.....
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Another brand new 104mm block, didn't your rebuild use a brand new block as well? Just how many blocks do you need Nick?

I've heard SimonP talk about doing a 3.0L 16V turbo but I didn't realise Nick was considering it as well
 
ORIGINAL: Diver944

ORIGINAL: nick_968

I have a complete 968 engine (remove from my 968) and also a brand new 104mm (3.0 968) bare block.....
Click to expand...

Another brand new 104mm block, didn't your rebuild use a brand new block as well? Just how many blocks do you need Nick?

I've heard SimonP talk about doing a 3.0L 16V turbo but I didn't realise Nick was considering it as well
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I don't know if he's seriously considering it, I read one of his posts somewhere that said it was a possibility at some stage.
 
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