RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Sorry it's not a retro engine, but it's going in a retro car I'm re-building this engine to go in my mini (1999 passat 1.8t sport). I got it basically free, because the cam belt had gone, resulting in the need for a new head, and these rather tasty marks in the pistons. Now I've thoroughly checked them over, and this is the only damage on them, and no material's been removed at all, just displaced. Obviously I'd remove the burrs and blunt off the edges of the damage, but I'm just wondering if it's worth it, or if they're scrap. It's also worth bearing in mind that this engine will likely see 300bhp at some point, and that these pistons are forged. If they're no good then the engine'll probably go in the bin, and I'll look for a decent 2nd hand one, as the bill for re-building it looks like it's heading fast towards 4 figures even doing it my self. They're not cheep engines to build Anyway, some pictures of the offending pistons (the damage on all 4 looks identical):
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Whether they are 'knackered' is probably very much down to budget I think mate, if the sides/skirts are ok and the CROWN aren't cracked then I'd just fettle them back something like and stick them in, you've got bigger things to worry about at this point in the build.
More to the point, why not leave it alone and use that engine for mocking up and buy a running motor (probably for less than the cost of pistons/rings/gaskets/bolts..) when the rest of the car is done ?
Just my 2p's worth
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'A' series trigger wheels and sensor brackets, 205 GTi radiator brackets, general fabrication and machining - www.gsmotorsport.net
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I'd probably use them, but if I was spending a grand on rebuilding the engine I think I'd just get another set.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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More to the point, why not leave it alone and use that engine for mocking up and buy a running motor (probably for less than the cost of pistons/rings/gaskets/bolts..) when the rest of the car is done ? Just my 2p's worth Cheers That is the other option, and one that's becoming increasingly likely. The problem is that these engines fetch good money, so I'd be lucky to get a low mileage one for any less the the re-build is going to cost. The other advantage is that re-building the engine allows me to uprate the conrods, which are the engines only real weak link. Like you say, it's not the priority of the build at the moment, although it does need to be running by early spring 2011, as I'm doing the engine management as a college project, and I need to be able to get it on the rollers to map it with enough time to do the write up. I'm still going through my options in my head really, just wanting to know if these are shot, as a new set's bound to be a few £££, so if they are, it'll stop the option of re-building this engine from being a viable option. Also to clear things up, 4 figures for the re-build isn't me being silly and buying fancy everything, I've totaled it at £829 so far for just valves, valve seals, head bolts, head gasket set, piston rings, oil pump and water pump. Then there's still the bearings and a bunch more gaskets and seals left to go, as well as paying somewhere to re-hone the block. They're just bloody expencive to re-build! Piston rings come in a £70 per cylinder, over £250 worth of valves, oil pumps £120 ect.. ect.. Just had a look on ebay, I'm looking at £500ish for a bare engine on over 70,000 miles. I suppose its a fair chunk cheeper, as all the ancillery's are good on this engine, just need the tall engine, but it's still on 70k. Guess it depends how flush I'm feeling. (Not very as it happens! haha)
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Last Edit: Jun 7, 2010 19:35:28 GMT by RobinJI
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You would be able to get pistons matched up at a decent factors for not a lot of money.....id definatly replace
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seen plenty of bare 1.8t engines go for around £100, they only seem to fetch good money if they have everything for a conversion.
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make sure none of the ring lands are pinched up, if not, the fettle back and use I say, the head I'm using on the imp had a split washer go through it some time back. It mashed up the combustion chamber good and proper, but I'm still using it on the supercharged engine! If you have the cash to splash then get new ones, but if not check for cracks, make sure the ring lands are not pinched, and then use
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Are the rings still free? they don't look like they've been hit hard enough to pinch the lands but its something to check. One thing you will need to do is get the dremel or sandpaper out and remove any high spots and sharp edges as they will make hotspots and promote det. being a turbo motor det is more likely so normally a set of pistons would be a good idea. would probably be fine so long as you don't go upping the boost. Beaten to it by blownimp!
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Yeah, any damage would be smoothed out nicely before they went back in. The ring lands haven't been effected in the slightest, it's only superficial damage as far as I can tell. They're forged mahle pistons as standard, and seem pretty tough. The thing is I do plan on increasing the boost a fair bit, I'd love a 300bhp map for having fun, and around a 200bhp for when I need a bit more control, but we're talking about boost pressures well above 1.5bar to achieve this. I know the engine will take this normally, just not sure now it's got these marks. If it was just a case of sticking them back in and seeing if it blows up I'd definitely give it a go, but I'm not really willing to trust my self to make the call of weather they're going to be ok not to damage a £1000 engine.
Hmm.. I guess the answer's just going to be to get a new engine for it. Ah well, like I said, this ones cost me nothing, I sold the other parts of the car for more than I bought it for, and some spares wont hurt.
To be honest I made this topic while I was still pricing up the re-build, and having seen the price I'm looking at just to put it back together, even if the pistons hadn't been touched I'd be looking for a 2nd hand tall engine at this stage. Probably worth mentioning this engine's on 190000+ miles, so I really can't get away with not replacing the pumps or any other bits.
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