Why are pistons??
Discussion
Why are pistons handed?, ie marked front, I assume they have an offset pin to reduce side loads on the piston/bore, do you need to use handed pistons if you are using with short skirts?
The reason I ask, I have found some lovely forged BIKE pistons that tick all the boxes for my up-coming RV8 build, but weigh about half the weight of Omegas, and I can even get them with flat tops or PopUps to raise the compression if needed.
Ian
The reason I ask, I have found some lovely forged BIKE pistons that tick all the boxes for my up-coming RV8 build, but weigh about half the weight of Omegas, and I can even get them with flat tops or PopUps to raise the compression if needed.
Ian
Pistons are handed for three possible reasons.
1) If the crown shape is non symmetrical to match the combustion chamber and create a squish band.
2) If the valve cutouts are of different sizes to match the inlet/exhaust valves.
3) If the gudgeon pin is offset to minimise rocking slap forces as the piston traverses BDC and TDC. Usually the pin is offset about 1mm to 1.5mm towards the thrust side of the engine block which keeps the piston loaded to one side.
I have seen unhappy consequences resulting from the use of centrally located gudgeon pins which unfortunately some of the American piston manufacturers still seem to think is the way to go, or at least they can't be arsed to do it properly. It becomes more critical to use an offset as the piston skirts become shorter. I recall rebuilding a Daimler Dart 2.5 V8 many years ago which still used central pins but the pistons were very long with full skirts, the rpm and specific power output wasn't that high and there were no unusual wear patterns apparent. Try the same on a high rpm slipper piston race engine and I suspect it would end in tears.
It certainly did for a customer of mine once who tried to build his VW race engine with forged American pistons, Hairyarse I think they were, with central pins which caused the piston skirts to slap themselves to death or seize in the bores in short order. The manufacturer had no clue why this was happening and just kept advising more bore clearance until eventually they were running them like a dick up a drainpipe but still they kept seizing. In fact more clearance just made it worse as you'd expect.
Eventually they sent a worn set to me for a an expert opinion on their troubles and after about 30 seconds of measuring I fell off my chair laffing. Hadn't laffed so hard since granny got her left tit caught in the mangle.
Anyway on my advice they went back to OE bog standard cast VW pistons with offset pins and had no further problems. You can't beat a decent quality OE cast piston for anything up to about 100 bhp per litre IMO. Most of the forged pistons people buy are a waste of time and money and just make more noise, less power and wear out quicker.
1) If the crown shape is non symmetrical to match the combustion chamber and create a squish band.
2) If the valve cutouts are of different sizes to match the inlet/exhaust valves.
3) If the gudgeon pin is offset to minimise rocking slap forces as the piston traverses BDC and TDC. Usually the pin is offset about 1mm to 1.5mm towards the thrust side of the engine block which keeps the piston loaded to one side.
I have seen unhappy consequences resulting from the use of centrally located gudgeon pins which unfortunately some of the American piston manufacturers still seem to think is the way to go, or at least they can't be arsed to do it properly. It becomes more critical to use an offset as the piston skirts become shorter. I recall rebuilding a Daimler Dart 2.5 V8 many years ago which still used central pins but the pistons were very long with full skirts, the rpm and specific power output wasn't that high and there were no unusual wear patterns apparent. Try the same on a high rpm slipper piston race engine and I suspect it would end in tears.
It certainly did for a customer of mine once who tried to build his VW race engine with forged American pistons, Hairyarse I think they were, with central pins which caused the piston skirts to slap themselves to death or seize in the bores in short order. The manufacturer had no clue why this was happening and just kept advising more bore clearance until eventually they were running them like a dick up a drainpipe but still they kept seizing. In fact more clearance just made it worse as you'd expect.
Eventually they sent a worn set to me for a an expert opinion on their troubles and after about 30 seconds of measuring I fell off my chair laffing. Hadn't laffed so hard since granny got her left tit caught in the mangle.
Anyway on my advice they went back to OE bog standard cast VW pistons with offset pins and had no further problems. You can't beat a decent quality OE cast piston for anything up to about 100 bhp per litre IMO. Most of the forged pistons people buy are a waste of time and money and just make more noise, less power and wear out quicker.
Marf said:
Pumaracing said:
good stuff about pistons
Is there a brand of pistons you would recomend if upgrading to forged?Most of them are actually not too bad but also most of them are not really needed in the engines they get fitted to. Unless you're turning serious rpm or developing ungodly amounts of power you'll do just fine on the pistons god fitted to your engine in the first place. If you do feel the need to go forged then you won't go far wrong with names like Mahle, Accralite, Omega or Cosworth. The yanks have upped their game a bit recently so you might also try JE.
I'm looking at an engine currently which has Woosner pistons in it and they appear to have survived a decent amount of abuse without too much protest and they're certainly cheap.
This is a lovely tale of engine development and has a certain amount to say about pistons. Whatever your background you're unlikely to read it without learning something.
http://www.ducatimeccanica.com/kevin_race_engine.h...
I've used quite a few forged pistons and haven't noticed them rattling, they are from the US but not JE. I've had poor service from JE from a communication point of view but their pistons seem ok. I won't use them again though. I think Mahle have a very good alloy so next time may try them. Woosner have a very good reputation from what I hear but I've no experience of them.
ETA, I did go through a spell of trying high silicone eutectics but they cracked under high boost so it was back to forgings. That said, it was a pretty careless customer but I can't take that sort of chance again. If they had a solid skirt they may have survived and no doubt he had some detonation causing the problem in the first place. So, it's forgings for me most of the time.
ETA, I did go through a spell of trying high silicone eutectics but they cracked under high boost so it was back to forgings. That said, it was a pretty careless customer but I can't take that sort of chance again. If they had a solid skirt they may have survived and no doubt he had some detonation causing the problem in the first place. So, it's forgings for me most of the time.
Edited by Boosted LS1 on Friday 9th October 23:05
I think I will stick with forgings, especially as I going to stuff a fair bit of gas down the bores, i do know what you mean about slappy pistons, my Omegas slap about quite badly, not sure if its down to the engine being quite worn, but its pretty severe, I also have a mate who has a 5.0RV8 turbo engine, he had pistons made for this engine in the states, they sound terrible, using the spec they supplied its fookin awful, ended up changing the block and reducing the clearance by a silly amount, Im still thinking about the bike pistons, but TBH I think the skirts are far too short, and narrow,
I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
Boosted LS1 said:
^ They'll be a set of Fast freddies Omega's. Don't ask me why they call him Fast Freddy, lol If you get a problem you'll be stuffed. If you buy from the US you can get replacemants in weeks, not years.
I need some quotes and options from you Mike. Wheres best to email you?dbv8 said:
Boosted LS1 said:
^ They'll be a set of Fast freddies Omega's. Don't ask me why they call him Fast Freddy, lol If you get a problem you'll be stuffed. If you buy from the US you can get replacemants in weeks, not years.
I need some quotes and options from you Mike. Wheres best to email you?
Anything I spec is ordered after I've had the block and heads. I'd never order from a UK manufacturer though.Boosted LS1 said:
dbv8 said:
Boosted LS1 said:
^ They'll be a set of Fast freddies Omega's. Don't ask me why they call him Fast Freddy, lol If you get a problem you'll be stuffed. If you buy from the US you can get replacemants in weeks, not years.
I need some quotes and options from you Mike. Wheres best to email you? Anything I spec is ordered after I've had the block and heads. I'd never order from a UK manufacturer though.I was going to do my heads myself but i would also be interested in a quote to 'finish' off the heads and fit too. I am trying to save money doing as much as possible myself but would consider sending you my block.
Pumaracing said:
Pistons are handed for three possible reasons.
1) If the crown shape is non symmetrical to match the combustion chamber and create a squish band.
2) If the valve cutouts are of different sizes to match the inlet/exhaust valves.
3) If the gudgeon pin is offset to minimise rocking slap forces as the piston traverses BDC and TDC. Usually the pin is offset about 1mm to 1.5mm towards the thrust side of the engine block which keeps the piston loaded to one side.
I have seen unhappy consequences resulting from the use of centrally located gudgeon pins which unfortunately some of the American piston manufacturers still seem to think is the way to go, or at least they can't be arsed to do it properly. It becomes more critical to use an offset as the piston skirts become shorter. I recall rebuilding a Daimler Dart 2.5 V8 many years ago which still used central pins but the pistons were very long with full skirts, the rpm and specific power output wasn't that high and there were no unusual wear patterns apparent. Try the same on a high rpm slipper piston race engine and I suspect it would end in tears.
It certainly did for a customer of mine once who tried to build his VW race engine with forged American pistons, Hairyarse I think they were, with central pins which caused the piston skirts to slap themselves to death or seize in the bores in short order. The manufacturer had no clue why this was happening and just kept advising more bore clearance until eventually they were running them like a dick up a drainpipe but still they kept seizing. In fact more clearance just made it worse as you'd expect.
Eventually they sent a worn set to me for a an expert opinion on their troubles and after about 30 seconds of measuring I fell off my chair laffing. Hadn't laffed so hard since granny got her left tit caught in the mangle.
Anyway on my advice they went back to OE bog standard cast VW pistons with offset pins and had no further problems. You can't beat a decent quality OE cast piston for anything up to about 100 bhp per litre IMO. Most of the forged pistons people buy are a waste of time and money and just make more noise, less power and wear out quicker.
Good post.......1) If the crown shape is non symmetrical to match the combustion chamber and create a squish band.
2) If the valve cutouts are of different sizes to match the inlet/exhaust valves.
3) If the gudgeon pin is offset to minimise rocking slap forces as the piston traverses BDC and TDC. Usually the pin is offset about 1mm to 1.5mm towards the thrust side of the engine block which keeps the piston loaded to one side.
I have seen unhappy consequences resulting from the use of centrally located gudgeon pins which unfortunately some of the American piston manufacturers still seem to think is the way to go, or at least they can't be arsed to do it properly. It becomes more critical to use an offset as the piston skirts become shorter. I recall rebuilding a Daimler Dart 2.5 V8 many years ago which still used central pins but the pistons were very long with full skirts, the rpm and specific power output wasn't that high and there were no unusual wear patterns apparent. Try the same on a high rpm slipper piston race engine and I suspect it would end in tears.
It certainly did for a customer of mine once who tried to build his VW race engine with forged American pistons, Hairyarse I think they were, with central pins which caused the piston skirts to slap themselves to death or seize in the bores in short order. The manufacturer had no clue why this was happening and just kept advising more bore clearance until eventually they were running them like a dick up a drainpipe but still they kept seizing. In fact more clearance just made it worse as you'd expect.
Eventually they sent a worn set to me for a an expert opinion on their troubles and after about 30 seconds of measuring I fell off my chair laffing. Hadn't laffed so hard since granny got her left tit caught in the mangle.
Anyway on my advice they went back to OE bog standard cast VW pistons with offset pins and had no further problems. You can't beat a decent quality OE cast piston for anything up to about 100 bhp per litre IMO. Most of the forged pistons people buy are a waste of time and money and just make more noise, less power and wear out quicker.
v8ian said:
I think I will stick with forgings, especially as I going to stuff a fair bit of gas down the bores, i do know what you mean about slappy pistons, my Omegas slap about quite badly, not sure if its down to the engine being quite worn, but its pretty severe, I also have a mate who has a 5.0RV8 turbo engine, he had pistons made for this engine in the states, they sound terrible, using the spec they supplied its fookin awful, ended up changing the block and reducing the clearance by a silly amount, Im still thinking about the bike pistons, but TBH I think the skirts are far too short, and narrow,
I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
One of the problems with off the shelf generic forged pistons is the manufacturer often has no idea how the block in any particular engine expands in response to temperature changes or alters shape in response to thrust and other forces and these obviously determine the piston skirt profile and bore clearance required.I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
When an OE manufacturer designs a piston for a production car they'll test dozens of piston shapes and clearances to get the optimum balance between life, noise and power output. The amount of skirt ovality might be adjusted and similarly the diameter of the piston ring land region which is circular but needs to have the right cold dimension so it expands to close to bore size when hot.
Just taking a generic forging blank machined to fit a specified bore size in an unknown engine, putting a generic skirt profile on that and then taking your best guess at the bore clearance and ring land diameter required is hardly a guarantee that anything will work very well as you've found. Usually the bore clearance specified is far too high so they don't get comebacks for seizures but the price you pay is godawful piston slap and a short life.
Without some R&D which few people have the resources for it's little more than a lottery to hope it'll all work straight out of the box.
But to be fair, the US manufacturers have had years of experience with designing pistons for all sorts of applications, street, race and strip. They'll get feedback from their customers and design accordingly. Sure, they may not do their own in house scuff tests but lots of customers have already done that for them over the past 40-50 years.
Going back to more ordinary cast pistons, I can think of one well respected manufacturer who supplies pistons for just about every engine on the planet, often running less then 001" bore clearance. I doubt they've tested every piston family in it's respective engine but they do/did offer something like a 300'000 km warranty or something pretty mind boggling like that. So somewhere along the way they have aqquired enough experience to make a long lasting piston without needing the engine. So, some off the shelf stuff is excellent just don't buy from somewhere to cheap as you get what you pay for.
Going back to more ordinary cast pistons, I can think of one well respected manufacturer who supplies pistons for just about every engine on the planet, often running less then 001" bore clearance. I doubt they've tested every piston family in it's respective engine but they do/did offer something like a 300'000 km warranty or something pretty mind boggling like that. So somewhere along the way they have aqquired enough experience to make a long lasting piston without needing the engine. So, some off the shelf stuff is excellent just don't buy from somewhere to cheap as you get what you pay for.
Pumaracing said:
v8ian said:
I think I will stick with forgings, especially as I going to stuff a fair bit of gas down the bores, i do know what you mean about slappy pistons, my Omegas slap about quite badly, not sure if its down to the engine being quite worn, but its pretty severe, I also have a mate who has a 5.0RV8 turbo engine, he had pistons made for this engine in the states, they sound terrible, using the spec they supplied its fookin awful, ended up changing the block and reducing the clearance by a silly amount, Im still thinking about the bike pistons, but TBH I think the skirts are far too short, and narrow,
I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
One of the problems with off the shelf generic forged pistons is the manufacturer often has no idea how the block in any particular engine expands in response to temperature changes or alters shape in response to thrust and other forces and these obviously determine the piston skirt profile and bore clearance required.I have seen a set of Manley forgings which are 3.7" and full skirted, I might go for these, damn sight cheaper than Omegas, but will need fetteling to fit, so Im also thinking that I will need new rods and possibly bushing the rods to suit the small ends,
When an OE manufacturer designs a piston for a production car they'll test dozens of piston shapes and clearances to get the optimum balance between life, noise and power output. The amount of skirt ovality might be adjusted and similarly the diameter of the piston ring land region which is circular but needs to have the right cold dimension so it expands to close to bore size when hot.
Just taking a generic forging blank machined to fit a specified bore size in an unknown engine, putting a generic skirt profile on that and then taking your best guess at the bore clearance and ring land diameter required is hardly a guarantee that anything will work very well as you've found. Usually the bore clearance specified is far too high so they don't get comebacks for seizures but the price you pay is godawful piston slap and a short life.
Without some R&D which few people have the resources for it's little more than a lottery to hope it'll all work straight out of the box.
If anyone's interested in another of my long and rambling stories, one of the reasons I know what I'm talking about with pistons is I've actually made them from scratch on my own machinery. It was one of my madder projects about 15 years ago with a mate of mine but we were looking for engine products to make and sell. We'd already done billet cranks in house from EN40B and a set of billet conrods from EN24T. I decided to find out if we could make and sell pistons and I actually chose the 94mm Rover V8 one to start off with.
First step was to make the casting mould from two huge chunks of cast iron. I found a local aluminium casting foundry who could pour the pistons for us. I researched my aluminium grades and settled on LM13, a common high silicon piston alloy used in cast pistons since about the second world war. The first batch we cast had some porosities in them. I hadn't put enough volume in the runners and risers of the mould to feed the castings enough as they cooled. We hacked a bunch more material out of the mould tool and the second batch of pistons came out really nice. I had those sent away for heat treatment to strengthen them and then we got down to machining.
First step was to make a mandrel to hold the rough castings with to turn them down closer to finished size. I did all that on my old Colchester Student lathe before my mate took over with his CNC lathe and turned the ring land area, ring grooves, piston dish and the skirt.
The biggest problem is oval turning the piston skirts which are not round as you might think but elliptical by about 20 thou. No ordinary CNC lathe, or any other lathe, can turn an elliptical shape. In production this used to be done in the old days with hydraulic copy lathes which reproduce the shape on a steel master profile made on a grinding machine onto the actual piston. Nowadays it's done with fancy multi axis CNC machines which can turn any shape you programme into them.
To get round this I designed a godawful complicated linkage with gears and cams which moved the cutting tool on my friend's CNC lathe in and out by 20 thou as the piston rotated. I drew it, he made it but he didn't make it sturdy enough. It worked but shook itself to bits at anything over about 50 rpm.
Next try was to approximate an oval shape with offset turning. If you hold an item in a lathe slightly off centre then the cutting tool will just remove metal from one side to start with. I wrote a computer program to work out the amount of offset required to generate a given amount of material removal from the side of the skirts. We then turned the whole skirt to the finished major diameter we wanted i.e. across the thrust and anti thrust axis and then used offset turning to remove material from the gudgeon pin sides until there was just an inch width of metal left at the original major diameter on each side of the skirt. I know this is hard to explain without drawings.
Anyway all that's now left is the gudgeon pin hole to bore and hone. In production it would be done by fine boring and then roller burnishing to get the last few tenths of a thou out. I had to fall back on reaming. The test engine was going to be the Pinto one in my old Sierra and I bored a block out to 94mm, did a big valve head and cam for it and prepped a crank and rods. The gudgeon pin in a Pinto engine is 24mm so I bought a 24mm reamer and actually drilled and reamed the pistons on my own knackered milling machine. With a bit of care I got the holes a perfect sliding fit on the new pins.
That was it basically. A short while later I had a car running with pistons in it I'd designed, cast and machined myself, or at least with my mate's help. It went like s*it off a shovel until one of the crappy Piper Cams valve springs broke and dropped an inlet valve onto a piston. The piston was so tough it just snapped the head off the valve, rammed it back up the inlet port and the engine carried on running on three. I removed the rockers from that cylinder so the exhaust valve stopped opening too and it actually went very nicely on just three cylinders. I had it up to 125 mph on the M3 with a prospective customer in his Porsche following me back from a race meet one day like that.
He later said the offbeat exhaust note from an engine going like stink on just 3 of its 4 pots was unlike anything he'd ever heard before. A bit V8ish but with a harder edge to it. He was so impressed by how quick one of my engines was on only 3 pots that it was this which decided him to have his own race engine built by me.
I ran it for months like that on just three until one day another of the bloody springs snapped and left me on only two pots. I later found out that Piper weren't having their valve springs heat treated properly and other people were seeing them snap like carrots too. I limped it back home 20 miles and that was the last time it turned a wheel. I bought another car, laid the Sierra up on the drive and it's sat there ever since. I stripped the engine down to see how the pistons had survived and they were ok. Not good with such an imperfect skirt shape and a bit scuffed in places but they didn't break. The ring lands and pin bores were still perfect. If we'd subbed out the skirt turning to a proper piston manufacturer we could have made perfectly decent sellable pistons but the project never went any further. By then several other companies were selling 94mm Rover pistons for not much more than £25 each and it was pointless to try and compete without all the proper tooling.
I've still got a couple of hundred castings, the mould tooling and 500 cylinder sets of rings left over (496 actually because I used the first 4 in my engine) which will never get used but at least it was fun and taught me a lot. I had to learn about piston ovality, taper, barelling, bore clearances, metal expansion ratios, casting processes, piston alloys, ring land sizing and all the relevant machining ops. Primarily though I learnt that some things are just best made by specialists.
However, maybe one day I'll finish machine another set up and stick them in an engine just to prove a point again. It's hard to beat the satisfaction you get from driving something you can tell people I actually made the bits in that. Not just sketched them out and had someone else make them but actually made them with your own two hands.
First step was to make the casting mould from two huge chunks of cast iron. I found a local aluminium casting foundry who could pour the pistons for us. I researched my aluminium grades and settled on LM13, a common high silicon piston alloy used in cast pistons since about the second world war. The first batch we cast had some porosities in them. I hadn't put enough volume in the runners and risers of the mould to feed the castings enough as they cooled. We hacked a bunch more material out of the mould tool and the second batch of pistons came out really nice. I had those sent away for heat treatment to strengthen them and then we got down to machining.
First step was to make a mandrel to hold the rough castings with to turn them down closer to finished size. I did all that on my old Colchester Student lathe before my mate took over with his CNC lathe and turned the ring land area, ring grooves, piston dish and the skirt.
The biggest problem is oval turning the piston skirts which are not round as you might think but elliptical by about 20 thou. No ordinary CNC lathe, or any other lathe, can turn an elliptical shape. In production this used to be done in the old days with hydraulic copy lathes which reproduce the shape on a steel master profile made on a grinding machine onto the actual piston. Nowadays it's done with fancy multi axis CNC machines which can turn any shape you programme into them.
To get round this I designed a godawful complicated linkage with gears and cams which moved the cutting tool on my friend's CNC lathe in and out by 20 thou as the piston rotated. I drew it, he made it but he didn't make it sturdy enough. It worked but shook itself to bits at anything over about 50 rpm.
Next try was to approximate an oval shape with offset turning. If you hold an item in a lathe slightly off centre then the cutting tool will just remove metal from one side to start with. I wrote a computer program to work out the amount of offset required to generate a given amount of material removal from the side of the skirts. We then turned the whole skirt to the finished major diameter we wanted i.e. across the thrust and anti thrust axis and then used offset turning to remove material from the gudgeon pin sides until there was just an inch width of metal left at the original major diameter on each side of the skirt. I know this is hard to explain without drawings.
Anyway all that's now left is the gudgeon pin hole to bore and hone. In production it would be done by fine boring and then roller burnishing to get the last few tenths of a thou out. I had to fall back on reaming. The test engine was going to be the Pinto one in my old Sierra and I bored a block out to 94mm, did a big valve head and cam for it and prepped a crank and rods. The gudgeon pin in a Pinto engine is 24mm so I bought a 24mm reamer and actually drilled and reamed the pistons on my own knackered milling machine. With a bit of care I got the holes a perfect sliding fit on the new pins.
That was it basically. A short while later I had a car running with pistons in it I'd designed, cast and machined myself, or at least with my mate's help. It went like s*it off a shovel until one of the crappy Piper Cams valve springs broke and dropped an inlet valve onto a piston. The piston was so tough it just snapped the head off the valve, rammed it back up the inlet port and the engine carried on running on three. I removed the rockers from that cylinder so the exhaust valve stopped opening too and it actually went very nicely on just three cylinders. I had it up to 125 mph on the M3 with a prospective customer in his Porsche following me back from a race meet one day like that.
He later said the offbeat exhaust note from an engine going like stink on just 3 of its 4 pots was unlike anything he'd ever heard before. A bit V8ish but with a harder edge to it. He was so impressed by how quick one of my engines was on only 3 pots that it was this which decided him to have his own race engine built by me.
I ran it for months like that on just three until one day another of the bloody springs snapped and left me on only two pots. I later found out that Piper weren't having their valve springs heat treated properly and other people were seeing them snap like carrots too. I limped it back home 20 miles and that was the last time it turned a wheel. I bought another car, laid the Sierra up on the drive and it's sat there ever since. I stripped the engine down to see how the pistons had survived and they were ok. Not good with such an imperfect skirt shape and a bit scuffed in places but they didn't break. The ring lands and pin bores were still perfect. If we'd subbed out the skirt turning to a proper piston manufacturer we could have made perfectly decent sellable pistons but the project never went any further. By then several other companies were selling 94mm Rover pistons for not much more than £25 each and it was pointless to try and compete without all the proper tooling.
I've still got a couple of hundred castings, the mould tooling and 500 cylinder sets of rings left over (496 actually because I used the first 4 in my engine) which will never get used but at least it was fun and taught me a lot. I had to learn about piston ovality, taper, barelling, bore clearances, metal expansion ratios, casting processes, piston alloys, ring land sizing and all the relevant machining ops. Primarily though I learnt that some things are just best made by specialists.
However, maybe one day I'll finish machine another set up and stick them in an engine just to prove a point again. It's hard to beat the satisfaction you get from driving something you can tell people I actually made the bits in that. Not just sketched them out and had someone else make them but actually made them with your own two hands.
Edited by Pumaracing on Friday 16th October 07:54
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