which piston has smallest dish volume, STi V4 or V5 ??
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Ian,
Why don't you just ask the big question, instead of feeding little bits of info?
If you are looking at getting a sti5 engine, or whatever, just say so, it makes it a lot easier for people to give the info you need.
Sti 5 is phase 2, steer clear.
sti3/4 phase 1, with "forged" pistons, pistons should match sti 1,2,3 & 4 heads, and wrx heads.
Paul
Why don't you just ask the big question, instead of feeding little bits of info?
If you are looking at getting a sti5 engine, or whatever, just say so, it makes it a lot easier for people to give the info you need.
Sti 5 is phase 2, steer clear.
sti3/4 phase 1, with "forged" pistons, pistons should match sti 1,2,3 & 4 heads, and wrx heads.
Paul
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Paul,
the question i asked above is all i need to know. i do not plan on getting a different engine, i am keeping mine, including the heads.
however, i am fitting the cosworth pistons and they dont make one for the legacy, so need to know which spec (V4 or V5) will keep the compression as near as poss to standard without lowering it too much.
ian
the question i asked above is all i need to know. i do not plan on getting a different engine, i am keeping mine, including the heads.
however, i am fitting the cosworth pistons and they dont make one for the legacy, so need to know which spec (V4 or V5) will keep the compression as near as poss to standard without lowering it too much.
ian
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one further point, pistons V1 to V4 are same cosworth part number, V5 is different.
however, due to the fact that any of the above pistons have a larger volume dish than the legacy ones, either will fit, just a case of which.
however, due to the fact that any of the above pistons have a larger volume dish than the legacy ones, either will fit, just a case of which.
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if you fit them, you will be left with too low a C/R.
So you either need to get some with less dish to match you heads, or get some impreza heads (about £240+vat a pair).
You could measure your current pistons, and get cosworth ones machine to same.
If you are boring the block +0.25mm, this will raise the C/R a little. If you are not boring the block, just cleaning the current one, I would be tempted to S/H pistons and get the heads, but that's just the skinflint in me talking.
Paul
So you either need to get some with less dish to match you heads, or get some impreza heads (about £240+vat a pair).
You could measure your current pistons, and get cosworth ones machine to same.
If you are boring the block +0.25mm, this will raise the C/R a little. If you are not boring the block, just cleaning the current one, I would be tempted to S/H pistons and get the heads, but that's just the skinflint in me talking.
Paul
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measure the dish volume.
Put piston/rings in block, preferably on rod.
Put at tdc.
Use perspex plate with hole in, seal onto block with grease, use paraffin in burette (or narrow syringe if you haven't a burette) to measure volume.
best thing I can suggest at the moment really.
I was just talking to someone that said head volume was same on legacy, but Stevie's info contradicts this, who knows.
Paul
Put piston/rings in block, preferably on rod.
Put at tdc.
Use perspex plate with hole in, seal onto block with grease, use paraffin in burette (or narrow syringe if you haven't a burette) to measure volume.
best thing I can suggest at the moment really.
I was just talking to someone that said head volume was same on legacy, but Stevie's info contradicts this, who knows.
Paul
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another legacy owner on here tried to fit impreza heads, only to find they wouldnt work properly due to the legacy pistons.
used to use that measuring method on my mantas when building different engines.
used to use that measuring method on my mantas when building different engines.
I did not say that it wouldnt work. On a standard engine, with std boost, it would probably be fine. Mine was only det above 6500rpm, at 14+psi boost.
There is no impreza piston that will go with a legacy head and still maintain the same CR, unless perhaps a N/A piston may suit. There is nothing wrong ( IMHO )with using second hand pistons. Whats wrong with a set that has perhaps 70,000K out of a big end failure engine. If the big ends had not failed, would those same pistons still be condemned for replacement at that milage. Im sure the pistons you removed form your engine, that have not melted, or received damage from the heat because of the excess boost/weak mixture, are in excellent condition, as are the bores.
Yes it may be cheapskate to some, but you do seem to have a grip on whats involved inside an engine, so would be able to make a fair judgement on the condition of a piston before fitting.
I am using, and 2 other friends are using sec hand sti4 pistons in their legacy's here, with no probs whatsoever ( with impreza heads of course) .
Head volume on a UK legacy will not be the same as an impreza. The dish on the legacy piston mostly consists of valve cutouts, and little actual dish. They use the same HG as impreza's, and run the same CR. The head volume has to be larger.
I would also confirm with GGR that the cosworth pistons will fit a std block. When a friend bought them a while ago, they only did oversize sizes, partially because of the A/B piston thing. So if you do intend on buying a set, then you may need a re-bore too.
Unless building a ***** out engine, the cossy pistons would be out of my league. If I was spending the money on them, Id get rods etc too. Otherwise, there are loads of sti pistons about. If it was me, i'd just get them, and a matching set of impreza heads.
Funny....thats whats in my engine..lol
If you really want it fixed on the cheap, I do have my old legacy pistons, all of which are mint.
[Edited by ustolemyname??stevieturbo - 7/30/2002 5:53:25 PM]
There is no impreza piston that will go with a legacy head and still maintain the same CR, unless perhaps a N/A piston may suit. There is nothing wrong ( IMHO )with using second hand pistons. Whats wrong with a set that has perhaps 70,000K out of a big end failure engine. If the big ends had not failed, would those same pistons still be condemned for replacement at that milage. Im sure the pistons you removed form your engine, that have not melted, or received damage from the heat because of the excess boost/weak mixture, are in excellent condition, as are the bores.
Yes it may be cheapskate to some, but you do seem to have a grip on whats involved inside an engine, so would be able to make a fair judgement on the condition of a piston before fitting.
I am using, and 2 other friends are using sec hand sti4 pistons in their legacy's here, with no probs whatsoever ( with impreza heads of course) .
Head volume on a UK legacy will not be the same as an impreza. The dish on the legacy piston mostly consists of valve cutouts, and little actual dish. They use the same HG as impreza's, and run the same CR. The head volume has to be larger.
I would also confirm with GGR that the cosworth pistons will fit a std block. When a friend bought them a while ago, they only did oversize sizes, partially because of the A/B piston thing. So if you do intend on buying a set, then you may need a re-bore too.
Unless building a ***** out engine, the cossy pistons would be out of my league. If I was spending the money on them, Id get rods etc too. Otherwise, there are loads of sti pistons about. If it was me, i'd just get them, and a matching set of impreza heads.
Funny....thats whats in my engine..lol
If you really want it fixed on the cheap, I do have my old legacy pistons, all of which are mint.
[Edited by ustolemyname??stevieturbo - 7/30/2002 5:53:25 PM]
