Can high comp pistons be skimmed to low comp ?
04-09-2009, 10:20 PM
#121
thanks chip it seems out of al the experts on here you and jimbo are the only ones who even understand what im saying!!!!i shouldnt bother but i cant stand someone telling me i cant do something that me and just about every proper engine builder has done forever...cheers danny
04-09-2009, 10:21 PM
#122
WRONG !! lol 
Mr clever dick
oh and why would you accept that you can give a cr spec on a set of pistons without having the remainder of your engine to measure ?
you can simply have the pistons made to the dimensions you require, as we have had done many times.
and if i then buy a set of pistons they will still have the crown thickness i spec'd not the crown thickness your mahles gave you at factory 8:1 - what you have machined off to change the cr on the cheap.
im sure thats what cosworth do whan building their race engine, just find a close piston then machine it down
just remind me where you work so i dont contact you for anything engine related
With all the respec harvey has im sure if all his customers had unlimited budgets he wouldnt be selling heavily machined pistons like you pal.
Mr clever dick oh and why would you accept that you can give a cr spec on a set of pistons without having the remainder of your engine to measure ?
you can simply have the pistons made to the dimensions you require, as we have had done many times.
and if i then buy a set of pistons they will still have the crown thickness i spec'd not the crown thickness your mahles gave you at factory 8:1 - what you have machined off to change the cr on the cheap.
im sure thats what cosworth do whan building their race engine, just find a close piston then machine it down
just remind me where you work so i dont contact you for anything engine related
With all the respec harvey has im sure if all his customers had unlimited budgets he wouldnt be selling heavily machined pistons like you pal.
.2 is taken with valve poskets, not affecting the crown thickness really,
so all you need is .3 and this over a 80mm piston (leaving 5mm around the outside for example) isnt alot to be fair
what your saying is dead right, a piston made to spec is going to be much closer to right than a non custom one, but still some machining is needed, this is the big argument here i think
04-09-2009, 10:29 PM
#123
what he/i am saying is that machining a piston away from that manufactured spec is not the best or ideal for best purpose. you would use the tool/parts designed for that job.
its a bit like grinding down a full size spanner when you need a stubby one. cool analogy !
04-09-2009, 10:31 PM
#124
if i machined a piston from 8.1 cr down to 7.6 and put valve cut outs into them how much meat do you reckon iv taken off???and if you ordered a set the same spec as my machined ones you reckon youve got more crown depth???as for being wrong with ksa cr,well ididnt state as a fact,i asked a question...as for needing my services,why would you with al your knowledge???how many big power engines have you personaly built???can you buld me one cos al my pistons fall apart in the bores...they are so heavily machined...
and your right, you would never be building me an engine.
04-09-2009, 10:35 PM
#125
i dont think thats what he is saying at all, of course the pistons are machine finished, but they are made for that machine finish from a blank/billet/die/pressure cast method.
what he/i am saying is that machining a piston away from that manufactured spec is not the best or ideal for best purpose. you would use the tool/parts designed for that job.
its a bit like grinding down a full size spanner when you need a stubby one. cool analogy !
what he/i am saying is that machining a piston away from that manufactured spec is not the best or ideal for best purpose. you would use the tool/parts designed for that job.
its a bit like grinding down a full size spanner when you need a stubby one. cool analogy !
04-09-2009, 10:35 PM
#126
mahles, 8-1 and a normal spec is around 7.5 for example
.2 is taken with valve poskets, not affecting the crown thickness really,
so all you need is .3 and this over a 80mm piston (leaving 5mm around the outside for example) isnt alot to be fair
what your saying is dead right, a piston made to spec is going to be much closer to right than a non custom one, but still some machining is needed, this is the big argument here i think
.2 is taken with valve poskets, not affecting the crown thickness really,
so all you need is .3 and this over a 80mm piston (leaving 5mm around the outside for example) isnt alot to be fair
what your saying is dead right, a piston made to spec is going to be much closer to right than a non custom one, but still some machining is needed, this is the big argument here i think
do you think when mahle where given the dimensions for the oe yb pistons they were told, also make them thick enough in the crown, deep enough from the 1st ring land so that people can machine the shit out of them to reduce the compression, or so that the can be pocket by 10mm ?
that answer is no - i can already tell you that.
04-09-2009, 10:38 PM
#127
i dont think thats what he is saying at all, of course the pistons are machine finished, but they are made for that machine finish from a blank/billet/die/pressure cast method.
what he/i am saying is that machining a piston away from that manufactured spec is not the best or ideal for best purpose. you would use the tool/parts designed for that job.
its a bit like grinding down a full size spanner when you need a stubby one. cool analogy !
what he/i am saying is that machining a piston away from that manufactured spec is not the best or ideal for best purpose. you would use the tool/parts designed for that job.
its a bit like grinding down a full size spanner when you need a stubby one. cool analogy !
No manufacturer specs the final volume for my pistons, I do, what I do is get them made to a ballpark that is slightly higher CR than I want, then that way I can dry build it, measure the CR, then adjust the pistons accordingly.
And I do so by giving them to a machinist who will do them exactly as they need to be done, just like JE or whoever would.
Its only a bodge like you are implying if you turn round and machine them with an angle gridner or something, lol
04-09-2009, 10:38 PM
#128
wrong nob head..how can you have what crown depth you want??not unless your going to have them protrude out the block??then youd have to have them machined!!!or would you just get shorter rods to save machining????
04-09-2009, 10:39 PM
#129
but maybe what you are missing perhaps is when they produced these pistons they also told you the block deck height, rod length, crank stroke, and head thickness. and they were all (wait for it............................) to their oe std dimensions for a virgin engine, not one of your re-machined/re-worked 6000hp race engines
04-09-2009, 10:44 PM
#130
i know fill well that cosworth did specifically make low comp pistons, i was buying them from them in 1994, so well done- your right,
but maybe what you are missing perhaps is when they produced these pistons they also told you the block deck height, rod length, crank stroke, and head thickness. and they were all (wait for it............................) to their oe std dimensions for a virgin engine, not one of your re-machined/re-worked 6000hp race engines
but maybe what you are missing perhaps is when they produced these pistons they also told you the block deck height, rod length, crank stroke, and head thickness. and they were all (wait for it............................) to their oe std dimensions for a virgin engine, not one of your re-machined/re-worked 6000hp race engines
04-09-2009, 10:44 PM
#131
i know fill well that cosworth did specifically make low comp pistons, i was buying them from them in 1994, so well done- your right,
but maybe what you are missing perhaps is when they produced these pistons they also told you the block deck height, rod length, crank stroke, and head thickness. and they were all (wait for it............................) to their oe std dimensions for a virgin engine, not one of your re-machined/re-worked 6000hp race engines
but maybe what you are missing perhaps is when they produced these pistons they also told you the block deck height, rod length, crank stroke, and head thickness. and they were all (wait for it............................) to their oe std dimensions for a virgin engine, not one of your re-machined/re-worked 6000hp race engines
Any of us rebuilding an engine, need to make adjustments, and machining the pistons is the most "correct" way of doing so.
04-09-2009, 10:46 PM
#132
No manufacturer specs the final volume for my pistons, I do, what I do is get them made to a ballpark that is slightly higher CR than I want, then that way I can dry build it, measure the CR, then adjust the pistons accordingly.
And I do so by giving them to a machinist who will do them exactly as they need to be done, just like JE or whoever would.
Its only a bodge like you are implying if you turn round and machine them with an angle gridner or something, lol
And I do so by giving them to a machinist who will do them exactly as they need to be done, just like JE or whoever would.
Its only a bodge like you are implying if you turn round and machine them with an angle gridner or something, lol
"wrong nob head"
im going to remove you from my viewable posts now as i cant be arsed with talking to people like you who onbviously dont know what your doing.
good luck.
oh and btw read my last post with my quote of "i spec the engine correctly" so yes i can have 6mm crown or a 10mm crown or even a 20mm crown if i really wanted to, as i would spec to what i need, unlike you who would machine the std parts.
04-09-2009, 10:56 PM
#136
wel thats what i just said (apart from i have mine made final before i recieve them)
i see your aptitude for a technical conversation coming through again
"wrong nob head"
im going to remove you from my viewable posts now as i cant be arsed with talking to people like you who onbviously dont know what your doing.
good luck.
oh and btw read my last post with my quote of "i spec the engine correctly" so yes i can have 6mm crown or a 10mm crown or even a 20mm crown if i really wanted to, as i would spec to what i need, unlike you who would machine the std parts.
i see your aptitude for a technical conversation coming through again
"wrong nob head"
im going to remove you from my viewable posts now as i cant be arsed with talking to people like you who onbviously dont know what your doing.
good luck.
oh and btw read my last post with my quote of "i spec the engine correctly" so yes i can have 6mm crown or a 10mm crown or even a 20mm crown if i really wanted to, as i would spec to what i need, unlike you who would machine the std parts.
05-09-2009, 04:30 PM
#143
05-09-2009, 04:34 PM
#144
PassionFord Post Whore!!
what a poor attitude to have for a so called propper engine builder you just seem a bit mardy to me
05-09-2009, 05:04 PM
#145
im not going to be called names mate and be told i cant do something that iv been doing for years by someone...your right though i shouldnt lower myself but hey its only a name and a bit of frustration..if you look at my other threads your see i speak to everyone with the respect im spoken to...if someone wants me to build them an engine then they will get a good engine at a good price and id always bend over backwards..if they dont want me to then fine im not trying to poach work and if because iv stuck up for something i know about and got a bit heated with someone on the net and thats enough for you not to come and see me then id say fine your loss mate...i have alot of respect for alot of the engine builders on here but i can assure you i can do the same job in most cases for alot less money...cheers danny
05-09-2009, 07:50 PM
#146
PassionFord Post Whore!!
im not going to be called names mate and be told i cant do something that iv been doing for years by someone...your right though i shouldnt lower myself but hey its only a name and a bit of frustration..if you look at my other threads your see i speak to everyone with the respect im spoken to...if someone wants me to build them an engine then they will get a good engine at a good price and id always bend over backwards..if they dont want me to then fine im not trying to poach work and if because iv stuck up for something i know about and got a bit heated with someone on the net and thats enough for you not to come and see me then id say fine your loss mate...i have alot of respect for alot of the engine builders on here but i can assure you i can do the same job in most cases for alot less money...cheers danny
05-09-2009, 09:11 PM
#147
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I think people are taking things to extremes here, 99% of low comp or rebuilt yb's have got standard mahle pistons in with the valve cut outs and bowl machined to give you the desired cr. For most general applications this is fine, as it is well within the tolerences of a STD piston, and has been proven as such for decades! However, in the ideal world, if you are building a mega engine, you would spec a custom piston that would need zero or absolutly minimal modification away from the or dimensions to give you the desired cr/squish/valve cut outs/ bore clearance etc etc....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
05-09-2009, 09:31 PM
#148
I think people are taking things to extremes here, 99% of low comp or rebuilt yb's have got standard mahle pistons in with the valve cut outs and bowl machined to give you the desired cr. For most general applications this is fine, as it is well within the tolerences of a STD piston, and has been proven as such for decades! However, in the ideal world, if you are building a mega engine, you would spec a custom piston that would need zero or absolutly minimal modification away from the or dimensions to give you the desired cr/squish/valve cut outs/ bore clearance etc etc....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
06-09-2009, 11:41 AM
#153
Looks to be a lot of good info in this thread even if it did go off track a little.
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
06-09-2009, 01:29 PM
#154
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Looks to be a lot of good info in this thread even if it did go off track a little.
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
06-09-2009, 02:03 PM
#155
Looks to be a lot of good info in this thread even if it did go off track a little.
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
What would you do then if for some reason you had split the motor and had to skim the head or deck the block, would you just throw your custom spec pistons out and order a new spec or machine them to bring the comp ratio back in line ?
06-09-2009, 04:09 PM
#160
Testing the future
I think people are taking things to extremes here, 99% of low comp or rebuilt yb's have got standard mahle pistons in with the valve cut outs and bowl machined to give you the desired cr. For most general applications this is fine, as it is well within the tolerences of a STD piston, and has been proven as such for decades! However, in the ideal world, if you are building a mega engine, you would spec a custom piston that would need zero or absolutly minimal modification away from the or dimensions to give you the desired cr/squish/valve cut outs/ bore clearance etc etc....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
However, in the real world for 99% of people building a yb to a reasonable level of tune, a set of mildly machined mahles will do the job for realistic money....
