Can high comp pistons be skimmed to low comp ?
03-09-2009 | 09:43 PM
#82
amount if shite thats posted on here these days ! pmsl ! 
you order a set of custom pistons, go for it, put them straight in your engine, and watch them hit the head, every time, piston manafacturers will normally make the pistons slightly bigger, you can machine them down, cant put more back on them
every tuner on the forum and in the world most likely machine pistons day in day out,
we order custom sets, but do you take the chance that the company are going to be right ? on a 25k 800odd bhp build ? nope didnt think so,
dont know if you know, but when building engines you leave certain abouts of piston out of the block, 6, 8 , 10 thou for example, the custom pistons arnt going to be within thousands of an inch.
also what if the block is faced and slightly more was taken off the further towards you get to the back of the block,
each piston is going to need a different amount taking off the top to be the same as the others,
but then, when your taking material off the top, your loosing area in that bowl, therefore raising the compression ratio, so now you have to take some material out of the bowl area to compensate for that,
custom pistons, WONT go straight in
jim
i did think it was you mate lol, you always end with cheers danny !
you order a set of custom pistons, go for it, put them straight in your engine, and watch them hit the head, every time, piston manafacturers will normally make the pistons slightly bigger, you can machine them down, cant put more back on them
every tuner on the forum and in the world most likely machine pistons day in day out,
we order custom sets, but do you take the chance that the company are going to be right ? on a 25k 800odd bhp build ? nope didnt think so,
dont know if you know, but when building engines you leave certain abouts of piston out of the block, 6, 8 , 10 thou for example, the custom pistons arnt going to be within thousands of an inch.
also what if the block is faced and slightly more was taken off the further towards you get to the back of the block,
each piston is going to need a different amount taking off the top to be the same as the others,
but then, when your taking material off the top, your loosing area in that bowl, therefore raising the compression ratio, so now you have to take some material out of the bowl area to compensate for that,
custom pistons, WONT go straight in
jim
i did think it was you mate lol, you always end with cheers danny !
03-09-2009 | 09:58 PM
#84
machining pistons is always a cheaper alternative, not always the best alternative, if you are so much the pro b19, then you would recommend the correct custom piston to suit the spec that would not need machining if you have given the correct spec, but then again, you would just get harvey to build it for you from what i can gather on here.
03-09-2009 | 10:06 PM
#85
read my posts and jimbos post you knob..as said fucking loads most engines have got machined pistons..mind you you know more than me and more than jimbo and his dad and every other top tuner!!!id go to jimbo and his dad any day for advice on something i wasnt sure about and im defo going to ask them to dyno my new engine but as for building me an engine,i dont think so..iv built shit loads mayb not 700+bhp but lots of 500+and a couple of600+ engines so im ok there cheers...
ok what ever - cock.
03-09-2009 | 10:37 PM
#87
one thing, im not a trader on this site, the other i dont build engines for the general public directly.
take that as you will.
and my apologies to the OP for being part of the post diversion
03-09-2009 | 10:43 PM
#88
Im loving this how you seam to think this is something i coudnt do - yet know nothing about me
one thing, im not a trader on this site, the other i dont build engines for the general public directly.
take that as you will.
and my apologies to the OP for being part of the post diversion
one thing, im not a trader on this site, the other i dont build engines for the general public directly.
take that as you will.
and my apologies to the OP for being part of the post diversion
03-09-2009 | 10:48 PM
#90
if you know so much about building a cossie engine answer my simple question,your replies on this thread alone have already told me you know very little as your saying you shouldnt machine a piston!!!!try building 10 engines to different crs then tell me you didnt have to machine any pistons...twat!!!
listen pal, your not doing your professionalism any good here now are ?
I have no reason to even want to talk engines with you what-so ever, even less with someone who has the aptitude you display. you carry on pal.
03-09-2009 | 10:53 PM
#91
yeah your right...its just so annoying being told something you know is bollox cos youve done it day in day out for years...i think if he answered my question he would end up contredicting himself..oh well iv had enough now..
03-09-2009 | 11:13 PM
#95
Setting an exact CR on an engine almost always involves machining the pistons IME.
Other options are:
Run the pistons up or down the bore a bit (effects squish)
Change the thickness of the head gasket (effects squish)
Machine the head (not really much of an option on a pentroof design like a YB)
Other options are:
Run the pistons up or down the bore a bit (effects squish)
Change the thickness of the head gasket (effects squish)
Machine the head (not really much of an option on a pentroof design like a YB)
03-09-2009 | 11:17 PM
#96
Setting an exact CR on an engine almost always involves machining the pistons IME.
Other options are:
Run the pistons up or down the bore a bit (effects squish)
Change the thickness of the head gasket (effects squish)
Machine the head (not really much of an option on a pentroof design like a YB)
Other options are:
Run the pistons up or down the bore a bit (effects squish)
Change the thickness of the head gasket (effects squish)
Machine the head (not really much of an option on a pentroof design like a YB)
03-09-2009 | 11:18 PM
#97
How is them machining it ok, but J1mbo doing so not ok?
04-09-2009 | 12:21 AM
#99
It means that instead of having the pistons at the optimum point (normally considered to be about 5thou proud of the block face but different applications will vary) you either let them further into the gasket, or stop them shy of the top of the block to alter the amount of unstroked volume above them.
04-09-2009 | 06:24 PM
#101
It Wasnt Me!
Joined: May 2003
Posts: 22,752
Likes: 8
From: Scottyland
Err, no they actually make you a 'custom' set of pistons from alloy blocks, to the specification you give them, that's why it takes 6 weeks (or longer) from phonecall to delivery.
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
04-09-2009 | 07:36 PM
#102
Err, no they actually make you a 'custom' set of pistons from alloy blocks, to the specification you give them, that's why it takes 6 weeks (or longer) from phonecall to delivery.
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
04-09-2009 | 07:40 PM
#103
Err, no they actually make you a 'custom' set of pistons from alloy blocks, to the specification you give them, that's why it takes 6 weeks (or longer) from phonecall to delivery.
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
04-09-2009 | 07:57 PM
#105
I've found that life I needed.. It's HERE!!
iTrader: (20)
Joined: Dec 2004
Posts: 1,454
Likes: 1
From: West Sussex
It means that instead of having the pistons at the optimum point (normally considered to be about 5thou proud of the block face but different applications will vary) you either let them further into the gasket, or stop them shy of the top of the block to alter the amount of unstroked volume above them.
So is that done by machining the block face?...
04-09-2009 | 08:00 PM
#106
so you cant answer the quetion???if you cant answer the question how the fuck are you going to order these special custom pistons you nob!!!how many big ybs you built???oh yeah obviously none!!!
04-09-2009 | 08:28 PM
#107
It Wasnt Me!
Joined: May 2003
Posts: 22,752
Likes: 8
From: Scottyland
Yea, easiest answer is, give JE the dimensions/stroke blah blah blah, tell them what CR you want, and let them make the pistons...seeing as it's their job, or is that too easy?
Anyway, think we've fucked up this guy's thread enough...you not got a YB to build or something?
Anyway, think we've fucked up this guy's thread enough...you not got a YB to build or something?
Last edited by vroooom ptssssh; 04-09-2009 at 08:29 PM.
04-09-2009 | 08:50 PM
#108
Yea, easiest answer is, give JE the dimensions/stroke blah blah blah, tell them what CR you want, and let them make the pistons...seeing as it's their job, or is that too easy?
Anyway, think we've fucked up this guy's thread enough...you not got a YB to build or something?
Anyway, think we've fucked up this guy's thread enough...you not got a YB to build or something?
04-09-2009 | 09:22 PM
#112
any chance you could put any pics up of pistons in bores???have you measured the head yet??do the pistons come to the top of the bores???tell me to get lost if you want but for some reason i just would love to see know how the cr was achieved as i bet its as iv already stated earlier in the thread..mind you iv seen a few different ways..cheers danny
04-09-2009 | 10:15 PM
#116
Err, no they actually make you a 'custom' set of pistons from alloy blocks, to the specification you give them, that's why it takes 6 weeks (or longer) from phonecall to delivery.
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
see my post before, you may learn something, but, i guess im baffling you with bollocks right...
04-09-2009 | 10:38 PM
#117
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.
04-09-2009 | 11:13 PM
#118
Err, no they actually make you a 'custom' set of pistons from alloy blocks, to the specification you give them, that's why it takes 6 weeks (or longer) from phonecall to delivery.
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
seriously cant see them finding a piston that's a close match off the shelf, to machine it down to what you want...
Take it you's have never actually bought a custom set of pistons? jus done it the cheap way and machined them all down? lol Dont see why you'd STILL need to machine pistons after buying 4 identical
Try it.......
http://www.jepistons.com/pdf/customp...-orderform.pdf
Over, and out...
04-09-2009 | 11:14 PM
#119
then when the pistons turn up they protrude 25 thou because the blocks been decked and you didnt know this...then you realise the heads been skimmed a bit more than the customer stated..then the customer changes thier mind on the cams so you need deeper vavle cut outs!!!thats why we often buy a piston to the closest spec because every engine is different and untill you dummy build and measure it al you dont know what pistons to buy...its ok buying a custom spec piston when your using a new block and a very good head casting but even then sometimes you might need to machine the pistons...anyway youl never get it so im not posting on this anymore..we havnt ruined anyones thread as hes just getting someone who knows what they are doing to build it>>>hence having the pistons machined to suit no doubt???
Exactly, until you have done a dry build you cannot possibly know the exact spec of the pistons that you require.
04-09-2009 | 11:16 PM
#120
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.