theohighland
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| posted on 29/8/06 at 07:54 PM |
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new pistons?
im looking to buy some new pistons, how do i know if i need std. bore, 0.5mm, 1.0mm?
any help would be greatly appreciated
cheers, Theo
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DIY Si
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| posted on 29/8/06 at 08:01 PM |
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The current pistons should say on the crown what they are. If you need them due to a rebuild, it depends how big you want them.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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theohighland
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| posted on 29/8/06 at 09:22 PM |
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thanks, so does that mean i could have any of the three if i wanted?
cheers, theo
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omega 24 v6
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| posted on 29/8/06 at 09:34 PM |
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NO if it's already bored +.5 then you can only rebore it to the next largest size (if the bore cleans up at that) i.e. +1mm. Are you
rebuilding the engine yourself?????????
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theohighland
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| posted on 29/8/06 at 10:09 PM |
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well i was looking to renovate slightly and was looking on the rally design website and saw a selection of pistons and was considering replacing them
myself.
Is this a bad idea?
So what your saying is you can keep going up if you want to (obviously you cant go back down)
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Chippy
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| posted on 29/8/06 at 10:22 PM |
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You can only fit pistons that the engine has been bored out to accept. Why do you want to replace them, does the engine burn oil, or just a whim. If
its not using oil, then just de-coke, new rings, and refit. Spend the money on go faster bits.  ATB Ray.
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theohighland
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| posted on 29/8/06 at 10:44 PM |
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well i was looking to recon it but i am using a dohc so cant really tune it all that much, so thought i'd do my best to get it run at its best
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rusty nuts
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| posted on 30/8/06 at 05:44 AM |
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Check out the price of parts before you strip the engine. You may decide it's not going to be "locost"
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mcerd1
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| posted on 30/8/06 at 08:33 AM |
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If you do decide to strip the bottom end you'll need to:
- measure the bores and check for wear and roundness (they can become oval with time) - you'll need at least an internal micrometer to do this
- if the sizes are within the tolerances (you'll find these in the Haynes book) you can just get new pistons of the correct size (i.e. to match
the bore size)
you might find that the old pistons are fine too - in which case you'll only need rings
-important- If you don't get it re-bored you'll need to borrow a ridge reamer and remove any small lip around the top of the bores before
fitting the new pistons
-if they are worn or oval you'll need a re-bore, a decent engine builder will charge about £50 for this and tell you what pistons you need (a
reputable builder would also measure the bores and tell you what needed done - if anything)
btw - the same logic applies to the crank (which may need re-ground another £50) as you'll need new bearing for it as a minimum
also you'll need a complete set of gaskets and seals
-Robert
[Edited on 30/8/06 by mcerd1]
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James
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| posted on 30/8/06 at 11:16 AM |
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quote:
Originally posted by rusty nuts
Check out the price of parts before you strip the engine. You may decide it's not going to be "locost"
I'd agree.
I would have thought that for the cost of rebuilding the DOHC (assuming you mean the Sierra one) then you could get a Zetec in there.
More power and lighter too.
HTH,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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Chippy
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| posted on 30/8/06 at 09:17 PM |
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To give you an idea of DOHC parts prices, I fitted a new set of drybollick followers to my Misses's Granny, (four years ago), £12.50 + VAT EACH,
and there are eight of the little b*****d's. Not a cheap motor to overhaul.  Ray
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MikeRJ
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| posted on 30/8/06 at 10:14 PM |
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quote:
Originally posted by Chippy
To give you an idea of DOHC parts prices, I fitted a new set of drybollick followers to my Misses's Granny, (four years ago), £12.50 + VAT EACH,
and there are eight of the little b*****d's. Not a cheap motor to overhaul. Ray
That's pretty much the same price as Vauxhall wanted for 20XE followers when I had my 16vGTE years ago, and there are 16 of them!
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02GF74
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| posted on 30/8/06 at 10:35 PM |
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quote:
Originally posted by theohighland
well i was looking to renovate slightly and was looking on the rally design website and saw a selection of pistons and was considering replacing them
myself.
Is this a bad idea?
So what your saying is you can keep going up if you want to (obviously you cant go back down)
first question is do you need new pistons? measure bore as said - you can use a piston ring in the bore and use feeler guageto measurethe gap - psu
it down the bore with the puston to keep it square and meaure again - if much difference, bore is out of round.
obviously you only measure the bore where the rings contact - that'll be nice and shiny & worn.
seom, if not all ngines can be reclaimed by drilling out and the fitting liners so you can put in smaller pistons - but unless very rare or had
liners to sart with, would be very ££££
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Findlay234
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| posted on 30/8/06 at 11:08 PM |
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Have you seen "The Worlds Fastest Indian" (brilliant film btw)
Cast your own..... LOL
http://artfulbodger.2ya.com/
http://www.backyardmetalcasting.com/
Guess munro did go through a few before he got the technique right
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