Ian
11 posts
Joined: 05/12/2005 19:53:39
Location: United Kingdom (Excluding channel Islands)
Pistons for a 998
I am building a 998 engine for my first mini, i am just wondering if anyone knows how good the flat top mega performance pistons are, or if there is annother set of pistons(around the same price) that anyone can recomend, so far these seem to be the best but if anyone knows any other it would be excellent Ian
Posted: Dec 05, 2005 08:02 PM
j. monk
28 posts
Joined: 19/09/2005 20:07:38
Location: rochester United Kingdom (Excluding channel Islands)
998 turbo and piston q
are minispares pistons the +20 silicon ones supplied with piston rings
hav been told a t3 turbo is too much for a 998 is this true. what else do i need other than the turbo to do a turbo conversion
was also thinkin of the minispares turbo cam
ill be usin a 12g940 head
it will be a daily runner and money isnt exactly flowing what do you guys recommend.
thanks
Posted: Apr 24, 2007 02:16 PM
John
1948 posts
Joined: 28/05/2006 16:49:46
Location: cambridge United Kingdom (Excluding channel Islands)
998 engine in standard form has a few weak points for turbo charging ect. when i say weak point it doesnt mean they have to be replaced but they would be quite likly to fail.
con rods of standard 998 have a bolted small end these are a weak point and even sometimes break in standard engines (look on wanted section on here) the best repacements are those used on 1100 and 998 cooper these are alot strounger.
pistons may be ok but strounger ones are a safer bet will need to be dished. the compression ratio will need to be cept low around 9:1 at the highest or u may have a problem with knocking.
centre main bearing will need a cap on it to strengthen it.
a performance 2 core rad is a good idea if u dont want it to boil every 5min.
with a 998 u will not want to put too stroung a cam on it, something under 270 duration should be ok, some cams timmings are setup specially for turbo aplications
in the head ul need a cold running plugs eg ngk bp8es
the valve quide tolerances on the exhaust will need to be quite large as it will get very hot. ul also need to make sure it doesnt have a cap around the guide to reduce oil flow down it as some people put on. on a turbo the oil will be need to conduct the heat from the valve.
for a turbo its either ebay or serch for an old metro turbo. if u get one stick to metro turbo engine as its a very stroung 1275 engine with many uprated parts.
if money isnt flowing ud be better to get a 1275 a a starting base as it will produce more power with fewer mods, its quite easy to get a non blown 1275 to 90+bhp for around £1000 if u buy all parts new
Posted: Apr 24, 2007 04:00 PM
Luke6040
210 posts
Joined: 17/11/2005 17:00:38
Location: Wolverhampton United Kingdom (Excluding channel Islands)
998 Pistons.
Hey,
I'm rebuilding a 998cc 1986 A+ engine, and some noob has tried to turn the Engine over by putting a screwdriver on the piston and hitting it (stress), and its left some nasty scrapes.
Do you think i could get away with just smoothing the surfaces off? If not what pistons would of been fitted as standard? Thanks for all your time Luke
Posted: May 02, 2007 09:33 PM
there are two types depending if ur engine was high or low compression. most were high compression so will have flat topped pistons. low compression ratio had dished pistons. whichever it was u want flat topped for economy and power if not compression ratio will be too low. if its a standard engine standard pistons will be fine even in quite heavily tuned engines they shud be ok. minispares do also sell better quality ones that are gd if ur planning on doing many mods. if ur planning on changing pistons prob best to go up a bore size either +10 or +20 so it will last longer. cheak its not been rebored already. if ur looking for cheap solution second hand set off ebay shud be fine as new sets arnt cheap.
Posted: May 02, 2007 09:50 PM
Tim
1849 posts
Joined: 18/10/2004 09:40:59
Location: Bournemouth United Kingdom (Excluding channel Islands)
It may look like someone's hit the top of the piston with a screwdriver, but this is often the result of something getting sucked into the engine whilst running without an air filter. I've got two pistons like that in my engine - happily the marks aren't too deep and the engine runs fine.
Posted: May 03, 2007 06:48 AM
yeah if it doesnt look too serious, then shud be fine, cud even be spark plug if head has been skimmed. if it is covered in dents over 1mm deep i wouldnt risk it as it may crack in extream cases.
Posted: May 03, 2007 12:45 PM
Well the mark is in every piston and lines up nicely with a screw driver. Ill try and get away with it then. Fingers crossed there ok lol
Thanks for your time, Luke
Posted: May 03, 2007 01:46 PM
prob best on ur wallet, for cost of rebore new pistons ect u cud pick up second hand 998 engines. so if piston did break just get anouther.
Posted: May 03, 2007 01:58 PM
lol this is second hand engine ..... erm .. i think i got done
Posted: May 05, 2007 12:44 AM
i know it is, just ment it be cheaper to find anouther rather than buy new pistons rebore ect.
Posted: May 05, 2007 02:11 PM
ooo sorry, true but i might try and get some second hand pistons first, iv got the kit to put em on con rods and stuff so not to bad.. and i was thinking about re-bore anyway because it been standing without spark plugs in anyway....well we shall see.
Posted: May 05, 2007 06:42 PM
one word of warning which hopefully somone can confirm. post around 85 i think it was they changed the small ends on the con rods on 998's to the non clamp type like those fitted to the old 1100's and 998 cooper. im not sure if u got a type of piston designed for the clamp small ends if it will fit or need modification. id of thought it would be ok but just hopefully somone can confirm this.
Posted: May 05, 2007 09:04 PM
ooo oki i think i know what u mean i should be pullin em out 2moz so will a picture make it any clearer?
Posted: May 08, 2007 08:17 PM
998 Pistons!!!
Help, I really need some 998cc pistons There for a 1986-1989(i think) engine so i think its the puch fit pins,
Oversized would be great but i just need anthing at the moment lol Thanks for your time Luke
Posted: May 19, 2007 03:01 PM
could try them for second hand ones might get a cheap set.
http://www.mini-metro.co.uk/componants.html
Posted: May 19, 2007 03:07 PM
998 pistons NEEDED
Hey
I really need a set of 998 pistons for my project. +20 +40 etc would be great id like flat top and cir-clip type unless they're with con rods.
Any help would be great Thanks for your time Luke Lumley
Posted: Dec 04, 2007 06:34 PM
Roobz
223 posts
Joined: 15/12/2005 01:31:36
Location: Redbridge United Kingdom (Excluding channel Islands)
http://www.minispares.com/Product.aspx?pid=37863
http://www.minispares.com/Product.aspx?pid=38643
Posted: Dec 05, 2007 09:14 PM
wrinkly
59 posts
Joined: 10/09/2004 08:51:29
Location: POTTERS BAR United Kingdom (Excluding channel Islands)
pistons
the 80 thou oversize 998 pistons are flat top only
Posted: Aug 05, 2005 03:51 PM
850cc Exhaust systems?
best on a 850 to use a small bore lcb or 'cooper manifold made by maniflow' both are wel suited to tuned 850's (£70 approx). then attach a rc40 kit £50 which will sort the exhaust out its cheap and has good note and gives gd power. all alloy intakes fit all standard mini heads but u want one to suit the carb. u will most likly have a hs2 this is best replaced with a hs4 or hif38. hs2 is small even for an 850. then u will need a alloy intake manifold with 1.1/2" bore. they normally can be fitted to a manifold bore a 1/4" larger but on a 850 fitting it to a 1.3/4" manifold is a bad idea 1.1/2" is what want. these arnt easily avalible new so ebay has them cheap. most now made are 1.3/4" bore as this is just about ok on a 998 and gd on a 1275. as for con rods u need 1100 ones or 998 cooper ones these dont have a clamp small end. these arnt easily avalible new so il have to do hunting. as for pistons its very hard there were few gd pistons made for the 850 in the 60's and most of these havnt been made for 40 years now. standard ones have a slot in them so they run quiter but its a weak point. u can get 948 ones for a sprite and skim the block to suit this is ur best bet, heprolite made some gd ones for 850 but are super rare they also made some slightly better than standard ones. it says about fitting sprite pistons to 850 in vizards book of tuning minis, its gd book as published in 70's it tells u period parts reqired for tuning 850's ect. anouther option it to get a 998 block and fit 998 pistons to ur 850 crank or just use 998 crank. cant rember is 850 block can take 998 pisons as block casting is differnt it has thinner walls
Posted: Oct 30, 2007 10:56 PM