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MiniK
 Post subject: Turbo Pistons
PostPosted: Wed May 19, 2004 3:17 pm 
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Ive asked this before on the old Ausmini but thought id ask it again, seeing as more people frequent here now.

Does anyone know where dished pistons can be sourced? I think most of the poms are using cast Hepolite's with a 10cc dish( which i think are standard on the metros).

Anyhow any help will be greatly appreciated :D

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drmini in aust
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PostPosted: Wed May 19, 2004 5:19 pm 
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You can buy Hepolite 21250s from MiniSpares. They are 9.4:1. Bit high, I reckon, if you are adding a serious amount of boost. But you can hack the chambers out in the head... :P

Whatever, DON'T use 21251s. They are too weak for this application.. :cry:

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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MiniK
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PostPosted: Thu May 20, 2004 8:46 am 
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Crikey...yeha 9.4:1 is a tad high......

i think im going to have a proper look around...... 8)

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turbomini
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PostPosted: Thu May 20, 2004 3:42 pm 
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you could use the 9.75:1 standard hypertec or hepolite pistions... but u could only run SFA boost like 5 pound.. (on regular 98 fuel that is) or just find some stocker pistions 8.8:1 i used them for quite a while as long as its not pinging theres no problems.. my cars still running with them.. no problems yet
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kazjim
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PostPosted: Thu May 20, 2004 7:02 pm 
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Mine's a 998, and I run the AE (Hepolite) 20773's (all 3 compression rings ON !)

Running 14+Psi regularly.. no reliability probs yet!

J

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drmini in aust
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PostPosted: Thu May 20, 2004 7:18 pm 
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21251s (8.8:1) will work, but they are a bit weak for lots of boost and high rpm. There's not a lot holding the crown on- as the oil drain slots are huge. Yes they are cheap....

I've got a set in my wife's 1293A+, but it ain't getting revved hard or boosted.. :wink:

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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MiniK
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PostPosted: Wed May 26, 2004 11:49 am 
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drmini in aust wrote:
21251s (8.8:1) will work, but they are a bit weak for lots of boost and high rpm. There's not a lot holding the crown on- as the oil drain slots are huge. Yes they are cheap....

I've got a set in my wife's 1293A+, but it ain't getting revved hard or boosted.. :wink:


any idea what amounts of boost these things would hold though?

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drmini in aust
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PostPosted: Wed May 26, 2004 5:37 pm 
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No idea whatever. They are a cheap low compression road piston and not designed for turbo use... You blow it, you risk it.. :lol:

I'd get some Hypertecs, grind the head chambers out if you have to.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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MiniK
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PostPosted: Wed May 26, 2004 6:09 pm 
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drmini in aust wrote:
No idea whatever. They are a cheap low compression road piston and not designed for turbo use... You blow it, you risk it.. :lol:

I'd get some Hypertecs, grind the head chambers out if you have to.


Hypertecs? Where do i find them?

The standard metro items would be ok wouldnt they if i could find them...there part no. is 20831.

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drmini in aust
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PostPosted: Wed May 26, 2004 7:36 pm 
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Dunno that number. Hepolite 21250 is a 9.4:1 piston made for Metro turbo. Thicker crown etc than 21251...
Just open out the chambers... stock is 21.4, mine are 28.0cc, you can get them made even bigger. 8)

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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MiniK
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PostPosted: Thu May 27, 2004 3:02 pm 
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well karcraft said that Hepolite dont make the 20831's anymore:(

i might have to look into those 21250's then....

Kev do you have any idea what the comp ratio would work out to be using those pistons, with a chamber say 28cc's in size or larger, and 20" overbore?

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minitec
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PostPosted: Thu May 27, 2004 3:28 pm 
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dave, all I can say is what James had as a sig on Minimania.....

vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh........
vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh..........
vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh.........
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MiniK
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PostPosted: Thu May 27, 2004 5:01 pm 
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minitec wrote:
dave, all I can say is what James had as a sig on Minimania.....

vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh........
vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh..........
vvvvvvvvvvvvvvvvvtttttttttttttt psssssssssshhhhhhhhhhhh.........


:lol:

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MiniK
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PostPosted: Thu May 27, 2004 9:13 pm 
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Got a qoute from MED in the UK for 210 pds for a set of dished omega pistons 20" over.......plus 40 pounds shipping......

So about $680.......

Naturally if theres a cheaper option i wouldnt mind taking it :P

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kazjim
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PostPosted: Thu May 27, 2004 9:22 pm 
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And Everyone still wonders why i did a 998 ?

sheesh, for the money you spend on a set of pistons, i could build a whole engine !!!

only 300cc's less ..... just wind another 7Psi into it, and you've increased the "theoretical" displacement another 50% ! (so a 998, at 14psi has the torque of a 1500cc !!) - something like that anyway........

J

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