Hepolite 20832A Pistons?
Turbo Mini Forums

Just knocked down both of my engines, Turbo lump has 20831A pistons with a big chunk out of no2 and corresponding chunk out of bore, Not mic'd it yet but I think the block is shagged.

Other engine (12H907) has 20832A pistons. I think its a pre 84 metro engine but these look exactly the same as the turbo pistons with maybe less dish, anyone know what pistons I have here?

I maybe lucked out as the 12H907 has Turbo main bearings... (Could this be the earliest report of these bearings in a metro engine?) any reason not to use this for my turbo build??

Edited by Turbo Tel on 1st Nov, 2006.

website:- http://www.terryhunt.co.uk

Are both pistons of the slipper design?

not sure what "slipper" is but both pistons are absolutely identical apart from the dishing. I am pretty sure the 20831's are standard turbo pistons. The only thing I find on 20832's when I google is someone selling a set as "cooper-S" pistons on e-bay

item# 180045101130

website:- http://www.terryhunt.co.uk

the slipper pistons have cutaways were the gudion pin goes have a look under neath and sea if they are round retangular in shape.

always looking for them bigger bunches of bannanas

No, they are not slipper pistons.....

They look exactly like the turbo pistons, that is what I find strange. I thought NA metro engines had slipper pistons and only turbo's had full skirts.

website:- http://www.terryhunt.co.uk

Well... seems that no-one has any idea where these pistons came from. I have CC'd them and they are around 8cc otherwise they look identical to standard turbo pistons, rings, crown height and construction. This would make them good for 10.5 compression ratio.

Edited by Turbo Tel on 6th Nov, 2006.

website:- http://www.terryhunt.co.uk

i found the same number on mine pistons in what suposed to be a turbo engine.
but reading what turbo tel wrote it's more likely that it is not, damm........

well now i know a need new pistons......

10.5 compression will surely blow my turbo block

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

they are early mg metro (n/a pistons)

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

naturally asperated, i.e. non-turbo pistons.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

not the answer i was hoping for but now i know.

thanx for the info

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

nothing wrong with 20832 , casting is the same ,they are strong pistons
if your bore are ok,
bore the dish carefully from whatever you need between 10and 15cc

so if i skim a little off to get a lower compression where back in buisness

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

Machine the dish, skimming wont give you much

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

Off of each piston to get 10-15 cc on each piston and it doesn't affect your swept volume as the dish is the same at the top and at the bottom of the (1293cc) stroke, it only affects the compression ratio.



Terry

Edited by Turbo Tel on 18th Dec, 2006.

website:- http://www.terryhunt.co.uk

i measured the piston and i also found 8cc.
the head i.m planning to use gave me 23 cc

this gives me a compression of 9.62 (see below)

if i take a cc or 2 off the head i,m back in buisness

please correct me if i,m wrong



http://www.geocities.com/MotorCity/5353/cylhead.htm

Engine (CC): 1275
Piston Dish (cc): 8
ring Land Volume (cc): 0.78
Gasket Volume (cc): 4.2
Piston/Deck (cc): 0.99 Unswept Volume (cc): 36.97
Total Above (cc): 13.97 Swept Volume (cc) : 318.75

Chamber Volume (cc) : 23 Compression Ratio: 9.62

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

is this going to be a turbo engine?

yep.
a normal turbo engine as a compression of 9.4 if i,m right.
so it's alsmost there

Edited by paneermeel on 20th Dec, 2006.

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

you must add volume in the head, not take them avay to get the CR lower

that is what i,m planning on doing.
to grind my chamber open by a cc or 2.

only apparently you get a compression of 10.5 whit these pistons. but when i use the link to calculate the compression i get a lower reading, 10.01. that is with a chamber of 21.4cc.
so or my calculating is off or turbo del uses a differant head as standard. that is what i,m trying to find out.

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

Try and get lower than 9.4:1 if you can. 9:1 is a good compromise.

Your numbers look OK to me,

I used std head cc (21.4) and slightly different values for land head gasket etc and a flush deck (which was a mistake, its probably about 1 cc in reality)

The difference between 10.5 and 10 is under 2cc so It doesn't take much!


Funny thing was the engine didn't seem to be an MG version so these pistons may have been fitted later.

Terry

website:- http://www.terryhunt.co.uk

hello, were back again.

i got a new set of ring for my pistons but the lowest ring is differrant. the orginal ring is thicker than the new one(3.00).
the are federalmogul R41570. which rings did you use?

maby you can give me the partnumber

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

On 12th of Feb, 2007 at 09:17pm paneermeel said:
hello, were back again.

i got a new set of ring for my pistons but the lowest ring is differrant. the orginal ring is thicker than the new one(3.00).
the are federalmogul R41570. which rings did you use?

maby you can give me the partnumber

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