hi, i'm woundering if there is much power difference between flat top pistons and dished. i have try'd to look around for info and i carn't find much info on this subject. if anyone could tell me the diff i would appreciate it

You have to be more specific about the type of engine you are talking about, some engines need to have flat tops to get good compression while others must have a dish.

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

If you're talking 1275 motors...
Years ago forged flat tops were the go for racing, Mahle and others made them. C/R was around 12:1. I ran a set in my 1310 road car (with head chambers enlarged) for 50,000 miles.
However, Vizard and others since have found that torque and power in an A series engine were better with dished pistons.

Most dished pistons have a simple radius dish in them, but there are also offset dishes, and other dishy shapes.

Here's a pic of the dish in a Russell Engineering one, it has been developed using flowbench and engine dyno to produce more power.It's the one on the right...
The one on the left is a flat top +.080" piston for a 998.
They are flat to get increased compression with the bigger chambers used in smallbore motors.

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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.

hi, i'm rebuilding a 1275 rehoned to 1360 with medium head work done, RE-13 cam which i have to send away. if anyone could tell me what time graham business shuts so i can call him. i'm planning to use hastings piston rings and i think hypertec pistons.
thanks

He's there until around 5.30 most days, except Sunday.
Let the phone ring out, he's a busy man.

He sells both his Russell Engineering pistons and Hypatecs, in 73.0mm size (1360cc).

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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.

thats probly what it is. i have tryed to ring him and know one answers the phone...

how much are his pistons

He's a one man band, only him to work and answer phone too. No time to sit at the desk and grab it after 3 rings....
Ring him, and let it ring out...

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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.

does anyone have a price on the pistons

at least (drmini in aust) is willing to help......

Around $280/set I think, for either the Russell or the Hypatec.
That was a while ago, so indication only.

WITH rings.

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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.

back on topic, saw these on turbo minis , never seen any like that befor

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1152cc turbo A-series now with 125.7hp at the wheels !

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Almost looks like a diesel piston. I thought the guy machined the teets off though ben?

Regards

Daniel

And to the others b&%#ing, GROW UP. It's stupid pointless arguments that stopped me contributing on the hotbricks forum years ago. Where is it now????

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

As the Doc mentioned use flat tops when the chambers have been enlarged. I am going to install RE Flat tops in my 1098 rebuild as I am putting a 295 head on with 28cc chambers as opposed to the original 202 head with 21cc so in order to get the compression back without shaving bulk amounts off head and block you use flat tops - dished pistons can be anything from 6 to 9cc in the dish depending on the style

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

OK, crappy posts aside, the real issue here is not what dished or flat top pistons will do for you but what it will do for your compression ratio. Essentially the whole point of flat tops (unless there is another reason unbeknownst to me) is to raise your compression. This is particularly useful for small bore engines as the compression ratio is quite low if using normal dished pistons.

If you are skimming your head and decking your block then the smart way would be to figure out how much chamber volume there is on your head before figuring out what pistons you want.

I can tell you for certain that you can get about 10:1 compression easily by skimming the head slightly and using hypertech dished pistons. Anymore than this and it would be sky high (probably not what you want on a road car...). Graham's pistons are good if you are going ot go for 1360 but, hypertechs aren't bad and they are roughly $100 less. But graham's pistons are the bees knees...

I use hypertechs in mine, they are a good piston which, coincidently, Graham claims is a design stolen from him in the first place!!!

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Lillee - 1969 Morris Mini K

Since doming the piston increases its surface area (marginally) would there be any difference in power (force = pressure x area)?

I run Hypatech 73mm, C/R is 10.7:1 and it's fine on 98 octane, with the RE282 cam. Graham says I could even go a bit higher.
For an RE13 cam though, 10.5:1 is about it, I found 11:1 was too much.

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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.