its too late for me, my engine is too far along to go back and remachine everything and aquire new pistons at hundreds of dollars cost not to mention even more time (its taken over 4 months already), so its run them and see what happens...

hope the rings bed in okay...

I just spoke to the man, He said that he's put them into 100's of motors with no problems. They are designed specificly to be that way and he has tried recessing them more and all it does it break rings.

Quote unquote...

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Lillee - 1969 Morris Mini K

A couple of hundred dollars shouldn't really be much of an issue when building an A-series.

In all seriousness

maybe your engine builder should have called graham before stressing you out mate, I know you probably dont know much of graham (other than what you have heared) but if he has mad a piston a particular way then it will be a good thing. Ur motor builder probably would have been better off just giving GR a quick call to find out his view. but im sure your motor will be fine if he fitted the rings and pistons well

How far away do you guys recon the 100" over 1100cc pistons will be?

Cheers

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When I spoke to Graham last week he said his order has gone "missing". That is the manufacturer says it was made and shipped but there is no paper trail to show what happened to it. The order is being reworked and they are trying to tell Graham that it will be the normal 90 day lead time but GR is jumping up and down saying they stuffed up they should fix sooner - Just have to wait and see

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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!

FWIW- for fun I just looked at my 73.0mm Hypatecs for the stroker...
Yes the 1st and 2nd rings are flush with the top ring lands,
BUT..
diameter of the piston there is only 72.1mm.
In reality the land surfaces do not touch the bore, even when hot.
So, there really is ~0.4mm back clearance, when assembled into bore.
Less the couple of thou piston to bore clearance....

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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.

I think the confusion is the back clearance is the ring groove/ring and bore related difference, nothing to do with the outer diameter of the piston.

As discussed in another thread, the piston diameter for bore clearance calcs is the bottom of the skirt perpedicular to the gudgeon. The crown is alot smaller, well over half a mm in most cases depending on the type of piston.

Measuring the back clearance with reference to the OD of the piston is incorrect.

You need to measure the OD of the ring groove+ the (ring width x 2), subtract this from the bore to find the back clearance.

I had to machine the ring grooves deeper & wider for my turbo engine because I changed the ring type/width to suit the application. This is the only time I have ever had to do this so I can't see why the engine builder would be concerned if the rings were supplied to suit the pistons

If the back clearance is not what you asked for (why anyone would specify this is beyond me) then call GR. If the engine builder thinks this calc is wrong then he/she is not an engine builder and should go back to gardening

Regards

Daniel

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

technical things aside..... and expanding on my original comment .... the more I read about these pistons the more I like them. I know what I'll be getting when I require new pistons ..

i didnt specifically ask for backclearance, from what i am to understand its industry standard for pistons to have backclearance, these pistons dont, GR says they're fine but it should be known before you choose these pistons.

they're not a problem to me as far as backclearance,
the pistons dont meet my requirements in another fashion, which is no fault of the pistons themselves.

From your original post I assumed you asked for additional backclearance or some other mod specifically to suit your build.

Hence my original Q

You say the pistons compromise your engine build, if so it in what way so we can take note/comment/whatever.

regards

Daniel

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

OK here is the post that will end this thread

Graham and I measured a hypertech piston as well as his own pistons and the ring land is the exact same clearance to the piston on both. ie. Hypertechs and Grahams pistons are exactly the same design and measurements.

OK so is anyone having problems with their hypertechs?

Quote Unquote "Stop living in the past. If your mechanic is telling you the pistons don't work, you need a new mechanic. It's all been tried and done before with 10,000's of hypertech pistons out there"

Thanksverymuch.

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Lillee - 1969 Morris Mini K

my mini mechanic, a piston manufactuer and my machine shop all said i should have backclearance in my pistons..

GR said he's sold many of them and they're fine..

i've already spent my money, so i am using them as is, and i do not expect the pistons to be a problem.

this is not the past, this is happening right now, you should accept there are other people out there with worthy opinions and expertise with minis.

i was shown a set of hypatechs, they are not the same piston, they have a different dish shape, they come with fitting instructions and hastings rings.

http://www.minisport.com.au/prod46.htm

The Nippon ringset that comes with the Russells is of higher quality than the Hastings. Don't worry, be happy.

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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.

We are not talking about dish shape are we so what is your point?

If you aren't happy with them, return them but don't come on here to complain about them when they are the same as many other types of pistons in design for the ring lands. This is my point.

Well good luck with your build, I sincerely hope everything turns out well for you.

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Lillee - 1969 Morris Mini K