I'm thiinking that exact thought Kev .... Strong, Light and well up to the job of MASSIVE revs .... should hold under boost too, if I keep the detonation under control .....

I'm told that there are some Kwakka ones that are nearly perfect.. need to bore the block 0.035" over though .... Weird size for the next engine builder to find !!

J

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Now you`re talking,,,we used suzuki pistons years ago & i use kwaka valves sometimes in race heads too



oops,,,there goes another secret

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Thanks Matt & Kev for the info so far

Matt to clarify when you state rip the tops of the pistons..this would grop them down the bore increasing volume..But this up sets squelish..

My head (12G940) has been modified then skimed to get 21.2cc to get the compression up to 10:1 with 12cc pistons.. the car went like of bucket of piss with a 266 Cam hence a 1360 is being built.

Also i have not included the ring land to give me some margin for error

what are your thoughts on compression ratios for a roady engine?

Cheers

Bernard

Yep Ty, that's where the last set came from. GR has 73.0 ones in stock too.

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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 ran 11.1 in my 1310 roadie (VP3 cam) with the flat tops for a while, it was too high. Ran it then with 2 gaskets, but it had no squish and wasn't so good.So I opened out the chambers and dropped C/R to 10.4. Ran well.
This 1360 I've just built is running 10.7:1 with an RE13 cam, 1.5 rockers and 45 dellorto. Fuel is 98 unleaded with Flashlube. No pinging, even though it's running 40* max advance (open chamber head).
So far, so good. 800 miles and counting, not been over 7000 yet.

<edit> Hypatec pistons (stock) are .010" down the bore, my last one was .020" with the Mahle flat tops..

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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.

dropping the piston down the bore is not as good as opening up the chamber, that`s for sure,,,no argument from me,,,but!!!!!!!!!!.... i can`t see that it would be the reason why an engine would run like a bucket-o-puss, not at all

that`s just not how it works,,,

My 1510cc roady (& many many other engines i`ve built) have had the pistons sitting a fair way down the bore (I mean LOTS))) & they have all run like a champion,,,i would have looked elsewhere in the engine build for the """Running like a bucket-o-puss""" reason, that`s for sure

dropping the piston down the bore a little (or even a lot for that matter) does not "kill" an engines performance,,,yeah, it drops a tad,,,note """A TAD""" ,,,but that`s all,,,it`s pretty well almost not noticeable in my books,,,as long as the rest of the donk is sweet, then it really shouldn`t be an issue


& i like to rest my road engines on 9.5-10:1 max,,,definately with de-shrouden, re-shaped & pollished chambers

a stock cyl head chamber & engine sizes around or up to 1360ish would definately have some pinging problems, even on premium fuel, if they`re set up with 10:1 comp ratio,,,it`s highly recomended by lots of the well known mini engine builders that 9.5:1 is usually to high for the sh!t fuel we have in this wonderfull country

if fairly stock engine,,,i`d run a max of 9.3:1,,,,if it`s a largish capacity & has quallity chamber work & a mildy or hotty cam, then 9.5-10:1,,,much up from there & you`re in trouble

saying all that,,,,i run my 1510 on 10.3:1 & no ping ,,,but then i`m cheating with such a big donk

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

C/R you can run with a given fuel (on the road) depends a lot on the cam. If the cam had a fair duration (say 270*) and overlap, and doesn't come on until 2,700 rpm or more, you can get away with higher C/R, as there's no enough real compression down low to make it ping.
Mine is OK at 10.7:1 with 98 octane unleaded, but I bet it would ping like mad with a stock cam.

Not that I would use them on the street, but- look at race cams for example, people run C/R of 11:1 or 12:1, sometimes more. They have to, to make these cams work as intended.

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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.

The car ran poorly because of the cam 266 meg regrind NZ ..

have since found out that the cam grinds here in nz are not the best and that the 266 meg needs to be spot on to work properly.. it went ok 49.5 BHP at the wheels on the dyno but as i will only being droving it in the week end and to club night i would like 70-80 bhp

Yes i dialed the cam in with a degree wheel, and tripled checked it ..

The cam i am going to use is a RE13..from Oz ..

My block is being rebored at the moment and should be back in a couple of weeks and my engine builder (yes i am having the block professionaly built and the deal is i get to put it together under tution) as he is a member of our car club..

I have a question re the Hypertec pistion what are the best ring to use, i was supplied hasting rings which are not chrome molly which is my preference..but cast iron

Do you have to modify the pistons too fit hastings rings eg the back cut on the rings as my engine builder as been adivised that if we use these rings the pistons ring land need to be back cut to get the ring tension wright ..

I have upmost confidence in my engine builder and the machinest doing the boring but
it dosn't hurt to check..

I used the Hastings rings, out of the box- they came with the 73.0mm Hypatec pistons. Top ring is chromed.
Commonly used for race motors here, can't be too bad...

My last motor had Mahle flat top 1310 pistons and Hepolite rings, they were plain cast iron (not chrome). I did 45,000 hard road & track miles before I seized a piston on a track day. Rings still had some tension left..

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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.

interesting .. my rings do not have a top chrome ring just cast iron..

do you recall the part number of the rings you used..

On the Hypatec leaflet inside, it says
"Part Number P-AU1275*1H

Piston Ring Set PR1521.

Minimum clearance 0.0015"
Measure at 0.500" from bottom".

On the outside of the Hastings ring box,
it says on the bar code- RS1521000CR4H
On the label behind that it says 2C 4347
Also on that label is A1005B CHROME

Hope this all helps. The Hastings ring box was in the Hypatec box with the pistons...

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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.

Just spoke with GR. The new Hastings ring sets the pistons come with now are not chromed top ring, but they are not plain iron rings. He says they are fine, for road or race.

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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.

Thanks Kev

hopefully my block will arrive this weekend from the engine recondtioner..

cheers

B

by the way beranrd if you want chrome rings you must ask for them, they are a bit more expensive but i have had no problems with either types of rings in the past.

49.5hp damn so close to the 50 you wanted.
Now your really are doing it right, i hope to get more than my 68hp i got last time but time will tell once you have built your motor.
i have the gaskets you have requested and they only come in a bottom end gasket set nothing else.

Oh by the way beranrd also be carfull with the hypatec pistons on the cranks we use they tend to stick out about 12-15thou and can cause a few issues if you leave them that hig, the block must be virgin and the crank really good to make sure it hasnt been taken down at all, but phil would know that anyway.

How far down the bore are we talking about here

I would have thought that during combustion you would be tending to burn the thin film of oil off the bore walls and start to build up a carbon ridge/coating from the head interface on down

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"Show me the Mini!"