Hi I am just wanting some info on offset boring an 1100 to take +100 pistons. My block is already bored +040 and has a bit of wear im not worried about it being its last bore but the bore walls already look pretty close together, would it still be possible to offset bore it if the +040 over bore wasn’t offset bored in the first place? and what are some other things to watch out for I have heard that the piston can foul on the distributor shaft? Also would anyone recommend a place to get the boring done in eastern Melbourne.
Thanks

Trouble with offset boring once the bore is already big is that you need to take at enough out of the bore on the non-offset side to clean it up, so the amount you can shift the bore is limited. Better off digging up a standard bore block. There should be plenty of 1100/998 blocks around

I think the story with the pistons hitting the distributor shaft is that the skirts are quite long, so even if not offset they'll hit. Solution is just to machine the dizzy drive down

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If at +.040" now yes it can be offset bored to +.100 just fine.
The pistons don't normally hit the dizzy shaft, the ones that did were an early batch.

Main problem to watch when offset boring is #4 bore breaking into the oilway from the pump. It gets pretty thin there and yes I've seen it happen on a Sprite block.

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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.

Do the small bore blocks get offset bored same as a 1275? ie 1 & 2 go towards the waterpump 0.015thou and 3 & 4 go towards the clutch 0.015thou?

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there is a lot of meat between #2 and #3, so I wouldn't think so... you'd want to move #1 towards the water pump, #2 & #3 closer together and #4 towards the oil pump

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Smallbore blocks are different bore spacing, #1 and #4 each move out .015", and #2 and #3 move closer together .015" each.

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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 for that. so would anyone recomend a good engine machinist that could do the job around melbourne? also what is a good bolt set for the main caps are the standard bolts up to the job or am i better off fitting some arp bolts? it is a track motor with a wedged crank and it does see some pretty high revs sometimes.

maybe talk to 850man, he might know who is good to use



talking to a mate at Hay last weekend he told me all about the 7 port Cooper S motor he built for his moke that went like an utter rocket... until a standard rod bolt let go

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Orger Engines in Bayswater
http://orgerengines.com.au/

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HI minieleven11
Dont offset the bore for .100 over size as this size bore is the limit for small bore head gaskets, even with this size the gasket will hang over the bore a little bit, when i do this size bore i put a slight chamfer on the top of the piston to help clear the gasket at tdc.
Graham Russell

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OK, that makes sense. I was wondering about the head gasket. Will the cylinder walls and the head gasket between the bores be capable of running fairly high compression around 13:1?

Hi Graham,
If boring out to +.100" or even to 68mm, why not just throw a 1275 (1100S) head and 1275 gasket on (after pocketing the block)?
Worked for me, years ago... the damned 1220cc thing flew!!

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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.

also try BNB Engines in Clayton, 155 Westall Rd, Clayton South VIC 3169
(03) 9547 9674.
http://bnbengines.com.au/index.html
they do offset boring and honing Etc
they do alot of MGB and Austin 7 stuff.

Hi Minieleven11
No you won't have any problems with the head gasket and please dont run any thing like 13 to one in a miniit willonly cost you HP all the race engines i build only run 11.5 to one some times they may sneak up to high 11smay be 12 if the head has to be skimed but i never go any higher.


Hi Kevin
I like the small bores because they make a much better spread of torque and the same hp.
Graham Russell

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"It's better to be not informed than ill-informed"

I was thinking of running e85 as an option if I was going to run 13:1 but I think it might be a bit difficult to get the tune right. I will be using av gas otherwise with lower compression. Thanks for the info!