Ok, started a new topic to get right down to it. See my other post if you havent read the sad story. This is a 94 Spi Cooper.
http://www.theminifo...howtopic=195854
Ok, so the block has been to the machinist and it looks like a bore in needed. The block has never been bored before and it only a few thou out. If I am going to do it, what would you all suggest? I would love to take the opportunity while I have it to add a few more ponies to the car with an over-bore. I was thinking of going up to a 1293cc. Is that reasonable? Any other suggestions on bore size and pistons to use? Minisport has the Hepolite Slipper that will give 10:1 ratio. Am I asking for trouble?
The motor is getting a brand new crank with all bearings and thrusts, new cam bearing with an SW5 cam timed to 107, standard head with lapped in valves, turbo oil pump, and all new gaskets of course. Running the original SPi ECU and a full Maniflo header back system.
To Bore Or Not To Bore...
Started by
brivinci
, Jul 28 2011 05:01 PM
6 replies to this topic
#1
brivinci
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Posted 28 July 2011 - 05:01 PM
#2
Sprocket
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Posted 28 July 2011 - 06:03 PM
1293 is classed as a standard recondition oversize so should have little effect on any insurance or statutory testing.
To be honest 1293 is pretty much a standard engine and you will find it hard to quantify any power gain just as a result of the slight capacity increase.
If on the other hand, you want as much out of the engine as you dare, then 1380 would the option, wut could render the block scrap another 10 years from now, at a time when blocks will be even rarer and more expensive, but then, that is something you have to consider whether its worth going to 1380, or just sticking with a standard oversize. Me personally took it one stage further and went to 1399
To be honest 1293 is pretty much a standard engine and you will find it hard to quantify any power gain just as a result of the slight capacity increase.
If on the other hand, you want as much out of the engine as you dare, then 1380 would the option, wut could render the block scrap another 10 years from now, at a time when blocks will be even rarer and more expensive, but then, that is something you have to consider whether its worth going to 1380, or just sticking with a standard oversize. Me personally took it one stage further and went to 1399
#3
the_r_sole
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Posted 28 July 2011 - 06:15 PM
lol, the nigel tufnel of the mini world!?Me personally took it one stage further and went to 1399
#4
brivinci
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Posted 28 July 2011 - 08:23 PM
Good point about the block. Also, I am over in the US so blocks are even rarer, there is no insurance issues and I drive the car no more then 3-5 thousand miles in a good year. Probably way less now that I have a wife and a small child.
So, if I were to bore it up to 1380, do you have to do anything with the crank? Also, if I were to bore it to 1293 or whatever but added high compression pistons (10:1) would I see any real improvement. I mean, regardless what actually gets done, it needs to be bored. I guess its whether I go the "full-bore" or not:-) What kind of power gains are seen in just bringing it up to 1380? Again, with stock head and ECU.
So, if I were to bore it up to 1380, do you have to do anything with the crank? Also, if I were to bore it to 1293 or whatever but added high compression pistons (10:1) would I see any real improvement. I mean, regardless what actually gets done, it needs to be bored. I guess its whether I go the "full-bore" or not:-) What kind of power gains are seen in just bringing it up to 1380? Again, with stock head and ECU.
#5
icklemini
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Posted 28 July 2011 - 09:14 PM
Couple of things to check:
Is your block linered?
Why the turbo oil pump?? (totally not needed and wastes energy!)
Depending what you want out the car - you could just go the next size up (1293), new decent pistons, etc.
Spend a bit of money on the head and liven that up...
Should have a nice motor then
Why the stock head? - thats gonna limit the power output...
Is your block linered?
Why the turbo oil pump?? (totally not needed and wastes energy!)
Depending what you want out the car - you could just go the next size up (1293), new decent pistons, etc.
Spend a bit of money on the head and liven that up...
Should have a nice motor then
Not especially - you wont be revving it any more than standard...So, if I were to bore it up to 1380, do you have to do anything with the crank?
Why the stock head? - thats gonna limit the power output...
#6
Sprocket
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Posted 28 July 2011 - 10:16 PM
If the engine you have is a Cooper, it will already have a compression around 10:1. The non cooper have 9.4:1
Never having used the 'Hepolite' AE pistons on a fresh block, i'm not sure what the compression height of them are, but all the other pistons I have used normally have a slightly shorter compression hieght to allow a skim on the block to freshen it up. I would measure the compression ratio before deciding what does or doesn't need machining to get your 10:1 compression ratio, as i'm not convinced just bunging new pistons in a block with a standard deck height will give you the 10:1 CR they state.
Never having used the 'Hepolite' AE pistons on a fresh block, i'm not sure what the compression height of them are, but all the other pistons I have used normally have a slightly shorter compression hieght to allow a skim on the block to freshen it up. I would measure the compression ratio before deciding what does or doesn't need machining to get your 10:1 compression ratio, as i'm not convinced just bunging new pistons in a block with a standard deck height will give you the 10:1 CR they state.
#7
brivinci
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Posted 29 July 2011 - 04:33 PM
Thanks all. I was just going off of Mini Sports site for the 10:1 bit.
About 800 miles ago, I had the head and block skimmed to give a perfectly flat surface (and get a tiny bit more compression). The machinist just took as little as he could off to get it perfect and fresh. I would think it could go more if I ever needed to.
I am not dead set of any particular number or spec really. I have an empty block staring me in the face and I would just love to do whatever I can at this point to improve it. Although I said this the last time...I would rather not have to pull it again in the near future:-)
Oh, and yes its a 94 SPi Cooper so I guess i would just be buying the 10:1 pistons as replacements rather then an upgrade.
On going to a 1380, can the OEM ECU even handle that properly? I need a head at some point but would that just throw it over the edge of what the ECU can manage?
About 800 miles ago, I had the head and block skimmed to give a perfectly flat surface (and get a tiny bit more compression). The machinist just took as little as he could off to get it perfect and fresh. I would think it could go more if I ever needed to.
I am not dead set of any particular number or spec really. I have an empty block staring me in the face and I would just love to do whatever I can at this point to improve it. Although I said this the last time...I would rather not have to pull it again in the near future:-)
Oh, and yes its a 94 SPi Cooper so I guess i would just be buying the 10:1 pistons as replacements rather then an upgrade.
On going to a 1380, can the OEM ECU even handle that properly? I need a head at some point but would that just throw it over the edge of what the ECU can manage?
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