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| Home > Help Needed / General Tech Chat > Stroking a 998 | |||||||
 9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
16th Nov, 2007 at 10:08:38am
I've calculated that if I shorten the stroke of a 998 crank by 40thou with a 20thou overbore I'll end up with 1000cc.
Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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 8604 Posts Member #: 573 Formerly Axel Podland |
16th Nov, 2007 at 10:31:48am
It's possible, but you would have to reduce the crank pin diameter by at least 80 thou which would weaken it. Conrods and bearings are the next problem.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
16th Nov, 2007 at 10:38:25am
I'm not bothered about the few extra cc of a 20thou overbore. Although not strictly in the regs it's a stndard overbore and you can't buy 998 blocks anymore, so what can you do?
Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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8604 Posts Member #: 573 Formerly Axel Podland |
16th Nov, 2007 at 10:45:11am
Calver made the comment yesterday that the P20950 pistons could be dished (as you have done already).
Edited by Paul S on 16th Nov, 2007. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
16th Nov, 2007 at 10:47:35am
I can't remember how much it got decked now, no more than 20 thou iirc Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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8604 Posts Member #: 573 Formerly Axel Podland |
16th Nov, 2007 at 10:55:38am
Have you still got those dished 20950s?
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 12307 Posts Member #: 565 Carlos Fandango Burnham-on-Crouch, Essex |
16th Nov, 2007 at 11:02:16am
i'm sure i remeber seeing sleeves for smallbor blocks somwhere. On 28th Aug, 2011 Kean said:
At the risk of being sigged... Joe, do you have a photo of your tool? http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1 https://joe1977.imgbb.com/ |
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9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
16th Nov, 2007 at 11:18:38am
On 16th of Nov, 2007 at 11:02am mini13 said:
i'm sure i remeber seeing sleeves for smallbor blocks somwhere. Don't tell me things like that. Paul, I've half moved at the moment, so the pistons I have that can be measured are at my old house in Macclesfield. I'll be back there on Monday, so I'll give them a measure and PM you. Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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 143 Posts Member #: 1506 Advanced Member Cheshire |
16th Nov, 2007 at 11:43:31am
http://www.minispares.com/Product.aspx?pid=33694 Check out the (slow) progress at.......
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12307 Posts Member #: 565 Carlos Fandango Burnham-on-Crouch, Essex |
16th Nov, 2007 at 12:28:38pm
thats them,
On 28th Aug, 2011 Kean said:
At the risk of being sigged... Joe, do you have a photo of your tool? http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1 https://joe1977.imgbb.com/ |
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8604 Posts Member #: 573 Formerly Axel Podland |
30th Nov, 2007 at 04:34:53pm
If you use an 850 crank and +0.100" P20950 pistons you get 966cc.
Edited by Paul S on 30th Nov, 2007. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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4314 Posts Member #: 700 Formerly British Open Classic The West Country |
30th Nov, 2007 at 07:14:25pm
On 30th of Nov, 2007 at 04:34pm Paul S said:
If you use an 850 crank and +0.100" P20950 pistons you get 966cc. 67.1mm bore 68.2mm stroke Any good? I guessed that is what you where thinking when I saw the wanted add. My only concern would be how strong the crank is, IIRC the 850 crank is not know for it's strength. Although if you go the 850 route what about IMP pistons? I think +10 IMP pistons with an 850 crank gives you 999cc. Rog and myself looked into this about a year ago, but I can't remember if we posted anything or just talked about it. Here's some nice reading for you: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=125219 Ironically the first post by Paul is probably the most usefull. Edited by Rob H on 30th Nov, 2007. Isambard Kingdom Brunel said:
Nothing is impossible if you are an Engineer |
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8604 Posts Member #: 573 Formerly Axel Podland |
30th Nov, 2007 at 07:34:44pm
How weird. I had forgotten all about that post.
Edited by Paul S on 30th Nov, 2007. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 7765 Posts Member #: 74 I pick holes in everything.. Chief ancient post excavator |
2nd Dec, 2007 at 11:42:10am
On 16th of Nov, 2007 at 10:31am Paul S said:
It's possible, but you would have to reduce the crank pin diameter by at least 80 thou which would weaken it. Conrods and bearings are the next problem. Isn't it the other way around? If you are reducing your stroke by 040. you'll need to reduce the crank diameter by half of this. IF, the crank doesn't need a regrind anyway. 040 bearings are OK to get hold of. Ask Richy. On 13th Jul, 2012 Ben H said:
Mine gets in the way a bit, but only when it is up. If it is down it does not cause a problem. |
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8604 Posts Member #: 573 Formerly Axel Podland |
2nd Dec, 2007 at 12:29:07pm
On 2nd of Dec, 2007 at 11:42am Vegard said:
On 16th of Nov, 2007 at 10:31am Paul S said:
It's possible, but you would have to reduce the crank pin diameter by at least 80 thou which would weaken it. Conrods and bearings are the next problem. Isn't it the other way around? If you are reducing your stroke by 040. you'll need to reduce the crank diameter by half of this. IF, the crank doesn't need a regrind anyway. 040 bearings are OK to get hold of. Ask Richy. Your right as usual, but in this case only half right! I was wrong in that to reduce the stroke 40 thou, you need to reduce the throw by 20 thou. But you still need to grind the pin 40 thou thinner to move the centre 20 thou. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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7765 Posts Member #: 74 I pick holes in everything.. Chief ancient post excavator |
2nd Dec, 2007 at 01:15:10pm
Yes. I had to think quite a while on this. Interesting. :)
On 13th Jul, 2012 Ben H said:
Mine gets in the way a bit, but only when it is up. If it is down it does not cause a problem. |
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 703 Posts Member #: 105 1st to provide proof of a running Bimmy Conversion! Brisbane ,Australia |
30th Jan, 2008 at 02:33:53am
I`ve been running my 1510cc engine @ over 100hp for well into 8 &1/2 -nearly 9 years now on a .080 under crank
www.miniman.com.au
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7765 Posts Member #: 74 I pick holes in everything.. Chief ancient post excavator |
30th Jan, 2008 at 07:30:46am
I agree. Why haven't you gone the 970 route instead Wil? Everything will be stronger, make more power etc.. On 13th Jul, 2012 Ben H said:
Mine gets in the way a bit, but only when it is up. If it is down it does not cause a problem. |
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9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
30th Jan, 2008 at 08:04:07am
On 30th Jan, 2008 Vegard said:
I agree. Why haven't you gone the 970 route instead Wil? Everything will be stronger, make more power etc..  Mainly because I have a sitload of 998 engines and no 970s. Bottom end strength isn't a problem either, I have the same crank from my first 998 turbo machined 8 years ago. Also, I don't need any more revs, they'd be great for a circuit racer, but not needed for the hills. 7k gets me to 105 mph, and I only ever get there at avon park. Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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