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| 1275 head on 998 block.. its possible... https://www.ausmini.com/forums/viewtopic.php?f=5&t=9141 |
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| Author: | kazjim [ Sun Jul 17, 2005 4:22 pm ] |
| Post subject: | 1275 head on 998 block.. its possible... |
but just really, freaking hard ! You hear people discussing pocketing the block to allow the exhaust valves to clear.... Well, this is it... 
Tell you what, that tests your nerves ! still not certain it will run, but there is plenty of clearance and i HOPE i've done it all right.... Oh well, there is another two virgin 998 blocks sitting there ! J |
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| Author: | Lillee [ Sun Jul 17, 2005 4:52 pm ] |
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Good onya for having a go James. I've only ever seen that in text books  
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| Author: | drmini in aust [ Sun Jul 17, 2005 7:02 pm ] |
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Looking good, James. Hey it looks like the head stud holes could maybe do with countersinking.. watch there's no metal pulled up around them or it could give you head gasket problems.. yeah I know you've been there..
D'Oh, he says... 
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| Author: | gafmo [ Sun Jul 17, 2005 7:33 pm ] |
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I maybe getting this done to my second 998/1098 block also 
What did you do it with mate 
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| Author: | kazjim [ Sun Jul 17, 2005 8:06 pm ] |
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First attempt was with the hand-drill and some mounted stones.... - bloody things lasted about 20 seconds each and left a huge radius in the corner... Popped out and bought an electric die-grinder and some 1/2 mounted cylinder stones... Set to about 28,000rpm, and away you go..... the worst part is the butterflies in the stomach (if i ferk this up, i need to put my hand in my pocket again....) J |
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| Author: | drmini in aust [ Sun Jul 17, 2005 8:25 pm ] |
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Don't worry James, others (including moi) have trodden this path before.. 
It's worth it!
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| Author: | Curly [ Sun Jul 17, 2005 8:54 pm ] |
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It's a worthwhile modification, especially if you have a spare Cooper 'S' head lying around. The bigger valves make it breathe easier even though there is more shrouding around the valve in the area of the block cut out. I've been running a Cooper 'S' head on a 948 Bugeye Sprite motor (in a Sprite) since 1997 and it hasn't missed a beat. 
Note the yellow painted '950' casting on the block below the exhaust pipe, just so people don't confuse it with a 1275.
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| Author: | drmini in aust [ Sun Jul 17, 2005 10:31 pm ] |
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Looks nice, Curly. Back in the mists of time I had an 1100S head on a 1098 bored to 1220, with 544 cam and twin Amal Monobloc carbs. It flew! Until a circlip broke and a gudgeon pin kissed the bore.. 
Done a couple of these motors (Sprites in MMs) since, but I used PTFE buttons instead of circlips.
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| Author: | kazjim [ Mon Jul 18, 2005 4:47 pm ] |
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Doc, I just had a thought.... I Finally got around to using those magical Valve stem seals of Todd's (From MM) (Still got 4 left) They had to go on the INLETS didnt they ? - NOT the exhausts.... or was it the other way around ? You need lubricatin on the exhausts more i think...... - I'm getting old doc, starting to forget things...
J |
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| Author: | Curly [ Mon Jul 18, 2005 7:02 pm ] |
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Kazjim, there's normally no need for stem seals on exhaust valves. You might use them if the guides or stems are particularly badly worn, but I always leave them off and have no problems. |
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| Author: | kazjim [ Mon Jul 18, 2005 7:29 pm ] |
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Thank god.. those valve springs are particulary heavy and a bastard to put on.... didnt want to have to do that again! J |
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| Author: | drmini in aust [ Mon Jul 18, 2005 7:29 pm ] |
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Yep put them on the inlets. I put a bit of Loctite inside as the brass sleeve tends to get loose if you hit it too hard. They are great, those Viton seals of Todd's. I took them off after 10,000 miles (for engine rebuild) and they were so good I put them back...
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| Author: | kazjim [ Mon Jul 18, 2005 8:05 pm ] |
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I've still got 4 if anyone else wants them..... bought 8 by mistake - only use 4 per engine.... if anyone wants them, drop me a PM.... J |
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| Author: | Boostedmini [ Thu Jul 21, 2005 10:30 am ] |
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hey jim if you do stuff it let me know as i have two motors at home that have had it done so you can copy if you like, both have been decked for the 1220 mod with imp pistons, still has the 648 cam and 12g940 head on it too
let me know if you wanna squizzy
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| Author: | kazjim [ Thu Jul 21, 2005 11:50 am ] |
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Thanks Grant, Ive got another 2 998 blocks here.... One with an 1100 Crank / pistons already in it.. just needs a quick tidy and away it goes... WIll know in the next week or so !! J |
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