Don't forget to crack test the crank , a mate built a fresh 1275 engine , run it for about 1500 k's , then the crank let go
, PITA having to do it again ,$$$$ .
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| 1275 Rebuild questions https://www.ausmini.com/forums/viewtopic.php?f=2&t=81877 |
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| Author: | Wakes01 [ Sun Jun 23, 2013 4:06 pm ] |
| Post subject: | 1275 Rebuild questions |
I picked up a 1275 a few weeks ago for few hundred with go gearbox, including head tho. came from an 1100s im told Started stripping it down as it was stored for 15 years and its full of crap (found a lizard on top of a piston) but turned over fine, even had oil on the bearings. The bores are 70.64mm cheap calipers so might be off but i thing thats the standard bore so i feel i got a really good deal. How do i know what i want? I've never rebuilt a motor. I have a Gregorys book (no. 64) Is there a better book i should get? I realize ill need a new oil pump, gaskets and all that but pistons i guess i go +.020 and get it re bored. mains and conrod bearings how do i get the size for them? Wheres the place to get parts? Minisport? karcraft? UK? |
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| Author: | drmini in aust [ Sun Jun 23, 2013 4:24 pm ] |
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Sounds like it's stock bore. Check the bores for any scores etc or it may not clean up at +.020". Safer then to go +.030" or +.040". I like Hypatec 9.75:1 pistons, from either Minis Plus or Minisport SA. However both places are out of stock and waiting for a shipment. ACL bearings are good and made here (in Tassie) I get from karcraft because they are close to me. You need to get the crank measured accurately, if there is any scoring or ovality the crank will need a regrind. Do NOT buy bearings until you have the crank sizes confirmed. Use a micrometer, calipers are not accurate enough. Gregory's #64 is a good book, better than many of the others. |
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| Author: | BALLISTIC [ Sun Jun 23, 2013 8:48 pm ] |
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Pulling apart & slotting parts together is the easy part. Need a good machine shop, get cylinder head checked out, also i would reccommend you get crank, rods, etc balanced. |
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| Author: | goodie [ Mon Jun 24, 2013 9:10 am ] |
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Don't forget to crack test the crank , a mate built a fresh 1275 engine , run it for about 1500 k's , then the crank let go , PITA having to do it again ,$$$$ .
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| Author: | drmini in aust [ Mon Jun 24, 2013 10:45 am ] |
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goodie wrote: Don't forget to crack test the crank , a mate built a fresh 1275 engine , run it for about 1500 k's , then the crank let go
, PITA having to do it again ,$$$$ .Yep always check this before (buying) grinding or refitting it. A year or so ago, my favourite crank grinder had 6 big journal 1275 cranks to do, he found 4 had cracks in em. 
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| Author: | low n blown [ Mon Jun 24, 2013 2:22 pm ] |
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For a roady don't bother getting it balanced. Its an expense that you needn't worry about unless you are running a race engine. If you have a huge bank balance then there are lots of nice things to do, but not essential. |
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| Author: | TheMiniMan [ Mon Jun 24, 2013 4:24 pm ] |
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i always balance our engines now-days,,, you never know who, or what has butchered or swapped out over the years so -->nearly every reciprocating component """could""" be out of whack,,, maybe not,,, maybe just a few items are out of balance,,, maybe not,,, ??? How would you know unless you get it all balanced??? & ,,, it`s not fun finding out """After""" you have spent all that time & money & effort on your engine build,,, then fitted it to your car... & got it all running , , , only to find out it`s a harsh vibration-monster that could have been sorted for a few hundred dollars early in the build process it`s just not worth being cheap about building any engine edit--> that`s just my opinion & advice anyways |
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| Author: | John Smidt [ Mon Jun 24, 2013 8:58 pm ] |
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When thinking about Pistons Do not forget Graham Russell pistons and they are Not expensive |
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| Author: | drmini in aust [ Mon Jun 24, 2013 9:29 pm ] |
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John Smidt wrote: When thinking about Pistons Do not forget Graham Russell pistons and they are Not expensive
Graham's 1275 pistons are very good, however he does not keep +.020 +.040 or +.060. He carries the next sizes up- 72.5, 73.0, 73.5 and 74.0mm. |
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| Author: | low n blown [ Mon Jun 24, 2013 10:52 pm ] |
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TheMiniMan wrote: i always balance our engines now-days,,, you never know who, or what has butchered or swapped out over the years so -->nearly every reciprocating component """could""" be out of whack,,, maybe not,,, maybe just a few items are out of balance,,, maybe not,,, ???
How would you know unless you get it all balanced??? & ,,, it`s not fun finding out """After""" you have spent all that time & money & effort on your engine build,,, then fitted it to your car... & got it all running , , , only to find out it`s a harsh vibration-monster that could have been sorted for a few hundred dollars early in the build process it`s just not worth being cheap about building any engine edit--> that`s just my opinion & advice anyways Are you telling me every engine you build you get everything balanced????? Really Matt?????? |
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| Author: | TheMiniMan [ Tue Jun 25, 2013 9:53 am ] |
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Yep , absolutely--> now days i do & not everything gets balanced Greg, but certainly the crank, rods/pistons, flywheel/clutch assy & the front pulley as a minimum too many engines i`ve had to tune for people in recent years where they have vibrated horribly & had to tear them down to have balanced because the builder skimped on it & didn`t do it if they had done it they would have found the huge problems that we have in recent times it`s just not worth the muck around no matter what engine it is anymore maybe 20 years ago the average engine was still mostly factory & in reasonable balance , they were balanced from the factory & they did a decent job of it but i`m sorry mate but these days if you don`t have it balanced then you will find out at some stage that you should have i`m rebuilding a little 850 engine for a fella at the moment & i`ll be balancing the guts of it too mate,,, yep even a little old 850 donk is getting the right treatment like i said earlier Greg,,, if you don`t do it then how do you know what is (or isnt) in balance ,,, or """"how far"""" out of whack it is?????????? How many people would you like me to point you to, who have recently experienced this same problem?... some of them are reading this i bet 
Now,,, in saying all that, i can say that i wouldn`t bother balancing my own 1510cc engine when i throw it back together,,, because it`s already been balanced when i originally built it,,, so there are some exceptions obviously if you had a donk that was perfectly singing at high revs withy no bad vibes at all then cool... obviously no cracked crank or out of whack balance at all ,,, so you would just rebuild it without re-balancing it right??? Me too Greg... Me too. But lets be smart here ,,, if you didn`t know the previous life of an engine,,, & you had to rebuild 5 or 6 of these un-known history mini power units a year (every year for many many years)... & you can sit at your computer telling some fella who you don`t even know,,, about an engine you have absolutely no idea about,,, never even seen or heard it before ,,, let alone never even driven it before,,, & you are going to say "don`t bother to balance it"???? sorry,,, i can`t do that Greg. |
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| Author: | Lillee [ Tue Jun 25, 2013 10:48 am ] |
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low'n blown wrote: Are you telling me every engine you build you get everything balanced????? Really Matt??????
It isn't rocket science...  All you need is a crank balancer and a set of scales, belt sander and bench grinder (and know-how)
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| Author: | norton [ Tue Jun 25, 2013 3:20 pm ] |
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When checking crank journals when does one draw the line and say this one needs a regrind ? is any amount of ovality ok ? And I was once told if you run your thumbnail across the surface and can feel grooves it needs a grind, not real scientific |
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| Author: | TheMiniMan [ Tue Jun 25, 2013 3:56 pm ] |
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norton wrote: When checking crank journals when does one draw the line and say this one needs a regrind ? is any amount of ovality ok ? And I was once told if you run your thumbnail across the surface and can feel grooves it needs a grind, not real scientific
yeah you really do want them to be round yes
& if there`s grooves that you can actually feel,,, then maybe just a linish will not cut it & it would usually need a grind ... so yes, more than likely. |
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| Author: | drmini in aust [ Tue Jun 25, 2013 4:09 pm ] |
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I'd say any more than .0005" (1/2 a thou) of ovality, and it needs a regrind. And IMO a centre oil pickup is a great investment, I've seen a lot of cranks over the years with bad big end journal ovality (worst was .007") purely due to oil starvation. On roundabouts particularly, the oil runs away from the stock pickup if the level is at all low. If you can't afford a centre pickup, add an extra 1/2 L of oilz above the full mark. 
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