ausmini
https://ausmini.com/forums/

crank end float / thrust bearings
https://ausmini.com/forums/viewtopic.php?f=5&t=17850		 Page 1 of 1
Author:  simon k [ Mon Apr 03, 2006 10:42 pm ]
Post subject:  crank end float / thrust bearings
my engine reconditioner ordered new thrust bearings for me, and after I put the motor together I've found that they don't have any end float - one side has .001" and the other side I can't get my .001" feeler guage in.... so I'd say I need some that are a wee bit thinner - they only cost $12 for the set, so am I right in thinking I'm better off buying new ones than breaking out the oilstone?

UNLESS there's a special method to measuring the end float - something different to put them in, put the centre bearing cap on, and stick a feeler guage between the bearing face and the crank web... :?: :?

I measured it with the caps torqued down, and without

I don't want to wreck anything else....

another one - is there anything special about big end nuts? the motor had some normal looking nylocs, so I went to coventry fasteners and bought some new ones, browsing the karcraft catalog they're $17 each... ? solid tungsten or what??
Author:  drmini in aust [ Tue Apr 04, 2006 7:35 pm ]
Post subject:  Re: crank end float / thrust bearings
skssgn wrote:
my engine reconditioner ordered new thrust bearings for me, and after I put the motor together I've found that they don't have any end float - one side has .001" and the other side I can't get my .001" feeler guage in.... so I'd say I need some that are a wee bit thinner - they only cost $12 for the set, so am I right in thinking I'm better off buying new ones than breaking out the oilstone?

UNLESS there's a special method to measuring the end float - something different to put them in, put the centre bearing cap on, and stick a feeler guage between the bearing face and the crank web... :?: :?

I measured it with the caps torqued down, and without

I don't want to wreck anything else....

another one - is there anything special about big end nuts? the motor had some normal looking nylocs, so I went to coventry fasteners and bought some new ones, browsing the karcraft catalog they're $17 each... ? solid tungsten or what??

Simon,
You want .003" bare minimum, do not believe anybody who says you want less. I have the (almost) spun centre main shells to prove what happens at Wakefield Pk running .003".. :cry:
If you are going to do anything but potter about, I would want .005".
My 1360 now is running .006", which is around what GR recommends.

Most accurate measurement method is put a dial gauge on end of crank, torque the bearings all up, then pry the crank each way with a screwdriver.

GR says those new thrusts have the p/no stamping on the back which makes them appear thicker, paper them off first.
I get mine surface ground, as I have thin ones (S crank in 1300 auto block).

Those S big end nuts are aircraft grade steel, not the usual chinese nylocs...
they are worth it.
Personally, I now only use ARP bolts & nuts, either the S set or the BB Ford ones.
The latter will fit with very minor mods, and you get 16 for $100+ rather than 8 for $174. 8) p/no is 155-6002
Author:  simon k [ Tue Apr 04, 2006 9:00 pm ]
Post subject:  Re: crank end float / thrust bearings
thanks Kev....

drmini in aust wrote:
You want .003" bare minimum, do not believe anybody who says you want less. I have the (almost) spun centre main shells to prove what happens at Wakefield Pk running .003".. :cry:
If you are going to do anything but potter about, I would want .005".
My 1360 now is running .006", which is around what GR recommends.


I think I've heard (read) you say that before....

drmini in aust wrote:
GR says those new thrusts have the p/no stamping on the back which makes them appear thicker, paper them off first.



I checked that after I read GR's article in TME - they were flat, but still too thick. I went and saw my reconditioner today and he said the oil stone is the go

drmini in aust wrote:
Those S big end nuts are aircraft grade steel, not the usual chinese nylocs...
they are worth it.

went back to coventry's this morning and made sure I had high tensile ones - which I do.... safe?

drmini in aust wrote:
Personally, I now only use ARP bolts & nuts, either the S set or the BB Ford ones.
The latter will fit with very minor mods, and you get 16 for $100+ rather than 8 for $174. 8) p/no is 155-6002


what are the mods and is that a karcraft part number? I'm guessing that the mods might be to grind the head off the bolts to fit into the rod?

I'm a bit worried about the main bearing studs too.... do they ever let go?
Author:  drmini in aust [ Tue Apr 04, 2006 10:30 pm ]
Post subject: 
If those nuts are hi tensile that's great, but ask them what the grade is. Grade 8 should be OK.But be aware that lots of dodgy fasteners are coming out of Asia now.

That part no is the ARP number for the Ford bolts & nuts, not Kc's.
The heads are a little wide one side, 10 secs on a linisher fixes that.
I got them from http://www.vpw.com.au/

Cooper S main studs are good, you might fit ARPs for a racer but otherwise the stock ones are fine.
Same goes for the main cap bolts used in all other 1275s.
Author:  simon k [ Thu Apr 06, 2006 7:45 pm ]
Post subject: 
thanks Kev - you're a star ;)
Author:  Lillee [ Fri Apr 07, 2006 9:28 am ]
Post subject: 
While we are on this topic, I was reading my mini service manual from 1972 in bed last night (as you do) and it clearly says end float must be set between 0.003 and 0.008. So setting it to 0.003 is like the absolute limit lower limit. Kev's suggestion of 0.005 or 0.006 sounds much better...
Author:  TheMiniMan [ Mon Apr 10, 2006 7:02 pm ]
Post subject: 
Kev has it right, do what he has suggested,

But !!!---->also i allways set the lower thrust clearance with way more than the uppers (more like 10-15thou for the lowers & 5thou for the uppers) this way the crank doesn`t push as much on the main cap when it flexes,,,the most of the thrust work is then spent on the block instead of the cap allowing for much more prolonged main cap & bolt life & loweres are basically only left in there to hold the uppers in place.

some people prefer to use 4 bolt main caps &/or main cap straps instead, but i don`t see any reason to bother with all that.

easy-peasy
Author:  smac [ Tue Apr 11, 2006 6:17 am ]
Post subject: 
Upper and lower relative to when the engine is in place, or when you're working on it?!
Author:  drmini in aust [ Tue Apr 11, 2006 5:28 pm ]
Post subject: 
Matt means make the clearance looser on the cap thrusts... :wink:
Personally I reckon that reduces the bearing thrust area by 50%, but whatever floats yer boat... :lol:
Whatever, just don't make em tight. Des hammill's books reckon .001-.002" is OK, it's plain to see he's never raced one!


BTW my 1310 (which I used to spin to 8K) had .012" end float when stripped for a piston problem, the thrusts and S crank were still in perfect condition.
Crank (untouched) is now spinning again in my 1360. :P
Author:  simon k [ Tue Apr 11, 2006 6:20 pm ]
Post subject: 
well, I set them at .004", and the top ones were tighter than the bottoms, so I should be doing OK :D

the motor will be lucky if it ever sees 6k rpm the way dad drives...
Author:  TheMiniMan [ Tue Apr 11, 2006 10:52 pm ]
Post subject: 
i`d rather 50% less thrust area than a walking main cap

heaps & heaps of engines only have upper thrusts these days anyways
Page 1 of 1 All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/