| ausmini https://www.ausmini.com/forums/ |
|
| Gearbox update... https://www.ausmini.com/forums/viewtopic.php?f=2&t=17297 |
Page 1 of 1 |
| Author: | TimB [ Sat Mar 18, 2006 11:47 am ] |
| Post subject: | Gearbox update... |
The story thus far.... There were too many bits in my box that were past their useby date, would've been around $2000 to rebuild. (OUCH!) I've ended up with a change-over gearbox and had a 3.44:1 diff put in it for good measure. Now I'm checking a few things on the motor. I've inspected all the bearings which are showing some wear, copper starting to show but no grooving or nasties. Crank has been machined 10 thou in the past. The surfaces on the crank seem smooth so I'm going to order a set of bearings. The end float on the crank is 5 thou with standard set of washers, it has been suggested that I try and get this back a little with new washers. I'm also going to put in a doudle row timing set and new oil pump. Still haven't pulled the head off yet, conflicting opinions on whether or not to relpace rings. What's involved in replacing the rings? Can I do a compression test while the engine is out or does it need to be at operating temperature? |
|
| Author: | CPOCSM [ Sat Mar 18, 2006 1:12 pm ] |
| Post subject: | |
IMO do the rings while the motor is out. It is false economy otherwise. The rings are straight forward but lots of care is needed IOT not scuff the pistons. If there is any wear whatsoever on the skirts of the pistons - replace them. The Hypatecs are going cheap at the moment and are a pretty stable piston(weigh about 245gms with gudgeon pin). They are cheap but not nasty. Usually when you buy the piston set they come with rings(Hasting rings were with the ones I bought...). Good luck with the overhaul... Hooroo Rob Forsyth Miniot!! |
|
| Author: | drmini in aust [ Sat Mar 18, 2006 7:57 pm ] |
| Post subject: | |
.005" crank endfloat is fine for a performance 1275 (or bigger) motor, I had .002-.003" at Wakefield Pk and at 1000 miles from rebuild, ran the centre main as a result. 
When I pulled it down again, it had spalled the thrust washer surfaces and bits like fish scales were sitting in the bottom of box. These cranks flex a lot at high rpm- you are better with too much than too little. I gave it .006" this time. 
|
|
| Author: | TimB [ Sat Mar 18, 2006 9:56 pm ] |
| Post subject: | |
OH I hate these conflicting points of view, makes it hell for us beginners. Thanks for your view though Doc, what do you think considering it's a stocko 1100 and I drive like an old man? |
|
| Author: | drmini in aust [ Sun Mar 19, 2006 6:13 am ] |
| Post subject: | |
TimB wrote: OH I hate these conflicting points of view, makes it hell for us beginners.
Thanks for your view though Doc, what do you think considering it's a stocko 1100 and I drive like an old man? 3 or 4 thou, as 1100 cranks flex a bit too. don't go LESS than .003".
|
|
| Author: | CPOCSM [ Sun Mar 19, 2006 7:11 am ] |
| Post subject: | |
Doc - do they all flex the same or is it just a think with the A series(now you have me thinking...) Do the 998cc have the same issues - I am going to hazard a guess and say no. Hooroo Rob Forsyth Miniot!! |
|
| Author: | sumanovic [ Sun Mar 19, 2006 8:10 am ] |
| Post subject: | |
sorri 2 kill your forum...didnt kno wher else 2 post this... i been told that straight cut gearboxes are essential 2 for a mini, but some people have told me that they are difficult to drive... so very confused
could you clear this up for me please... sumanovic |
|
| Author: | Lillee [ Sun Mar 19, 2006 8:23 am ] |
| Post subject: | |
Unless you are making huge hp (120hp++ at the wheels) forget it...your are looking at big $$$$. Even then I'd still say try normal gearbox, if you break it then buy a SCCR... |
|
| Author: | sumanovic [ Sun Mar 19, 2006 8:27 am ] |
| Post subject: | |
oh ok, thanks for clearing that up 
have a gd one...im of to do study
sumanovic |
|
| Author: | drmini in aust [ Sun Mar 19, 2006 9:24 am ] |
| Post subject: | |
CPOCSM wrote: Doc - do they all flex the same or is it just a think with the A series(now you have me thinking...)
Do the 998cc have the same issues - I am going to hazard a guess and say no. Hooroo Rob Forsyth Miniot!! Rob, All A series cranks flex because they are 3 main bearing, even a 998. Maybe not as much. I'd not go below .003" for these either. The issue here is if the oil cannot get out of the centre bearing, via the thrust washers to lubricate them, the whole thing heats up and the oil can break down. I had heat marks in the centre main bearing cap of the 1360, and it went real close to spinning the shells. Lucky the crank just cleaned up at next undersize. No I wasn't giving it a big rev either... 
|
|
| Author: | Mike_Byron [ Sun Mar 19, 2006 9:31 pm ] |
| Post subject: | |
On the issue of rings - the older I get the more i tend to believe that if you have scuffed pistons then you also have bores that that have been worn into a oval shape. The cost of pistons doesn't vary much with size - ie 10 thou or 20 thous doesn't cost any more that standard sizes, and yes, they come fitted with rings. It costs about $100 for a next size rebore and by and large they chemically clean the block as part of the process. In any casre you are starting with an engine that you know to have good bores and therefore good compression. I know that the costs for "reconditioning" an engine can climb through the roof very quickly but.... if your going to re ring and use new pistons then also rebore. IMO |
|
| Author: | drmini in aust [ Sun Mar 19, 2006 10:03 pm ] |
| Post subject: | |
Right now, one Mini parts shop wants about $130 just for a set of rings, another wants only $175 for pistons AND rings. 
Add just $100-150 for a rebore and hone- and fitting rings alone makes less and less sense. If you want good performance, you just cannot beat straight round bores with the right piston clearance.
|
|
| Author: | Lillee [ Mon Mar 20, 2006 7:43 am ] |
| Post subject: | |
Yes a certain mini spare parts place is selling brand new hypertec pistons and rings for pretty cheap, check Ebay
|
|
| Page 1 of 1 | All times are UTC + 10 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|