| ausmini https://www.ausmini.com/forums/ |
|
| Cylinder head help... https://www.ausmini.com/forums/viewtopic.php?f=2&t=69666 |
Page 1 of 1 |
| Author: | miniman_998 [ Thu Mar 24, 2011 10:51 am ] |
| Post subject: | Cylinder head help... |
Running an 1098 out 60 thou, balanced bottom end with al the good bits and a pretty big cam. Currently running a 12g202 cylinder head with some porting, using extractors and a 1 1/2 su thats jetted to suit. Want to run a weber, and think i will upgrade the head to something better flowing again. What im after is advice on which head to go for...?? Pros and cons of these... Any help muchly appreciated. |
|
| Author: | drmini in aust [ Thu Mar 24, 2011 11:28 am ] |
| Post subject: | |
Either find a 12G295 head, or get your 202 ported to similar spec and bigger valves fitted. Russell Engineering does this in Sydney, I'm sure there are other Mini engine folks near you who do the same. Another alternative is to notch the block for exhaust valve clearance, then fit a 12G940 or 12G1316 head. These give good power with little work, but you will lose some low down torque. |
|
| Author: | miniman_998 [ Thu Mar 24, 2011 12:33 pm ] |
| Post subject: | |
Only other thing of concern i have us the crank is currently 40thou under... Doing some headwork isnt likely to over stress the bottom end? |
|
| Author: | Mike_Byron [ Thu Mar 24, 2011 5:56 pm ] |
| Post subject: | |
A crank ground to .40 isn't excessive. It really depends of how the car is driven. Thrashing will put a lot of stress on any crank. Spirited driving is not the same thing. A well developed engine that is balanced and with the right gear on it will spin to 7,000 quite easily and as long as its not a sustained 7,000 then a 40 thou grind is not a problem. Lighting up the tyres and dumping the clutch up the gears and down the gears places a big load on the crank regardless of its grind. Mike |
|
| Author: | Bubbacluby [ Thu Mar 24, 2011 6:22 pm ] |
| Post subject: | |
But being an 1100 crank i would NOT recommend you running it to 7000. All sorts of bad things happen to 1100 cranks at these revolutions. I wouldnt be keen on running it over 6000. |
|
| Author: | drmini in aust [ Thu Mar 24, 2011 6:34 pm ] |
| Post subject: | |
IMO 7000 is fine as a maximum, but not for continuous running. I used to buzz my 1220 with a std balanced, shotpeened 1098 crank to 8,500 back in 1968. Sure I cracked it eventually, but it took 20,000 miles of abuse. No, it didn't break. A crank at -.040" though, a lot depends on how smooth & big the corner radii have been ground on the journals. A 1098 is not the stoutest crank BMC made (but nor is it the worst- that award would go to the 803cc A30 crank). 
|
|
| Author: | Mike_Byron [ Thu Mar 24, 2011 6:37 pm ] |
| Post subject: | |
Yeah I did say well developed and balanced engine. I agree with Bubba but if all the bits and add ons arn't working together properly it wont spin to seven anyway. Mike |
|
| Author: | Bubbacluby [ Thu Mar 24, 2011 6:44 pm ] |
| Post subject: | |
I was basically just going on what happened to my brothers motor. 
Ive never had an 1100motor Didnt you have imp pistons or something like that in yours as well though Doc? |
|
| Author: | drmini in aust [ Thu Mar 24, 2011 7:04 pm ] |
| Post subject: | |
Bubbacluby wrote: I was basically just going on what happened to my brothers motor.
Ive never had an 1100motor Didnt you have imp pistons or something like that in yours as well though Doc? Yes back in the 60s us poor people couldn't afford 1275s, so we used to fit a balanced 1098 crank and rods, and offset bore the buggers to 68mm and fit Imp pistons. Imp pistons were cheap and available new, even Repco had them on the shelf. Sadly, not any more. Good ones from UK cost a bomb... if you can find them. Yes I know JP still makes some in SA, but I'd not use them in a performance Mini motor (PM me if you must know why)
|
|
| Author: | 850man [ Thu Mar 24, 2011 7:09 pm ] |
| Post subject: | |
Contact British Sporting Cars in Bendigo. Simon Young has had many years experience modifying mini heads and will be able to get the best out of your Mini. www.britishsportingcars.com.au/ If you want to come down to Melbourne you can use Martini Heads in Bundoora. I use him for all my head work and he has been producing quick Mini heads for 30 years, he knows all BMC heads very well and looks after a number of the Group N Race and Targa Tassie Mini heads too. www.martiniheads.com.au/ |
|
| Author: | 68Rusty [ Thu Mar 24, 2011 7:49 pm ] |
| Post subject: | |
drmini in aust wrote: Yes back in the 60s us poor people couldn't afford 1275s, so we used to fit a balanced 1098 crank and rods, and offset bore the buggers to 68mm and fit Imp pistons.
Imp pistons were cheap and available new, even Repco had them on the shelf. Sadly, not any more. Good ones from UK cost a bomb... if you can find them. Yes I know JP still makes some in SA, but I'd not use them in a performance Mini motor (PM me if you must know why) I still can't afford one Working towards it for one day though!
I am working on a 202 head myself, bought 31mm inlets and 29mm exhaust valves, mild porting. Road cam, 40mm delorto, LCB extractors and RC40 muffler, 100thou over pistons, balanced bottom end and a few other bits and pieces. From what I have read and asked this will be a good combination for a good reliable road motor pushing a 3.44 cooper S diff with some good torque. I will have to wait and see for now before I can let you know 
No mater which head you go with you need to get your compression up to get some decent results, many threads on this around the place. |
|
| Author: | miniman_998 [ Fri Mar 25, 2011 7:40 am ] |
| Post subject: | |
My engine was built by Simon at British Sporting Cars about 18mths ago. Its a fantastic engine that makes lots of torque and goes extremely well.. 110mph @ 7,000rpm in ideal conditions is as good as it will give. Only once and i wont take the poor old girl there again but certainly impressed... Simon did recommend not taking my engine over 6000rpm to assure it will last forever that way. The engine has proven itself time and time again. Its not fast by any means but makes strong power for what it is and thats what its all about for me... I guess putting the little thing up a hill and racing the clock is pushing me in a direction to seek a little more power... thanks kindy for all advice. I cant help but think id be best to leave the 1100 as it is, enjoy it and get myself a speced up 1275 for the most beneficial results. |
|
| Author: | miniman_998 [ Fri Mar 25, 2011 7:41 am ] |
| Post subject: | |
Compression is about 9.5:1 from what i can remember. All about the volumetric capacities 
|
|
| Page 1 of 1 | All times are UTC + 10 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|