19 replies to this topic

[martin_mini]

I tried to find this topic, but I couldn't find it anywhere. I apologize in advance if I am asking this question the 100th person.

 

 

A brief description about my engine. It is a 12A2AG01 engine and my head is 12G940.

 

I have a stage 1 kit. Full exhaust systems with Twin HS2 Carbs (1.25"x 2) both fitted with cone K&Ns. Others are stock.

 

by the way, I am going for a "mildly to fast everyday use ROAD CAR"  not HARDCORE so low rpm range 80-90 percent of the time

 

I have another topic about thinking of changing a 1.5 Rocker, but our friends seemed to disagree and enlighten me with changing a cam is whole lot better. SW5-07 or Kent 266

 

Today I discussed with a local shop. They mentioned about uprating the valves and go for a 35mm IN / 29mm EX

 

 

 

My question for you guys are should I:

 

 

1. Go for ONLY O/S valves 35/29?

2. Go for ONLY SW5-07 kit or Kent 266 kit?

3. Go for BOTH cam change and O/S valves?

 

Please also state reasons why you think your choice is best. I plan to install all of this when I do a full rebuild overhaul (cleaned, relube, polish head).

 

 

Your help and opinions will be highly appreciated.

Edited by martin_mini, 13 October 2016 - 12:45 AM.

[nicklouse]

well the head is the biggest restriction so a worked head with bugger valves will make a big difference.

 

cam it depends on what is in the engine now. what did it come out from?

 

if you are going to change the cam then you may as well overhaul the engine as you will need it out and split.

 

I would not bother with 1:1.5 rockers on a low revving road car.

[nicklouse]

and a decent exhaust is a must.

[carbon]

The 35/29 valves in mildly ported head together with MD 266 cam work well for me, with valve lift of 8.0mm at the valve.

 

This is on a 1293 with twin HS2s, Maniflow Freeflow + twin box RC40. CR = 9.8:1

 

Also running distributor with modified advance curve - if you don't modify the advance curve the engine will likely run like a dog

[martin_mini]

The 35/29 valves in mildly ported head together with MD 266 cam work well for me, with valve lift of 8.0mm at the valve.

 

This is on a 1293 with twin HS2s, Maniflow Freeflow + twin box RC40. CR = 9.8:1

 

Also running distributor with modified advance curve - if you don't modify the advance curve the engine will likely run like a dog

 

Thanks Nicklouse.

 

Carbon, I find that my setup will be going the same path as yours only mine is standard 1275cc. About "running distributor with modified advance curve" which distributor did you buy? did you buy the performance distributor ones from minisport?

If so please share me a link. Thank you so much.

 

I am still looking forward for other opinions! Thank you.

[Dusky]

Aldon yellow should work well here.

[carbon]

Aldon yellow distributor has 12 deg of mech advance, and for 266 cam the Aldon Yellow version with vacuum advance is the one to go for. This should work OK for your 1275 with 266 cam using the A+ sintered rockers that give quite low valve lift. Suggest 8 deg static timing (plus 24 = 32 deg at max advance) with this set-up.

 

If you go to 1.25 or 1.3 rockers then a 1275 with 266 cam is likely to need more advance at tickover and low rpm, but about the same at higher rpm. I'm running 1.25 rockers and this is using distributor with 10 deg of mech advance. Suggest 12 deg static timing (plus 20 = 32 deg at max advance), and the springs are one very weak primary spring and a medium secondary spring giving advance all in by about 3000-3500rpm. Vacuum can is 4-11-7 type.

 

Suggested timings are all using Shell V-Power 99 octane.

 

The distributors I use are ones I have modified from suitable Lucas 25D base units, but it's possible to do same mods with most other Lucas distributors.

 

I'm still using points as I have never had issues with them for fast road use and can't be bothered to change to electronic.

[martin_mini]

*bump*

[nicklouse]

*bump*

why bump it what more info do you need than has been given?

[nicklouse]

ok lets remind people about your other topic.

 

http://www.theminifo...-roller-rocker/

 

first thing that you must understand a GOOD engine is built from matched parts and that starts with the cam. everything else is then done to make that single item work as it should.

 

so you change the cam, that will work best with a certain Compression Ratio so then you have the head worked on with suitable valve sizes and modified chamber and then skim head or block to get the correct CR which or how much from which depends on many things and should be decided by the engine builder.

 

high lift rockers on a road car nope.

 

but the correct valve springs for the cam are a must.

 

so who is building your engine? do they know much about the A series or are they relying on you to provide the info?

[martin_mini]

ok lets remind people about your other topic.

 

http://www.theminifo...-roller-rocker/

 

first thing that you must understand a GOOD engine is built from matched parts and that starts with the cam. everything else is then done to make that single item work as it should.

 

so you change the cam, that will work best with a certain Compression Ratio so then you have the head worked on with suitable valve sizes and modified chamber and then skim head or block to get the correct CR which or how much from which depends on many things and should be decided by the engine builder.

 

high lift rockers on a road car nope.

 

but the correct valve springs for the cam are a must.

 

so who is building your engine? do they know much about the A series or are they relying on you to provide the info?

 

Thanks Nick for the reply. A local shop here in Thailand is building the engine. From what I noticed, the builder is quite experienced.

 

But I am asking for infos so I have I will have a pretty clear view on what I will have to face next. I live all the way in Thailand and local shops here doesn't supply us with lots of parts. Therefore if I want to modify anything I have to understand on what I have to buy, so I can order and hand it over to local builder. Local builder may have some parts but doesn't come cheap.

[carbon]

Would recommend reading through a copy of David Vizards 'Tuning the A-Series Engine'. This covers a lot of the key issues with tuning the classic Mini and is a really good starting point.

 

But it's very unlikely that any modified engine will perform well 'out of the box' unless it is set up correctly. And this is where in addition to a good engine builder you really need a competent rolling road operator who has access to all the parts you will need

 

For tuning you will need a suitable selection of SU needles and paired dashpot springs as a minimum, as you're talking about using twin HS2s. You will probably also need some distributor advance springs if you want to get the advance curve correct.

[mikal]

Go Stealth box with programmable ignition advance curve. Awesome bit of kit. Just fitted one, car goes like a scalded cat...

Also very reasonably priced. $240 all up in Australia, no idea in your money but then the pound drops daily!

[ryomini]

Like others have said a different profile cam WITH a tuned head and springs (assuming the head is good and the valve guides are good and the cam bearings are good etc)  - more money and a balanced crank

I use a slightly lightened flywheel and I just love the lighter feeling of the engine, very easy for town and with the higher rpm also a good little cruiser

your FD ratio will also decide if you want acceleration or better fuel economy

 

I am under the impression that some people believe just changing the cam makes a big difference - unfortunately it is not so

[martin_mini]

Like others have said a different profile cam WITH a tuned head and springs (assuming the head is good and the valve guides are good and the cam bearings are good etc)  - more money and a balanced crank

I use a slightly lightened flywheel and I just love the lighter feeling of the engine, very easy for town and with the higher rpm also a good little cruiser

your FD ratio will also decide if you want acceleration or better fuel economy

 

I am under the impression that some people believe just changing the cam makes a big difference - unfortunately it is not so

 

Thanks Ryomini, I assume you have 1275, SW5-07 cam, home ported, steel flywheel. I have a 3.44 FD what about yours?