21 replies to this topic

[1275austin]

. The guy i am sourcing the pistons from also has a cam from a metro so i am planning on fitting that as well.

Dont want to sound patronising, but, we assume its from an MG Metro or sport or Vanden Plas,not just any old Metro. They're just Mini cams in Metros otherwise.Better check,there are identification marks to tell you. Well done with the sleeving etc

yes its an mg metro cam

[1275austin]

That's good advice from Doug. With regard to your block, don't go to 1380 as it effectively renders the block unsuitable for further boring later and they are never going to make any more blocks, at least not at a sensible price.
If necessary, there must be machine shops in Canada who can do engine re-boring. If it won't clear the score at +0.060" best advice is to have the engine sleeved back to 1275 and fit new P21253 standard pistons. Sleeving is a very common practice and some Minis even came new with sleeves. It effectively gives your block a fresh start with full re-build capabilities in the future.
With regard to the cam, the Kent 266 is very good for road driving (as opposed to real competition). it's almost identical to the MG Metro cam. However, to make such a cam work well you do need a head with some gas-flowing done and the 35.6 mm inlet & 30.5 mm exhaust valves, plus good induction and exhaust systems.

http://i1165.photobucket.com/albums/q584/rydermann/MiniParts.jpg

Here is a picture of new parts ive got a hold of. Mg metro cam, 73mm Dished pistons, new timing chain, new oil pump etc...
Still need to get a cylinder head figured out. Not sure if i should see about having my stock head machined and ported or try and track down one that is already performance built ie an mg metro head or similar. Would you still recommend those valve sizes with the bigger pistons fitted? What would be an optimum compression ratio to have for this engine spec? Thank you!

[ACDodd]

I have settled on a figure of 9.75:1 with the MG metro cam and get better results than running 10:1 or higher.

[Cooperman]

Yes, 9.75 to 10:1 will be good with current pump petrol. Any higher and you will probably need an octane booster.
It's surprising how much improvement the larger valves give when complemented b y a light clean-up of the rough mis-matched areas in the combustion chamber and part-removal of the valve guide bosses in the inlet & exhaust tracts.
73 mm pistons will give 1360 cc. Strictly speaking you should offset-bore for that size, but if you are sleeving one cylinder that may not be an option. IMHO the best option would be to have all 4 cylinders sleeved and fit 21253 pistons at standard size. That way you have 'saved' a block for further re-boring. A 73 mm bore without offsetting will not allow any further re-boring and the block would probably then be scrap.
However, 73 mm would work OK so long as you use a really top quality head gasket as the land between cylinders 2 & 3 will be very small.
Good luck with the re-build.

[1275austin]

Yes, 9.75 to 10:1 will be good with current pump petrol. Any higher and you will probably need an octane booster.
It's surprising how much improvement the larger valves give when complemented b y a light clean-up of the rough mis-matched areas in the combustion chamber and part-removal of the valve guide bosses in the inlet & exhaust tracts.
73 mm pistons will give 1360 cc. Strictly speaking you should offset-bore for that size, but if you are sleeving one cylinder that may not be an option. IMHO the best option would be to have all 4 cylinders sleeved and fit 21253 pistons at standard size. That way you have 'saved' a block for further re-boring. A 73 mm bore without offsetting will not allow any further re-boring and the block would probably then be scrap.
However, 73 mm would work OK so long as you use a really top quality head gasket as the land between cylinders 2 & 3 will be very small.
Good luck with the re-build.

Thank you, if i run premium petrol will that allow me to run a higher compression for more performance? Or is it not worth it? I did not think offsetting for 73mm pistons was necessary? If my engine at some point needs further reboring in the future cant i just sleeve the cylinders next time and start over? I thought this route would be cheaper because i only needed to purchase one sleeve and i had the 73mm pistons made readily available. Plus the added power and torque of a large bore. Yes the head gasket i have is very high quality i was told. I have the number for a cylinder head machinist with a flow bench and i am wondering in your opinion do you think it is a better choice to take my stock head to him and have the modifications you suggested done to it, or is it better to try and source a ready built performance head from say MiniSpares or somewhere. Im just weary about taking an A series head to a machinist here as minis are not nearly as common in Canada and i dont know if my money would be well invested unless the machinist had flow maps proven to make horsepower. Thank you? oh also would 1.5 rockers and a lightened flywheel be a good addition to this spec?

[dklawson]

I understand your concerns about the cylinder head.

I would contact the folks at Seven in CA and ask them what they can offer for a performance head. Yes, you could order one from the U.K. but shipping charges will be very high. Remember Seven is at least in North America and they are affiliated with Fortech Racing. They can provide you a performance head.

[1275austin]

I understand your concerns about the cylinder head.

I would contact the folks at Seven in CA and ask them what they can offer for a performance head. Yes, you could order one from the U.K. but shipping charges will be very high. Remember Seven is at least in North America and they are affiliated with Fortech Racing. They can provide you a performance head.

Okay i have emailed them, thank you. Im going to also contact the guy i bought the pistons from and see what he can do about a head for me if i choose to not have mine machined. Hes rather remarkable, been racing and building minis for over 30years. His race mini is 958Lbs and makes 135Hp. (claimed its the fastest in North America) He has contacts all over for many different mini parts he may be able to get me a head at a decent price.