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What Should I Rebore My 1300 Metro Engine To And What Pistons Should I Buy?

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#1 olliewiltshire

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Posted 17 January 2016 - 12:24 PM

Hello guys,

I'm currently feeling a bit lost! I have a 1300 metro engine with a few mods which I will list in a moment! It was already rebuild with new piston rings before I brought it and they seem to now have given up on life also. I am looking to rebore up but I'm not really sure what are my choices and what Pistons to get for my current mods! Is there anyone that could help me with this as I am a little out of my depth and not sure where to go from here!
My current Pistons have this number on them "21963 7 N39" which I believe to be the standard piston (correct me if I'm wrong). They are also engraved with a big little "B" on them! My current spec is :
mg metro 1300
ballanced crank
286 kent cam
Metro turbo oil pump
MED ST1 ultra light assembly
hif 44 carb (k&n filter, 100" needle)
city e diff
cooper spi stage 4 head
Duplex timing chain
65DM4 Distributor
Radtec alloy radiator (extreme version)
Stage 2 maniflow manifold
Brake disc conversion
Mini sport Stage 1 exhaust
Spaz shocks

If any one could help guide me that would be great :)
Thanks
Ollie

#2 Bulatovic

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Posted 17 January 2016 - 01:13 PM

I've got a set of these lovely pistons (+040). willing to sell if you're interested:

http://dt-vps.co.uk/...&product_id=108

I doubt you can go much better than that other than going for forged omegas

#3 olliewiltshire

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Posted 17 January 2016 - 01:28 PM

W

I've got a set of these lovely pistons (+040). willing to sell if you're interested:
http://dt-vps.co.uk/...&product_id=108
I doubt you can go much better than that other than going for forged omegas


Would I need to get it re bored for these? How much would you sell them for mate?

#4 Bulatovic

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Posted 17 January 2016 - 02:07 PM

You'd need 2nd overbore from standard +040. +020 is the first overbore.

PM'd

#5 sonikk4

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Posted 17 January 2016 - 02:09 PM

Go the next size up so if standard +0.020" = 1293. This then gives you plenty of life left in the block for future rebores.



#6 gazza82

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Posted 17 January 2016 - 04:52 PM

You need to match the piston dish to avoid altering the CR too much.

But these are same piston type ... http://www.minispare....aspx?pid=37860

You should (or get someone to) measure bores to see if you really need a rebore ...

Edited by gazza82, 17 January 2016 - 04:59 PM.


#7 Fast Ivan

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Posted 17 January 2016 - 05:31 PM

I'm not sure how well the spi will cope with a 286 cam, emissions will be an issue I would have thought 

 

EDIT: I assumed it was an spi due to the head spec?


Edited by Fast Ivan, 17 January 2016 - 05:35 PM.


#8 Cooperman

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Posted 17 January 2016 - 08:48 PM

For a 286 cam you need pistons which will run to just under 7000 rpm without failure. Maximum power will be at 6400 rpm, so change up will be at 6800 rpm. For this a better quality piston will be needed. Omega do excellent pistons. I use Karl Schmidt pistons with my 286 cam. They are very expensive but will take over 7500 rpm.

To keep it 'on the cam' will require a straight-cut close ratio gearbox and a low FDR, a 3.76:1 or lower. The 'City E' final drive will be absolutely hopeless as it is far, far too high. A 286 must have a very low FDR and CR gear set or it will simply 'bog down' between gears.

This will be ideal for competition, but it will not be a good road car with a 286 as it will be revving high all the time. If it is not revving a lot, then it will not be giving of its best and a 276 or even a 266 would be better.



#9 Spider

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Posted 17 January 2016 - 11:11 PM

The Hypertec Pistons will run to 7200 RPM, no risk at static CRs up to 10.5:1 CR (and a Dynamic CR of 8.7:1)

 

Attractively priced too, I use them in probably 95% of my builds.



#10 Mini Manannán

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Posted 18 January 2016 - 01:21 AM

Especially when they're New Old Stock eh Chris?! :D



#11 Mini Manannán

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Posted 18 January 2016 - 01:21 AM

The Hypertec Pistons will run to 7200 RPM, no risk at static CRs up to 10.5:1 CR (and a Dynamic CR of 8.7:1)

 

Attractively priced too, I use them in probably 95% of my builds.

 

Especially when they're New Old Stock eh Chris?!  :D



#12 nicklouse

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Posted 18 January 2016 - 09:24 AM

Hello guys,

I'm currently feeling a bit lost! I have a 1300 metro engine with a few mods which I will list in a moment! It was already rebuild with new piston rings before I brought it and they seem to now have given up on life also. I am looking to rebore up but I'm not really sure what are my choices and what Pistons to get for my current mods! Is there anyone that could help me with this as I am a little out of my depth and not sure where to go from here!
My current Pistons have this number on them "21963 7 N39" which I believe to be the standard piston (correct me if I'm wrong). They are also engraved with a big little "B" on them! My current spec is :
mg metro 1300
ballanced crank
286 kent cam
Metro turbo oil pump
MED ST1 ultra light assembly
hif 44 carb (k&n filter, 100" needle)
city e diff
cooper spi stage 4 head
Duplex timing chain
65DM4 Distributor
Radtec alloy radiator (extreme version)
Stage 2 maniflow manifold
Brake disc conversion
Mini sport Stage 1 exhaust
Spaz shocks

If any one could help guide me that would be great :)
Thanks
Ollie

My thoughts.

not knowing what a stage 1 Minisport exhaust is and there is only a passing comment on the manifolds.

get the good inlet manifold or mod your current one. exhaust manifold/exhaust. Big is not best.

diff 3.44 is what you want.

 

bore and pistons. depend on the CC in the head and if you can also have that worked. and the expected revs for the cam.

 

so you need to do some math to work out what you have now and how you are going to get to where you need to be.

 

and I hope you are not a city driver as that cam will be a pain.

 

finally the turbo oil pump. some say it does too much.



#13 Dusky

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Posted 18 January 2016 - 10:06 AM

Funny that the FDR vs cam comes on here today. 

Had a nice 'discussion' with someone on facebook yesterday. Apperently running a 300° cam with a 2.7 diff . 

Glad that there is some sense spoken here atleast, facebook seems to be full of 150 bhp stage 1 mini 998's! * rant over*

 

For pistons I use 21253 in my engine, AEG 643 cam and a ported 35X29 valve head. 
Turbo pump sounds a bit much to me too, especialy as the new minispares pump ( the cheap one) pumps more litres/ minute than the rover turbo pump ( calverst site has some flow figures)

 

I would also advice using a recurved distributor ( Ac dodd does this service) or get a alson yellow ( with vac for any road going engine)

 

cheers



#14 Cooperman

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Posted 18 January 2016 - 11:19 AM

Cam choice is determined by the intended use of the car. For a road car the 286 is entirely inappropriate. It needs to be kept at over 4500 rpm and ideally between about 5500 and 7000 rpm if it is to show any benefits over a 266 or a 276.

To stay 'on the cam' a closer ratio gear set is needed which means a higher 1st gear. In turn this dictates a low FDR in order to be able to pull away with decent acceleration and not too much clutch slipping.

That is why the old Special Tuning Close ratio gear sets are used and these seem to be available only in straight-cut form these days.

I found a 3.44:1 far too high for pulling away and after just one event with that set-up I fitted a 3.9:1 in my 'S', but I reckon if you are not pulling away up any steep hills a 3.76:1 would work. That gives a cruising speed of about 15 mph/1000 rpm in top gear- so not a main road cruiser. But then, you don't fit a 286 for road cruising, you fit it for ultimate performance in a rally car.

Too many cars have their driving characteristics spoiled by being 'over-cammed' and there are some really 'nice' road cams which give improved torque and power exactly where it is needed. That is from about 2500 rpm up to 6000 rpm with smooth initial 'pull' from about 2000 rpm.

There are cam graphs to enable the correct selection to be made.



#15 Carlos W

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Posted 18 January 2016 - 11:23 AM

Cam choice is determined by the intended use of the car. For a road car the 286 is entirely inappropriate. It needs to be kept at over 4500 rpm and ideally between about 5500 and 7000 rpm if it is to show any benefits over a 266 or a 276.

To stay 'on the cam' a closer ratio gear set is needed which means a higher 1st gear. In turn this dictates a low FDR in order to be able to pull away with decent acceleration and not too much clutch slipping.

That is why the old Special Tuning Close ratio gear sets are used and these seem to be available only in straight-cut form these days.

I found a 3.44:1 far too high for pulling away and after just one event with that set-up I fitted a 3.9:1 in my 'S', but I reckon if you are not pulling away up any steep hills a 3.76:1 would work. That gives a cruising speed of about 15 mph/1000 rpm in top gear- so not a main road cruiser. But then, you don't fit a 286 for road cruising, you fit it for ultimate performance in a rally car.

Too many cars have their driving characteristics spoiled by being 'over-cammed' and there are some really 'nice' road cams which give improved torque and power exactly where it is needed. That is from about 2500 rpm up to 6000 rpm with smooth initial 'pull' from about 2000 rpm.

There are cam graphs to enable the correct selection to be made.

 

the other issue is, if you're going to start revving to 7000rpm you're going to want a fully balanced set up. 

 

And then there's engine wear.......







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