21 replies to this topic

[matthew_leech]

Looking for some quite broad yet detailed advice here!

First ill explain how this has all come about. In my clubman estate (see my thread in my signature) I have the original low mileage 1098 engine. A cracking, very reliable unit. With just me in it feels nippy around town. However on the open road the final drive results in the engine revving too high, a comfortable and economical speed being around 50-55mph. Disregarding the engine noise the shell has been comfortably to 80, above that is a little hairy 

Currently I am interested in taking Noddy (my mini) to the Alps and driving around the Riviera into Monte Carlo ect. For this Noddy would need more go. And be able to cruise nearer 70 mph.

So, here came about the engine build I am currently doing.

In a nut shell the engine needs to be a sort of “sports tourer” 80bhp and similar torque, region. But it has to be reliable.

These are what I already have for this build:

90s cooper A+ 1275 engine – going to need a rebore to 1293 & crank regind.

Gearbox – going to be a guesswork’s rebuild, 3.1 final drive (a compromise between top speed and acceleration)

1.5 roller tip rockers – impulse buy, not sure if they will be used

Hiff 44 carb – rebuilding this currently

It will have a full maniflow exhaust too (not yet purchased)

The normal freeflow inlet and airfilter.



Now for my questions 

Cam shaft – what do you recommend? I still want a smooth idle, and usable power without having to scream the engine, I have the option of the 1.5 roller rockers too.

Cylinder head – to achieve the results I am after would a stage 3 be overkill? Just porting the standard head be enough?

Duplex timing gear – necessary?

Cros pin diff – necessary? Or will the hardened guesworks one be sufficient?

I am sure more questions will follow!



Thanks in advance,

Matt

[Jordie]

driveable engine been key requirement.....id go for something like

266 with 1.5 rockers should be ok.
stage 2 head, double valve springs
duplex not absolutely nessecary, but might aswell if your getting a adjustable set to time the cam correctly.
best person to ask would be GuessWorks i guess?

[jamiestevenbell]

i would go for the 276 cam and just sell the rockers to spend on better headwork, and go for a stage 3head, and imo its not worth debating weather or not to fit the duplex timing chain. Its just something i would have done anyway

[dklawson]

It's your choice really and you will need to start looking at costs to determine what is in your budget. I would think more along the lines of how you will use the car in the long term, not just on your upcoming trip.

I prefer cams with low-end torque rather than high-end power. That will equate more to acceleration than the ability to drive at high-speed. Therefore, the 266 cam or the SW5 might be nice along with changing the final drive to give you a bit taller gearing for highway cruising. Duplex timing gears... why not? 1.5 rockers? They are expensive and they transfer higher loads onto the tappets and cam lobes. Personally I would retain the regular rockers but it is your choice.

I would be interested in what others tell you about x-pin diffs. I am considering one myself.

[Cooperman]

I would go for an MG Metro or Kent 266 cam (they are almost identical). For the head, an MG Metro head with the 35.6 mm inlet valves would be good especially if the combustion chambers and inlet and exhaust tracts were to be smoothed and cleaned up. Set the compresion ratio at around 10.3:1 and use the HIF44 carb on an alloy inlet manifold with all the casting flash smoothed away.
The 3.1:1 FDR will be fine and a slightly lightened flywheel would be good too.
Think about a better distributor, like an Aldon 'Yellow'.
With regard to X-pin diff, I always use one in my rally cars, but for road cars I normally just buy a Mini Spares competition spec one.

[matthew_leech]

Thanks for all the great feedback.

with regards to how the car is going to be used, it will be used for fun and holidays. But be able have a bit of go if I feel like it. However the tourque, reliabilty and cruising speed are what I am ultimatly after. With that some extra power will be a by product. Plus anything will feel better than the standard 1098 which is in there currently.


Cost is not a major issue as this is my big splash out before saving for a house. I want to make sure what I do is 100% and will give the results I am after.


I have been doing alot of thinking about the final drive, my best friend has a sports pack, and that did cruise nicely, I am just wanting to retain some livelyness for the twisty bits. However if the engine spec gives the extra tourque to pull the longer gears then it would make sense to be able to cruise at a higher speed! - this is what i am most undecided on currently!

[Cooperman]

A 266 cam (or MG Metro) with either a 12G295 or a 12G940 (with valve clearance issues sorted) will give excellent road manners and will very well with a 3.2:1 or even a 3.1:1 final drive ratio. A lightweight flywheel will be good as well.

[MrBounce]

My Mayfair had a similar spec to what you're planning and it was a lovely engine. +30 1275 with a 266 cam, standard non-verto flywheel, an MED Road/Comp head and twin 1 1/4" SUs with K&Ns. I had it rolling roaded down at MiniSpeed back in 2002 and it was fantasticly smooth and tractable. 79BHP with similar torque. Would sit all day at 85 (on a private road officer). Diff was a 3.44 (gearbox was standard). So yes, I believe the spec you're suggesting will be exactly what you're after

[matthew_leech]

cooperman, you say with the metro head 12g940, that there will be clearance issues? what would these be and how would you suggest over coming them?

Edited by matthew_leech, 30 May 2012 - 09:42 AM.

[matthew_leech]

cooperman, you say with the metro head 12g940, that there will be clearance issues? what would these be and how would you suggest over coming them?

[jaydee]

cooperman, you say with the metro head 12g940, that there will be clearance issues? what would these be and how would you suggest over coming them?

On the 1098 it will need pocketing or other work-around, but on overbored 1275s cant be a problem as 940 is a 1275 head

[matthew_leech]

that what i was thinking!

all the work is going on the 1275, just keeping my 1098 in as it is for now!

I always keep everything original from the car, just incase i ever want to revert back to standard!

Thanks again!

[Cooperman]

Sorry, I didn't read the OP correctly and assumed it was a bored-our 1098.
The head you need is the 12G940 MG Metro head with the 35.6 mm inlet valves and, ideally, 30.5 mm exhaust valves, then cleaned up and gas-flowed a bit.
I built a 'blueprinted' 1275 engine for a rally Mini which had to have a 'standard' engine. It was a 1990 Cooper 1275 bored out to 1330 cc (max allowed under trhe regs. It had MG Metro Cam, MG metro head which was just 'cleaned-up' a bit, Aldon dizzy, cleaned up inlet manifold with HIF44 carb, Duplex timing chain, RC40 twin-box exhaust, centre-main strap, and a very accurate build in terms of cam-timing and parts matching. It gave 84 bhp at about 5700 rpm and was super to drive. It had a 3.44 final drive and did a timed 0 - 60 in 10.2 seconds in full rally trim (2 spare wheels, extra equipment, etc).

[matthew_leech]

sorry for the confusion my OP was a fairly large one, I just wanted to get across the end result I am after from this engine build.

Your engine you built there sounds like a very similar spec to what I am aiming for. I am really impressed with that hp ouput from that spec, I hope my build will achive that kind of output.

You mention the accurate build, I understand the cam timing, but could you expand on where parts were matched, and how this was done?

Thanks again!

[Cooperman]

All manifold joins were matched including the carb to inlet manifold and exhaust to head. I allowed a slight 'downwind step for the exhaust so that the exhaust flanges were just slightly bigger than the exhaust ports in the head. The cam was timed in at 2 degrees advanced from recommended, i.e. 104 degrees with the MG Metro cam, to allow for initial chain stretch. The block deck was machined to bring the pistons absolutely flush with the deck at TDC and the head was skimmed to give 10.5:1 C.R.
Although not strictly legal within the regulations for the rallying I was doing, I did slightly re-shape the head chambers to de-shroud the valves a bit and I removed the nasty step around the valve seats. I also slightly 'improved' the inlet & exhaust throats but left the surface with a roughish finish to keep it looking standard, especially where I ground some off the very intrusive valve guide bosses. I did actually shorten the valve guides by about 3 mm thus reducing their intrusion into the inlet & ex. tracts.
Inside the carb I did a bit of subtle improvement like removing a bit from the butterfly spindle and knife.edging the butterfly leading face.
I changed the piston rings for a set of 'Total-Seal' rings made by a company in Phoenix, Arizona. They have a 'gapless' 2nd ring and are fantastic. My friends in the USA who race aeroplanes use these type of rings in their race engines.
At the carb inlet I used a K & N filter with a 'stub-stack'.
Exhaust manifold had to be the standard 1990 Cooper twin down pipe set-up and I fitted a Maniflow twin-box centre-exit system to keep it quiet enough for rallying.
I changed the fan for a 6-blade export steel one.
Distributor was Aldon 'Yellow'.
'Blue-printing' is very labour intensive, but can make such a difference to final output. That is why well-built engines done by the engine-build companies are so expensive. A good blue-printed engine can give power similar to cheaply-built (thrown-together!) more highly-modified engines , but will give better road-manners and much increased reliability.
I hope all this helps you with yours.