How much power will this motor make?
Discussion
1380cc built by MED
Cross drilled and wedged crankshaft, all lightened and balanced including flywheel and rods
286 Kent Cam
Duplex timing gear and chain
1.5 Ratio high lift full roller rockers
MED Big valve stg 3 Head ported and polished
Twin Oil filters (before and after oil pump)
Straight Cut, Close Ratio Gearbox with 3.1.1 Final Drive
I am looking at a Mini that has this motor + gearbox installed.
It should be pretty fast, I assume... ? I have never driven a 1380, let alone one built like this.
I have heard nothing but good things about MED, so I assume it is reliable too?
Will the straight cut 'box be loud and annoying and make my ears bleed?
Cheers!
Cross drilled and wedged crankshaft, all lightened and balanced including flywheel and rods
286 Kent Cam
Duplex timing gear and chain
1.5 Ratio high lift full roller rockers
MED Big valve stg 3 Head ported and polished
Twin Oil filters (before and after oil pump)
Straight Cut, Close Ratio Gearbox with 3.1.1 Final Drive
I am looking at a Mini that has this motor + gearbox installed.
It should be pretty fast, I assume... ? I have never driven a 1380, let alone one built like this.
I have heard nothing but good things about MED, so I assume it is reliable too?
Will the straight cut 'box be loud and annoying and make my ears bleed?
Cheers!
You don't say what the induction system is. On twin 1.5" SU's and with good inlet & exhaust breathing you could expect up to c.115 bhp at the flywheel. You would need a really good dizzy to get that too.
With a S/C, C/R box you'll find a 3.1 final drive very high, even if you have 10" dia wheels. First will go on forever and you'll be slipping the clutch to pull away. With a 286 cam, big valve head, etc, I run a 3.9:1 on my Cooper 'S' and even then 1st can seem a bit high, especially if pulling away from rest up any sort of hill. I just have to spin the wheels until it finally grips. The problem is that it's not really going to pull cleanly below about 3000 rpm and will be very lumpy low down, but great at between 5000 and 6500, which is where the C/R box comes into its own. That's really a good spec for a rally engine where you run a low final drive just to get acceleration and are not too interested in untimate top speed. At 7000 rpm mine is doing just about 100 mph and that's quite enough on gravel!
And, yes, the S/C box is dreadfully noisy, especially if you have S/C drop grears as well.
With a S/C, C/R box you'll find a 3.1 final drive very high, even if you have 10" dia wheels. First will go on forever and you'll be slipping the clutch to pull away. With a 286 cam, big valve head, etc, I run a 3.9:1 on my Cooper 'S' and even then 1st can seem a bit high, especially if pulling away from rest up any sort of hill. I just have to spin the wheels until it finally grips. The problem is that it's not really going to pull cleanly below about 3000 rpm and will be very lumpy low down, but great at between 5000 and 6500, which is where the C/R box comes into its own. That's really a good spec for a rally engine where you run a low final drive just to get acceleration and are not too interested in untimate top speed. At 7000 rpm mine is doing just about 100 mph and that's quite enough on gravel!
And, yes, the S/C box is dreadfully noisy, especially if you have S/C drop grears as well.
Drive it. There are so many diffrent things that could have an effect. It is also depends what you are used to. I drive a 1380 but with larger valves and a 296 cam so that car would drive more easly than mine but if all you are used to is moden cars you may not like it.
With the gear box (also a 45 weber)and no carpet and insulation I find that I cant drive my car for to long with out ear defenders. With carpets and insulation it may not be to bad.
Drive it and see, it should at least be fun
With the gear box (also a 45 weber)and no carpet and insulation I find that I cant drive my car for to long with out ear defenders. With carpets and insulation it may not be to bad.
Drive it and see, it should at least be fun
If that motor doesn't make 110 bhp at the flywheel with that spec it hasn't been screwed together or set-up properly. It will make for a very quick road car, if tractability isn't your main priority. A shorter final drive would make it easy to drive at the expense of top end speed. I hope it isn't going to be daily driver, as it'll do your head in (The g'box quite literally) and you'll pay for the performance at the pumps. A softer cam would be my choice in an identical spec build for the road (SW5 or 266). With an SW5 It'll not be much slower in the real world, will run better low down and not chuck half your fuel out of the exhaust port until the thing comes on the cam.
Did any one mention emissions on a 286. Ho ho ho! What age vehicle is it going in?
One thing is for certain tho', it'll be a lot of fun
Did any one mention emissions on a 286. Ho ho ho! What age vehicle is it going in?
One thing is for certain tho', it'll be a lot of fun
With a standard gearbox, you may find that the box is not strong enough if you intend using the full power potential. Also, the standard gear ratios will be a bit wide for that spec of motor and you will find that you often are 'bogging down' in the wrong gear but that a change down means you are revving its proverbials off. The suggestion to change to a softer cam would, of course, solve all of these problems by increasing the low end torque and spreading the useable power over a wider power band, albeit with a loss of maximum top end power. Then a standard box could be OK. On a road car it is seldom that the full power of such a hot engine is ever used really.
I know it will mean a strip-down of the engine, but as a daily road car you would be rebuilding it fairly often anyway if left in the original quoted spec. I would think that around 20,000 miles between rebuilds would be a maximum if you use most of the power often.
I know it will mean a strip-down of the engine, but as a daily road car you would be rebuilding it fairly often anyway if left in the original quoted spec. I would think that around 20,000 miles between rebuilds would be a maximum if you use most of the power often.
Cooperman said:
With a standard gearbox, you may find that the box is not strong enough if you intend using the full power potential. Also, the standard gear ratios will be a bit wide for that spec of motor and you will find that you often are 'bogging down' in the wrong gear but that a change down means you are revving its proverbials off. The suggestion to change to a softer cam would, of course, solve all of these problems by increasing the low end torque and spreading the useable power over a wider power band, albeit with a loss of maximum top end power. Then a standard box could be OK. On a road car it is seldom that the full power of such a hot engine is ever used really.
I know it will mean a strip-down of the engine, but as a daily road car you would be rebuilding it fairly often anyway if left in the original quoted spec. I would think that around 20,000 miles between rebuilds would be a maximum if you use most of the power often.
Thanks for all of the info!I know it will mean a strip-down of the engine, but as a daily road car you would be rebuilding it fairly often anyway if left in the original quoted spec. I would think that around 20,000 miles between rebuilds would be a maximum if you use most of the power often.
Do you really think this motor is only good for 20,000 miles?! Wow.
If I go to a slightly milder cam, will that extend the motor's life much?
With a softer cam and not trying to use 7000rpm to wring the best out of it all the time - the absolute minimum the engine should do would be 60K. If not, you need to find a more competent engine builder. 100K isn't uncommon on an 85-90bhp A-series that has been screwed together with care and set up properly.
If you decide to to put that 1380cc motor in its current state of tune on a helical road box, don't worry about engine rebuilds,as you'll be rebuilding the box long before the motor needs any attention
If you decide to to put that 1380cc motor in its current state of tune on a helical road box, don't worry about engine rebuilds,as you'll be rebuilding the box long before the motor needs any attention
If you changed from 5-1 rockers to 3-1 and tuned the carb for torq and not power, this may give you what you want with out changing the cam. I had a mini making 85bhp sprinting and hillclimbing and the standerd gearbox was ok.
I would run it with the box it came with and see if its ok. If not then change the box but exept you will have to drive more gently and the box wont last so long.
I would run it with the box it came with and see if its ok. If not then change the box but exept you will have to drive more gently and the box wont last so long.
DanGT said:
If you changed from 5-1 rockers to 3-1 and tuned the carb for torq and not power, this may give you what you want with out changing the cam. I had a mini making 85bhp sprinting and hillclimbing and the standerd gearbox was ok.
I would run it with the box it came with and see if its ok. If not then change the box but exept you will have to drive more gently and the box wont last so long.
Torque breaks gearboxes not power.I would run it with the box it came with and see if its ok. If not then change the box but exept you will have to drive more gently and the box wont last so long.
The primary weakpoint on a mini transmission is a compbination of the Drop-gears and differential, strengthen one and you will more than certainly have to strengthen the other.
If you are wanting this for a road car (with regular driving), the above advice is sound just add a softer cam to that list, but at the end on the day its down to personal preference, do you prefer lumpy low end but peaky top or limited top but good bottom. Or somewhere in between?
If your gearbox has never been rebuilt, now would be the time while its out of the vehicle, additionally knowing you have a good box stands you in good stead for the future.
Interesting reading all this, I am taking notes for when (if ever) I get my motor stripped down and rebuilt (again)
My gearbox has a liking to crunch into reverse and I have been wondering about replacing it or putting up with it.
One thing that comes to mind; when you read various tuned engine suppliers bumf, the seem to sit the engine on a standard (rebuilt) box, without strengthening or maybe with a "crosspin(?)" diff.
Waiting for the bang?
My gearbox has a liking to crunch into reverse and I have been wondering about replacing it or putting up with it.
One thing that comes to mind; when you read various tuned engine suppliers bumf, the seem to sit the engine on a standard (rebuilt) box, without strengthening or maybe with a "crosspin(?)" diff.
Waiting for the bang?
If you think about it, it is not surprising that Mini gearboxes do't last long. That box was originally designed for around 30 bhp and to run on 80 grade gear oil. It's since been used with much more power and with thin engine oil to lubricate it.
The diff pin is another matter and the cross-pin seems like the answer to diff pin problems.
As above, a mild engine will last a long while if assembled properly. However, a 'hot' engine using loads of revs (say upwards of 6000 rpm a lot of the time) will require regular rebuilding to keep it fresh and reliable, and that's assuming only top-grade parts were used in the original build. However, the 'box will always be the weak point in reliability. The only real answer is a mild engine with a standard box for a road car to avoid the horrendous noise from the S/C gears. Alternatively accept regular box re-builds or learn to tolerate the whine from the S/C gears.
The diff pin is another matter and the cross-pin seems like the answer to diff pin problems.
As above, a mild engine will last a long while if assembled properly. However, a 'hot' engine using loads of revs (say upwards of 6000 rpm a lot of the time) will require regular rebuilding to keep it fresh and reliable, and that's assuming only top-grade parts were used in the original build. However, the 'box will always be the weak point in reliability. The only real answer is a mild engine with a standard box for a road car to avoid the horrendous noise from the S/C gears. Alternatively accept regular box re-builds or learn to tolerate the whine from the S/C gears.
Cooperman said:
accept regular box re-builds
Do you remember how long it has taken to drag the engine and box out this time? I'm 55, I might not live long enough to do it again....Cooperman said:
the whine from the S/C gears.
that's where the noise is from, didn't know I had s/c gears, I thought it was the wife and young son making the noise..... time for bed i think
Skyedriver said:
Cooperman said:
accept regular box re-builds
Do you remember how long it has taken to drag the engine and box out this time? I'm 55, I might not live long enough to do it again....Cooperman said:
the whine from the S/C gears.
that's where the noise is from, didn't know I had s/c gears, I thought it was the wife and young son making the noise..... time for bed i think
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