Rebuild Performance Upgrades - Classic Mini Engine

Secret To Buying An Engine For Your Classic Mini

Whether you’re simply replacing your Classic Mini’s engine or moving up to a powerunit that’s got more muscle, buying an engine is a complicated matter.  How much power are you looking for? How authentic is authentic?  What options should you consider?  What option are available that you didn’t consider? (Believe us when we say the options available are mind blowing.)

So it’s not surprising to say the secret to replacing your Mini's engine someone who can guide you through the process.  Find an expert who knows Mini engines and understands that no two engines are alike.  For example, the horsepower of a basic 1275 can range from xx to xx. And how much horsepower you get depends on how much you’re willing to pay. Or maybe you want an aluminum head rather than the traditional cast iron head. Or competition head studs rather than classic studs.

Our experts can identify your needs (and wishes) and work out a detailed plan to get you the engine you want.

If you're looking to build the ultimate road or race engine, let Mini Mania build it for you! In this video we give just one example of the higher end racing components available to create the ultimate in Classic Mini Cooper power units. If you'd like us to quote on the engine of your dreams see our contact information below.

Here are some links to the products seen in this video:

Multiweb Crank Kits:

Duplex Timing Chain Set:

Heavy Duty "S" Type Damper Pulley:

Machined Pushrods:

And at the end of this document are some of our top engines (1275 and 1380 engines).


Hi guys, it's Brendan from Mini Mania. Today, we're going to go over some of the race items that we can install in race motors that we build here at Mini Mania and for those of you who don't know you know we can we could rebuild you basically anything and build you basically anything.

This is a an engine that we're putting together that has some really high-end components, and since we hadn't done a video on the high-end stuff before I wanted to kind of just go through some of the things that we can build for you.

This is a an engine that's going to have a high end crank and this type of crank is a lot different from the stock crank. As you can see this is a stock crank right here this particular one is from a later mini and it's got, it has these one in three-quarter inch Rod journals here. This one's more like the Cooper S style, it has the one in 5/8 rod journals on it.

If you'll notice this is the special balanced crank and it has these sort of faux journals in it, which differs from the style that you have with the stock crank and it puts a lot of that rotating mass right down there, right down the center of the crank.

It's designed to take lightened and special straight rods, so the type of rods that are going to go in this and you can see the way that that is oriented,  so that's pretty cool.

The rods compared to the stock rod , they're a lot, they're a lot lighter to begin with. These are about 12 and a half ounces lighter than the stock rods and for anybody who's ever actually built one of these knows that, you know the rods are offset as you can see right there.

These particular rods are not offset. These are straight. They're all straight and so they're also going on to a lighter piston.

These pistons, they're about 4 inches lighter than what would be sort of a stock replacement piston.

This is a high compression knurl piston. This is the AE equivalent that you can get now, very nice pistons. These particular ones, they're shorter and they're lighter.  

You can see about the difference in size pin height is also slightly different because the length of these particular rods is different; and so we're going to be taking all of these higher end components. We're going to be putting them in a block that's been prepared.

1275 BLOCK
The 1275 block that's been prepared, we're going to be using a CL race bearings and it's going to go in a block that's been set up for this. For this crank and rotating assembly, it's also going to get a lightened flywheel and it's going to get some other goodies and we'll come back.

After the crank is in and we'll talk a little bit more about some of these other Higher-end components that we're going to be putting in this high respect race engine.

Ok, well as you can see, we've installed the multi web MED Crankshaft here in the block. You know these multi web Cranks are really extraordinary. You know, they utilize a, you know a straight con rod and by using the straight con rod it's a six-inch con rod. It's sort of an i-beam style. This comes as a kit from MED engineering in the UK.

You can see the MED on the side here, and by using the straight Conrad on this incredibly well-balanced crankshaft, because it takes and has this weight again that I mentioned is all the way down the centerline of the crank it really reduces any sort of side loading that you might get

On a traditional crank and a traditional offset Connecting rod in an A series engine and this eliminates all that so it makes an incredibly Well-balanced Rotating assembly. 

This block as you can see has got the MED aftermarket main bearing caps, it's got a four main center bearing cap and so that should provide some extra rigidity for this very nice set up here. And again Tony has installed.

The rings on these forged pistons, which come with the kit. The kit is the crank and the rods and the pistons and it also gives you the bearings.

So if that's something you want to look into if you want to build in a very serious, very very hot or hot Road or race engine and then this is pretty much the pinnacle of where you would be for the crank rod and piston technology at this point.

After this we'll get a little bit of footage of Tony installing the Pistons and you can take a look and see the way that those straight rods and everything work out and we'll do that in a little while. You know, one of the interesting things this crank is it's actually slightly heavier than than a factory crank.

It is not necessarily any lighter, it's just that the weight that it does have is actually balanced down the center axis of the of the crank.

However doing this as a kit, one of the nice things is these pretty slick straight rods and these pistons, these are actually lighter by a good three and a half pounds over the factory rods and pistons. 

That alone taking three and a half pounds off of your your rotating mass it's definitely going to allow you to accelerate more quickly, and this engine is also, it's also going to have a light and flywheel and we'll see that at some point during the build.

So ,  one more bit of lightning that we're going to add to this engine, so that it'll be able to rev up very quickly. These pistons are actually marked with an F For the front of the engine so you face them all the same direction. We already have number one in and just give you a quick show on how we do that.

This particular set by the way, you can order it in different over sizes. This is a 1330 set.

So these are 60 over pistons just so, you know you'll have to really finesse this stock for the key way once you get that on the end of the crank and you also might have to take some Emery and stuff to get  that snout ready for the gear it takes a little bit of fettling, but we'll be able to do it.

Okay, well we discovered something when we were putting together the timing setup.

As you can see that this particular set, it's one of the slipper ball vernier style timing chain setups. When we got it on here we noticed that there was quite a bit of slack actually in the chain. So what we're actually going to do will just end up putting a tensioner on this and we'll take up that little bit of slack that we've got.

Which is no big deal that the tensioners aren't really designed for the duplex chain setup, but you can use them certainly there's no issue to using a tensioner or on it on a duplex chain. So that'll just take up that little bit of slack and then we should be good to go. So once this gets dialed in timing wise we'll move on from there.

This is a cast iron 12G940 Head that MED prepared and it's a very nice head. It's also got a very nice set of the 1.5 lifts roller rockers as you can see, so it's pretty slick setup.

This particular one was also ported; you can see the porting. So this is going to be a really nice flowing head and that's what's actually going to go on that engine over there. You'll see that a little later on too when we get this up on the test stand and we can start to run it okay.

So we have the tensioner on there now and we have the cam timed. This particular cam is a piper cam and it total lift on it is 105 degrees so that's what we've got a set up and ready to continue building.

Ok, well the head is on front covers on the damper pulley is on you'll notice that it's got the belt on. Actually already we noticed that it's a little tight here in between front breather and and the damper so we just put that on ahead of time just slid that into place and then put the damper on the water pump installed over on this side.

You see that we've got one of our Mini Mania breathers connected where you'd normally have your mechanical fuel pump and so we just add that, as a breather engine like this needs, to have good positive crankcase ventilation, so we're going to do that with this kind of an engine.

You can see that this head came from, and MED prepped it nicely. It has It's been nicely ported and polished and it's got this large MED Rocker cover on it. It's going to be a good-looking motor as well as a nicely running and very fast engine.

So the next step we're going to do is we're going to build a straight cut rod change box,  and it's also going to have a complete straight cut and drop gear set so when we're a little bit further along than that, I'll show you that too.  

Another thing that this gearbox is getting, is going to be limited slip diff, quite the setup. So we're going to start to put that together and you'll see in a little while.

One thing that we needed to do, we made a couple marks inside the gearbox. It turns out that the gearbox actually had to be clearanced a little bit for this for this crank, the studs, for the one main bearing cap on the end right here and here clearance that a little bit.

But then we had to remove a little bit of material here, basically because this counterweight right here on the crank was coming up and it was hitting there and then of course on the opposite stroke it was banging it in the other direction.

So we actually had to clear it, clearance it so it would clear this, this counterweight there right there. So we had to do that. 

This was a little bit of extra work, but now it's done and it clears it. Just fine.

So the flywheel cover on, and this is the light and flywheel that's going to be going on here with the clutch package already attached to it. So pretty much, all we got to do is just get the flywheel bolt on there, tighten her up and this engine is going to be ready to go on the test stand probably tomorrow.

As you can see, we have our engine on the test stand and this particular one's going out with an Alden distributor Novak and it also has a pair of HS41 and a half inch SU carburetors and those were rebuilt here at our shop by Ed Dorado. 

So we're going to run this, for a little while and I'll just get a little bit of video of this running for you. You can see how it's going.

Okay, well we ran the engine on the stand and we ended up actually putting some higher octane fuel and ran this on some higher octane fuel because it turns out that this one has higher compression than we initially, initially thought and It ran much better on the higher octane fuel. So this one's pretty much ready to be boxed up crated up and shipped out.

If you're looking for a higher end Mini engine or one for your Sprite or Midget and inline engine, just let us know.

Let us know what you're talking about, thus know what kind of horsepower you might be looking at you know if you're going to be doing track days, or if you just want a hotter street engine.

If you really just want to build something that is unlike what most people put in their cars let us know we can build it for you and you can get in contact with us.

The contact information is right up there and the information on this video and you can leave a comment, let us know, like the video and subscribe to our site. If you have an idea for a video that you'd like us to do leave it in the comments we do read them and we'll see you next time.