Midget 1500cc engine

What can be done with this engine in order to make more power? I am thinking a carburetor swap would be the first thing to change.

we talking MG midget? The 1298 is a better choice

mad_machine wrote: we talking MG midget? The 1298 is a better choice

Do you mean the 1275 A-series in the Midget or the 1296 for the Spitfire?

I have a 1500 that is why asked.

The 1500.. I imagine it can be built up to be near as robust and probably more powerful than the smaller engines.. the trouble is, back then the English tax laws were based on bore.. so small bore LONG stroke engines were the norm. that 1500 has a longer stroke than you might think possible. It really limits the rev characteristics

I know the 1500 in the US had the single Zenith-Stromberg and a 7.5:1 compression so it was making 53bhp. However the European versions had a 8.0:1 compression. I was thinking that with either twin SU carburetor or a Weber and some higher compression pistons and camshaft.

dump the 1500 and drop in a 1275 engine with a datsun tranny swap and call it a day. There is more aftermarket support for the 1275 engines, as they were used in more cars.

I mean you can make some power with your 1500, but your going to see a limit real soon. Intake, exhaust, and header, you start in the same places as all cars. For a carb swap, downdraft or side draft webers, most opt for dual side draft weber carbs but they aren't cheap. You can swap the diff for some added speed as well, either a limited slip or open model.

Check out minimania and moss motors

IIRC twin SU would be what they came out of the factory with over here. As digdug18 says, the engine isn't that massively tunable compared to the A-series and the emphasis is on torque, not power with these.

Given that you've got low-compression pistons, I don't think that sticking more carbs on will make a massive difference. I'd in order to get decent power out of it, you're probably looking at a complete teardown & rebuild.

How about a supercharger?

Hmm. Low compression engine ... Small S/C ... Megasquirt...

Sounds like a good starting point.

I race a ~1500 Midget~

If you watch rod bearings and thrust washers, it's an OK engine. I change thrust washers and rod bearings every 25 hours. They'd last twice as long in a raced 1275.

Swap to 9:1 pistons and the Euro twin carb setup. You can chop a few lbs off the flywheel for a more snappy start too. Do not shift above 5800 unless it's a balanced engine.

The older 1275 is better, but the 1500 can be fine for normal street use.

aeronca65t wrote: I race a ~1500 Midget~ If you watch rod bearings and thrust washers, it's an OK engine. I change thrust washers and rod bearings every 25 hours. They'd last twice as long in a raced 1275. Swap to 9:1 pistons and the Euro twin carb setup. You can chop a few lbs off the flywheel for a more snappy start too. Do not shift above 5800 unless it's a balanced engine. The older 1275 is better, but the 1500 can be fine for normal street use.

Do you know how much power you are making and what distributor are you using? If the engine is balanced how much later would I be able to shift?

I'm using s 25D Lucas with a Petronix unit.

I estimate I'm making about 75 HP at the wheels. Thats actually based on a quick estimate off of my top speed. My GPS showed 107 mph at NJMP in this car with a 3.9 final drive and Toyo 888 185/60-13s. A standard 1500 Midget can do a max of 93 mph.

My car is "semi-balanced", has a race cam, a milled head (my true comp ratio is 10.5:1), a header and a very large single carb (S&S with 2-1/8 barrel). Minimum octane I will run is 100 and I prefer 115 leaded. With the 100 octane, I run 28 degrees of total ignition advance. More like 32 degrees with the better fuel.

I forgot to say, but you can cut 0.100" of the head easily to raise compression. I think 0.125" is the max. But don't take too much off or you'll have problems running street gas. I'd say 0.062" off would be good.

These 1500 engines can run almost 7000 if balanced, but you still need to watch rod bearings and thrust washers no matter what. The smaller 1296 engine (closely related to the Triumph-built 1500 and often called the "1300") has a much shorter stroke and will spin to almost 8000 if balanced. Both the 1296 and the 1500 (Triumph-built) engines can make more power than the Austin 1275 unit because they have better head design......but the 1275 has a tougher bottom end and can be spun to 8500 pretty easy.

By the way, the 1275 engine requires a different trans, so a swap needs more than just the engine (the transmissions are completely different but both are decent).

I'm building a new race car and that one (an Austin A35) will have a 1275.

Well I have a 78 Midget with a beat to crap body but an engine and transmission and '74 with no engine but a good body minus the floor boards and frame rails across the floor. Can anything be done to improve the bottom end? If I kept the stock compression pistons, what kind of compression would I expect from shaving the heads .062"?

If your 1500 is a 49-state federal car, taking off 0.062 might get you close to 9:1 comp ratio.

The only way I can think to really improve the bottom end would be by adding balanced Carillo rods and a billet crank. Figure about $3000 for just the parts (but if you went that far, there's a ton of other spendy stuff that should be done at the same time).

better off swapping an 1800 from an MGB?

The Spitfire 1500 has almost exactly the same bore and stroke as a Honda D16, so the architecture is not really that archaic. The stroke is so long because the bores could not be increased any more (bore pitch), and Triumph had to increase the displacement to compensate for losing power to US Federal smog requirements. Kastner's books detail modifications to the crank and oiling system that will make the conrod bearings live. Pin the thrust washers to prevent them dropping. For a street car, get a cam for low and midrange torque rather than high RPM horsepower, and you will be happier. Get the Euro spec dual 1.5" SU carbs and manifold. Megajolt Lite Jr will allow you to run best timing without ping.

Carter

Ok so I can't afford the Carillo rods and crank. What are the Kastner's books?

Kas Kastner's book is ~Here~

Personally, keeping the engine build moderate and just using a 5800 rpm redline will serve you well. You don't need a ton of horsepower to have fun in a Midget....it's a "momentum car".

Pinning the thrust washers is OK for folks who intend to drive high mileage and never check crank thrust ( a pretty simple job). Sitting at a light with the clutch pedal down is especially hard on them. I can't think of any racers I know that bother to do this, because they keep an eye on the thrust numbers.