Tim Suddard
Tim Suddard Publisher
6/29/18 8:55 p.m.

While often lamented, Triumph’s 1500cc, four-cylinder engine is still owned and loved by thousands of enthusiasts. Almost 100,000 of these engines were used in the 1973-’80 Spitfires, and nearly as many were used in MG Midgets sold from 1975 and later.

Right off the bat, this larger engine delivered more torque than its predecessor. More torque, as we know, helps produce better acceleration numbers.

But there were some problems. Detractors complained of durability and drivability issues.

These engines were known to be delicate, especially if over-revved. The three-main-bearing design did not lend itself well to hard use. Thrust washers needed to be maintained, or crank walk would destroy them as well.

The biggest problem with these engines, however, had to be the single, emissions-era Zenith Stromberg CV carburetor. To save money and meet the ever-stricter U.S. emissions standards, American-market versions of this 1500 were fed by just one carb, not the dual SU setup found on earlier Spitfires.

While adding main bearings and redesigning thrust washers is not an easy feat, at least one of the engine’s problems can be addressed: without much headache better carburetion.

Some enthusiasts opt for a Weber DGV down-draft or single side-draft 40 DCOE setup. These are both good solutions, but we went with an even easier fix on our 1973 Spitfire.

In England, Triumph Spitfire 1500s were sold with dual SU carbs. A nifty-looking, dual-inlet air cleaner wrapped in a black crackle finish was part of the package. The factory paired these preferred carburetors with a free-flowing, cast-iron exhaust manifold that emptied into twin pipes. These SU carburetors may be older technology, but they have served many owners very well through the decades. They’ve even won countless SCCA championships.

For about $400, we sourced a set of these carbs, the proper intake manifold, a factory European exhaust manifold and a downpipe from Quantum Mechanics. This firm finds these parts overseas and imports them for American enthusiasts. Because these parts are designed by Triumph to fit the cars, the swap is a snap and the results are nothing short of remarkable.

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TR8owner HalfDork
7/1/18 4:24 p.m.

I was always much more partial to the 1296cc Spitfire engine than the 1500. Maybe because its the one I raced back in the day, but it always just seemed better balanced than the 1500 for some reason. As for the MG Midget, I preferred the 1275. Had one on the street will all the competition Cooper S parts. It went like stink. Always seemed like a sacrilege putting a Spitfire engine into a Midget.

clshore New Reader
7/13/18 8:59 a.m.

In reply to TR8owner :

The 1300 Spitfire and MG motors shared quite a lot; iron block, 3 main bearing crankshaft, similar bore & stroke, similar cylinder heads, similar carbs, similar power.

But the US emissions regs sucked away both torque and power. A larger motor was needed.

The MG motor was incapable of being enlarged, just getting it to 1275 had required engineering handsprings (offset conrods? Really?).

But the Spitfire could be easily stroked to 1493 cc to regain some performance.

Given that MG and Triumph were both owned and built by BLMC, choosing the Spitfire motor for both was a no brainer. At least the MG stayed 'all British'.

3/25/20 1:49 p.m.

I did the SU conversion source from Quantum Mechanics along with a 5 speed transmission also sourced from Quantum.  It has transformed the Midget into a nice little cruiser.  I tried the Weber DGV for a while but the SU's are more responsive plus I get better gas mileage ( the 5 speed helps).   I replaced the original exhaust header with a Pacesetter which increased the pipe diameter to about 2" but have learned there are better ones available.  I was not aware of the header from the UK.  I also experienced the thrust washer failure which ruined the crank so my advice is to keep your foot off the clutch as much as possible.  All in all, even though there are more desirable sports cars out there the 1500 Midget has been a fun car to have owned for the past 18 years.

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