mrlee
mrlee
12/6/18 12:42 a.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.

 

spitfirebill
spitfirebill MegaDork
12/6/18 9:03 a.m.

The one problem I have had with going to the twin SU setup is I don't have the associated carb linkage and it seems to be unobtanium.  If you are going this route, be sure it is included in the setup you buy.     

Alfaromeoguy
Alfaromeoguy Reader
12/10/18 12:43 p.m.

On the head, remove the oem valve springs,and fit some beehive spring, YouTube has video on this,also on th e net,some information,it does help upper end power

Tim Suddard
Tim Suddard Publisher
12/10/18 4:56 p.m.

I had this swap on a Spitfire and it really imporved drivability. On the Spitfire we have now, it has a single Weber DCOE sidedraft and that works well too.

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