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 …
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.
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'.
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.
I remember reading a brief article in Road & Track back in the 70s that with the two SU setup, there's a problem that at higher RPM the mechanical fuel pump doesn't deliver enough gas, causing fuel starvation. The solution is an electric fuel pump in the trunk, and bypass the mechanical pump. But not just any pump--SU carb float valves will allow gas by if it's under too much pressure, so you need a low-pressure pump or pressure restrictor in the system.
The problem with the thrust bearing is serious, and every Spitfire (or GT-6, or TR-6) owner should know how to check crank end play. I know I was able to replace the thrust bearing in my TR-6 by dropping the pan and removing the rear main bearing cap, but can't remember if it the same on the Spitfire. A fair amount of work, but nothing too technical, and it saves the engine. And oversized washers are available if there's wear on the crankshaft. And it's easier/cheaper than replacing the crank and rebuilding the engine!
Tim mentions the Weber DGV as a suitable alternative carb. It might be suitable for some situations but the Spitfire (MG Midget) configuration is not one of them. The downdraft sends the mixture down to a flat surface in the intake manifold where it splatters and pools rather than smoothly reaching the head. This is due to the manifolds available for that adaptation. Sidedraft carbs are the best alternative, especially twin Weber DCOEs. Single DCOEs on the 8 port heads suffer from uneven fuel distribution between the inside two cylinders and the outside two owing to the unequal runner lengths of the available intake manifolds.
Inferior steel in the crankshaft, narrow bearings and thrust washer inadequacy posed issues for the 1500 and on top of that the single carb is a negative, as your test showed A competitor in my race group used to refer to his 1500 as "Mr Floppy" (referencing the crank, which precluded using high rpm).
There is nothing inherently wrong with a properly designed 3 main bearing engine. A frind ran a Ginetta G4 with a 3 main Ford MAE - 3 main, 9500 rpm red line (albeit with a short stroke)
I built a 1500 engine for my '72 Spit back in the day. Similar upgrades but I milled .125" off the head, sourced a pair of SU's from a '67 Spit, and installed a header from Victoria British. Those upgrades transformed my previously 1300 powered car, and it did well at club autocrosses.
Still slower than my prius, these are tractor engines from the 50s. Sold my spit last year and it was one of the few cars I never regretted selling. Thanks for the article though it just reinforces my decision.
porschenut said:Still slower than my prius, these are tractor engines from the 50s. Sold my spit last year and it was one of the few cars I never regretted selling. Thanks for the article though it just reinforces my decision.
That is not true but often repeated. The Triumph SC (small car) engines were never derived from tractors. Both BMC (B series engines) and Triumph (the Vanguard/TR wet liner engine) also used the engines in all sorts of different applications - main vans, boats and tractors, but they weren't designed for agricultural use in the first place.
wspohn said:porschenut said:Still slower than my prius, these are tractor engines from the 50s. Sold my spit last year and it was one of the few cars I never regretted selling. Thanks for the article though it just reinforces my decision.
That is not true but often repeated. The Triumph SC (small car) engines were never derived from tractors. Both BC (B series engines) and Triumph (the Vanguard/TR wet liner engine) also used the engines in all sorts of different applications - main vans, boats and tractors, but they weren't designed for agricultural use in the first place.
My apologies. Guess 3 mains and a thrust bearing that falls out were state of the art back then.
porschenut said:My apologies. Guess 3 mains and a thrust bearing that falls out were state of the art back then.
3 main engines were definitely more common but Triumph had a lock on using only half the thrust washers other manufacturers (like MG) did in that period - a definite shortcoming,
I raced both 3 and 5 main bearing MG engines and the 3 mains were dealing with slightly less drag and seemed a bit stronger and quicker revving, but bearing life when run to high rpm was better on the 5 main engines - they didn't get around to making 5 main versions until 1965 and Triumph never did go with 5 mains for their 4 cylinder sports car engines.
This guy does a good job of outlining the issues with the 1500:
http://triumphspitfire.rickbaines.com/weaknesses-of-triumphs-1500-engine/
My spit was a 79, and when I compare it to the other tech available at the time it just looks sad. Yes I know it was built from parts in the 50s and the design never changed. There are some things I liked about the spit but not enough to keep it around. And the engine was a huge part of that.
In reply to wspohn :
Triumph had a lock on using only half the thrust washers
Yeah, except for Mazda, Ford, GM, Toyota, Mercedes, Nissan, Honda, etc.
The big issue with Spit motors was not wear on TW, it was preventing them from dropping.
Pinning them with a couple of 4-40 flathead brass machine screws is a simple effective solution.
You'll need to log in to post.
