Incorrect. A cursory wikipedia search
will tell you that the four pot came later than the V8. It was designed as a V and then cut in half. The heating issues came from an inadequate rad and bad production practises. The engine itself is a sound design.
( Kroney, Mon 18 Feb 2013, 15:37, 2 replies, latest was 13 years ago)

Well, except for the iron block and alloy head.
Or the lol-worthy expanding timing chain.
( Kroney, Mon 18 Feb 2013, 15:40, Reply)

A cursory wikipedia search
is going to make you look a bit of a chobber here.

"The Triumph V8 is a 3.0 litre V8 developed in house by Triumph for the Triumph Stag. This was basically two Triumph Slant-4 engines 'stuck' together. It consisted of a single overhead cam cast iron block with aluminium heads"
( the mighty badger Aphrodite, on a bar stool, by your side, Mon 18 Feb 2013, 16:11, Reply)

Just in case you needed me to check for you as well.
"The Triumph Slant 4 engine was used by Triumph in the Dolomite 1850, the Dolomite Sprint, and the TR7. It was also used by Panther in the Dolomite-based Rio"

You're welcome.
( the mighty badger Aphrodite, on a bar stool, by your side, Mon 18 Feb 2013, 16:13, Reply)