The Triumph Dolomite Club - Discussion Forum

Just to come back to this, I think when they say “substantial change” that they mean “replaced with different to stock”. I think they mean more along the lines of modification to the stock running gear/axles that deviates from how it left the factory (i.e. like-for-like replacement of parts for maintenance or repairs)

For example, replacing carbs with electronic injection or changing the final drive ratio would be a “substantial change”. Replacing a bad sprint engine with a better sprint engine wouldn’t be that substantial but replacing a bad sprint engine with a modern engine would be too substantial to argue the benefits. It likely could be argued for some other historic cars like pre-war cars/pre-war replicas where the engine isnt easy to come by and therefore it’s more cost effective/ efficient to fit an alternative engine

I spent a bit of time wading through the quagmire of wooly and imprecise definitions but my take is that:- a car is "substantially altered" if the number of cylinders is changed (ie from 4 to 6 or or the capacity is increased by more than around 50%. Though it's not explicit, the implication is that, if you use an engine from a different maker, that is enough to make it out of bounds, regardless of size or capacity or number of cylinders.

Personally I don't see anything to be gained from debating (or leaving open to debate) whether or not your car is immune from MOT for one reason or another. Surely it's worth £50 or less a year to cover one's behind!

The only GOOD thing I take from these different sets of rules is that neither DVLA OR DVSA have anything at all to say about brake upgrades which are "free" in both cases.

Steve