hi does any body know what engine will fit the serpent quattro iv . ive just dug this out of mothers loft with intention of refurb engine is no good but cant see anything to fit. please help... current engine is a master 3.5

You have to use an old type of engine, without an SG crankshaft.
Like this OS


Or modify the car (my suggestion) to put in the latest type of engines and clutch systems... a Centax 2 clutch can even work of the Quattro gearbox....

Here you have an (old) picture which give you an idea what you need to do...



You can see I brought the brake disks to the inside of the bearing block, this is what you need to do, to make room for a modern "SG" type of engine....

An engine with a SG crankshaft will work also, just grind off the 5mm shaft.

The only thing I am afraid of is the screwholes. Older engines had them closer to each other, so far I know some RTR engines like Force still use this mounting. In that time there were 2 types of mounts, one for Picco and one for Novarossi solving this issue.

True, but the screw holes under the chassis, are still the same, so together with modern engine mounts, it will work again...
2 years ago I went with my Quattro to the track with a Mega ZX mounted on it, I fired up the engine, opened up the throttle, and the brake disks flew around my ears.... They broke immediately... they were a bit dryed out.
I had the idea back then, to run the car during the Serpent nitro tour, I even had Serpent HQ behind me, they prommised to give me some donuts for this race, but everybody knows what happend to Serpent then....