Marcos Maniacs

Hi there
The Buick/Rover V8 is not that much heavier than your original 1600 but it will be a tight fit in the engine bay.  I believe the length is fine but it's relatively wide and in the -bay of a wooden chassis car it will be a struggle.  And as has been said, the much higher torque of the V8 will put strains on the rest of the drive train and its anchoring points in the wooden chassis. I have a feeling you live in the US, so the "sensible" route here is the modern equivalent of your straight four; the Ford/Mazda Duratec four.  And since you have good access to the 2.3 litre version from the Ranger I'd go for that.  With a bit of outside work on it (ECU, throttle bodies and a good header) you will have an easy 200-220 HP in an engine weighing LESS than your old unit.

With a steel chassis Marcos (that came in 1969) it would be different. The 3 litre Volvo straight 6 or Ford V6 are heavy, and I know that a small block Ford V8 with alu heads and an alu B&W gearbox weighs in at LESS than the Volvo/Ford combos.  The Ford (Essex) V6 is almost 200 kg while the Duratec is around 100 kg.  And such a difference in mass is really noticeable in the front of a light weight car, even if it's situated far behind the front wheels.

I agree that Marcos used several different engines through the years, first Volvo B18, then Ford 1600/4, 2 litre V4 and 3 litre V6, Volvo 3 litre L6, Buick 215/Rover 3.5 litre V8, Ford Pinto 2 litre and later - when the width of the car increased came modern Ford 5 litre V8.  Tha last models with the new body shape had Corvette LS engines, but then the chassis was probably "rearranged"

But good luck with your project :-)