The Hindustan Ambassador arrived in India in 1957 as a rebadged, indigenized Morris Oxford Series 3. Hindustan Motors had simply decided to call the car the “Ambassador”. This was the case until 1962 when the Ambassador Mark 2 was introduced. With the arrival of the Mark 2 its predecessor became the “Mark 1” even though it was never branded as such and never wore a “Mark 1” badge. A badge it did wear was the “OHV” which stood for the Over Head Valve BMC B series engine under the bonnet. The Mark 2 brought along “major” changes like the new Morris Mini-esque mustache grille, a change in bumper guards and few changes to the interior.
Speaking of Mark 2s, this particular 1970 Ambassador Mark 2 was bought by my great grandfather and has been in our family ever since. As a kid I came home from the hospital for the first time in this car. I grew up going to school everyday in this car. I got hooked onto classic cars because of this car.
In short, this car is very special to me. So when I realized that the car had been sitting for 3 long years and was not being used due to engine issues, I decided to bring her back to life. While the engine was in running condition, it lacked power and burned oil. So, in order to understand exactly what would be required to fix the engine, we started with testing the engine….
Testing the Engine
Generally a complete rebuild would be ideal for an engine this old and in this condition. But as an experiment and challenge we decided to try and rejuvenate the engine without undergoing a full rebuild.
We started with a leak down test to check how the valves and piston rings were sealing the combustion chamber. The results were not surprising: all the piston rings and most of the valves were leaking compression. The following video goes into detail on how the engine was tested:
Disassembly and Inspection
Next, we dove right into the engine by taking the cylinder head off and inspecting it. Not only were the valves leaking, the valve faces and guides were completely worn out. In order to fix this, the head was sent to the machine shop to get new valves, guides and a resurface. The entire process from disassembly to inspection is covered in these two videos:
Then we focused our attention on the block and the pistons. Luckily the bores didn’t have a “wear-ridge” or “lip” at the top, making it possibility for us to get away with just honing the cylinders. The pistons and rings were further investigated to check for wear and locate the sources of compression losses. The following video goes over how we inspected the cylinder block:
“Machining” the bores
After inspecting the cylinders, we took the pistons out and analyze them further. The pistons and rings were definitely worn down. However, since we were not aiming for a full rebuild, we decided to solve the problem with new rings and reuse the pistons. Following a thorough inspection we honed the cylinders to get back the oil retaining cross-hatch pattern on the bores and prepared for assembly! The entire process from disassembly to honing the cylinders is covered here:
First start in 3 years!
With the rebuilt cylinder head in hand and the bores prepped for new piston rings, we began re-assembling the engine! The entire process can be watched here:
And that my friends concludes our 1970 Ambassador Mark 2 engine overhaul. It was surely disheartening to have redone an entire engine only to find the clutch stuck to the engine! But, a lot of time and some ingenuous tinkering later we managed to free the clutch without having to take the engine or gearbox out. Now that’s how she looks rolling down the road: