Thread: 186 or 202 - which is the better engine

186 heads have flat seat plugs, 13/16" hex. 202 heads have taper seat plugs, 5/8" hex. The 202 also has non-adjustable rocker posts unlike the 186 which had nuts to screw down the rocker posts. The 202 used to be known for cracking pistons and then throwing rods, 186's less so. My brothers original HG 186 panel van broke a piston 450km from home, that was fun. My neighbour's HQ 202 broke a piston at around 80,000 miles. Any reconditioned motor with non genuine pistons would be unlikely to suffer like this though. !86's are shorter stroke, easier to get revs out of.

I would also suggest finding a genuine 186S, as these engines were naturally higher revving than the stock 186.

I also agree about the 202 being susceptible to throwing rods etc.
Was an RAA mechanic for some time, a chap came into my garage, said his engine was "knocking" and the alternator light had come on.
A quick look found the problem, # one rod had knocked the alternator off.

One other thing is 202's overheat easier where a 186 can handle a bit more heat/ poor cooling like when I used to have a SIII 88 with a 186 and the radiator rusted through the bottom tank, made the engine so hot it would not stop running when I turnt the ignition off so I had to stall the motor! Got a new radiator and she started first go and ran perfect till I sold it. Only prob.I had was it did not like water, even heavy rain and the engine would die, but that was more poor electricals.
One other warning they have lots more power than the LR engines so can snap rear axles in LR diffs.

The 202 and 173S had 9.4:1 compression ratio, the highest CR of this engine series. If you fit a 186 head to a 202 block then the CR may be a bit much to run properly on 91 unleaded and you may have to use the expensive stuff. As to revs, the 202 was used in the GTR's with option XU1 and ran up to 7,000 rpm for 500 miles at Bathurst. All to do with having the right internals and preparation. Get the rods and crank from a blue engine. Any decent crankshaft shop can do the relatively minor mods required to fit the fully counterweighted crank into a red engine. Use quality forged pistons and away you go to rev its ears off.

Originally Posted by Brian Hjelm

The 202 and 173S had 9.4:1 compression ratio, the highest CR of this engine series. If you fit a 186 head to a 202 block then the CR may be a bit much to run properly on 91 unleaded and you may have to use the expensive stuff. As to revs, the 202 was used in the GTR's with option XU1 and ran up to 7,000 rpm for 500 miles at Bathurst. All to do with having the right internals and preparation. Get the rods and crank from a blue engine. Any decent crankshaft shop can do the relatively minor mods required to fit the fully counterweighted crank into a red engine. Use quality forged pistons and away you go to rev its ears off.

Yep, totally agree, or use Starfire rods out of the 1.9 litre OHV four cylinder, they are basically XU1 rods.

The 202 also makes better torque, you can't beat cu.in. IMO.

Originally Posted by rick130

Yep, totally agree, or use Starfire rods out of the 1.9 litre OHV four cylinder, they are basically XU1 rods.

The 202 also makes better torque, you can't beat cu.in. IMO.

The blue engine used the so-called "Starfire" rods.

From one who has been stuck on the side of the road...
The standard camshaft gear on the 186 was fibre (made from cloth and resin) to reduce the gear noise. It doesn't like the hydraulic lifters pumping up at high revs. There are aftermarket aluminium gears available which are stronger.

We had the 186 in a 2a and a 202 in my brother's series 3, the 186 was plenty strong enough to break rear axles. We preferred the 186 over the 202.

Cheers
Ron

I had both, but they were in such different condition it would be hard to compare. The 202 was freshly reconditioned and ran beautifully, the only problem was the distributor drive gear, which was nylon and stripped so was replaced with a steel one from a 186.

The 186 I had was quite worn out and ran on LPG and petrol and would struggle to top 95.

The age of these engines now would mean the condition would be more important than the model.

Jeff