105 or 120 to 160

[Crutts1]

Hi All,

I am new here and to MG ZR's in general; I am wanting to build a car for the MGCC MG Trophy. At present it looks like I easier (and cheaper) to get a 105 or 120 and upgrade it to a 160. My question is, can anyone tell me the exact differences apart from the engines please?

Cheers

Joe

[JOHNDQ]

If your building a car for the MG Trophy you will need a 160 there the only engines you can use. In answer to question tho only real difference is the engine, gearbox and brakes

[Crutts1]

It can be any model, just need to swap the engine and box to comply

[JOHNDQ]

Yeah doesn't matter about the shell just needs the 160 drivetrain as they are all the same just make sure it doesn't have a sun roof. The 160 does use bigger front brakes and a different front sub frame to the 105/120 tho

[Evil C]

Judging from the actual amounts of money that I have seen ZRs changing hands at recently, would it really be cheaper to convert a 105 or 120?

A 120 will only require as a minimum, a change of engine, engine wiring loom, brakes, and engine ECU or remap (although the ratios in the PG1 gearbox fitted to the 120 are not the same as those in the PG1 fitted to the 160). There were even less ZR 120 built than there were 160, so finding a decent condition 120 as a base may not be that easy

As the 105 uses a different gearbox, converting a 105 will require (in addition to the items mentioned above), gearbox and mounts, gear linkages, drive shafts, and front crossmember (the one for the 105 is a different shape from the one fitted to the 120 and 160, and the standard 160 downpipe, as well as most if not all aftermarket and performance downpipes, will foul on it).

[JOHNDQ]

Thats true yes the 160 ZR PG1 box does help bring the car upto speed tho. Worth noting the 105/120 use same sub frame only the 160 has a different one due to the larger downpipe will definitely be a easier job to convert a 120 if you can get one. Do you have the 160 engine etc as there getting hard to find these days. I'm building mine to run in 750 motorclubs hot hatch series

[Evil C]

Worth noting the 105/120 use same sub frame only the 160 has a different one due to the larger downpipe

The 120 (and the dervs) have the same front crossmember as the 160 (which I can verify from having had two 120s )

[JOHNDQ]

Seems strange both 120s I had had the standard from sub frame (both MK1's)

[Evil C]

Front crossmember (or front beam) is definitely same for both 120 and 160 (+diesels). It has a definite crank shaped rear profile, whereas the one for the 105 (and the petrol Rovers up to 1.6 litres) have a rear profile which is much straighter across (or at least, more of a gentle curve).

The 120/160 front crossmember also has the threaded bolt holes for fastening the plastic undertray which was fitted as standard to both models (and a larger undertray for the diesels) - the crossmember for the smaller engines doesn't have any fixing holes for the undertray.

Apart from the shape to accomodate the 160 downpipe, and the undertray fixings, the two crossmembers are the same, so it is possible to fit a 105 type front crossmember to a 120 - the 120 exhaust manifold and downpipe are identical to the 105, so there is no fouling issue, but it means deleting the undertray (which is probably now missing from a lot of 120s and 160s anyway). It is quite possible that accident damaged 120s may have had the front crossmember replaced with one from a 105, either in error, or because a cheaper second hand 105 one was easily available from a breaker at the time (120s and 160s are much less commonly found in breakers due to the much lower numbers built).