Avi
Avi New Reader
8/7/19 8:08 p.m.

What are the differences between the MGB rubber and metal bumper cars?

Say 1971 and 1977 models

iceracer
iceracer UltimaDork
8/7/19 8:18 p.m.

I think the rubber bumper cars have a higher ride height.

pointofdeparture
pointofdeparture PowerDork
8/7/19 8:20 p.m.

Someone else will be able to get far more specific than this, but I believe the rubber bumper cars were heavier, less powerful due to changing emissions regs and I believe had worse factory suspension settings too (something about increasing the ride height to meet pedestrian impact regs comes to mind). All fixable issues but the metal bumper cars are generally more desirable.

L5wolvesf
L5wolvesf New Reader
8/7/19 8:29 p.m.
pointofdeparture said:

Someone else will be able to get far more specific than this, but I believe the rubber bumper cars were heavier, less powerful due to changing emissions regs and I believe had worse factory suspension settings too (something about increasing the ride height to meet pedestrian impact regs comes to mind). All fixable issues but the metal bumper cars are generally more desirable.

Yes this is most of it. My first AutoX car was an MGB. The rubber bumper cars, a.k.a. the Baja B, was to meet bumper height requirements so bumpers would meet vs one going under another.

Engine wise I believe the later cars also had "air pumps" as part of the emissions requirements. They also came with a single Stromberg carb vs dual SUs. A notable number of those were converted to the Weber 32/36 which required replacing the header. 

freetors
freetors Reader
8/7/19 9:27 p.m.

The entire front subframe is different between the two which is where the ride height difference comes from. You can swap in the CB subframe to lower to it's original height if you can find one.

NOHOME
NOHOME MegaDork
8/7/19 11:21 p.m.

Significant difference in ride height and power. Later cars do not like to go around a corner.

The ride height correction is MUCH more involved than most people think. Head over to the MG Experience for what is required to do a proper retrofit of ride height. 

Power in the later cars is non existent; your lawn mover will have more torque and hp. With the Zenith carn the lawnmower also has a better chance of actually running.

Extra 200 lbs or so in the later cars does not help the case

The dash in the later cars was just more uglier. 

The only thing bad with any wiring in any mg is the previous owner

three wipers is just weird.

The later cars are the best for engine swaps. 

The later cars were better built/assembled than the later cars; hence more solid feel.

The later cars are up to 15 years younger, and that in itself is a value proposition when buying a used car.

mad_machine
mad_machine MegaDork
8/8/19 12:42 a.m.

I believe you can swap the bumpers with only a few holes to be welded up

wspohn
wspohn Dork
8/8/19 1:23 p.m.

You guys have done a good job of listing the changes. The engines were lower compression, slightly different cam, inferior exhaust manifold integral with intake and single valve springs and timing chain - basically the spec they used in their sedans like the Austin/Morris Marina.  They still please people who just want a sporty car to tootle around in for the summers, but they are a far cry from the early cars with chrome bumpers and better spec if you are an owner that enjoys good handling and at least somewhat spirited performance.

Chrome bumper cars are better spec higher output but are also often rustier because they are older, so you have to make a decision of exactly what you want to end up with. If performance is your thing, the early car is probably the way to go.

As far as engine swaps are concerned, the later cars are a bit roomier in the tunnels as they were designed to use the all synchro transmission that needed more space, but the early cars can be modified to suit with little trouble.

MG made two 'engine swaps themselves. One was the Rover 3.5 alloy V8 derived from the BOP 215.  The other was a straight 6 developed from the Austin Healey 3000 engine. In that one they needed heroic measures to get the engine in, including totally different front suspension using torsion bars instead of the coil spring MGB suspension.  This is an MGC I owned for several decades, with a modified triple carb engine that put out about 30 more bhp than stock.

 

RoddyMac17
RoddyMac17 Reader
8/8/19 1:57 p.m.

As already stated, ride height increase, single stromberg, different dash.  But also..

A 1977 would be a mark 4, so power brakes, rear sway bar, different rear springs, different side mirrors (compared to the 71), different dash, steering wheel, center console, and shift lever/knob.  The dash had different switch gear.  The rad is mounted further forward, and the pedal boxes have a slightly different shape at the tops.  Body wise, the bit of sheet metal under the driveshaft at the back is different (due to ride height changes), and the rear quarters are missing the tips as the bumper covers that area.  The fuel tanks sender is different.  

To convert a RB to a CB crossmember is relatively easy, but you do have to also swap the steering rack as the pinon shaft is a different length.

81cpcamaro
81cpcamaro Dork
8/8/19 1:57 p.m.

The 1975-80 MGBs have the GT V8 firewall, so swapping the V8 in is a bit easier, clearance is already there. 77-80 have the radiator more forward, in the same place as the V8 cars had, just the inlet/outlet is different on the radiator. 1975-76 will still have the radiator in the early car position.

Ride height difference between chrome and rubber bumper cars is only 1". Swapping the early crossmember in will lower it, but like NOHOME said, it is more involved than just that. Enough that after talking with a few who have done the crossmember swap, I am staying with the stock crossmember in my 75.

75-76 cars don't have a sway bar at all, front or rear. 77-80 have front and rear sway bars.

wspohn brings up good points, the MGC does have different front suspension than the B. I do like the Cs though, maybe one day I will have one.

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