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4 Quick Questions

Started by march2013, February 15, 2013, 10:40:58 AM

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A couple of quick questions. First, my 1977 MGB has the original "Rostyle" wheels 14" -what tire size do you suggest? Second - the bottom clamping bar rotted off under the rear rubber bumper, the bumper seems secure, should that clamping bar be replaced?  Third - A mechanic replaced my throttle cable and eliminated the two throttle linkage return springs that went to the air filter, he said the spring on the carb "Zenith,Stromberg" is all that' s needed - is that correct? Fourth - Can the motor mounts be replaced without pulling the engine?

Thank you in advance.

Don Boudwin


Let me address your questions as they were asked.

1) The largest size tire the MGB body will accommodate without modification is a 185R70-14.  This is what I've used for years and like the ride and handling associated. 

However, I'm using oversized wire wheels on my car (14X6 as opposed to the stock Rostyle wheel at 14X4.5).  While the 185's will fit the stock Rostyles, the narrow rim width is not as well suited to them and there is potential fault putting those large tires on such a narrow rim.

With those wheels, I'd suggest staying with a maximum of a 175R70-14 as they fit the rim width a bit better and still maintain a decent footprint to improve the ride and handling over any of the stock size tires. 

2) The lower clamping plate is not structural, but does secure the plastic bumper cover to the frame.  If it were my car, I would replace it

3) On the Zenith carb, there are shaft-mounted return springs that should do the job, but then so do the HIF4 series carbs.  I've had the external springs break and find the throttles not seating adequately without them.  With the age of the car and the fact that these springs do weaken with age, I would have left those external return springs in place.

4) Yes the motor mounts can be done with the engine in the car.  I've done it myself.  Takes a bit over an hour using a floor jack.  Remove the bolts and raise the engine up from the front using a wood block along the front of the oil pan just enough as to be able to slide the mounts out and in.  The hard part is in lowering the engine to make sure all the bolt line-up.  because of the lack of clearance, drift or alignment pins tend to be too long.  I was able do without, but just some long bolts to be removed later can help.  I have put the bolts holding the mounts to block loosely in place and used a long pry bar and wood blocks to make the engine and mount positions final as necessary.

A tip to save skinning your knuckles is to invest in  a couple of "stubby" box/open-end wrenches, as they fit more easily in the tight spaces around the block.  The ratcheting types are expensive (about $60 a set from Sears or Lowe's), but work best.  You really only need a few sizes (maybe 7/16", 1/2" and 9/16"). I am not sure if you even need all these, but you can check on your car first.  Also, be sure to order new flex-lock nuts and bolts.  Makes re-installation easy and assures they lock down tight and stay there.

I hope that helps you.  Let me know if you have any other questions or I can be of any help.

Art Isaacs

American MGB Association
phone/text: 773-769-7084

North America's oldest and largest club for all MGBs, MGB-GTs & Midgets.  A nonprofit organization founded in 1975 and offers color magazines, emagazines, technical advice, member recommendations on service shops, registration of your MG, a tradition of service & FREE member classified ads that appear in the magazine & on the website.

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