Tech Tips: MG MGA

EXPERT: Glenn Lenhard 
Glenn’s MG and British Car Repair
(888) 521-9890

There are many assemblies that look at first glance like they are able to be assembled either of two different ways, but when they are examined more closely, you will see a difference that is critical to proper operation. One such assembly is the bonnet pin sliding latch plate.

This plate has a hole in the center that has a protrusion on only one side that keeps the pin from being pushed sideways by the tension of the spring. If this plate is put on the wrong way, your bonnet can latch itself against this fixed plate, and will be impossible to open without great difficulty.

This protrusion is also quite often just worn away and, of course, this is something that is easily overlooked. This is not mentioned in any manuals.

Many owners of British cars have broken down when the SU fuel pump decides to stop functioning without warning. In our shop, we offer an alternative, and in fact my own MGA has had one of these installed for close to 30 years.

The Facet Interrupter fuel pump is a design that dates back to the 1950s when it was produced by Bendix. I have removed several of these original ’50s-era pumps from cars brought in for restoration, and they still work. Hitachi then purchased the rights to produce the pump, and it was factory equipment for Datsun all through the 1970s, when the cars still had carburetors.

Facet now has the production rights, and it is available from many sources, including hot rod shops and the marine industry. Even some auto parts stores sell these, such as Advanced Auto and Carquest.

It is available in low pressure versions that are required for SU carbs. As an added bonus, this pump has mounting ears that exactly line up with holes of the MGA mounting bracket welded to the frame of the car. There is also an internal nylon mesh fuel filter that can be removed and cleaned on a regular basis. The bottom of the pump just twists off for access. If you never want to be towed in due to a bad fuel pump again, this is the one to use.

Fender welting is another thing that is a bit of a dilemma for the MGA owner. The original gray welting is a half-round version that is very soft, and does not lay down straight in the fender joints.

The material that is being used now, and for many decades, also begins to break down chemically and turn black from collecting dirt and such. It is not easily cleaned. If you start paying attention to what this original style looks like on other MGAs, you will see the esthetic problems from the material darkening, and the waviness of the installation.

Most of the MGAs that are restored here at the shop have custom fender welting, color coordinated to the car. We choose between the black full-round welting easily found at VW parts suppliers, stainless steel welting that can be purchased from Dennis Carpenter Ford Restoration Parts, and interior vinyl sewed over a nylon tube.

We have used the stainless on Old English White cars, black on darker colored cars, and then the vinyl version will either match the body color, or the interior color, depending on the required effect. I do this with good reason. All of these are period-correct methods used on many European and British cars of the era. Stainless can be found on Austin-Healeys and Triumphs, body-colored vinyl on the MG T-series cars, and black on Volkswagens.

If you are tired of the bottom seat cushion flipping up and coming away from the seat frame, drill a hole through the frame and insert a screw into the wood support. It is easily removed for cleaning under the seat when needed.

Anti-theft device: All MGAs have a dash switch for the optional fog light marked “F.” If you do not have fog lights, you can hook up the fuel pump to this switch. Now you have an “F for Fuel” switch.

Turn the switch off when you park the car. If someone decides to steal the car using either a key or a jumper wire across the ignition switch, they will make it about three blocks down the road before the car will just run out of gas. I can absolutely guarantee that they will just get out of the car and run away instead of calling a tow truck.

Yet another different use for the “F” switch: If you wish to run an auxiliary electric radiator fan for any reason, use the switch as an “F for Fan” switch. In fact, the output yellow/red wire is already sticking out of the harness near the radiator.

When rebuilding MGA brake calipers, break off or pull out the centering pins from the bores and use the less expensive MGB caliper pistons. The pin-style retraction system used on the MGA calipers was found to be unnecessary.

EXPERT: Carl Heideman

Eclectic Motorworks
(616) 355–2850

MGAs can rust severely, and anything on the lower 6 to 10 inches of the car can be rusty or even gone. Lower A-pillars and much of the B-pillars can also be heavily damaged. The rear fender and a shut-face panel in the doorjamb hide the B-pillars, and sometimes they’re almost completely missing–even if the fender and shut face have been replaced.

Corroded inside frame rails can be welded very successfully, and repair parts are readily available. The battery tray is the area most prone to rust; again, repair parts are available, although not all of them are of the highest quality.

Common red flags are poor door/fender fit, doors that pop open, and doors that don’t close easily. Even MGAs with solid bodies can have issues with doors not shutting properly or latches popping loose over bumps. While the factory pieces can be repaired, it’s usually easier to replace the latches and strikers with new parts.

It’s essential that the new door parts are properly lubricated and adjusted or they won’t offer any benefit. The cone-shaped strikers need shimming and sometimes even minor bending to properly mate with the latches. The latches benefit from a liberal dose of grease, especially where they contact the strikers.

The MGA chassis is very robust and holds up well to collisions. A sacrificial, replaceable front chassis extension usually takes the brunt of an impact. However, it’s common to find poorly repaired collision damage at the front of the car; look between the radiator and grille for evidence.

MGAs allow for a lot of parts swapping. For instance, early drum-brake examples can upgrade to discs from later cars or even MGBs. Engines, too, can be transplanted from other MGAs as well as MGBs. Anti-roll bars, rear axles and many other components are also interchangeable.

The downside of this ability to mix and match parts so easily? Some cars are not what they appear to be. It’s worth hiring an expert to help identify the parts in a particular MGA. Values seem pretty much unaffected by this parts trading, except when it comes to the rarer Twin Cam models.

MGAs tend to run a little hot, especially at highway speeds. We feel that as long as the engine stays below 195 degrees, there is nothing to worry about. (In fact, the engine is usually happier thanks to today’s ethanol-blended fuels.)

If the engine is running hotter than 195 degrees and the cooling system is in good shape, look at the distributor and timing. Many cars have worn distributors that are too far advanced at idle, making them not advanced enough at higher rpm. Check for 32 degrees BTDC timing at 3500 rpm (vacuum disconnected). Anything less can cause hotter temps at speed. We’ve seen hot-running cars with timing set as as low as 22 degrees BTDC.

MGAs have wooden floorboards that actually age very well. The most common problem area is under the driver’s seat. If the driver is heavier than a jockey, the aged board can sink too close to the exhaust system and occasionally even catch fire. Have someone check for clearance while you sit in the driver’s seat. If there’s no clearance or no heat shield, it’s time for a replacement.

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View comments on the CMS forums
wspohn Dork
11/29/18 9:32 a.m.

MGA - one of the best looking British sports car from the classic era.  I've owned many of them and still have three.

But non-original fender welting just looks totally wrong. On a Volkswagen Beetle, who cares? On a classic MG when you can get it right rather than wrong for the same price, caring is the difference. OEM is silver plastic - anything else smacks of ignorance or indifference.

Jordan Rimpela
Jordan Rimpela Digital Editor
10/11/19 8:11 a.m.

In reply to wspohn :

I couldn't agree more. 

8/20/21 12:12 p.m.

Agree, nonoriginal welting looks strange, except (maybe) in rare cases. Moss Motors welting degrades within 2 years, cracks and turns black. I hear B&G has better-quality stuff.

The Facet fuel pump is extremely (and continuosly) noisy and often overpriced. I removed it after a week. 

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