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MG MGA - Flame Trap Position

I know we have had this debate before about the position of the flame trap and the concensus was that it fits to the second manifold stud in from the back of the engine.

However, I was just looking through my books to see if I could find the original spark plug wire positions for Russell Egge, when I cam across an original photo of a new 1600 MkII engine compartment (taken in 1962/3) showing the flame trap attached to the rear stud of the firing order brass plaque (where I have always had mine attached). See image. The photo is in P. Olyslager's MGA Motor Manual.


Steve Gyles

Can;t help you with placement, I just wish I had the holder for mine!
Steven B


They are available new, although you may have to buy the flame trap and pipe as well. Replaced mine a year ago.

Steve Gyles

Attached is a picture of the rear of a 1600 engine I have that came from a parts car. The location of the ground strap at the (incorrect) rear of the engine indicates some things have been changed over the years, but I suspect that the "flame trap" position has not been changed. It's looks to be attached to the second stud from the rear.


LP Pittman

Thanks Larry, that actually tells me a lot. From the previous thread on the topic about a year ago I had always assumed, from what everyone was saying about the manifold stud attachment point, that the flame tube was tucked down behind the heat shield adjacent to the stud. The picture I posted above could well be as per your image.

I have to say, though, why did the factory want to make the attachment point so difficult to access when there was the firing order plaque stud right along side?!

Steve Gyles

Clausiger definitely shows it on the second manifold stud. I recently fitted a new one on my 1600. The original one had been fitted incorrectly to the first stud and was upside down and had broken off. I found that the lengths of pipe either side of the trap on the new one made it impossible to fit it to the first stud without turning it upside down and the only way was as per Clausiger , although I did have to re-bend the pipes a bit to get them to fit clear of the manifold. As a point of interest James at Bob West advised me not to bother fitting it saying they now don't bother to fit them any more. David

Larry -
In the image you provided, I can't understand why they would run the copper vacuum tube right against the manifold, hottest part of the car. (Unless I am not seeing it correctly.)
Steven B

Larry's photo is more or less how it was on my very first engine many moons ago.
dominic clancy

Dumb Question:

I've never heard the term "flame trap" before. Is that the heat shield between the carburettors and the engine block?
David Breneman

There are no dumb questions.
The flame trap is part of the vacume line to the distributor. The following is from Barney's web site on ignition.

My question is this: Is the oblong metal chamber necessary, or can I just run a rubber vacuum line from the distributor to the carburetor without the chamber?"

Keep the fuel separator on the engine. The vacuum line on the MGA with H4 carburetors is connected to a port in the bottom side of the rear carburetor venturi, just at the bottom edge of the butterfly throttle plate. This is down stream but quite near to the main fuel jet. If (when) conditions allow liquid fuel from the jet to dribble along the bottom of the carburetor throat, the fuel can enter the vacuum port and be drawn into the vacuum tube en-route to the vacuum diaphragm on the distributor. The fuel separator is there to prevent liquid fuel from getting to rubber diaphragm.

Later model MGB have the venturi vacuum port on top of the carb throat where liquid fuel is less likely to enter the vacuum tube. Still later models use a vacuum signal ported from the top of the intake manifold where it is extremely unlikely to ever see liquid fuel. With the bottom venturi tap on the MGA it is more important to use the fuel separator in the vacuum line to the dizzy.
Kris Sorensen

Well, ya learn something every day (if you're lucky).
David Breneman

Hi all - I've been following this thread for the last couple of days - wondering whether I ought to fit the flame trap or not . A PO fitted it with a plastic tube that I have left for the 4 years I have owned it - seems to work OK - as Bob West indicates via David's post. Now reading what Kris says - maybe I should retro fit the flame trap - and it will fit the original appearance a bit more - cheers Cam
Cam Cunningham

Hi all mine is mounted on first stud, don't know if right way up

g c pugh

another shot

g c pugh


Your engine bay looks too clean. You need to start driving the car!

It would be logical, as described by Kris, for the pipe that comes out of the top to be attached to the distributor. Otherwise there is the possibility that neat fuel could find its way to the distributor. Conversely, I suppose it could be argued that vapour is more likely to catch fire/explode in the distributor.

Steve Gyles

Hi Steve didn't realise you were supposed to drive them as well as clean them

g c pugh


My mga twin cam Service Parts List shows the bottom of the flame trap going to the Distributor. I have attached an image. You cannot check on a Twin Cam car as the factory put out a Service Bulletin for all Twin Cam owners to remove the vacuum advance. Later production cars did not have vacuum advance.
What does the pushrod parts list show?
Maybe we need to know how the internal construction of the flame trap works (maybe it just has wire gauze like the old Davey designed miner's lamp).


Mick Anderson

Hi this seems to show correct position 26 says to dist. and 27 to carbs


g c pugh

This thread was discussed between 10/10/2007 and 15/10/2007

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This thread is from the archive. The Live MG MGA BBS is active now.