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MG MGA - Volkes Air Filter Holes
I have just had my carbs apart yet again - front piston rubbing again, but properly sorted this time. Car felt slightly off tune on the way to work today. However, when taking the Volkes air filters off I noticed that I had previously put the rear one on upside down, effectively blocking the the 2 holes on the carb mating face. Question: Does this make any difference? What do the 2 holes do? Steve |
Steve Gyles |
Those are air pressure vent holes which, I believe, impact the movement of the piston. Regards, M.D. '57 Coule |
M. D. |
If that's the case it could account for my very poor fuel consumption recently, plus the little choke needed from cold etc etc. Test run tomorrow could be interesting. Car has not felt quite right for about 3 months now - since I last had the carbs apart. Steve |
Steve Gyles |
I think you've found it, Steve. Let us know. |
Derek Nicholson |
What a difference this morning. Needed choke like the old days. Idle has jumped from 800 to 1200 RPM. Let's see if that now improves my fuel consumption from 18MPG. I could kick myself for putting the filter box on 180 degrees out. Just did not pick up the error down in the dark inaccessible corner of the engine bay. Steve |
Steve Gyles |
Just spoken with Bob West. He confirms what M.D. has said and the symptons I have been suffering. Interestingly, he says that he frequently gets customer cars in for setting up that have the rear air cleaner installed 180 out! So, if any others of you out there are having mysterious carb problems and indifferent performance, have a look at your air cleaners! Steve |
Steve Gyles |
Good to hear you seem to be sorted. Seems like it'd be a good idea, though not original, to paint a nice white arrow on the inside of the filter backplate marked "UP". Must try and remember to do this to mine next time they're off. TTFN |
Derek Nicholson |
Regarding the holes: They are not vent holes. Their intended design is to allow atmospheric air to enter the underside of the piston. This in turn is offset by reduced atmospheric air on the top side of the piston from the induction manifold. All of this is counterbalanced by the piston spring, damper and oil selected to provide proper rise and fall of the piston and in turn the needle resulting in the proper fuel mixture based on engine demands. Don |
Don Tremblay |
Steve, Could you offer a brief summary of what type of problems you were having. I noted poor fuel milage and no choke but were there other symptoms?. Gordon |
Gordon Harrison |
Holes in general do nothing, if you look at one, there isn't anything there, more intersting is that they weigh nothing no matter how big they are. They are also very important and not enough credence is given to them. There must a fan club or something for them. Terry |
Terry Drinkwater |
Terry: I appreciate your wholesome humour! Gordon: The engine generally appeared to be working ok, although it seemed to be going a bit flat at higher revs. Unfortunately, I was also experimenting with different distributors and electronic ignition, so the cause of the symptons got a bit blurred. i.e. I had made the big mistake of creating too many variables at the same time: rebuilding the carbs, changing the dizzy and changing the diff to 3.9. It all came to a head on the way to work yesterday. I had accelerated up to 70-75mph indicated (closer to 75, speedometer underreading according to GPS). As I peaked my acceleration I was forced to lift my foot slightly because of a dawdler ahead, but the engine maintained its revs. I put this down to lag in the carb pistons and decided to inspect them for freedom of travel last night. The front piston was a bit sticky, then I removed the filters and the rest is history. Engine tonight was noticably very lively. Yippeeeeeee! Steve |
Steve Gyles |
Hi Steve I'm glad you've sorted it, I kwew my useless advice would come handy! Get the electronic ignition back on, I'm sure it will be OK. Re- the holes, I'll send you some photo's of the Sprint car I am building, you'll see what I mean. Still haven't found the babe! Terry |
Terry Drinkwater |
Terry If you can't find a 'babe' for posing on the bonnet of your car I'm sure we can all suffer a picture of you for the Gallery! The Coupe element on this forum need more examples posted. Just been for a longer drive and can absolutely confirm that my engine performance problems I have had since the end of July are well and truly sorted. And all due to a couple of pressure balancing holes being inadvertantly blanked off. I had never looked closely at them and always assumed that they were a couple of spare filter box attachment holes or suchlike that would be drilled out for some other vehicle type. I never paid any attention to them! Ho humm, such is the fun of owning and maintaining these vehicles. Steve |
Steve Gyles |
Just had another thought. Is it also likely that this problem may have affected the vacuum offtake to the distributor? i.e. A badly lagging piston would create a false vacuum value for any given engine acceleration, messing up the advance curve. Steve Steve |
Steve Gyles |
This thread was discussed between 29/11/2006 and 01/12/2006
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