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MG MGB Technical - uphill battle

new carb made engine more responsive but i still have no real uphill power. IT kind of stays where it is and when it reaches the top it perks up again. A friend thinks i should time it to tdc at 2500 to 3000 rpm and not 15deg at 1500 rpm/He thinks its still too retarded hence the lack of up hill acceleration . The plugs are still black and sooty but better than before . I am thinking I should retime the dynamic way again. What about the timing chain? Any thoughts, thanks , Doug
dd doug46chief

Doug. I am not clear on what your friend thinks you should do. "A friend thinks i should time it to tdc at 2500 to 3000 rpm and not 15deg at 1500 rpm/" What does this mean? This would mean, to me, that your friend advocates retarding the timing even more than it might be right now. Some recommend setting the timing to 32 to 34 degrees before top dead center (BTDC) at about 3,500 to 4,000 rpm as this is the nominal full advance. The factory figure is 33 to 37 deg at 4,500 rpm with the vacuum advance line to the dizzy disconnected and plugged.

Have you run a compression check? Set the valves recently? Could the new carb be leaking air around the gaskets? Which carb did you recently install? How steep is the hill? Are your brakes dragging? All kinds of things could be causing your "problem", but you need to look at them in a systematic manner.

And, if you wish our help in sorting things, we need to know the dizzy your are using, preferably by model and specification number, and the carb you are using. That will help us understand what is happening/what might be happening.

Les
Les Bengtson

Les, I timed the engine by using the flywheel 10 deg mark and1500 rpm to the strobe light. My friend is saying keep advancing the dist at 3000 rpm to the tdc mark on the flywheel instead of the normal 10 deg mark at 1500 rpm. the dist is aftermarket electronic patronix. compression is fine at 155 to 160, valves are good,carb not leaking and the plugs are light brown as i checked them just now so mixture is good.carb is a weber dg elec chocke and it is open when warm and all works well. no air leaks,hill is about 20 degre,brakes are free.The marks on the flywheel are from tdc to 20 deg, how do i time it the way u say 33 to 37 deg before tdc? thanks , Doug
dd doug46chief

Have you checked the vacuum advance on the on the dizzy ? Barrie E
B Egerton

Barrie

The problem is unlikely to be with the vacuum advance as this only really comes into play with a high manifold depression ie on light throttle running. Doug's problem is on uphill roads, when the throttle will be wide open. This means very little manifold depression and hence no vacuum advance.

Doug

You say you have an aftermarket distributor, is this a new distributor or is it a Petronix unit fitted to your old distributor? If it's your old distributor I'd get the advance checked. In my experience the issue is worn/stretched advance springs. You can set it correct at low RPMs but you won't get enough advance at higher RPMs. The best way to test this is using an advance timing light, you just run the engine up to speed, say 4500 rpm, turn the dial on the timing light until the timing mark line up with TDC and read the advance from the dial.

Bob
R.A Davis

BOB ,its a new distributor. What dial on the timing light?
dd doug46chief

There are several types of timing light, not all have the advance control that Bob mentions. This allows you to set any amount of advance (within reason) by turning the knob to the desired number of degrees, then turning the distributor until the pulley notch is against the TDC mark. Conversely to read the actual timing at any rpms, turn the knob until the pulley notch is at TDC, then read the advance off the knob. If your lights doesn't have a dial then you will have to try advancing bit by bit and see if you get any improvement. However you can go too far, and either causing pinking on acceleration (high compression), or stalling the starter (low compression).

"My friend is saying keep advancing the dist at 3000 rpm to the tdc mark on the flywheel instead of the normal 10 deg mark at 1500 rpm"

This is completely wrong. For a start you can't even see the flywheel, the timing marks are on the crank pulley - on an MGB engine at least. And as Les has pointed out TDC at *any* rpms is retarded way more than it should be. If you start at 10 degrees BTDC at 1500 - remember 'BTDC' stands for *Before* Top Dead Centre - and advance it further, you are going away from TDC, not towards it. TDC is the last pointer the notch on the pulley passes. You may need to confirm that the pulley notch and timing marks are correct for TDC. A simple rule of thumb for this is to remove No.1 plug and turn the engine until the piston is at the top of the bore, then see if the marks are about in line. Doesn't matter whether it is the compression or exhaust stroke. Making a new mark needs a little more science. If it is obviously wrong, perhaps the pulley is delaminating and the mark slipping round, in which case there is not much point in making new marks.
PaulH Solihull

What is the brand of your new distributor? Most of the new distributors, on the market today, are set up incorrectly from the factory with wildly inaccurate centrifugal advance springs. RAY
rjm RAY

Paul ok found the timing light with degrees. Forgive my ignorance but can u tell me what to set the wheel on the light and how much rpm? I read what les wrote,33 to 37 at 4500 rpm WHEN IT HITS the Tdc mark then im good ? thanks Doug
dd doug46chief

Doug

Try this link for distributor info, http://www.mgb-stuff.org.uk/curvestext.htm find the graph that nearest suits your engine and use that, as Ray says if it's a generic MGB distributor it may not suit your engine. The first thing to do is map the advance you're getting from it and compare that to what your engine should have.

Bob
R.A Davis

thanks Bob
dd doug46chief

Just a thought but have made sure your dgev carb (you name dgv with electric choke - this is classified a dgev) is working properly. The cause could be a defunct accelerator pump and power valve...You also mention having sooty plugs. One of the symptoms of a faulty pump and valve is a too rich mixture - check your co emissions with a tester. Mine failed its mot recently as it was at 9%. I then started investigating what the problem could be (here on the site with a thread - Les provide the info) and found the pump and valve problem. Service kits are easily avaiable.
Just a thought...
/Moss
Moss

Moss,carb is brand new out of box and works fine and plugs are light brown.
dd doug46chief

That's good then...
/Moss
Moss

If you are timing to 10 degrees BTDC at 1500 rpm then you turn the knob to 10, run the engine at 1500rpm, and turn the distributor until the flashes show the notch on the pulley is in line with the TDC pointer on the case.

If you are timing to 35 (say) degrees BTDC at 4500 rpm then you turn the knob to 35, run the engine at 4500rpm, then again turn the distributor until the flashes show the notch at the TDC pointer.
PaulH Solihull

Paul thanks. I did a simple test and turned the dist about an 1/8 " clockwise and it ran smooth . I adjusted the idle down and went off. it was as if the car was new. I tried to get it to ping going uphill in 4th around 40mph and it just keept gaining power.After shutting it down It started right up no hesitation.I would always time my indian m/c by ear and figured id try it with the mg. I am now going to see where its at with the light. THANKS TO ALL. DOUG
dd doug46chief

Well there you go. With the very different fuels in use today compared to when the specs were issued (and everything was new) trial and error is about the only thing any of us can do.
PaulH Solihull

This thread was discussed between 23/03/2012 and 29/03/2012

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