poor accelleration

[ronnie]

hi , ive already been on about this in the past. against the grain ive just changed my distributor from a lucas 25D to electronic ignition , new leads and coil , ( 68 moggy 1000 ) .I done this because there is a distinct lack of acceleration on the wee guy , and as the carb is brand new i changed the dizzy even although there seemed to be no apparent fault with it. Ive tried advancing the timing to the point of pinkin but even under heavy acceleration at low speed in top gear i just cant hear it pink , even with the dizzy advanced so much that will hardly turn over due to firing well before tdc it still wont pink so cant get the timing right
any advice greatfully received
ronnie

[Neil MG]

Did you tune the carb first?

[ronnie]

no not yet , not exactly sure where to start with that ??

[Neil MG]

It's very simple, first thing to do is have a look at the plugs. Very sooty, carbon build up - too rich. Light coloured or glazed - too weak. This be clearest immediately after a longish run.

To get an initial setting, when the engine is warm remove the air cleaner and lift the piston with the lifting pin. The reason you remove the air cleaner is so that you can see the piston as it should only be lifted 1/16" to 1/8" or 1-2mm. Check that the choke is fully in and that the jet is pushed home (up). Listen to the engine as you lift the piston, if it obviously speeds up then the mixture is too rich. You need to turn the mixture adjusting nut in, (upwards) by two flats, then try again. Count the number of flats out loud so you remember where you started. If the engine slows down then the mixture is too weak and you need to turn the nut out or down by two flats at a time. The correct setting is when the engine speeds up very slightly then settles back to normal. Generally for me it works like you think you hear it speed up but then when you release nothing happens and this is repeatable. Every couple of minutes you may need to open the throttle to clear any unburned fuel.

Another possible cause of poor acceleration and no pinking is poor compression!

[mogbob]

When you remove the air cleaner casing , check that the Filter is reasonably clean i.e not clogged up with dirt.Change ..if it is black with dirt/ oil/ muck , other wise the engine will effectively be struggling to " breath clean "air.
Bob

[bmcecosse]

First check must be a compression check - if the engine is knackered it will not accelerate - no matter how much new stuff you hang on the outside! And -is it a low compression engine ? When were the valve gaps last set?

[ronnie]

yea sounds like i need a compression test bmc , what kind of reading am i looking for and as i crank the engine over and am i doing with the throttle on tick over or full throtlle etc
ronnie

[MarkyB]

distributor from a lucas 25D to electronic ignition

Did you change the distributor or just put an electronic module in it?
If the vacuum advance isn't working the engine will be very unresponsive.

[ronnie]

distributor from a lucas 25D to electronic ignition

Did you change the distributor or just put an electronic module in it?
If the vacuum advance isn't working the engine will be very unresponsive.

hi mark , i changed the whole dizzy brand new , the engine sounds really smooth and responsive in neutral but a bit lame under power , done what i think is a geniune 35000mls
ronnie

[bmcecosse]

Compression test on a hot engine - so after a good run. With a brick on the throttle - and all spark plugs out. Ideally looking for 170 psi on each cylinder. Good idea to set valve gaps first.

[ronnie]

Compression test on a hot engine - so after a good run. With a brick on the throttle - and all spark plugs out. Ideally looking for 170 psi on each cylinder. Good idea to set valve gaps first.

cheers bmc will check compression tomorrow

[katy]

i just cant hear it pink

I have the same problem, but it's my hearing that's at fault, just can't hear the higher frequencys very good any more.

[ronnie]

i just cant hear it pink

I have the same problem, but it's my hearing that's at fault, just can't hear the higher frequencys very good any more.

lol thats what it might be , getting old , lets be honest most folk that own a moggy have got one foot in the grave anyway lol

[MarkyB]

Does it make any difference if you disconnect the vacuum advance?
Block the hole in the carb with a bit of plastic bag and a rubber band.
Take it for a short drive, the difference should be obvious.
Revs when not under load don't tell you much.

[ronnie]

thanks mark will try that to
ronnie

[ronnie]

hi , i was told to do the compression test with the engine at running temp , stupidly i did it without even starting the engine. I got a reading of about 125psi across the 4 cylinders , can anyone say how that sounds cold against being hot ??
ronnie

[bmcecosse]

Well - it's obviously somewhat low. But at least you suggest they are all pretty much equal? The idea of hot is to ensure the oil is nice and thin, and the battery fully charged ! Take a new set of readings....HOT this time.

[ronnie]

hi, bmc , you mentioned a few questions ago was it a low compression engine ?? , how would i be able to tell if it was and would about 120psi sound right for a low compression engine . Will the engine being hot have no bearing at all on the readings . Should i try a squirt of oil down the plug hole to see what difference there is ??

[bmcecosse]

Would have L in the engine number instead of H - and cold oil drags horribly in the bearings and the oil pump/filter..... But also the battery will be cold/perhaps not fully charged. After taking dry readings - a second set with a few squirts of oil is often done to establish if that helps significantly to 'seal up' the rings. Don't worry about the readings too much - as long as they are all similar - that's the main thing!

[ronnie]

hi , bmc , whats your opinion on me not being able to hear the engine pinkin even fully advanced .Years since ive heard an engine pink but i remember it oh so well but even in top gear fully loaded just a poor acceleration .Even in st gear taking away no perkyness about it at all . Didnt have much of a run but the plugs were pretty sooty
ronnie