32 replies to this topic

[Edington]

After starting back in October 2013 to totally rebuild my 1969 Morris Cooper (including £6K's worth of new panels and welding) not to mention countless hours of work I'm running out of ideas to get it to run right! It's back to original spec with the addition of an alternator (the correct one for it's age), an unleaded head, three branch manifold with maniflow exhaust oh and Cooper S discs. I have rebuilt the twin HS2's  setting them up with standard GY needles and blue springs. Starts on the choke at around 1,000 rpm and runs up to normal temperature but does pop and bang a bit. I've been adjusting the mixture and timing but it just doesn't sound right. The only other thing I can think of is possibly the cam shaft. I can't remember due to the passing years whether it was an original one or one I had as a spare. As I take pictures all the way through the build back in February 2014 I installed the cam shaft, so what does 2J74 mean stamped on the end?

 

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[croc7]

Call Ghostbusters (Ac Dodd).

[Earwax]

Hi Edington

 

The forum probably needs a bit more info to assist you.  I would be exhausting all possibilities ( without endangering the engine) before pulling the lump out.

 

As you stated you are running out of ideas - so you have probably done these checks - but I would methodically run through a list of Fuel / Air ? Spark / timing possible faults

 

Ideas for you to confirm or cross out below or just get your mind ticking over other possibilities?

 

 

2014 to 2022 - rebuilt engine sitting? - in oil ?  Manually spun? Sitting with rockers and springs on etc - sticky lifters? 

 

Tiny bit of blue rag in inlet tract?

 

If most of the above items are from 2014 rebuild i would be checking condition of leads/ points/ condenser

 

Fresh fuel ?  Gunk of old fuel stuck in the bottom of float bowls? Air leaks - spray water to check  Springs and pistons in SU carbs free and moving at about the same rate. 

Newly painted - check earth strap, distributor earth through body? 

 

Sometimes to narrow down the list of all possible elements- ....swapping out for known good say distributor/ Leads/ Coil / saves time 

 

Possible compression test to double check valves are seating. 

 

Tappets readjust when warm???? 

 

It is highly possible you have 2 culprits - with one masking another  - eg misfiring lead and stale fuel - so sometimes you have to completely recheck back over your list after you find one culprit

 

Good luck ,, it sounds as if you are close

[Aly-g]

Have you got a mechanicle fuel pump or electrical pump ? Might be the diafram gone weak in the pump or leaking.

Allan

[Edington]

Even though this rebuild has been over some years the important things have been recently stripped cleaned and reassembled. The twin HS2's against the manufactures setting up procedure, tank cleaned and fresh unleaded petrol used, electric fuel pump that works (some leaks checked that out), I'm using using my MGB GT dizzy, coil and leads all gaps checked. Also good compression on each cylinder. I'm interested to check cam shaft out so how can I contact Ac Dodd croc 7? Photo of cam shaft in situ attached.

 

 I suppose I could get a new set of spark plugs but the GNK one's I'm using seem to spark well.  Any suggestions which?

 

As this is essentially a stage one exhaust are the needles and springs correct? 

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[sonscar]

Is that rusty?Stuck rings?leaky valves?Steve..

[red81]

You haven't mentioned timing yet.  It's running so I assume you have it set up with a strobe or static.  I found when i did my 1500 MG midget that it started after a head clean but was really rough, so I adjusted by ear, turned the dizzy until highest rev then back a little, the timing mark is way out but she runs lovely.  Before I did that don't forget the obvious; plugs points leads coil air filters, just buy new its worth it. Your twin carbs have to be perfectly (air) balanced as well before timing and after.  Have you done a compression test. also if you have those wire mesh pancake filters they may not match your new needles check that spec.

[Spider]

,,,,,,,, but does pop and bang a bit.,,,,,,,,,

 

I do note you've been playing around with the mixture, but this is usually from a lean mix.

That can of course be from adjustment but also a vacuum leak. Has the car got a Brake Booster ? Try Disconnect and plug the fitting to the Manifold for starters.

Is the Cam timing right ? If it's a tooth out, it can also do this.

 

[weef]

Hi really need a bit more specific information. When you say "pops and bangs a bit" is that backfiring or spitting back through the carb ?. 

Does it run better if the choke is used ?. You have to be well off in your settings for the engine to misfire as suggested.

If the cam timing was a tooth out would this be noticeable from the position of the distributor skew gear, I dont know it is not something I have thought of but someone on the forum may know as it would save stripping the cover off to see. 

[Edington]

Many thanks guys for all your comments. You wouldn't believe the range of issues getting this to run. After many minis since my first one a 1964 Super Deluxe saloon bought in 1970 this last one has thrown up so many faults (hopefully this is the last) that I've ever had to deal with, but it's not going to defeat me even if I have to take the engine out again. Interestingly one of those not had before faults that I discovered after scratching my head was that the originally dizzy was not clamping very well and it started rotating randomly. There was wear on the dizzy and the clamp was worn as well. Hence my old MGB GT dizzy and clamp was perfect for the job (I previously taken it off the MG to fit electronic ignition). 

 

So in response to red81 I'll be trying that approach and in response to weef above it randomly back fires and spitting back thorough the carbs, timing spots on the two sprockets are aligned and when up to normal temperature choke can be pushed in.    

[sonscar]

Too lean or valves not seating very well would be my thoughts.Was the MGB dissy good as they suffer from leaking heater take off sometimes.Vacuum advance good?mechanical advance smooth?Random thoughts,Steve..

[weef]

Both spitting back through the carb and backfiring suggest to me an ignition issue, mainly a fault with the distributor cap/rotor arm . Although I am sure you have checked and rechecked this area it maybe worthwhile replacing the rotor arm, cap and leads with a known good set.

Another thought would be to check the exhaust is clear with no blockages causing excessive backpressure.

Spitting back/backfiring needs some form of ignition and a pathway, ie a spark arriving in a particular cylinder when either an inlet or exhaust valve is open and this random fault you have suggests a sneak path in the distributor area.

This explanation is not intended to "teach your granny to suck eggs" but it is all down to basics.

[Edington]

The last to posts made me recall I had an issue on a previous mini I had. I can't remember the specific problem but it was an unleaded head and one of the hardened seats had come loose (I've still got it in my workshop)  so I'll put that exercise on the programme of things to look for just above taking the engine out! Also I did fracture a rotor arm a few years ago on a very fast road mini at Castle Coombe mini action day, good place for that to happen as bought another on one of the many stands.

[Earwax]

Another thought or two

Warping of the manifold/ head once hot - causing a lean leak? 

I know you asked for info on the cam , but I don't recognise those letters numbers - sorry - if you decided time has come to pull the head ( and I don't think you are at that point yet - but you could measure the lift of each pushrod - I don't know what wiped lobe symptoms are sorry, and without more info then timing at dot to dot is about is good as you can do

Again just re iterating some suggestions from above - arcing in distributor /leads etc - maybe crank it over at night and look at the light show under the bonnet . Distributor weights stuck ????I would at least try another coil and or condensor.

 

As you said - it will not defeat you - keep at it. Cheers Darryl

[Edington]

Had another go at it this afternoon, garage is nice and cool! Started on choke third time and rotated the dizzy till speed increase then backed off slightly. Ran at a steady 2,000 rpm so backed off the fast idle screw(s), they are a pain to get at on twin carbs without burning your hand on the exhaust manifold! So down to about 1,000rpm, the strobe pickup up my ruff timing mark. Was running up to normal temperature with occasional back fire and varying engine speeds and didn't sound great!

 

What is beginning to worry me is that as mentioned above concerning the unleaded head with the loose hardened exhaust valve seat is that I could have sworn this head I put on a shelf in my garage but checking through the mountain of stuff (mostly MkI and MkII bits) but the only two heads I found were leaded heads. Could I have been so stupid as to fit it on this cooper? Nothing for it but to check. So off will come the head plus I can accurately set No 1 cylinder to TDC using a clock gauge, nothing much to do during retirement accept build another engine!