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Feb 22, 2023 16:01:57 GMT |
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I recently fitted another cylinder head to this 1275cc engine
I took the head off one engine and directly onto the other. I didn't alter valve clearances
Fuel is getting to the carb and there is a spark at each plug
The plugs are the correct position on the distributor. It has new plugs
When turning over white smoke can chug out of the carb
There is oil on the plugs
There is no mark on the timing pulley to check the timing
I think the oil in the dashpot has gone somewhere. It was empty and a couple of days ago i put some in and it now seems to have gone again
The engine last ran 12 years ago and has sat without a head since then. It ran for years with the existing ignition / fueling setup
The head is from an engine which hasn't run for a similar amount of time but was running fine when removed
The carb has been sat in a reasonably dusty box but looks clean inside the float chamber
2 gallons of fresh fuel have been put into the tank and pumped through until fresh looking fuel came from the pipe before connecting to the carb
Nothing in terms of timing / ignition has been altered since it last ran
The single biggest thing i can think of is fitting the head from another engine
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Feb 22, 2023 16:16:47 GMT |
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Hi, It sounds like, at the very least, that the piston rings are seized in their grooves, try putting some diesel in the bores and hope it frees them up. other than that it probably needs to come apart. TBH it's asking a lot for an engine that's been asleep for 12 years to run without problems.
Colin
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Feb 22, 2023 16:43:08 GMT |
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Is the thinking that the rings are allowing oil to get past and onto the plugs?
This would mean low compression? So a compression test would be worth while
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goldnrust
West Midlands
Minimalist
Posts: 1,816
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Feb 22, 2023 17:25:09 GMT |
I took the head off one engine and directly onto the other. I didn't alter valve clearances .... The single biggest thing i can think of is fitting the head from another engine Checking the valve clearances would be high on my check list. The differences, in manufacture or wear, between the two engines could easily allow for some of the valves being held open and that in turn would mean no compression, and in turn could be a cause of your white smoke coming back out of the carb. |
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Feb 22, 2023 17:28:10 GMT |
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The fact it's actually turning over after 12 years without a head on is a blessing never mind running. There's obviously oil getting in the combustion chamber somewhere, either rings, valve guides or head gasket. What were the mating surfaces like when you put it back together? Remember you're dealing with surfaces where 0.0010" can make the difference between sealing and leaking.
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ChasR
RR Helper
Long Time Rambler
Posts: 9,929
Club RR Member Number: 170
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Feb 22, 2023 19:52:43 GMT |
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I think a few things need to be answered, before we start jumping to conclusions, but I think the posts above have been on the right track : i.e it's been asleep for a while, and had no head on the engine for a while, which will influence things
1) Can you hear any compression with it turning over, and is that compression even?
2) Have you done a compression test on the engine?
3) Did you slacken the rockers off when you torqued the head down onto the block (i.e was there any load on the valves when the head was torqued down)?
4) What Carb are you using?
5) Were either the head and/or the block checked the straightness? If so, how?
6) Did you torque the head to spec?
7) Did you use a fresh head gasket?
It probably is more than that, but it would be good to know what we're dealing with TBH.
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Last Edit: Feb 22, 2023 21:28:58 GMT by ChasR
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Sounds like your valve timing is 180 degrees out.
You can establish TDC by putting something like a thin screwdriver into the spark plug hole on cylinder 1 and watching it move until you can see the piston is at the top of the stroke. At the same time the valves must be closed on that cylinder to avoid the piston hitting the valves.
Personally I'm used to working on crossflow engines with a central spark plug but there will be a procedure for establishing TDC documented for the a-series engine in the MINI so look that up and follow it.
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stealthstylz
Club Retro Rides Member
Posts: 14,477
Club RR Member Number: 174
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Feb 23, 2023 12:55:56 GMT |
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I'd check the valve clearances first. If you haven't got feeler gauges just make sure they've got some by feel. There are too many variables to just swap heads without checking them.
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Feb 23, 2023 19:48:37 GMT |
I think a few things need to be answered, before we start jumping to conclusions, but I think the posts above have been on the right track : i.e it's been asleep for a while, and had no head on the engine for a while, which will influence things 1) Can you hear any compression with it turning over, and is that compression even? 2) Have you done a compression test on the engine? 3) Did you slacken the rockers off when you torqued the head down onto the block (i.e was there any load on the valves when the head was torqued down)? 4) What Carb are you using? 5) Were either the head and/or the block checked the straightness? If so, how? 6) Did you torque the head to spec? 7) Did you use a fresh head gasket? It probably is more than that, but it would be good to know what we're dealing with TBH. It turns over well and evenly. I tested the compression today. There is an even 100-125 psi across the cylinders I didn't loosen the valves when torquing the head down. Today i reset the valves. Around half seemed too tight I'm using a SU HIF44. The same one which it used to run on. Although it seems to be losing its dashpot oil Neither the head or block were checked for straightness I didn't torque the head i just did them up tight from the middle outwards I used a new copper gasket |
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Feb 23, 2023 19:51:39 GMT |
The fact it's actually turning over after 12 years without a head on is a blessing never mind running. There's obviously oil getting in the combustion chamber somewhere, either rings, valve guides or head gasket. What were the mating surfaces like when you put it back together? Remember you're dealing with surfaces where 0.0010" can make the difference between sealing and leaking. The mating surfaces looked ok. I cleaned them with wire wool but didn't measure their flatness Today it seems to be not making the plugs wet |
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Feb 23, 2023 20:01:20 GMT |
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I set the valve clearances with a 12 thou feeler gauge
I reversed the plug leads and it made no obvious difference
There is definitely a spark at each plug
Compression is even 100-125 psi across all cylinders
Fuel is getting to the carb
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Feb 23, 2023 20:43:49 GMT |
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The head needs torquing down to the correct level
Then the valve clearances need setting correctly , it’s been a while since I last did one but I’m sure inlet and exhaust are set different
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Feb 23, 2023 21:06:09 GMT |
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10 thou inlet, 12 thou exhaust from memory. Serial BMC A series owner since 1983.
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The issue is trouble starting. He has tested compression and got a good result. So whilst he should torque the head properly according to the factory procedure if he is getting the compression then it isn't head torque that's preventing it from starting.
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If your crankshaft is 180-degrees out of sync with your valves the wrong valve will be open/closed at the wrong part of the Otto cycle. i.e. you are trying to ignite the mixture on the exhaust stroke and you're blowing unburnt mixture out the exhaust. It'll never start like that.
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Feb 24, 2023 10:20:41 GMT |
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stealthstylz
Club Retro Rides Member
Posts: 14,477
Club RR Member Number: 174
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Feb 24, 2023 14:37:01 GMT |
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Cam timing could be 180 out quite easily, though distributor 180 out could also be a possibility.
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stealthstylz
Club Retro Rides Member
Posts: 14,477
Club RR Member Number: 174
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Feb 24, 2023 14:40:40 GMT |
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Did it have the distributor in when it was stood? If somebody has turned the engine over without it fitted iirc the drive gear lifts itself out of mesh.
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Feb 24, 2023 16:23:25 GMT |
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Admittedly I don't know the A-series well. But the theory in play is simply that your plugs are firing at the wrong time which can mean either the valve timing or ignition timing is incorrect.
I think if it's just your distributor out of phase you'll get backfiring. So I'd go with valve timing being the cause howsoever it has manifested.
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Feb 24, 2023 18:53:15 GMT |
Timing. Although i had already tried it i reversed the leads I also connected the Volvo to the battery to give some more oomph Using some cold start, it started. Sort of So i turned the distributor clockwise bit by bit and gradually it began to cough After about an inch of turning it fired up and ran well. Sounds so good after 12 years It now does this Taking it up the road the clutch arm has stuck down so i will have to fix that next then work on fine tuning it But result! I don't really know why it didn't start before when i swapped the leads but this time having the Volvo involved might have helped combing with the cold start How or why the timing is so out i don't know. I certainly haven't consciously touched the distributor but it appears to be backwards Thanks for the help and advice If there's spark and fuel it should start, correct!  |
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