Back pressure

[farmer]

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i'd just drill a larger hole in the oil catcher top!

[73 MK2 STAG]

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farmer wrote:

i'd just drill a larger hole in the oil catcher top!

yep think so, will do that tomorrow and i hope with red face i will come back and problem solved, however i do seem to get alot of condensation in the bottle !! para again.

[73 MK2 STAG]

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Hello all, Up bright and early this morning and taking FLYING FARMER AND FARMER ADVICE which was spot I might add and drilled a new whole the same size and the breather pipe of 13 mm. The previous hole in the cap was maybe 6mm and clearly lads you are correct that doesnt work. I took the Stagto a job I had to do which was a 90 mile round trip and she went very well indeed, no problems at all and the cap did not pop off this time. I took the pipe off and held the RPM at 3000 and the pressure seemed fine to me nothing out of the ordinary, it must of built up pressure in the oil catcher due to the hole being too small and popping cap. Any how onwent new cap and a nice drive home and the cap was still in place when I got back. AMS said to check when the oil filler capoff and I did, no fumes, no nothing besides a little oil spitting out when i raised the RPM, other than that at idle a very small change in RPM. So all seems fine but I still wanted to do the compression test none the less. Now after a 90 mile round trip I knew she hot so I let her cool down. Now out with all 8 plugs the plugs looked ok but as if she has been running rich !! a little black with brown on the tips of the plugs, i then cleaned them awaiting to go back in. I check the " STAG BY TRIUMPH REPAIR OPERATION MANUAL" for compression ratio and found that the 1973 onwards were slightly different to pre 1973. ENGINE TUNING DATA PAGE 05-1
Compression ratio 1973 onwards 9.25:1 Pre 1973 8.8:1

Working on 14.7 PSI TO 1 BAR This means 1973 onwards at 9.25:1 is in PSI 136 and pre 1973 at 8.8:1 is in PSI 129

So with this in mind I set out doing the compression test on my Stag. I must admit I thought the figures to be a bit low in manual. I expect them to more 150 plus !! Anyhow these are my reading done with motor warm BUT I DID NOT HAVE THROTTLE OPEN, not sure if that makes a difference, as I was on my own. I had rigged up a button in the engine so I could turn it over.
Cylinder7 112 psi 7.6 bar Cylinder 8 116 psi 7.90 bar
Cylinder5 112 psi 7.6 bar Cylinder 6 110psi 7.43 bar
Cylinder3 112 psi 7.6 bar Cylinder 4110psi 7.43 bar
Cylinder1 112 psi 7.6 bar Cylinder 2 120psi 8.20 bar
So if I take 120 psi being the highest and 10 per cent of that is 12 The difference between my cylinders is 10 between higest and lowest. A little tight or not ? To me if hadnt read the manual would be as depressed as anything right now, but they so seem low all the same or an I wrong ?? I do have to say even after a long run temp was spot on, hit 85 or just over and dropped back to 75 etc never once went over 87 degress but when got into traffic there was steaming like condensation coming from the tail pipes, you can see droplets of water just inside the tail pipes, in the oil catcher there was also condensation, so when oil does get thrown back into oil catcher it is mixing with the condensation thats why it gets creamy in there, but surely after a run like that there should not be condensation, ok in all fairness it was frezzing out but no rain ?? Have I just become paranoid or what !!! And now I have a new problemmy horn, radio, headlamp flasher, and clock all stopped working and ITS NOT A FUSE!!!! AAAHHHHHHH. Looking forward to your views.

ALSO CAN ANY BODY TELL HOW I CAN KNOW IF ENGINE IS PRE 73 OR NOT AS I HAVE HAD HER FOR NUMBERS OF MAYBE IT HAD AN ENGINE PRE MYSELF OWNING HER

all the best for now

[marshman]

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As I have always understood it the crucial things when testing the compressionare:

1.Are they all the same or close - within 10%
2.Do the pressures increase when oil is added to the bores.

You need to do the second test under the same conditions. As the pressures are quite even I would just try it on one cylinder - take all the plugs out though.

I would not be overly concerned about the actual pressures - they can vary due to temperature, cranking speed, throttle open or not, head skimming, gasket thickness etc.

The other crucial indicator is you say you are not losing water. The exhaust condensation is due to the cold temperatures - i was once told for ever gallon of petrol burnt a gallon of water comes out of the exhaust - not sure if its true but seems reasonable.

IMHO you have nothing to worry about on the engine side - the excess condensation is more likely due to the extended cold weather. The clue is it runs OK and is not using oil and water.

The electrical problem could possibly be due to the fuse box itself. They are well known for the rivets to breakdown through corrosion or just coming loose so that current does not flow from the wire to the fuse and vice versa. Check this first - i.e. volts both ends of the fuse and actually on the wires themselves.

Roger

[flying farmer]

imported post

All the figures for one bank are the same, and the figures for the other are similar.

Dont forget that all the chamber sizes might not be the same, particularly if the heads have been skimmed. If the head was bent like a banana before it was skimmed it is possible more was taken off the ends than the middle hence the higher compression here. I once had to have a head skimmed 10 thou more at one end than the other to get matched chamber volumes.

Dont worry if the figures are a bit low, if the throttles are shut the engine can't pull in a full charge

You will always get condensation in a catch tank unless the weather is very hot. About a gallon of water is produced for every gallon of petrol burned. If you consider the combustion pressure in the cylinder is probably several hundred psi at full throttle, it is easy to see that a fair amount of combustion gasses can squeeze through a 20 thou ring gap. These combustion gases carry water with them and it is this you can see condensing in the catch tank.

Similarly with the exhaust, grab the tail pipe after a drive on a freezing cold day and it will not be hot unless it has been a fast run. Don't forget a lot of water can be held in the silencer and it won't boil out untill exhaust pipe temperatures get over 100C

Neil

[73 MK2 STAG]

imported post

marshman wrote:

As I have always understood it the crucial things when testing the compressionare:

1.Are they all the same or close - within 10%
2.Do the pressures increase when oil is added to the bores.

You need to do the second test under the same conditions. As the pressures are quite even I would just try it on one cylinder - take all the plugs out though.

I would not be overly concerned about the actual pressures - they can vary due to temperature, cranking speed, throttle open or not, head skimming, gasket thickness etc.

The other crucial indicator is you say you are not losing water. The exhaust condensation is due to the cold temperatures - i was once told for ever gallon of petrol burnt a gallon of water comes out of the exhaust - not sure if its true but seems reasonable.

IMHO you have nothing to worry about on the engine side - the excess condensation is more likely due to the extended cold weather. The clue is it runs OK and is not using oil and water.

The electrical problem could possibly be due to the fuse box itself. They are well known for the rivets to breakdown through corrosion or just coming loose so that current does not flow from the wire to the fuse and vice versa. Check this first - i.e. volts both ends of the fuse and actually on the wires themselves.

Roger

Hi Roger

I should have meant that I did put some oil in one of the cylinders there was an increase but very small, it took it from 110 up to 113 psi, sorry I should have said that.
I did not do all as it was getting dark and cold and I was way beyond hungery at that stage, you I packed put her in the garage and now her with mug of coffee. thanks

[73 MK2 STAG]

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flying farmer wrote:

All the figures for one bank are the same, and the figures for the other are similar.

Dont forget that all the chamber sizes might not be the same, particularly if the heads have been skimmed. If the head was bent like a banana before it was skimmed it is possible more was taken off the ends than the middle hence the higher compression here. I once had to have a head skimmed 10 thou more at one end than the other to get matched chamber volumes.

Dont worry if the figures are a bit low, if the throttles are shut the engine can't pull in a full charge

You will always get condensation in a catch tank unless the weather is very hot. About a gallon of water is produced for every gallon of petrol burned. If you consider the combustion pressure in the cylinder is probably several hundred psi at full throttle, it is easy to see that a fair amount of combustion gasses can squeeze through a 20 thou ring gap. These combustion gases carry water with them and it is this you can see condensing in the catch tank.

Similarly with the exhaust, grab the tail pipe after a drive on a freezing cold day and it will not be hot unless it has been a fast run. Don't forget a lot of water can be held in the silencer and it won't boil out untill exhaust pipe temperatures get over 100C

Neil

Hi Neil

Yes very good point, and makes alot of sense. as the right bank looking from the front of the car, was extremely hard to get off at rebuild and had to be skimmed and yes its either end of it they are higher figures as to the centre two.

I never know that about water and temp, and also makes sense.

So all in all it looks like I paniced over nothing and then my Stag decided to give me a problem eg electricical lol.

I change the oil every 3000 miles and coolant each year with out fail. When she did give the problem with Jack shaft and water pump it cost me the whole engine rebuild as metal got down into the oil as made a mess of the oil pump. in the end cost me thousands back then in the good days when we were making some money now a days things have changed and work is a night mare and therefor cant afford to take chances. Not that one would anyhow ahh you guys know what I mean.

thanks again its great to able to chat which people in the know.

[ams]

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In view of your findings and that the compression test seems ok with measurements being fairly close together, I would just go back to enjoying your Stag. EvenIF the engine is breathing a little, this isn't a sign of impending doom. The fact that the car runs well and has good power suggests there is pleanty of life left.In factthere may not evenbe a problem at all other than the breather issue which you've sorted.

Cheers

Andy.

[73 MK2 STAG]

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ams wrote:

In view of your findings and that the compression test seems ok with measurements being fairly close together, I would just go back to enjoying your Stag. EvenIF the engine is breathing a little, this isn't a sign of impending doom. The fact that the car runs well and has good power suggests there is pleanty of life left.In factthere may not evenbe a problem at all other than the breather issue which you've sorted.

Cheers

Andy.

Hi Andy

I have used her most of the week, since sorting the breathing issue all seems fine. Today I was a little out of town and try to make it before rush hour, there were two others with me so 3 adults and she didnt skip a beat, Plenty over overtaking power on one straight and with the weight of us all and full boot, i put my foot down and she pulled very strongly and quickly from 70 up to 100 where i tapped off. If there was a compression issue i am sure it would of shown it then also no smoke when tapped off etc. when i got back I took out the plugs just to check and they look fine to me picture attached. The only issue is an oil leak from oil pump area which i will attend to next week think it could be the O rings.

[73 MK2 STAG]

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heres a close up some one maybe think this isnt good, but think they ok, please feel free to correct me
again thanks for all the help and advice