Back pressure

[73 MK2 STAG]

Hello everyone,

I have a Mk2 Stag with a Holley carb fitted, I have the breather pipe from the rocker cover to an oil catcher bottle. There is an hole in the top of the container to allow it to breath but it keeps popping of the cap.

I am concerned as this makes me worry about back pressure from the engine !!

She rarely needs topping up with coolant, or anything for that matter.

Oil pressure when cold is 55ish at idle when hot 40 plus.

Plugs all burn a rusty brown colour.

I had an issue while on motorway 70 plus MPH the temp would raise.

Fitted new sender had to go and test 5 till I got one that corrosponded with the gauge, eg 85 between the two dots the best i could get, some were show 85 degrees just at the RED on the gauge!

Thermostat another thing landed up going through 8 82 degree stats before i found open that was starting to open at 84 degrees and fully open at 90. Others I tested only started to open at 94 degrees.

So now she has a 82 degree thermo, fitted another temp and oil gauge to her.

my readings on temp she hardly goes over 75 degress !! at any point.


Getting back to my question,
1) back pressure from the breather pipe seems to be alot enough to pop off a screw on cap off the oil catcher bottle!
2) on cleaning out the oil catcher i found creamy substance in it, could be due to condensation eng bay temp etc. as there is sign of it on dip stick.
3) at times i can get a creamy substance on the inside of the oil filler cap. not alot at all and once wiped clean it takes ages for it to return.
4) My oil is clean nothing in it nor in the coolant.
5) She goes very well indeed as I said and doesnt use oil or water only the little that comes back from the breather pipe.

am I worried about nothing or should I check something else. I have had my Stag 9 years and this is a new one to me. The engine was rebuilt 25000 miles ago by a well known Stag man and he did a superb job.

welcome any views

[Snakey]

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I think a pressure test of the cooling system is on the cards....sounds suspiciously like the start of head gasket problems....Sssorry.

The TV8 boys will no doubt be more specific....my RV8 is very meagre with the consumption of head gasketssssssssssssssssssssss.

Good luck

[GDPR]

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Sounds like you have bore wear problems....... excess crankcase pressure can only be that really.

Have you carried out a wet and dry compression test yet?

Russ:dude:

[Arbman Al]

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I need a blood pressure test having seen Snakey's avatar return

[peter f]

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That reminds me - my shockers need replacing - they are a bit springy!

[73 MK2 STAG]

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Mant thanks guys for your replies,

My concern is the start of head gasket, but she is not overheating left her running in my drive for about 45 minutes, only intended for 20minutes and got busy cleaning the garage.
when I noticed the time I went out and the Kenlowe had kicked in temp gauge was showing 85 degrees and temp dropped back to 80 and kenlowe kicked out, took a good while still at ideal for it to get back to 85 for the kenlowe to kick again. Based on this I took it to be ok.

Bore wear, I totally agree would be the cause for excess back pressure. What I need to know is

1 what would be normal pressure
2 what would be excess pressure e.g how do I know the pressure I am getting is too much, the only reason i have noticed this is because I installed an oil catcher.
3 the engine was rebuilt and only has i am guessing no more than 30k on it with oil change every 3000 miles, full coolant change every year.


The way I do compression test is remove all plugs, insert my tester gauge to plug socket and turn over the motor with foot to floor on the gas pedal.

I will do a compression test on the engine, later today and report back, what do you mean wet and dry compression test ? ?

[Kevin Garrod]

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73 MK2 STAG wrote:

I will do a compression test on the engine, later today and report back, what do you mean wet and dry compression test ? ?

Do a test then put a drop of oil down the bore and test again if the pressure increases it suggests bore wear.

[73 MK2 STAG]

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yep the penny dropped when you said that about oil.

what compression should i expect to see reading wise when i do it???

[73 MK2 STAG]

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Kevin Garrod wrote:

73 MK2 STAG wrote:

I will do a compression test on the engine, later today and report back, what do you mean wet and dry compression test ? ?

Do a test then put a drop of oil down the bore and test again if the pressure increases it suggests bore wear.

hi kevin

is it better to have the stag warm eg get her warm prior to doing the compression test ?
would it make any difference to the readings if i did the test when its cold ?

[Kevin Garrod]

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73 MK2 STAG wrote:

Kevin Garrod wrote:

73 MK2 STAG wrote:

I will do a compression test on the engine, later today and report back, what do you mean wet and dry compression test ? ?

Do a test then put a drop of oil down the bore and test again if the pressure increases it suggests bore wear.

hi kevin

is it better to have the stag warm eg get her warm prior to doing the compression test ?
would it make any difference to the readings if i did the test when its cold ?

Oh dear you've found me out! I've never had to do a compression test on any of the cars I've owned, I'm just passing on 'received' wisdom. As I understand it the actual figure isn't too important but there shouldn't be too much variation between the cylinders, up to 10% is OK I believe. You should get somewhere around 100-150psi.

I'm not sure it matters if it's done hot or cold, I'll bow out now so someone who knows better can confirm.

[GDPR]

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Probably best to do it cold, except in the case where you have a misfire that appears when hot and that gives you a chance to check for sticking valves - however, you don't have a sticking valve problem so let's go with a cold engine.......

Do your 'dry' compression test on all 8 cylinders and note the readings - might be an idea to fully charge your battery before doing this, as it's going to get a bit of a thrashing......

Readings...... everyone has a different idea about this, but dry readings would be at least 150psi in an ideal world, a good bore, and spinning over on the starter at a brisk pace. You will also be looking for less than 10% pressure difference between cylinders.

I do my tests with the throttle full open and I count the compression strokes on the cylinder on test - usually 5 strokes unless the gauge shows significant continued pressure rise in which case count the required amount of strokes to get to final pressure and use that basis for all cylinders.

With the wet test, you are looking for the difference in pressures when tested under the same conditions as the dry test, but with some engine oil down the plug hole and into the cylinder - use a pump action oil can, and 3 strokes of the pump is usually the right amount.

A pressure rise of 15 psi or more is indicative of bore wear, and if you are more than 25psi up, then there is a lot of wear, or busted piston rings - or both.......

Let us know how you get on

Russ:dude:

[flying farmer]

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73 MK2 STAG wrote:

Hello everyone,

I have a Mk2 Stag with a Holley carb fitted, I have the breather pipe from the rocker cover to an oil catcher bottle. There is an hole in the top of the container to allow it to breath but it keeps popping of the cap.

I am concerned as this makes me worry about back pressure from the engine !!

She rarely needs topping up with coolant, or anything for that matter.

Oil pressure when cold is 55ish at idle when hot 40 plus.

Plugs all burn a rusty brown colour.

I had an issue while on motorway 70 plus MPH the temp would raise.

Fitted new sender had to go and test 5 till I got one that corrosponded with the gauge, eg 85 between the two dots the best i could get, some were show 85 degrees just at the RED on the gauge!

Thermostat another thing landed up going through 8 82 degree stats before i found open that was starting to open at 84 degrees and fully open at 90. Others I tested only started to open at 94 degrees.

So now she has a 82 degree thermo, fitted another temp and oil gauge to her.

my readings on temp she hardly goes over 75 degress !! at any point.


Getting back to my question,
1) back pressure from the breather pipe seems to be alot enough to pop off a screw on cap off the oil catcher bottle!
2) on cleaning out the oil catcher i found creamy substance in it, could be due to condensation eng bay temp etc. as there is sign of it on dip stick.
3) at times i can get a creamy substance on the inside of the oil filler cap. not alot at all and once wiped clean it takes ages for it to return.
4) My oil is clean nothing in it nor in the coolant.
5) She goes very well indeed as I said and doesnt use oil or water only the little that comes back from the breather pipe.

am I worried about nothing or should I check something else. I have had my Stag 9 years and this is a new one to me. The engine was rebuilt 25000 miles ago by a well known Stag man and he did a superb job.

welcome any views



I think everybody is missing the point here. If the cap is blowing off your breather tank the breather hole is too small. It needs to be the same bore as the pipe into the tank. I once had a problem with my first injected engine p*ssing oil out of every oil seal, filler cap and dipstick tube and it turned out the breather pipes cast into the rover plenum were carboned up internally. I had to remove a core plug to clean this out, but everthing was perfect afterwards
A touch of stag paranoia here I think
Neil

[ams]

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Hi,

I think you need to find out if you've got excesive blow by or impared crankcase ventilation. Try removing the oil filler cap with the enginerunning and increase the revs. If you get a load of fumes and pressure as you do this it may well be excesive blow by ie engine wear (best done with engine warm). If you get just a release of some pressure with little fumming, could just be a blocked breather.

I'm guessing the Holley carb conversion has been done a while, only I suspect the crankcase breathing system must have been altered to accomadate this. Just check all is as it should be here.

The recent cold weather may be responsible for added condensation in many a crankcase just now. This may explain the extra sludging. I'm trying to be optimistic..

Hope this helps.

Andy.

[73 MK2 STAG]

imported post

flying farmer wrote:

73 MK2 STAG wrote:

Hello everyone,

I have a Mk2 Stag with a Holley carb fitted, I have the breather pipe from the rocker cover to an oil catcher bottle. There is an hole in the top of the container to allow it to breath but it keeps popping of the cap.

I am concerned as this makes me worry about back pressure from the engine !!

She rarely needs topping up with coolant, or anything for that matter.

Oil pressure when cold is 55ish at idle when hot 40 plus.

Plugs all burn a rusty brown colour.

I had an issue while on motorway 70 plus MPH the temp would raise.

Fitted new sender had to go and test 5 till I got one that corrosponded with the gauge, eg 85 between the two dots the best i could get, some were show 85 degrees just at the RED on the gauge!

Thermostat another thing landed up going through 8 82 degree stats before i found open that was starting to open at 84 degrees and fully open at 90. Others I tested only started to open at 94 degrees.

So now she has a 82 degree thermo, fitted another temp and oil gauge to her.

my readings on temp she hardly goes over 75 degress !! at any point.


Getting back to my question,
1) back pressure from the breather pipe seems to be alot enough to pop off a screw on cap off the oil catcher bottle!
2) on cleaning out the oil catcher i found creamy substance in it, could be due to condensation eng bay temp etc. as there is sign of it on dip stick.
3) at times i can get a creamy substance on the inside of the oil filler cap. not alot at all and once wiped clean it takes ages for it to return.
4) My oil is clean nothing in it nor in the coolant.
5) She goes very well indeed as I said and doesnt use oil or water only the little that comes back from the breather pipe.

am I worried about nothing or should I check something else. I have had my Stag 9 years and this is a new one to me. The engine was rebuilt 25000 miles ago by a well known Stag man and he did a superb job.

welcome any views



I think everybody is missing the point here. If the cap is blowing off your breather tank the breather hole is too small. It needs to be the same bore as the pipe into the tank. I once had a problem with my first injected engine p*ssing oil out of every oil seal, filler cap and dipstick tube and it turned out the breather pipes cast into the rover plenum were carboned up internally. I had to remove a core plug to clean this out, but everthing was perfect afterwards
A touch of stag paranoia here I think
Neil

so many of friends tell me I am suffering from paranoia, I have had my Stag 9 years, landed up with doing a rebuild due to the water pump and jackshaft at the point of the gear shreading. cost a fortune, she has only covered less than 30000 miles sine rebuild with oil change every 3-4000 miles. coolant flush yearly.

I look after my stag very well and she serves me well, and any problems i have ever had was due to bad replacement parts in the past.

Neil what you say makes alot of sense and the whole was no where near the size of the pipe 12mm hole was maybe 7mm. Yes I have just seen a lovely oil leak on which has left a little puddle on garage floor.

many thanks

[73 MK2 STAG]

imported post

ams wrote:

Hi,

I think you need to find out if you've got excesive blow by or impared crankcase ventilation. Try removing the oil filler cap with the enginerunning and increase the revs. If you get a load of fumes and pressure as you do this it may well be excesive blow by ie engine wear (best done with engine warm). If you get just a release of some pressure with little fumming, could just be a blocked breather.

I'm guessing the Holley carb conversion has been done a while, only I suspect the crankcase breathing system must have been altered to accomadate this. Just check all is as it should be here.

The recent cold weather may be responsible for added condensation in many a crankcase just now. This may explain the extra sludging. I'm trying to be optimistic..

Hope this helps.

Andy.

Andy
thanks well the cold weather could certainly have something to do with it for sure. Yes the holley i put on maybe 6 years back. the breather hose used to run down the back of engine and down by the gearbox. Sometimes on club runs when i would open it up at times the fellow behind me would say notice a puff of smoke coming from under the stag etc, but only when I really opened it up. normally nothing.
My Stag has always even before the engine was rebuilt and still to this day even when warm at idle you would get a steady stream from tail pipe as if she was cold, like condensation no bad odours.

My car has plenty power no loss there at all.

Took oil filler cap off no fumes or anything from there just a large change in rpm at idle.

I use my stag alot to be honest and after 9 years of ownership, she driving as well as ever, everything seems fine besides what i have said in this thread.
Just something feels wrong! cant pin point it.

So I think wait for the weather to pick up and prey that solves one problem.
Make bigger hole for the breather on the oil catcher
find this new oil leak which seems to be come from bottom end.

maybe i am paranoid as everything seems fine from driving, oil pressure very good, temp is spot on. it just the signs she is showing. hhhmmmm. it was too cold to do the compression test i will do it tomorrow during lunch or something.

Another car my son has is show low compression i was thinking of putting in engine ametech restore anybody had any experance of it.

again thank you much for all the good advice and tips will let you know what the compression shows tomorrow