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Crankcase pressure Leaking oil dipstick


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Hi Guys,

 

Just replaced the PCV diaphragm and also a rebuilt fuel pump from Dave Davies. I now have oil coming out of the dipstick and a steady trickle under my fuel pump. Dipstick has the felt washer.

 

I noticed from the PCV diagrams that I don't have the disc part that goes between the diaphragm and the lid. All pipers are new.

 

When I disconnect the rocker cover pipe to the PCV the dipstick leak goes but the fuel pump leak remains...nuts done up very tight, correct 2 gaskets from Dave.

 

Would I be best to ditch the PCV and run a hose down by the block? How would I block off the manifold inlet pipe? Is there a kit?

 

Any thoughts greatly received

 

Colt

 

 

 

 

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Hi Colt,

 

The PCV isnt working and your crankcase pressure is high.

 

You'll likely have oil coming past the rear main as well.

 

Is your PCV plumbed in to the inlet manifold correctly? is there any restriction there? is it better if you leave out the rubber diaphagm?

If the answers are Yes, No , No then i guess the engine has significant blow-by and a block vent will help squeeze a few more miles out of the tired engine.

 

got any pics of the arrangement to share??

 

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Considering the emissions being dumped out the average Tr exhaust then adding a few fumes via an open vent pipe is insignificant! Dump the PCV it's just something else serving no useful purpose which could go wrong.

Pump flanges don't usual leak, is the flange flat or have you got a crease in the extra gasket Dave supplies, I use just the one standard gasket.

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Leak on dipstick has returned but much less. Also the car is smokey so I think il passing through to the carbs?

 

I believe the PCV is the culprit. Removing the diaphragm makes it run more erratically up and down.

 

Picture of set up below. I am fairly desperate to get this thing on the road now having spent 9 months re-commisioning so I ordered a new PCV

and the lower pipe as mine is a little kinked. Thanks for the offer Steph.

 

Ideally I'd prefer the breather like the TR4 but from what I've read fitting it low down on the block with the engine in place is a nightmare

so not sure on that. Is removing the PCV, running a pipe from the rocker cover over the carbs and blanking off the inlet manifold not enough on its own?

 

 

Breather_zpsv6zg0cvw.jpg

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Hi Colt,

 

Just venting the rocker cover likely not enough...all the gasses from the crankcase have to travel up the pushrod tubes to get out the rocker cover...that creates some backpressure downstairs and the leaks you are seeing. Your pic looks all quite original. The PCV is meant to suck the fumes out and prevent the backpressure...if the engine is worn it won't be able to keep up.

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Alternative arrangement is remove the leaking fuel pump and replace with a made up plate with a 1" pipe feed off it pointing downwards with a pipe on it venting to air (you could use an "alloy catch tank" on the inner wing and vent the rocker cover pipe AND this pipe to it if you preferred). Then use an electric fuel pump for fuel supply, Moss sell them or available through many sources, ...two fixes in one.

 

Mick Richards

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Colt,

 

Not sure if this is relevant but you do not have a TR4A type of PCV. It may make no difference but the TR one looks like this.

 

http://www.ebay.com/itm/Triumph-TR4A-GT6-MK2-MK3-NOS-PCV-Emission-Valve-/141887193376?nma=true&si=KYr7Yh%252BKWQUqbM%252FfrtZXX6iDB3s%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

 

Cheers

 

Graeme

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Thanks. Unusual looking cap, I replaced mine with a new one as it wasn't sealing properly. I may put the old one back on with the new seal.

 

Mick I like your suggestion, if the problem persists I may well go with that option and run 2 pipes down. 1" seems very large?

 

I have a new pcv on order to see if it cures the problem. What you say makes sense about the pcv sucking and keeping up.

 

The whole engine bay is a bit smoky currently.

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yes, but you don't have the original 4A vented oil filler cap which would provide significant breathing improvement....

+1

Also used on TR250.

 

What oil are you using?

I had fumes and oil mist issues until I went over from Auchan 20-50 (French supermarket) to Millers

 

Peter W

Edited by BlueTR3A-5EKT
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1" seems very large? "

 

Nope, gives the engine a chance to displace those crankcase gases at the bottom instead of blowing the oil out past the scroll seal on the crankshaft and trying to turn the rocker cover into a balloon via the push rod tubes. Obviously the better breathing helps remove any critical area of breathing on the top end of the engine also. That's why almost all the racers run a derivative of the same thing, the area behind the passenger wheel arch and up to the engine firewall and passenger toe boards looks made for an oil mist catch tank, which is where drivers place it, handy for the fuel pump cut out in the block (only about 12" directly above it)and the rocker cover breather can be routed that side also.

 

Mick Richards

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+1

Also used on TR250.

 

What oil are you using?

I had fumes and oil mist issues until I went over from Auchan 20-50 (French supermarket) to Penrite

 

Peter W

 

Maybe but the actual hole that vents in that cap is only about 1/16" in diameter.

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If your PCV is working you don't want a cap that vents too much, that would not allow the PCV to create a depression in the crankcase. However, that might be moot as your PCV doesn't look correct as Graeme observes. If you can get it working though you should be OK with a sealed cap as the depression will try to draw air through the dipstick tube. Your symptoms began when you replaced the PCV diaphragm, presumably it was OK before, so perhaps it was the wrong part for your PCV.

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Success! No more leaks or revving.

 

However....after setting the float levels the car ran, we then fiddled with the mixture controls on the carbs and it wouldn't start.

 

Finally got it running by removing the top of a carb and forcing air in. Now it will only run rich with black smoke, leaning the mixture makes it stall :(

 

Wondering if the stronger springs I bought for the carbs are not allowing the piston to move upwards?

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Success! No more leaks or revving.

 

However....after setting the float levels the car ran, we then fiddled with the mixture controls on the carbs and it wouldn't start.

 

Finally got it running by removing the top of a carb and forcing air in. Now it will only run rich with black smoke, leaning the mixture makes it stall :(

 

Wondering if the stronger springs I bought for the carbs are not allowing the piston to move upwards?

 

Firstly after dozens of hours data logging Strombergs with different springs, damper oils etc the one thing I can tell you is that unless tuning for performance (not road use) the last thing they ever need is stronger springs (correct springs yes).

 

Secondly be thankfull you have Stromberg's far easier to set up than SU's!

 

Not sure what you mean by removing top of carb and forcing air in? If by this you mean you unscrewed the damper and blew down it? But anyway whatever it sounds like the piston wasn't dropping properly, have you bent a needle?

 

When you say fiddled with the mixture controls? are these adjustable needle Stromberg's or adjustable jet Strombergs?

 

If it was me and I wanted to just get running OK'ish from where you are.

 

(I suggest that you do this one at a time as mixing up air slides etc can cause problems)

1) Remove the damper

2) Whip the top off the carbs

3) Extract the piston and diaphram

 

Examine the rubber diaphram does it have any holes (hold up to light) if it does order new ones and give up until they arrive.

Pour out any oil you filled the damper tube with.

Check that the needle looks straight, if its a sprung biased adjustable needle (i.e. you fiddled with the mixtures by using a special tool down through the damper tube) then initially set the needle so that the shoulder is flush with the surface of the piston (this is normally good enough for normal running) If its not sprung biased then just make sure the needle is fully seated.

Now refit the piston and diaphram, making sure that the tang on the diaphram locates in the little indentation in the carb body. Check as you doing this that the holes in the bottom of the air piston are towards the engine (it can be easy to fit the diaphram in the incorrect rotation).

Now put the top on the carb (dont fit the springs yest) just lightly fit the four securing screws so that we know its aligned.

Now through the carb intake lift the piston full height and let go, if it takes a couple of second to drop and closes with a clunk your probably OK. If it either takes forever or hangs up or doesn't fully close, then either the needle is bent, the jet in the bottom isn't centered, or there is **** on the air piston surface or the carb body surface. If it still isn't falling after you have checked those then this may be the time to check that someone in the past hasn't mixed up carb tops, air pistons and carb bodies (its easy to do if you have taken them both apart to clean and refurbish without realising that they are factory matched) Mark the bits up so you know here they came from and try playing mix'n'match between the two carbs. May get you nowhere, but easier than junking the carbs.

 

NB I can tell you from looking at your picture in post #5 you have the carb tops fitted 90deg out (and yes it does matter) the writing on the top should be sideways on i.e in the correct reading orientation if you are looking from the rear of the car forwards!

 

Untill the pistons drop smoothly with a clunk, its not worth going any further.

 

OK now fit the springs (I'd use the old ones if they look identical) and again check that both pistons drop at about the same speed.

 

 

 

OK a little bit of oil in the dash pots won't hurt, remember you only want to fill to just below the the top of the air piston inner tube, not the whole body. Me this time of year as its warmish if you have a 20/50 Mineral oil I go for that, if its synthetic then its too thick so go for something like ATF, to be honest as all your trying to do at this point is get in running cleanish it won't make much difference.

 

OK if you have adjustable jet carbs wind them both right up so that the jet is at the bridge and then wind down two full turns, it will do we aren't looking for fine tuning at this point.

 

Now slacken off the linkage between both carbs and make sure they move independantly.

Back both throttle stop screws off untill just clear, and then back on evenly maybe just two turns.

Check both chokes are adjusted the same, and not in action.

Nip up the linkage between both carbs

Give it a bit of choke

Give it a whirl.

 

Assuming the fuel pump is working, and you don't have fuel pissing out of the jets because of stuck needle jet, and you have static timing set anywhere between 5-15 btdc it should fire and run OK'ish.

 

If it doesn't then you need assistance!

 

If it does you now need to set them up properly.

 

NB even if you buy new/refurbished carbs you will still need to do most of this anyway, but at least you would know that the carbs are sound.

 

There are lots of good threads on setting up strombergs on the net, but a not bad one just at random is

 

http://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm

 

Alan

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Thanks Alan.

 

Most of that has been done. All new parts including jets, needles, diaphragms, spindles, butterflies, etc.

The front carb we got to go blue on the colourtune tool (lean) The rear carb we adjusted the mix knob all the way as lean as possible and it was still running yellow (rich) The car then wouldn't start or 30 or so attempts, then started immediately with the rear carb having no top or piston, we then found it would only start by manually lifting the pistons using the small lifting plunger on the carb. Today it started as normal. I have re ordered new standard springs for the pistons.

 

The pistons were sticky and I ran the lids over 1200 grit on a glass table which helped.

 

It really matters which way round the lid is??

 

Thursday night I will follow your order of things and rebuild them again and put standard springs back in

 

Colt.

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The fact that it started with no top or damper rod means that the piston could then lift a bit and you got some fuel/air mixture in, likewise manually lifting the pistons did the same thing. So something was making the pistons not want to lift. Strong springs won't have helped that.

 

Cleaning the pistons and the bore it runs in won't hurt, go for the lightly cleaning polishing approach rather than trying to remove metal. Without springs or damper rod but with the top on, the piston should slide easily up and down, if it doesn't you have a problem. NB you may need a tiny bit of lubrication between the damper tube on the piston and the bore of the cap to achieve this, but heavy oil even without the cap and damper installed will firm this up. NB with the piston and cap off check that the pistons slides smoothly in the cap before checking the same with them in the carb body.

 

Yes the bore on the cap and the piston were machined in the orientation I described and as they have now spent a few decades (or maybe not depending on when they were missplaced) running in that orientation moving them around or swopping bits carb to carb can result in missalignment. If you look closely at the cap and the body when you have them in the correct orientation you should see a small protrusion on both cap and body that align and are facing outwards. Whilst they may have been missplaced many times in the past it isn't going to do any harm at least trying to put them back the way they were intended to be.

 

Take the rebuild slowly and check that piston rise and fall as you go, even not having the cap level and firmly seated can cause the drop to stick when testing. By the time you get to having the springs in and the dampers and a bit of oil in there, they will require a reasonably firm pressure to lift. Given your description and as at this point we are trying to get it running OK'ish and not tune it, I might be tempted to just put a dash i.e. about 2ml of brake fluid or ATF in the dash pots rather than oil, it will make them a bit "lift" happy but initially that might not be a bad thing. And its dead easy to drain and refill (as by this time you will be able to get the cap off and the piston pulled in about 30 secs) :) I actually use a syringe with a bit of tube on to empty the dash point tube (but I might change the oil 4 or 5 times a day when testing).

 

I could be wrong but I suspect that the over richness on the rear carb was because the piston wasn't lifting enough and the air being pulled through a small choke gap was thus pulling too much fuel and way too rich. People tend to think that CD type carbs go rich because the piston has lifted too much or the needle is wrong, when quite often its because the piston hasn't lifted enough.

 

Put both jets back to about 2 turns down to start with again, the colourtune will help you.

 

Good luck

 

Alan

Edited by oldtuckunder
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NB. forgot two things:

1) check the damper rods aren't bent, that will hang up the rise and fall of the piston, they can be GENTLY straightened.

2) Slightly more subtle there should be a small needle sized hole drilled through the side of the damper cap about one thread down from the top and likewise about the same size hole drilled through the neck of the cap. These sometimes get blocked or the cap has been replaced and it doesn't have a hole. If either of these are blocked then air can't escape or be drawn back into the damper chamber when the piston rises and falls. The holes dont have to line up when the cap is screwed in, the air will find its way around the threads.

 

Alan

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