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Forum Categories => Tractors => Topic started by: cobbadog on 20 January, 2021, 04:26:42 pm

Title: Valve Timing
Post by: cobbadog on 20 January, 2021, 04:26:42 pm
For ages I have had an issue with this engine not running correctly.It runs really rough.
History was when I bought the tractor many years ago the oil pressure was way too low running at 5psi at running temp. So an engine rebuild was done using parts from davidbrownparts in the UK who were fantastic to deal with.
Since this was the first tractor engine rebuild I took my time disassembling the engine and took particular interest in this part of the engine, valve timing. I noticed at the time before undoing anything here that with the timing mark on the flywheel in the centre of the inspection hole, piston at TDC, both valves fully closed and the distributor facing #1 position that the dots on the cam did not line up with the gear on the crankshaft. Now at this stage the engine was running well but lacked oil pressure and compression was down a bit so I made my own new marks by making it have double dots on the crankshaft and cam gear. However if you look closely at almost the 1 o'clock position you will see some original dots there.
From memory when I discovered this I think I posted it up here and again from memory I was advised that this gear was possibly from a diesel engine and is why those dots are where they are.
So after trying many things over time I have now dug deep into here to see what really is the problem. As you can see the double dots are lined up as I found them when I stripped it originally and now they are still in the same position. I have been told that my next step is to put the engine on TDC and check the position of the valve at #1 and #4. At TDC #1 both valves should be fully closed and #4 should both be rocking, meaning the valves should be half open and half shut.

Does this sound correct?
My intention next is to remove the cam gear and rotate the cam until I get both valves closed at #1 and both on the rock or rocking on #4. Any thoughts are appreciated.
Cheers Cobba
Title: Re: Valve Timing
Post by: wee-allis on 20 January, 2021, 08:58:34 pm

Cobba,  with #1 piston at TDC, both #1 valves should be closed, with the correct tappet clearance and #4 exhaust valve almost closed and #4 inlet just about to open, ie "rocking. You can't improve on that for cam timing on s a David Brown or the majority of 4 cylinder engines, having a firing order of 1.4.3.2.

Personally, I doubt that your rough running is cam timing related. BUT I could be wrong. Been known to happen.

Steve.
Title: Re: Valve Timing
Post by: cobbadog on 20 January, 2021, 09:33:16 pm
Hi Steve and thanks for the info.
Your explanation makes more sense than one that was given to me a while ago so I will now look closely at what is moving and at what time.
IT was explained to me that the valves on #4 would be half open and the other half closed and from what I saw today that is not the case but your explanation might be what I am looking at.
I have a short day tomorrow with work so will get back to it then.
Thank you.
Title: Re: Valve Timing
Post by: cobbadog on 21 January, 2021, 04:35:15 pm
Well the cam timing is as I put it together and exactly as described in the workshop manual, both key ways facing down to 6 o;clock. Re checked the tappet clearances and all were good except one was a bit loose but not now.
Time to clean up and reassemble and look more in depth elsewhere.
Title: Re: Valve Timing
Post by: rustyengines on 24 January, 2021, 10:35:25 am
On most engines at top dead center both vales are just open (paper thickness) it is what is called vale overlap very common
Ian
Title: Re: Valve Timing
Post by: cobbadog on 24 January, 2021, 03:31:40 pm
Gday IAn. I'm not following the comment. If the tappets are not touching the valves and have the correct clearance are you saying that the valves are slightly open on #1? If so wouldn't that loose compression?
Title: Re: Valve Timing
Post by: rustyengines on 24 January, 2021, 04:54:42 pm
No the piston at top dear center the finish of the exhaust stroke

The exhaust valve about to close and the intake valve about to open this is where the rock should happen and tappets would just be touching

next 180 turn the inlet valve opens all but to end of stoke
next 180 turn compression stroke both valves closed
next 180 turn exhaust starts to open at bottom of stoke
next 180 piston at top as exhaust valve close and inlet opens

You only have check to this on number one piston
I think there is some confusion on what stoke I mentioned and you mentioned
Ian
Title: Re: Valve Timing
Post by: cobbadog on 24 January, 2021, 09:27:13 pm
Thanks Ian, #4 was the one you meant.
Not sure when I can get back to this this week but will try again tomorrow if time .
Title: Re: Valve Timing
Post by: cobbadog on 14 February, 2021, 04:16:46 pm
Well finally I am happy with the valve timing as it was from when I assembled the engine all those years ago and found no teeth missing and the valves are all timed correctly.
Next is the dizzy. So now I found out that I have a 'ring in' dizzy model DY4A and not the proper DZ4A. The difference is in the shape of the body as far as looking at it but I dont know what else. With a new condensor and coil it made no difference with the running of the engine with misfiring and flat spot. So I looked closer and today a mate noticed an issue with the rotor button. I would guess I have the correct rotor button for a David Brown even with the correct direction of the arm on the button but it is not a good fit on the shaft of the dizzy. There is a groove in the shaft for the drive lug to fit into and the drive drive lug is not as wide as the groove so it can move forward or backward. The mechanical advance is in good working order and has been cleaned up since I took the picture of the insides there. So at the moment I have it all back in place and static timed with "M" on the flywheel (Magneto) and the points just cracking and this is 7' or 8' BTDC which is where it should be set.
I once again drained the fuel tank and will dig out my endoscope and look inside it for flakes of rust. I am still getting fine rust settling in the glass bowl so I want to check that out and establish a good fuel flow to the carby. I will even strip the fuel tap and look inside again.
Title: Re: Valve Timing
Post by: oldgoat on 14 February, 2021, 09:53:03 pm
After you get it back together its probably time to borrow a timing light and check that the ignition timing isn't all over the place.
Title: Re: Valve Timing
Post by: cobbadog on 15 February, 2021, 04:40:06 pm
Yes, i have a timing light but I have to organise a battery pack to run it as the battery is on one side of the engine along with the dizzy and leads and the opening to shine the light into is way over the top of the engine and back at the bottom half of the bell housing. This is ok but I need to be quick because then the HT lead to the light has to sit on the exhaust manifold.

Some suggestions have been to use something similar to JB Weld and fill the gap on the shaft to centre the rotor. Getting this right could be a challenge if I go ahead with it as it could make the difference of a few degrees.
Title: Re: Valve Timing
Post by: voljon on 17 February, 2021, 08:36:27 pm
john, I have found that the DY4A distributor was used on Wolseley and rovers from 1946 to 1948, so the shape of the rotor top could be different and the arm on your DB rotor is messing with the timing as well as the loose fit. I have not been able to get a photo of a DY4A
rotor yet. regards,john
Title: Re: Valve Timing
Post by: cobbadog on 18 February, 2021, 03:54:07 pm
Cheers John,
I spent a little time after lunch to double check the fuel tap and that was all good. So I fitted that rotor button after double checking the sizes with the digital calipers and they were the same size. So turned on the fuel and started it up and it had a bit of a miss happening but I ran it for a while to warm it up and found it still had a flat spot but could not adjust that out with the air mixture screw and the 'miss' kept on happening.
So off with the dizzy cap and ran the multimeter over the HT and coil leads and again all were at 0.001 on the meter except the coil lead which was 0.003 but after a clean up of the spring to the carbon brush it did come back to 0.001 so that was good.
Did another start up and got almighty back firing happening so I shut it down and walked before I got too pissed off.
Will try again soon to find out what has changed so much.
Title: Re: Valve Timing
Post by: famous fitter on 18 February, 2021, 09:00:25 pm
Hi cobba.

Go out to the shed and start the tractor Tonight  , turn the shed lights off and look at the dizzy cap and leads In the dark . My guess is high humidity at your place today ??

See how you go.

Cheers Justin



Title: Re: Valve Timing
Post by: allisb on 19 February, 2021, 06:46:40 am
Guys, this is a real long shot.
But I can remember the apprentice working on a grey Fergie once, he?d rebuilt the engine and it ran terribly. Particularly at low revs. The reason? Valve springs. They looked ok, and in all honesty the new ones didn?t really appear that different. But that was the reason. New springs cured it, (along with a lecture from the boss)
Like I say, a long shot. But just throwing in my $0.02c in.
Title: Re: Valve Timing
Post by: cobbadog on 20 February, 2021, 09:51:28 pm
I re-visited the dizzy again today. We found the other day the rotor button is a poor fit onto the shaft. By this I mean that there is sideways movement on the shaft. Hold the shaft in the vice and with the back edge of the rotor button aligned with one of the lugs around the perimeter of the dizzy body that aligns with the terminals inside the cap then I could mo ve the rotor to the right by around 1/3 the width of these lugs which is possibly around 2mm.
Now thinking back there was what looked like a bit of cloth inside the rotor button and I thought it was a crude fix for a piece of felt that usually is found stuck in the end of the shaft as an oil holder and slowly let oil feed down the shaft to the bob weights. Now I am thinking this was a very crude way to remove this slack. I think the rotor button is not the correct one for this dizzy and have looked for a replacement.
I measured the gap in the top of the shaft that locates the rotor button then had to think outside the box to be able to measure the drive lug inside the rotor. SO good old blue tack came to the rescue. I rolled a piece up, stuck it inside the rotor and used a screw driver to push it against the drive lug. There is a difference of around that 2mm I mentioned earlier. So in the interests of being 'rough' I also replaced the piece of old cloth with some brand new cloth and made it into a "U" shape and sat it into the groove in the shaft and fitted the rotor button. It is now a firm fit. So while the dizzy was out I again stripped it down and went one step further than before and removed the bob weights to ensure they are clean and free to move and porperly lubed at the moment with light machine oil. When I spin the shaft the weights obviously move out as I do see them return back as it slows down. I also noticed that the weights do not return fully back to touching in the stop position. If I touch it they do but at the moment they wont and there is nothing stopping them returning. The springs are good and have tension on them but I have no idea why this is happening.

Then another helpful tip was put forward, bent or stuck valve even a bent push rod. So with out removing any push rods at the moment I rotated the engine and as each cylinder came up to TDC I was able to spin the push rods and there was no obvious siiiign of them being bent but I do relaise they need to be rolled on a flat surface to ensure this. The last time the engine was running it was bloody rough and some huge back fires with flames up the chimney, not good. So once again I checked the valves and looking especially at exhaust valves. All were to spec on the gaps but this does not mean that one or more are seating. Having said that, visually all valves both inlet and exhaust 'look' to be sitting at the same height. I am now thinking of removing the head and make sure that all valves are seated properly and that none are sticking. Sounds drastic but for a bit of time I can then discover if this is the source of my nightmares.

Hi allisb,
Thanks for that suggestion and is yet another reason to lift the head, strip it down. When the engine was rebuilt all those years back I did not replace the springs so this is a big help to jolt my head into gear.

I appreciated any and all input that will help me resolve this.
Title: Re: Valve Timing
Post by: allisb on 21 February, 2021, 09:24:47 am
Hi, I could easily be wrong. As I was once, (but that was last century)

But jokes aside, there has to be a reason for all this.

Thinking, while the rocker cover is off, with the valves closed, can you depress the springs by hand? Try turning it over as if you are setting the valve clearances, and press down on each one when it is closed.

All the very best with it
Rx
Title: Re: Valve Timing
Post by: cobbadog on 21 February, 2021, 01:24:17 pm
Cheers allisb,
I will check but when playing with both valves on #4 they are very hard to push down, to the point I had to use a screw driver to lever them down then pull it out quickly to get them to snap shut. Not the test you have asked for but will have ago at it tomorrow by trying just that. I cannot turn the engine over by hand at all with the spark plugs in so they come out first but very easy thing to do.

https://youtu.be/7Ec7MdevOyo

Above is a link to the video made today. No back firing or flames out the chimney, good start. Still has a flat spot from idle and this is as good as it gets at the moment and the air mixture is 3 turns out with very little if any black smoke at idle which is an improvement. After a lot of going back over what I have done  time and time again I did finally twig to a piece of cloth that was inside the rotor button. For years I thought this was suppose to be the missing piece of felt that sits in the centre of the shaft beneath the rotor button. Now I believe it was jammed in there to take up the slack between the drive lug and the groove in the top of the shaft. So I took the correct steps to fix this, made another bit of rag.  :o
It does centre the rotor to the groove and has removed that freeplay and since doing this it has stopped the back firing and flames. I am waiting for an answer about a new rotor button so will order it if it will be correct. Timing once again was set as a static timing to the "M" on the flywheel so next attempt will be rigging up the timing light to see what happens.
I am still very much considering to lift the head and check the valve faces and seats plus springs and look and feel for a sticky valve.
Title: Re: Valve Timing
Post by: oldgoat on 21 February, 2021, 11:45:37 pm
A compression test will save you dirty hands and the effort of undoing a lot of nuts. If the values aren't in spec then you can dismantle to your hearts content.
Title: Re: Valve Timing
Post by: cobbadog on 22 February, 2021, 04:11:18 pm
Did another compression test today on a cold engine and all came in at 65psi which I thought was a bit low. Then just now I remembered I did NOT open the throttle to full so will have another go tomorrow.
Bought a NOS dizzy cap genuine Lucas in box and a Bosch GL229 rotor button which suits this dizzy I have. Also found that the picture in the workshop manual is NOT one to suit the early 30C, must be to suit later models.
The DX4A and DZ4A were both original fitments to the 30C from 1949 - 1954 along with a long line of pommy cars Austin A90, Land Rover for just 2 years, grey fergy, Vanguard obviously Sunbeam one model and so on around a dozen vehicles all up.
Then when looking at it again today I saw this, the condensor wire which was running close to an earth and might be able to jump so I moved it 1/4 turn.
Title: Re: Valve Timing
Post by: allisb on 22 February, 2021, 06:51:36 pm
Sounds like the valve springs could be well ok. You may be on to it with the dizzy parts, especially if it has improved.
you?ll certainly expect better compression with the throttle open, but being all even is a good start. You may not have to lift the head.
You?re winning!
Title: Re: Valve Timing
Post by: cobbadog on 22 February, 2021, 08:58:41 pm
Thanks for the support. It has been doing whats left of my brain in for ages and yes it does feel as if I am getting somewhere.
Cant wait to do the compression test again but properly as last time I thought it was in the high 70's then get the new parts.
Title: Re: Valve Timing
Post by: cobbadog on 04 March, 2021, 04:46:42 pm
New cap arrived today and the rotor button I can pick up tomorrow and try to resolve this bugga once and for all over the weekend.
Title: Re: Valve Timing
Post by: allisb on 04 March, 2021, 09:11:14 pm
Fingers crosse for you
Title: Re: Valve Timing
Post by: cobbadog on 05 March, 2021, 09:13:34 pm
Cheers, the rotor button arrived today so at some stage over the weekend I ill have yet another go at him. With all this rain and humidity the grass is taking over everything and neds mowing so it will be done with an industrial mower, then get more done on the mower deck off Husky then this engine.
Title: Re: Valve Timing
Post by: cobbadog on 06 March, 2021, 09:11:18 pm
Well the new cap was fitted and the rotor  button is not correct. I believe they sent the wrong part so will check that out on Monday. Did a start up and ran it for a while before lifting the revs to maximum and back to idle after a brief run. Still sounds as if it is running on 3 cylinders sort of. So at idle again I started pulling the HT leads one at a time and seems that #1 is the missing pot. AS it was late in the day and I was stuffed from being hunched over the mower deck welding I gave it up and will get back to it tomorrow after more welding.
I will re-test the HT lead with the multi meter and try another spark plug and I have a lot of spare ones that I have been rotating about trying to find out what is wrong here. I was disappointed that the rotor button is wrong and I was hopeful that was going to be the problem, time will tell.
Title: Re: Valve Timing
Post by: cobbadog on 24 May, 2021, 04:15:55 pm
Well for a very long time but only when I could I have been having fun trying to solve a problem with the 30C. Found a slight issue with the needle and seat in the carby and replaced the seals on the main shaft to ensure no vacuum leak there. Went over to the ignition and replaced everything from coil to plugs and everything in between and yet it still ran rough. Pulled the front off the engine to double check the cam timing and also double and triple checked the valve clearances. All of this has been done over many attempts as time has been available and last weekend I sat down with him with a carton of beer and we had a very long talk about why he was being so bad. We talked for a while and then I went inside for lunch and when I came back for no reason he started running like he used to. So I then got down to adjusting the air bleed/mixture screw and got rid of the small flat spot and allowed him to run for a fair while. I took him for a drive up and down the driveway and thought this is good. Next time I will just sit down with him again with a carton of beer have a a talk should he feel that he wants to be naughty.
So today I fitted the tinware back on and went for a drive around the block as he has Club rego, even stopped at the service station and fueled up. It felt good to have him back to his old self and then I noticed an issue, a fuel leak so back home to sort that out. The main thing is that he lives again, the fuel leak is from the tank somewhere so will look closely at that and I am now convinced as to what the problem was so if it happens again I know where to go.
Title: Re: Valve Timing
Post by: ianoz on 24 May, 2021, 10:15:52 pm
Come on Cobba , Tell the truth .Beer indeed . You slipped a shot of Bundy rum in the tank , didn't you  ;D.
Mate good to hear Davey Brown is back to old self .
Title: Re: Valve Timing
Post by: cobbadog on 25 May, 2021, 09:27:11 pm
Haven't had a Bundy for over 30 years. Many moons back in the hard drunking days Winter was supported  by Captain Morgan shots with around half of the 10 - 12 schooners just to keep the bugs out.
Even though the drive was short it was very pleasing with David demonstrating his torque in H range 3rd by pulling out of a corner and up hill with no worries at all. Throttle response was also brilliant with little time taken to reach governed speed. It does put a huge grin on ya dial when it runs like this and really is why I'm not pissed off about the fuel leak.
Title: Re: Valve Timing
Post by: allisb on 26 May, 2021, 06:36:08 pm
Hi, just logged on.
That?s terrific news. Good to hear that he is back on track, after all those hours of work. Enjoy!
Title: Re: Valve Timing
Post by: cobbadog on 26 May, 2021, 09:59:49 pm
Enjoy we certainly will. Even on the short run before finding the fuel leak he still has a very torquey engine. His ability to take hard left corners and pull away in top gear uphill is amazing and this is with the oversized tyres on the rear as well. Will sort out the fuel leak as soon as possible so we both can go for a picnic up in the forrest again like we used to do.
Title: Re: Valve Timing
Post by: cobbadog on 05 June, 2021, 04:51:49 pm

Here is the latest and hopefully final response all but 1 because it might not be fixed. I found where the fuel leak was comming from, the fuel line was not seated properly to the fuel tank fitting, then I found that I did the unbelievable and actually fitted it back to front which is why it was sitting right. So corrected the problem and the connection at the tank was cured but now a slow leak at the fuel tap. So I ahd a close look and there was a slight mark on the edge of the flange, not on the taper, and this must have been where it was seeping from. I bought some 5/16" olives and nuts the other day thinking I will simply make a new fuel line and fit that. WRONG! 5/16" fittings dont fit the 3/8" outlets and fuel tap sizes. See the original fittings are unusually POMMY in design and although 5/16" is the tube size the original fittings step it up to be 3/8" and I have no idea why.
So on the phone to the metal yards in town for some new 12mm brass rod to make a new fitting and sweat this on wrong again biggest in town is only 10mm which is too small. A little bit more thought and I was on the lathe making a new fitting out of mid steel. This went well and I soft soldered it in place then installed it. Still a slight leak at the tap but all good at the tank. So to finish the day off I went back to the brass fitting and soldered it back in place then fitted it all back together with some Stag Jointing Paste which claims is good on petrol. So it is now out there curing over night. I put a tiny amount in the recess of the taper and around the flange under the nut. Tomorrow will tell.

So the pics will show a rough soldering job but it works along with my termimesh inline fuel filter to stop rust from getting to the glass bowl and carby.
 
Attachments
Title: Re: Valve Timing
Post by: asw120 on 05 June, 2021, 06:19:22 pm
Those fittings are available at hydraulic places. I got some recently.

Jarrod.
Title: Re: Valve Timing
Post by: cobbadog on 05 June, 2021, 09:37:01 pm
ok Pirtek here usually have everything but now it appears it depends on who you talk to. Cheers Cobba
Title: Re: Valve Timing
Post by: asw120 on 06 June, 2021, 08:13:14 pm
It's in their catalogue. Bloke couldn't remember the number and had to look it up while I watched. Just remembered he did have to get them in.

Jarrod.
Title: Re: Valve Timing
Post by: cobbadog on 06 June, 2021, 08:50:13 pm
Thanks for that Jarrod, The owner of the local Pirtek is a real gem and very helpful but has some staff that are very nice and polite but dont know the product.
I will see tomorrow hopoefully if the stag has done its job. Although it looks good the taper in the tap may be suspect.