Diesel Engine Rocker Configuration - Pass or No Pass

Don't know. Can you shim the rockers so that they are centered on the valves without throwing the push rods out of kilter?

No idea, really.

Hi Lyn, thank you for the response.

The rockers are close to the pedestal with no shims between. And some are IMHO far off. The valve stems are all within the head of the rocker, but I have differences from centered to offset to the outside.

Tomorrow I will publish close up pictures per pair and hope they show more.

To make it fit I will need to make the pedestals smaller or grind a little bit of the rockers' body.

I can't tell from the picture, but did you remember to install the valve stem seals?

I've only worked on gasoline engines, and until the valves are properly adjusted, the rockers and pushrods will be very sloppy.

This engine is in the sail boat. It had a timing problem - idler gear bearing gone. I gave it a complete new overhaul, upper and lower parts. timing chain, guides, tensioner etc...

The rubber seals are in place. Thank you D.

Many years ago it was explained to me that by putting the rockers slightly offset it causes the valves to rotate as the engine runs so that they don't develop a fixed valve seating position.

Given the general precisions and machining accuracy tolerances that modern engines are built to even on loose fit components the odds are that if your rockers set that far off they are probably designed to sit that way on purpose. Just a guess but being I have seen many engines that have rockers that sit offset just like yours it may be part of the design.

Your statement is correct. Slightly offset makes the valve rotate slightly.

Problem here is that some are centered, others not. The engine, once tuned will certainly run. I just wonder if the rockers are not too much compromised.

Thank you. D

If the rocker is assembled correctly it should always push the center of the valve stem if the parts are proppely made. Off center rockers really does NOT turn the valves, not even slightly. On some Merc.. Alfa and the better type engines a positve rotating gadjet is fitted between the head and valve spring. On other engines that has a little cup fitted over the valve stem end, there is a little play between the inside of the cap and valve stem end; the cap push against the special valve cotters, free-ing the valve so that vibration and/of air flow can turn the valve [hopefully]. So...off-set rockers does NOT turn valves;I have marked all valveheads to test this misconception to prove that on engines not fitted with rotators the valves always close in the exact same position.[Also..piston rings does not turn in their grooves] On the other hand...Cam followers are off-set to the camshaft and therefore the followers are turned so that the cam lobe shall not groove the followers.

So, do measure the rockers carefully and only then, if really neccessary, alter them to fit propperly...also check that the pushrods do not push the rockers at an angle.

Please pardon my school 2nd language English.

jurie-sa

Sorry to burst the bubble but rocker arms are ground with a slight radius on the end that contacts the valve stem in order to eliminate some side thrust and guide wear, any off set will initiate some rotation. If it becomes flat it will initiate less rotation but normally you will get some rotation. The only way this engine will have a problem is if they removed all the rocker arms from the shaft and did not install with proper offset where manufacturer specified those rockers as to position. This info comes from training and reading the engine manual for numerous engines for over 50 years. Only quoting the various manufacturers.

It doesn't look right to me....is it possible to have some wrong parts, did you compare the old with the new? In any case it's a judgement call, as to if you think it will work, and willing to take the blame if it doesn't...

When I have a look at the old ones, they had a better fit. All slightly offset. But with the same wear marks. The engine is a oldie. The concept is from British Leyland and it has been used in the Austin 4- cylinder London Taxi's for decennia. It also found its way in the Sherpa van. Plenty of these engines were put into river boats and also in yachts and sailboats.

I thought I had to buy a new engine like Yanmar, Kubota or Volvo because BL stopped production (bankruptcy) more than 20 years ago.

Google learned me that Sherpa engines still are built (NEW) in India and that Turkey has some engine manufacturers too. And at reasonable proces. Looks like this engine will last forever.

It is very economic 40-50 Hp @ 1,5 Gln/h. Plus, I keep the Moody original.

Crossed the Atlantic already 4 times.

I had the idea to use the old rocker if they fit better. They are not really worn out and look machined with more precision. I will bring all to the forum in case someone is interested.

I believe all valves are supposed to rotate, but I can't swear to it.

Grinding on the rockers sounds like a really bad idea.

Since you have the old ones, I would spend some time and do a side by side comparison, as well as possibly removing the new, (at least some of them), reinstalling the old, and determining what, (exactly), is different between the two.

Here I expressed myself very wrongly: grinding indeed is NO option. I has sand paper disk on a rubber backing disk in mind. With #200 grid. Problem afterwards is dealing with the residue.

I just think the old ones are made with more TLC. (tender love and care?) Or did I get the other batch? Thanks. D

Having not worked on diesels, I don't want to get you into trouble here. On gas engines I do this, and use a drill motor on the valve stems with a very light bumping action to get the valves seated properly.

My thinking here is that, (assuming your new parts are identical), that you should be fine once you get them adjusted.

Wish I could be more help.

I'd not sand them at all. The contact surfaces should have a mirror finish.

Don't sand, don't grind.

Take kramarat's advice.

Side by side comparison both on and off the engine is the only way to ascertain any difference between the new and the old.

You need to verify that you received the correct rockers for your engine.

Even if the box, container, bag, whatever, that the rockers were shipped in has the correct part number, verify that they are correct.

They don't look right to you - DOUBLE CHECK.

Looks to me as though there are two different offsets. If you swap the positions on number 1 (1st on left) intake and exhaust, it seems they may line up better. Likewise with the intakes on 3 and 4. Exchanging them may give a satisfactory alignment.

I agree; Seems to me it is just wrongly fitted.

As a matter of fact, diesel or petrol engines do not turn the valves except if it has positive rotation coller fitted or the free valve system where vibration is supposed to turn the valves.

jurie

It's a definite possibility.

Whenever I tear apart an engine, heads, etc., I always take a large piece of cardboard or a box, punch holes in it as I go, and place all engine parts, bolts, etc in the holes, configured just like the engine, so I know exactly how everything was.

I have followed your advise, but I didn't win enough space.

Disassembled everything and measured the parts. The rockers are identical within 0.15 mm.

I noticed that the rocker stands have some front- rear leverage, but that didn't solve the problem either. The new stands are all 22 mm thick and the old ones between 19,5 and 21. Since position 1 (cyl. 4) was broken, I had to re- machine the first on the left. The rockers show better now. I used 2 of the old stands in the middle and a new one also on cylinder 1 (right on the pictures).

I have tightened the head as in the book.

I foresee to run into a different problem: not enough clearance on 2 valves. Have a slight idea that the new products aren't that precise, or the valve seats are maybe too deep.

I will see to it tomorrow. Thanks. D.

They give that look. They must have been modeled on a sanding belt and by hand. Maybe on a Monday? But they have all the same specific working dimensions. For some reason they made the stand different. The old set had 3 thicknesses. The new ones are all the same.

Thinking about this further, I do remember now that the 60's and 70's Mopor V8's had specific fitting intake/exhaust rockers.

The rockers would bolt up but would not line up correctly if mismatched to they're respective intake/exhaust valve.

I also recall a slight (visual) misalignment even when installed properly. It was explained to me that the way they were set over the valve stem was to give slight rotation to the valve with each up/down cycle.

Maybe the same holds true for this little diesel?

kram - I did, and still do use the cardboard. That system has never let me down!

Long time i had been handling Albein Diesel engines, now obsolete perhaps. Later I dealt with Yanmar, Kabuta and Daia marine engines,etc

Would you care to see if your push rods are of the right length and placed snugly over the cam shaft and if the cam shaft is not worn??

Rockers are made of tough material and grinding them is not a good idea. Compare them with the old ones to check why they don't center up. Moreover if the push rods pass though some bushing check it for condition and replace if required.

They should also align with the rockers...check for broken tappet springs and valve guides. Also check valves for length...or height as you may call it.

I don't think fitting push rods on the rockers offside would be a good idea.

........................

Unless I'm mistaken, you have a warped cylinder head. When you released the head bolts, the rocker arm shaft remains straight, but the rockers bind. Tightening down the head should bring the head back down again eliminating the binding. Whatever you do, if you discover that it is the head that is warped, don't try to resurface it. Either use the head as is or replace with a new head. Is the head aluminum? They are notorious for warping.

I agree that if a head is warped, do not just mill the surface that mates with the block. If an aluminum head is warped, surface both sides. I have done this dozens of times with over head cam engines.

Rocker to valve stem misalignment: I agree that it looks odd and I would try to make a correction. Since you have the old set of rockers and it provides the fit that you are looking for, I would use it as a guide. I would disassemble the new rocker set and carefully examine each rocker. Perhaps their are slight variations between rockers that look identical when assembled. Perhaps the rockers are in the wrong positions, perhaps some of the rockers have a machining error. I would tag each rocker as to its position on the shaft before dis-assembly. On a flat surface, I would place each rocker on its side and compare offsets by making measurements or just comparing two at a time.

If the old rocker assembly is in good shape, I would consider using it. If the old rocker shaft is worn, I would consider using the new rocker shaft with the old rockers. Verify rocker to shaft fit as you do not want too loose oil pressure.

It really is not that unusual for after market third party parts to be manufactured with slight errors. Most people are not as observant as you. The new rocker set would probably work just fine as is. But I doubt that it would last as long as the original.

Hi Ron

Head is cast iron and machined very well. Brand new from manufacturer. So are all the parts I ordered. Thanks. D

I get the feeling that, since the rockers are cast, then machined - that it's not that critical so long as the rocker face is in complete contact with the valve top.

However, being anal I would dissassmble the rocker gear and compare inlets to inlets then exheats to exhausts to see how simlilar they have been made.

Then reassemble while taking into account the variation. Try to get the most close-to-centre over the valve as possible.

After magnifying that image, I feel that the rockers are not the same. Lay all of them on their sides and accurately measure the heights to center of adjuster and valve contact area. Get back to us.

Shock horror!! There is some frightenly wrong information in most of the replys so far ,too much to respond to indivualy.The 1.8 BMC Diesel engine was a good engine in its day ,very simply the rocker arms are not a correct assembled set , a good clue is the position of the pushrod in the pushrod hole in the cylinder head,the push rod needs to be central in the hole , or very close, and of course the rocker central on the valve.

The MGB 1800 and most of the BMC B series engines of that era use the same rockers and one source of accurare information could be found at your local library in Haynes Manuals , or similar publications.

I have reconditioned many of these diesel and petrol engines,and have mixed and matched parts, I had no choice those times as no other parts were available , the engines all ran fine after a little care with the rocker adjustment,( use the rule of 9 )a Google search will explain this if your not an old school mechanic. to summerise your "old" engine will run fine with a little more clearence on the rocker shaft,also dont hesitate to mix and match parts from a few sets of rockers,definitely no grinding , but dont hesitate to use shims , BMC did originally .I you are able to buy all new stuff then disregard my recommendations above.

Thank You,

As when the rockers show offset from the front, also the push rod holes are offset about the same way and size.

The head is cast steel (Iron).

Indeed these engines have good qualities as most of BL's. Many found a new line and Life under different names too. e.g. DAF trucks.

What I like about this engine in a boat is its reliability. This engine ran to the last minute up to when the timing slipped 4 teeth and the valves touched the pistons.

The push rods were all a little bit bent and that was it. It could easily straighten these again and re-use.

I surely come back with more details. I will measure everything.

The pedestals can cause this situation too when not properly sized. All parts are brand new (made in India ?)and the rocker shaft came assembled as "assembly". Paid extra for it.

At the end I had to take everything apart, since they assembled it in "mirror" view. The result now, I consider being very poor.

I will see what I can improve and come back with the results. D.

Thank you for this good info:

The 9 rule is indeed a time saver:

adjust 1 when 8 is fully open

3 with 6 open

5 with 4 open

etc...

I love this oldie. As the timing was completely messed up - the chain tensioner was broken - the shoe peeled off - the idler did lose the whole bronze bushing. A disaster scenario for most other engines. I only had those super long pushers bent and straightened these myself. The pistons held and so did the valves. In the De-carb set I found washers for the injectors too. The engine had none when I took the injectors out. Do I install them?

I have the rings to block the mist and 2 sets of {copper?} rings? The injectors however ( CAV ) stick out a lot already - studs will probably be too short when the rings are installed.

Thank you for your answer.

I would like to warn you that straightening the push-rods is not a practice that I would recommend. If you have the option, I would suggest replacing them, even with used ones. The harmonics of a push-rod at elevated RPM could cause a weakened, or slightly bent push-rod to fail at an inappropriate time. Just my two cents worth.

I totally agree with you. Only finding these push rods is not easy and I forgot to order these. I can order them in India, but probably when (?) they arrive here we will need to hide for hurricanes.

I've read about broken push rods in ford diesels, but the ones I deal here with are pretty flexible, long (1 foot plus) and 5/16" thick. Now they are definitely as straight as they really can be. Tested them on a glass plate and they don't roll to their "lame" side. A vise and 3 aluminum L pieces are a fantastic help. It goes also pretty fast, even with your eyes half closed.

I worked on Volvo before ( B18 engines) and these push rod were that hard that with a pin ground on one end, they made you a good scratch marker pen.

Every time I arrive in Florida, I am in heaven - those trips are shopping trips. Here, once you get involved in anything there is nothing to find for spare parts. The head had for the injectors 2 studs with 5/16 fine and course on the other end. Just opposite as the original head. Finding nuts was 4 hours shopping and I ended up with 8 nuts that weren't even strong enough for the 3.4 kgm torque.

Most of the parts have to be modified. Probably I am dealing with one of the first editions.

I always appreciate your input and learned a lot listening to you.

Take care and thank you. D.

DO NOT GRIND OR CHANGE ANYTHING. Older engines have this arrangement, I do not think you should be concerned. The reason for the rocker/valve offset is rotation. The arrangement causes a natural rotation of the valve,stopping area wear and seat problems, it spreads the wear point on the top of the valve, and stops grove problems in the valve seal area. As long as you have good oil flow, rely on the wisdom of those who designed it..

Wrong , dont give the OP anymore headache, your information is a generality, the rockers are assembled incorrectly or the set of rockers are from more than one set of rockers and mixed up.All BMC cars from that era used "Handed " rockers.do some research before you give wrong information.I have several BMC rocker shafts with rockers in my possesssion here. But have a nice day .

Sorry Mate; Only where special "positive rotors" are fitted does the valves get turned with every opening of the valve. Another plan is "slow rotors"....This kind has a little cap over the valve stem end....if the rocker push on this cap to open the valve, [About 3-4 thou clearance between valve stem and cap] the cap pushes on the special valve cotter, freeing the valve....vibration and airflow is now supposed to turn the valve.[Early Mazda 2 liter engines, and Mercedes used positive rotors; Strait 6 cyl International Harvester engines was converted to use slow rotors and sodium-filled valve stems [Like Mercedes and Alfa cars]

Very old mechy.....used to work on above mentioned.

Jurie

I just got back on the net. A HDD crash on the island is a very time consuming story. No doubt about how the people at BL have build engines. Their diesels have made and still make history. I've been just concerned about the 'freedom" the new manufacturers take in changing rocker stands' thickness with almost 3 mm. These are the differences I found between the old and new ones. Thank you for the answer. D.

The rocker arms are off set in order to rotate the valves, Leave them alone or pay the price. The valves have to rotate somewhat in order to keep a good seat, You may notice a special seat for the spring or the valve keeper retainers that even allow more rotation. This is normal for most engines.

I enjoy reading all the posts ,and rarely reply and never 3 times in one day,the photos show some of the rockers in the correct position and a few that are wrong hence the OP s concern,wheather the valves rotate or not is not the concern .The rotating may well be important and there many many very clever ways of doing this.

If the OP wants to get peace of mind with his repair,then i recommend he continues to seek as much information as possible, its even possible the pedestals are in the wrong position,I will try and get a photo of the parts I have here and post later.

I have seen the intake and exhaust valve rockers in different degrees of offset in order to achieve the desired rotation. If you rotate the exhaust too much you can wear out the seat or visa versa. My opinion after overhauling many engines gas and diesel is this, what you have is what was designed into the engine, go to the manual it may go into some detail. There is nothing wrong with your engine and if there was lubrication to the top end then wear on the rocker end of the rocker should be negligible. More wear is to be found on the rocker to shaft location and usually this is a bushing that can be replaced.

Firstly, don't grind anything.

Did you mark each part when you stripped the head? If yes and the rocker shaft holes are still a nice fit, use the old rocker arms in the same position as before.

Or do as somebody else said, check to see if you have two different types of rocker arm and place them in the best position.....what you have now will work, but setting up the clearances once a little bit worn will be most difficult to do accurately.

There is a tool made many, many years ago that helps with setting up worn rocker arms correctly, I have one in the garage (I think), I could photograph it if required and read the name off it if anyone wishes....it totally ignores wear and sets the gap correctly once calibrated. Calibration is really easy on a new valve and rocker, just note that value down somewhere and don't lose it!!!

Misalignment (differences from valve to valve) is not uncommon in these engines. (Check this article.) The misalignment in yours looks extreme. The normal offset to promote rotation is about 1.5 mm I would guess, from foggy memory. (This produces a circle on the top of the valve stem of about 3mm).

I am using the BMC manual of the 1800 cc. I checked the links. There are some differences between the 1500 and the 1800, but some of the points are really a completion of what I have.

The special tools I had to make myself here. On this island you need to work with what you have. Thank You. D

I am not experienced in these motors but I found this workshop manual Is it the same motor? look here it doesn't answer your question but I thought it could be handy if it is the right book.

I am not qualified (I'm an electrician) but have rebuilt quite a few motors in the past, some from the 1960's & in the older motors I have had the same problem they were petrol motors with almost identical set up on the rockers & If it was me I would try swapping the rockers, some seem to go to the right & others seem to go left possibly if swapped over they may sit better & solve the problem. As I said earlier I am not qualified so it is only my opinion not fact

As mentioned by a previous poster, the valves are deliberately rotated, but from my experience, only the exhaust valves were rotated.

Look at the layout of the head.If the offsets are only exhaust valves, it is ok.

Here some close ups "how it was".

This is cylinder 4:

This has been the most difficult and the question was actually most about these 2 valves,

Cylinder 3:

cylinder 2:

cylinder 1:

Great pics, Where is the problem? They are all seated exceptionally well and looks ready to make that trip across the pond again. Only when you do, you need to call me. I'll meet you in NYC.

It appears from the pictures that

1. You push rods are not straight or not rightly located

2. Rockers may also have got distorted or worn off..??

Genuine engines have all rockers equally aligned for all valves but here in the pictures some rockers seem out of place. This should be a matter of concern for any mechanic and the whole assembly of rockers/tappits, valves, valve caps, valve guides, engine head, push rods and even the condition of the springs, cam and cam bushes ought to be checked before switching on the starter!

Do not grind, smooth or remove any thing from the rockers. If they were hardened, you will be removing the hardness. The pushrods, and pushrod end of the rockers will center into each other. Remove the pedastal from one cylinder and allow the rockers to find the location that that brings the pushrod and rocker to a 90 degree angle. That is where the pedastils should be aligning the rockers. It may take some parts swapping up and down the rocker shaft till you get the right combination of parts to allow this.

There may be rockers and pedastels that are cast from the same mold, but machined slightly different after casting. Look close, and compare. Good luck.

Thanks Bob,

T thought I might have looked into this kind of trouble. That is why I asked the manufacturer to pre- assemble the rocker assembly to the head that I also bought. Great was my surprise that the rocker set had been assembled upside down, so that I had to take it apart before I could even install it. I found a satisfactory solution by using 2 stands from the old shaft assembly. The old ones are about 1/8 smaller at the machined part. I also experienced some trouble with the clearance on 2 valves.

Rather then taking the risk of damage, I have put shims of 0.4 mm under each stand and 2 extra of 0.2 mm under both central stands. (along the book)

After they have been broken in, I might as well remove the 4 and adjust the valve clearance again. This engine is an oldie. (1975)

Bob's first rule of auto repair. The last one that touched it screwed it up. So much for having the professionals assemble the rocker shaft. Good luck, and happy sailing.

The rocker arms have to be "off center" the reason behind this is that by having them of center the valve will every time "turn a bit", thereby avoiding that it returns every time at the same location of the valve seat.

The pictures are looking good and it shuold be this way

Brgds,

Jan Dirk Davidse

Do I see myself vindicated ? or still sitting on the stupid step ?