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MG MGB Technical - Rocker oil feed

Quick question for you please:

I dont seem to be getting much oil up onto the rockers after the lower end rebuild.

I have taken the shaft off, and blown through the holes on the shaft and on the rockers themselves, and I also blew down the hole into the head all with the compressor to clear any debris out that might have floated up when the engine was upside down.

I am getting good oil pressure on the gauge in the cockpit though.

Do you have any suggestions please?

Thanks

Paul
Paul Barrow

I rebuilt my engine last winter and like you I expected the flow of oil to the rocker to increase. Well it didn't - at least not much. I do get a little bit of oil accumulation on the top of the head but for the most part it looks like oil was just sprayed onto all the surfaces. (And it does cover all the surfaces.) At no time have I actually seen oil seeping out of the rockers but I'm sure it is happening. In spite of this the valve train is quite quiet for an MGB, and with lash set at .016" cold. Certainly not Honda Civic quiet but I'm confident that all is in order even with the low oil flow.
G Oakes

Thank G Oakes.

Any comments from anyone else please? How visible should the oilflow be?

I am running on a stock rocker shaft and rockers.

Paul
Paul Barrow

hi paul,
just fitted my rebuilt engine 300 miles ago and on tickover with rocker cover removed the drips of oil coming off rockers and running back down pushrod holes are more than 1 a second.hope this helps.


bob
1970 bgt.
Bob Taylor

Paul...
Did you have the rocker shaft all apart..If so you might have transposed one of the towers and thereby block the oil passage to the shaft.
Sandy
Sandy Sanders

How is that possible Sandy? 3 towers are the same, one has the locking screw for the shaft. Hard to see how it can go together any wrong way. The towes don't have oil holes except for the rear one.
Art Pearse

Vague memory here, so don't hold me to it, but I think there were some changes over the years for where the rocker feed was. So, if mixing and matching parts, it is possible to get the wrong combination and starve the rocker assembly. It is possible that I remember this from the A-series engines, but you may want to do a little research to find out for sure.

Also, is the plug still in the end of the rocker shaft?

Charley
C R Huff

Charley,
Your memory is fine - later heads have an offset oil hole so it is important to match the correct rocker pedestal to the head.

David
David Overington

Paul - There is not much oil coming out of the rocker shaft at all on the B series engines. It is not like on the XPAG engines where you will oil your garage ceiling if you leave the rocker cover off when the engine is running. On the B series engines, there is just a bit oozing our around the rockers. Cheers - Dave
David DuBois

Thanks David. Good to know I have not totally lost touch.

Charley
C R Huff

Sandy - thanks but no I was very careful NOT to dismantle the shaft, rather I used the springs to ensure that I had cleared the holes on the shaft, and then starting from the front of the engine/shaft used my compressor to force clean the shaft giving a good long blast in each port while holding the shaft vertically so that any debris/stoggy oil would be forced to the end of the shaft and ultimately out when I did the last port and aligned the last column to the port on the shaft.

Thanks David - it is a relief to know that I shouldnt be getting the floods of oil I get on my XPAG.

The mystery now though is what is causing the excessive noise when I load the engine up with revs. Initially I had thought it was a bottom end problem on the crank and the con-rods/shell bearings. That was why I rebuild the bottom part of the engine. A friend thought maybe it is a sticky valve/broken spring not causing the valve to come up as quick as the rocker, so giving rise to a tappety noise on load.

What do you make of that folks please?

Paul
Paul Barrow

I changed the head on a 1500 midget and was horified to see how little was coming out, nothing dripping, just splashing around, which took ages to start. By comparison I have seen more coming out of my B, dripping down rather than tiny spots splashing around, but that is only two examples.
Paul Hunt

Paul, You say that you did a "bottom end rebuild". Did this include the pistons? You could be experiencing piston slap due to excessive piston to cylinder wall clearance. RAY
RAY

Ray, only bottom end ... ie crank. Compression is fine on all 4 so I dont think it is piston wear per se ... unless I am misunderstanding the effect of piston wear. The car does get very little use (I should remedy that I know) so I wouldnt be surprised if something is sticking ...if that is possible.

Happy for any advice.

Paul
Paul Barrow

Paul,

You said: 'A friend thought maybe it is a sticky valve/broken spring not causing the valve to come up as quick as the rocker, so giving rise to a tappety noise on load."

Pull the valve cover and work all the valves by hand and see if any of them are sticky. It is possible, particularly if it sits a lot. If one feels weaker than the others, it could be a broken spring. Also, lay a straight edge across the top of the valve tips. They should be pretty much the same height if none are stuck and if they have not been worn or ground unevenly.

Also consider that a tappety noise on load sounds like it could be spark knocking (pinging, pinking) or whatever word you use. If it is available, try higher octane gasoline, or try retarding the spark, or try both and see if it changes or eliminates the noise.

Charley
C R Huff

Paul, your tappety noise under load might be a leaking exhaust manifold gasket. I just had that on my old Volvo 740. Sounded like piston slap. Tappet noise does not vary with load!
Art Pearse

Great idesa guys.

I had been thinking of replacing the spark leads anyway - I am running 4 point Bosch plugs and I wasnt sure that they are all getting the chance to spark. Guess I could pull them out and check that first though! I am also on a side entry cap.

Exhaust manifold is OK ... although the Merlin Stainless baffle box has develped a nice vent hole in it so that might be part of the issue there.

I will also look for weak/broken springs too. I like the idea of a straight edge over the tops of the valves to see if any are stuck down though, and Art thank you for your observation about tappet noise not varying under load (except for the frequency of repeatition though I guess).

Any other options will be looked into too so please post if you have any thoughts.

Paul
Paul Barrow

Paul,

Do you mean you want to check that all the plugs getting a chance to spark, or that all 4 points of each plug is sparking? I am reasonably confident that only one point of a 4-point plug will spark. The others are there for redundancy. The spark will go to the one with the least resistance.

Charley
C R Huff

I agree, I think only one fires at a time, it just moves around to which ever ones fires easiest (lowest voltage) which is why they don't wear, even a quarter as much, it seems.
Paul Hunt

This thread was discussed between 20/06/2009 and 29/06/2009

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