odd pushrod behavior

[No Regrets]

When you sat 'Two rockers are at different angles' this is quite normal!

As long as they all have an equal turn through two crank revolutions!?

It's pretty hard not to get these put together right, obviously the valves were refitted, ground in and the springs were all good and proper, the rest is just assembling isn't it?

 

[Ardenfour]

here's a pic. The rockers and shaft were not dismantled so can only go back in the original positions.

 

[vyv_cox]

As has been said, looks like the valve seats may have been recut. The 'springiness' could perhaps be because the push rod forces are no longer in line and some lateral load is being applied.

 

[Ardenfour]

jcorstorphine - the clearances were much less than before - the 5mm is roughly the amount i had to slacken off the adjusters to get the valves to close. the valve stems are higher than before. i did the solder thing and measured 0.53mm, manual says bump clearance should be 0.4 - 0.5, so clearance a bit large.
I could fit some kind of spacer below the rocker mounting block. this would raise the shaft and rockers would again sit horizontal, but then the decompression lever might not adjust enough.
Alternatively, grind some off the end of the valve stem, but would this have some kind of hardening on it? would get close to the collets as well.
Scottie, I dont understand how water in the block would bend a pushrod?

 

[Jcorstorphine]

Wow! Looked at your Pic.

I need to think about this,

OK thought about it.

It looks as if the valves are far too high and one concern I have is that the valve springs will not be in enough compression to give a good seal over time. If, as you say, you had to adjust the tappet by 5 mm then it follows that there is 5 mm less compression on the valve springs. Generally, valve lift is only about 7 to 9 mm (ish) so this being the case, I think you will have only about 50% of the sealing force.

I think that you may need to consider removing the head and get valve inserts fitted. Bit of a bummer, You did not mention which engineering shop you took it to but I had a bad experience of one in Glasgow who rebuilt my Ford diesel head for me to find out a year later that it had cracked valve inserts. And that was only after about 30 hours of very light running.

 

[Ardenfour]

what about washers under the valve springs? West of Scotland engineering done the work, after Pistons & Components said they couldn't. Odd thing is, if 5mm of material had been removed from the faces, surely I would need a 5mm shim under the block to get the bump clearance back to normal? As it was, I added another 0.3 shim and a shim cut from card, I guess another 0.4mm. The shop, I would have thought, would remove a similar amount of material from the head protrusion and valves to keep the relative dimensions.

 

[Jcorstorphine]

I would be worried that washers would come loose or move and cause the valve spring to break. However, if they were actually machined with an exact hole to fit the valve guide and a recess to locate the spring they may be ok but a bit of a bodge.

If as you suggest, West of Scotland Eng. had removed 5 mm for the head/block then the pushrod would be too long and you would have had no clearance. I think you should send the engineering shop a pic of the set up you have now and say that the problem is due to the valve seats being too deeply ground back.

Options being, Valve inserts or shorter valves. Still cant think of why you should have springiness under the pushrod unless as said before, it is due to the angle.

I would not be happy with the way the head is set up at the moment as the pushrods have been known to bend on MD series engines, mine did and from memory you can still buy them (so could be a consumable in Volvo's opinion)

Let us know how you get on, are you based on the Clyde.

 

[scottie]

jcorstorphine - the clearances were much less than before - the 5mm is roughly the amount i had to slacken off the adjusters to get the valves to close. the valve stems are higher than before. i did the solder thing and measured 0.53mm, manual says bump clearance should be 0.4 - 0.5, so clearance a bit large.
I could fit some kind of spacer below the rocker mounting block. this would raise the shaft and rockers would again sit horizontal, but then the decompression lever might not adjust enough.
Alternatively, grind some off the end of the valve stem, but would this have some kind of hardening on it? would get close to the collets as well.
Scottie, I dont understand how water in the block would bend a pushrod?

Water is not compressible so a cylinder full of water will shut the valves push rod will bend trying to open the valve

 

[Daydreamer]

I am not familiar with this engine but......

In the picture. I am assuming that the engine is at TDC on the compression stroke and that there is valve clearance. The valves seem to be at equal heights which I would expect. But I notice that the two rockers do not seem to be the same as each other which I dont ever recall seeing, handed pairs sometimes but never different. It also looks as if the further rocker locknut is actually quite high. I wonder if at some point in the past someone has replaced one rocker and 'modified' the pushrod to fit and that the push rods have been now swapped over. Possibly one pushrod is now sliding about in oily murk that is the bottom of the cam follower which might just account for the springy effect.

Its all very bizarre though.

 

[ghostlymoron]

what about washers under the valve springs? West of Scotland engineering done the work, after Pistons & Components said they couldn't. Odd thing is, if 5mm of material had been removed from the faces, surely I would need a 5mm shim under the block to get the bump clearance back to normal? As it was, I added another 0.3 shim and a shim cut from card, I guess another 0.4mm. The shop, I would have thought, would remove a similar amount of material from the head protrusion and valves to keep the relative dimensions.

I'm no expert but removing 5mm of material from the block and head (combined) seems an awful lot, I thought skimmimg normally maxed at a few thou. Your rockers look to be at a crazy angle now - the ones I've seen tend to be roughly horizontal and, if material has been removed, the pushrods would then be too long and the rockers tilting the other way. Something here doesn't add up IMO.

 

[rogerboy]

yes I agree

I'm no expert but removing 5mm of material from the block and head (combined) seems an awful lot, I thought skimmimg normally maxed at a few thou. Your rockers look to be at a crazy angle now - the ones I've seen tend to be roughly horizontal and, if material has been removed, the pushrods would then be too long and the rockers tilting the other way. Something here doesn't add up IMO.

 

[Bilgediver]

what about washers under the valve springs? West of Scotland engineering done the work, after Pistons & Components said they couldn't. Odd thing is, if 5mm of material had been removed from the faces, surely I would need a 5mm shim under the block to get the bump clearance back to normal? As it was, I added another 0.3 shim and a shim cut from card, I guess another 0.4mm. The shop, I would have thought, would remove a similar amount of material from the head protrusion and valves to keep the relative dimensions.

Did you put the old valves back or are they generic valves ie BMC. Maybe they now have stems 5mm longer than before. The valve and head sizes are pretty universal especially if the valve seats are cut to match BMC valve angles as cutters are available in Halfords etc.

 

[ghostlymoron]

yes I agree

roger, do you agree that I'm no expert or agree that something doesn't add up?

 

[rogerboy]

ha ha I agree something doesn't add up

 

[Jcorstorphine]

got my md1 back together after skimming the faces so I have to make quite a large adjustment to the valve clearances (the valves were 'dropped' according to the engineering co.) the valve end of the two rockers now sit angled upwards, whereas before they sat horizontal. I had to adjust them by about 5mm to close the clearance gap. is this a problem?
what is odd, the exhaust pushrod seems 'springy' - I adjust the clearance of the rocker, but I can press the pushrod end down about 3mm and it springs back up, as if there's a spring below the tappet.

any thoughts please?

Did you ever find the cause of the problem, was it wrong valves, too deep valve seats or too much skimmed of the head and blocks.

J.

 

[rogerboy]

what was the out come of this problem.

got my md1 back together after skimming the faces so I have to make quite a large adjustment to the valve clearances (the valves were 'dropped' according to the engineering co.) the valve end of the two rockers now sit angled upwards, whereas before they sat horizontal. I had to adjust them by about 5mm to close the clearance gap. is this a problem?
what is odd, the exhaust pushrod seems 'springy' - I adjust the clearance of the rocker, but I can press the pushrod end down about 3mm and it springs back up, as if there's a spring below the tappet.
any thoughts please?