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MGB Valve adjustment

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Boggsy64

Boggsy64

Jedi Hopeful
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Tearing apart my 1800v and when it took off the valve cover I was shocked to find the rockers were (for what I understand) absolutely loose. Meaning I could rock the "closed" valves rockers back and forth at least a 1/8" each. Meaning the ball on the end of rocker where the push rod is was completely out of the push rod end! If I am not mistaken when a valve is "closed" the rocker should be free to "rock" a little with only .015" gap between the rocker and the top of the valve.
Am I missing something?
 
I'm sure that others are closer to this issue than me, but I'll start.

Are all the rockers like that, or just some? Do you see signs of excess wear anywhere else, like loose rockers on their shaft? Is there plenty of oil in the top of the engine visible when you remove the valve cover? Are the adjusting screws on the rockers loose?

1/8" is way too much--you can't write that off to lack of timely adjustment or an error by the last guy who did it. If it's not something simple, like loose adjusters, there is likely some excess wear someplace. This could be caused by a plugged lubrication passage--you'd be shocked to see how small those passages into the head and rockers are, if they are anything like the Sprites and TDs I'm more familiar with. With luck, it's not excessive camshaft wear, but that's a possibility. How old is the engine?

Didn't you hear a lot of valve noise? I'll bet they clattered like crazy. Also, that much lash must really have sapped the engine's power.
 
Well pulled the cam and significant wear at top of each lobe. The buckets showed minor spalling. Everything else seems free from major, major damage. All eight rocker to push rod adjustment screws are set basically the same. There is about a 3/16" inch of screw above each lock nut.
I have not seen the rocker assembly before and when I first saw it I thought " how can this be?". I am not kidding there was so much slop that I could nearly pull out a pushrods with the rocker assembly in place! Upon tearing apart the engine none of the lock tabs were in place. My guess is a really poor job on this engine. Maybe they read the feeler gauge really really wrong.
Yes there was a lot of noise while running but my first experience with an MGB. The deposits on the valves and pistons is unlike anything I have seen (very heavy). I imagine I lost quite a bit of valve efficiency and flow. Can't wait to get it back together. I am sure it will feel like a rocket comparatively!
 
That certainly explains it. I'd suggest going through everything and making sure all the lubrication passageways are clear anyway, since you have dug into it. Some amount of the cam and lifter lubrication comes from oil returning from the head, flowing down the openings for the pushrods, so low oil flow to the head could still be an issue. If the lifters wear and get loose, the cam lobes will wear too.

The big question is why the cam wore. The replacement lifters for MGs are notorious for wearing poorly, and maybe the spalling of the lifters wore out the cam instead of vice-versa. After all, if it were just the tops of the cam lobes, the valve lash would still be OK when the valves are closed. So, you'll need a new cam anyway, and maybe it's worth the extra money to get a set of ARP lifters.

I think you'll be amazed at how much more power you have when it's all back together.
 
I'm in the process of feeling my way through a build of a second MGA 1500 engine from the pile of parts that came with my car. I'm finding that I can actually make progress by tackling one component at a time.

First was the rocker arm assembly. I had 2 sets of rocker arms. Both shafts were shot, and one set of rockers needed bushings. I used spacers instead of springs and now have one good rocker arm assembly. (The one that is now on the car was originally gaped to about 0.24" and was very loose, and contributed, I believe, to a misfire problem I was having.)

Then I rebuilt the head. Since I'm going for a race engine in theory, I spent about 40 hours porting the head (I wonder how that will turn out!). Up-sized valves and 7000 rpm springs. Pretty much finished, just some time to add the manifold bolts and the thermostat and cover.

Next up is the oil pump. Assuming I can use what I have, I will try to increase flow capacity. But then that will be done.

Then I plan to make a windage tray for the oil pan and get that welded in. That will not be a properly baffled pan, but should serve the purposes of this engine.

In the meanwhile, I am slowly assessing the block. Some of the connecting rod bearings are gouged, indicating dirt in the oiling system, but some other bearings seems to show evidence of oil starvation. So I have to figure that out. Probably have to open up the oil galleys (which I was trying to avoid), clean them out and maybe open up some of the oil passages in the engine. It took me a while to figure out the pistons. It appears they are 6 over 1600 dished pistons, giving the engine about 1640 cc. Now that the head is done, I'll figure the compression ration and perhaps order up some flat topped pistons. Then I have to figure out the camshaft, which seems too mild for this block.

In any event, by starting with the peripherals and breaking the job into little segments, I'm finding that I am not so overwhelmed with the project. Good luck with your build.
 
The last three MGB engines I built had completely worn out camshafts. The owners also had the same story about service. They all had taken their cars to various quick lube garages for oil changes. 'Modern' oils do not have enough ZDDP to lubricate cam lobes. So make sure you are using the correct oil for flat tappet engines.
 
For the camshaft's benefit, I was running 30 weight Valvoline Racing Oil until this spring when it was discontinued. Now running Valvoline 20-50 weight Racing Oil. If possible, try to get the type marked "not for street use" as it has a high level of ZDDP. But the street version of the racing oil is still higher than most. Joe Gibbs has a high ZDDP oil as does Abingdon Spares. I'm not sure the ZDDP additive is as good as using the manufacturer blended high ZDDP oil. For a while, my friend was using diesel oil for the ZDDP content, but that formulation has also changed recently as well.
 
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