CU Engine Rebuild II - aka "it's a bit too sticky!"

So, as mentioned elsewhere, for various reasons I'm taking my self rebuilt engine apart. The key issue is that it's was pretty tight on the rebuild and if anything is now tighter after 1K. As in I need to put a socket on a bar and a long handle in order to turn the engine over. I'd hoped (and been advised) it would loosen up, but nope!! Using a torque wrench as a rough measure, it needs 42/32Nm of torque to turn without clicking with and without the spark plugs in respectively.

Interesting there is a softer spot between -8 to +40 tdc where you can almost turn it by hand, but I assume that just because the pistons are at the apex of their compressions.

I have now stripped it back down to the block and there is a significant easing of the crankshaft after having removed the Heads, cylinders and pistons. I still need to measure the end float of the flywheel, but there is very little friction in it now. Not one finger, still need a strong hand grip to turn, but way better than with pistons on. However, there is a stiff spot at around 90 degrees on every rotation of the crankshaft which is confusing.

Hoping to get to measure the crankshaft float on Friday, which may also reveal something.

So, some questions come to mind.

1. What could be causing this sticking at 90 degrees in a block with no pistons or flywheel attached? It may become obvious as I open the case, but thought it worth asking.
2. does this sound like the key issue is with pistons/cylinders?
3. Is there a way of measuring the correct engine torque (how easy to turn) at any point in the rebuild/strip down so I have an idea of where the issue is, as I strip/rebuild. Torque wrench seems like a poor tool for such work but at least it's something.

As usual, thoughts welcome.

 

With the plugs out 32Nm is about double what it should be, but a socket on a bar and a long handle is tighter than 32Nm, unless you have a light touch.

The first thing you should check before anything is removed is the crankshaft float.

Was it easier to turn when you removed the rocker gear?

Now you’ve removed the pistons is there any scuffing on the cylinder bores?

With the pistons/cylinders removed it should be easy to turn by hand, with no tight spots.

At every step of a rebuild you check for free rotation.

An engine builder should not advise you that a tight engine will loosen up, it is far more likely to seize up.

 

With no flywheel there is no thrust bearing to stop the crankshaft from hitting the crankcase.

If it’s still tight with the pistons/cylinders removed I’d say the problem is elsewhere.

 

What oil pump are you running? Is it out now?

 

Flywheel needs to be on with shims when you are checking rotation. If you strip it further & haven’t found the cause of the tight spot it might be worth getting the crank checked in case it is slightly bent.

 

If you’ve removed the flywheel it’s too late to check the crankshaft thrust bearing float but it should now move in and out about 3mm.

orwell84 is alluding to the possibility of the bolts/rivets on the camshaft fouling the back of the oil pump – something you should have checked when you rebuilt the engine. But the camshaft has five bolts and rotates at half crankshaft speed so tight spots wouldn’t be every 90-degrees.

Next steps:
Remove the oil pump. It should be tight in the case and you’ll probably need to slacken the case bolts above and below the pump. If it’s an original oil pump don’t break the lugs off.
Inspect the back of the pump and the bolts on the camshaft for signs of contact. Post a pic of the pump and cam.
Tell us if the crankshaft rotates freely with the pump removed.

Important: When you remove the cam followers note where each one comes from and replace them in exactly the same position when you rebuild the engine.

 

Tbe nightmare would be a bent crank if its sticking without pistons or conrods.

 

Hi all

Thanks for taking time to look over this.

• Crankshaft float is 0.12mm with the flywheel, and 2.7mm without the flywheel
• Easier to turn without rocker gear but definitely easier to turn without heads and cyinders
• Oil pump is not fouling with Cam Gear. I explicitly dealt with that on the build. Removing oil pump didn’t impact on the stickiness of engine.

This is how it is turning without cylinders or oil pump but with flywheel on (which removed the 90 degree stickiness, so browny points to @77Westy for that) -

Cylinder state and Photos

• Cylinder # 1
• Cylinder # 2
• Cylinder #3
• Cylinder #4

The case is now split and the following are some vids of inners

• Right Hand Inners https://youtu.be/7uqyH6dV5cY
• Left Hand Inners https://youtu.be/rAg4QpR9Ig0
• Suspicious Rod Movement https://youtu.be/HYLVM1Ojr_M
• Rod, crank and Cam Movement https://youtu.be/rzjWSmwbJVM

Thats where I am up to at present.

 

Photos of the cylinders

 

And cylinder #4 cos of upload limit

 

Emm… well, the bearings look and sound knackered but I got a bit seasick. The crank isn’t sitting in the crankcase properly and it really isn’t a good idea to drop the rods on the cam or rotate the crank with the rods rubbing on the cam. And it sounds bone dry. At least the crank seems to rotate reasonably freely without the cylinders.

The crank thrust bearing clearance is fine and the crankcase looks clean, now you just need to clean, check and measure everything. Clean all the carbon off the pistons and combustion chambers, remove the valves and lap them in, if the seats are okay. #3 and #4 pistons are scored but will probably clean up okay, you’ll need to deglaze the cylinder bores and check the piston ring gaps before reassembly. The cam looks old/worn, what do the followers look like?

I thought I read 1,000 miles but you said the engine has done 100k miles, didn’t you?

 

I think you need to check your ring gaps, the honing wear looks unusual to me, I would expect it to me more or less even right up to the carbon near the top. Were the oil scraper rings fitted correctly?

 

Do you mean connecting rod bearing, then yes, I agree. That is an obvious concern. (Just done rod side clearance measure and they're coming in at 0.23-0.25 mm so at least they are well within tolerance.)

It is bone dry as one of the issues leading to another tear down was petrol in the oil, so any oil was ultra diluted, and petrol has evaporated off I guess.

What do you mean as regards the crank not sitting in the crankshaft properly? I realise that the crank must have lifted slightly on separating the parts, so the front bearing was spinning free of its dowling slightly, or something else?

Thanks for the pistons suggestions.

The Cam is actually only 1K miles old as it was installed on the last rebuild! Got it from the Engine Shop in Kent so hoping of good quality. The cam followers all look fine, though I had a struggle getting the cylinder#2 R hand one out (as looking from outside.) I had to extract it from the inside, and the edges were burred so that it couldn't be extracted from the outside. I guess that may be a symptom of something.

Just to clarify. The engine is of unknown mileage as it was a donor from another vehicle with no history. I've probably done about 15-20K Miles on it prior to strip and rebuild last year, since when I have done a further 1K miles under the erroneous understanding that the engine would ease up.

Also, sorry for the seasickness and I'll try and be more careful with the rods-cams........

 

I followed the Haynes manual on fitting the rings, so hopefully did it correctly, but it was a year ago and right now I doubt everything I've done previously so who knows...

It appears to me that the tightness in the engine is linked to the cylinders, as it got so much better on releasing them, so this is my main culprit in where the issue lies, but that could be a duff part or my own incompetence! Coin toss there!

 

So in effect, earlier on you were turning the engine with no oil and a monkey bar, any residual oil having been washed out by petrol? That may not have been sensible.

 

Check out the oil scrapers, IIRC you should see two colours where the ends butt up. One end on top of the other would be wrong.

 

Well, lack of common sense is definitely something I can be accused of of occasion, but actually, I forgot I put a couple of litres of oil in post clearing out the petrol infested oil so that I could check the turning, so in fact, there should be a decent coating of Oil, which makes the dryness of it more worrying...

 

I meant all of the bearings that are visible on the camshaft and crankshaft are knackered. And I meant don’t drop the con rods onto the camshaft and don’t rotate the crankshaft with the con rods resting on the camshaft. The cam will have a dent in it where you dropped the rod on it.

When the crankshaft is correctly located in the crankcase the bearings will not rotate. If you can spin the bearing the crank isn’t sitting in the crankcase and turning it is pointless.

I couldn’t see the end of the camshaft very well but you haven’t got star washers under the bolts, have you?

As a minimum you need to replace the main and cam bearings and almost certainly also the big ends too, and I’d also replace the pistons rings. When you rebuilt the engine last year what did you replace? It’s hard to believe it’s only run for 1k miles and the burrs on the cam followers are a concern, they should be a smooth sliding fit in the crankcase.

My guess is you stopped this engine just in time before it threw in the towel, but now you need to find what’s wrong – and there’s probably more than one thing wrong.

 

Hone marks looked totally wiped.

 

Even if you did put fresh oil in, if the engine was turned over with petrol instead of oil means there is then petrol in the oil system, and missing lubricating film of oil on all bearings.

The engine at Techenders that filled up with petrol overnight was not turned over before the oil was changed, so it still had good oil in the bearings , it turned out OK after the oil was changed and the cylinders were emptied of petrol.. .

Once you go to metal on metal, the bearings will start to get hot and melt to other surfaces and get stiffer and stiffer and hotter and hotter.. . Whatever radial clearance the bearing had would have vanished.