Assessing an unknown engine

[neilbardsley]

That honestly does sound like something to DIY? You would hate to have to drop the engine for a leak after 2kbof use?

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[RobFrost]

That honestly does sound like something to DIY? You would hate to have to drop the engine for a leak after 2kbof use?

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The engine is meant to seal without them. Most engines have nothing.

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[911hillclimber]

nearly 100% of mine failed during assembly, but non leak.

[RobFrost]

Due to workholding limitations, I had previously accepted that I would not be boat-tailing this engine. Especially since I didn't remove the cylinder head studs, restricting access to the webs. However I realised this could safely and accurately be carried out by hand with the side of a long reamer. So I did gently ease off the square edges of the webs around the cylinders in the end to improve gas flow. That's gotta add a half a horsepower at least.





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[RobFrost]

I gave the 964 oil pump one last clean and oil, reassembled and torqued up the nuts with loctite.



I thought i would have progressed further with this but I've not had as much time as I wanted. For example today, I was going to spend a full day but my youngest daughter wanted to go out and play tennis, and that has to take priority. The engine will still be here tomorrow, but my daughter will be grown up and gone in no time at all.

The screens went in the bottom of the case.



And it turned out they are a very tight fit alongside the larger oil pump, in spite of the room which has already been made. I'll have to be careful not to pinch that between the case halves on assembly, and I may even trim it.



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[RobFrost]

Putting the case back together is delayed as I had to buy more nuts so I continue with a few preparatory jobs...

Careful measurement revealed i would need to nick the oil screen to accommodate the larger oil pump. Better than milling down the tang on the pump.





Cylinder heads came back twin plugged. (I decided to avail myself of an expert and his jig for this job).





He caught one valve seat, which was a concern, but minimal and it seems fine. And he has marred the ridge near one of the gasket faces, which he warned might happen. I think that will also be fine.



JB weld over the oil plugs to reduce the risk of leaks, and to help keep them in.



And my daughter torqued up the oil pump and helped put the bearings in.



I remember putting the rubber pump to case seal under the pump but I did not check it was there immediately before tightening. That thought was keeping me awake last night.

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[RobFrost]

So not wanting to take any chances I decided to remove the oil pump and confirm the rubber seal was in place... it was.



I refitted the oil pump and intermediate shaft for the second time... a surprisingly fiddly job given the tabs on the nuts. Here it is all ready to go... except can you see the schoolboy error?



So I would be taking the oil pump out and fitting for a third time.



Apparently I am not the first to have made this mistake.



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[RobFrost]

It took me a couple of hours to get the flanges prepared with sealant, all the little oil seals on the through-bolts and to put the case halves together.

Sadly, it seemed quite hard to pull the case together and the crankshaft was so tight it would not turn. It seems to fit fine in the half case so I'm baffled why. Intermediate gear backlash maybe? Nothing makes sense because it was clearly a running engine in the past. I asked on Pelican if anyone can suggest reasons why.

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[PeterK]

Sometimes the simple things (if you’re lucky) …..if the cam chain is not correctly on the pulley, it can jam the crankshaft rotation. If so, loosen it by lowering it so that the links are all off the cog, then pull it back up & settle.

[SeanP]

con rods hitting the case after the chains as Peter suggested

[Lightweight_911]

I refitted the oil pump and intermediate shaft for the second time... a surprisingly fiddly job given the tabs on the nuts. Here it is all ready to go... except can you see the schoolboy error?

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- forgetting to fit the chains before installing the intermediate gear ?


.

[911hillclimber]

Yep, that was the mistake, so easy to miss.
Trust the crank now fully rotates and test through several rotations Rob.

Hard bit coming up!

Follow the Dempsey book.

[andytat]

Did you have the main bearing journals line bored Rob?
The magnesium cases will warp over time and very often
when new mains are fitted the fact that the case is a
little out of shape the extra material on the new
bearings will lock the crank.

Andy

[SeanP]

Is this the engine case that you welded on?
When you were welding did you have the case halves bolted together, or to a suitable surface plate?
Just thinking here the localised heat from the welding could have caused the case to move. If it was me I would be pulling it apart and getting someone to check the crank bore is straight and get it align bored and the case surfaced so that you know its all straight and true.

[RobFrost]

Did you have the main bearing journals line bored Rob?
The magnesium cases will warp over time and very often
when new mains are fitted the fact that the case is a
little out of shape the extra material on the new
bearings will lock the crank.

Andy

No, i didn't get it line bored. A guy on Pelican suggested the same thing.

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