Turning Engine by Hand

[HuD 91gt]

Hello everyone.

 

Sorry for the newbie questions.  

 

I now have my recently purchased L28 F54 block with flat top pistons combined with N47 head in my living room.  Ready to look over and hoping to install this summer.  The head was apparently rebuilt, onto a block with about 30,000 miles.  It had never been run.  I bought a very unknown condition engine.

 

I've taken the valve cover over and the head was certainly dissembled/cleaned, and after going through my "How to Modify your Datsun... book" I am reasonably certain that it will run without grenading completely..  What i'm concerned about is the block.

 

I took off the oil pan because it needed to be painted.  Since my current L24 oil pan leaks like my kitchen sink, I also planned on straightening this pan and getting a good seal with a new gasket.

 

What i've noticed and what is concerning me is the fact that when I turn the engine by hand I hear some fairly drastic air leakage around the rings.  So much that I don't even get a "pump" of air out the exhaust unless I crank the engine quickly.   I put some light oil in the chambers (I didn't have engine oil in my living room), and it may have helped a bit.  

 

Is there anyway I can check the condition of the rings without mounting this to a starter and doing a compression test?   Is that much leakage around the rings normal?  They can't possibly seal completely so i'm sure some leakage normal but this seems excessive.  Obviously a true compression test the engine should be an operating temperature but there must be some way of testing without installing the engine in the car.   When I turn the engine, I do feel the 6 compression strokes, but there is a definite difference in how much force is required to turn them.  This all is making me believe I may need to tear it down completely.  

 

Any pointers on where I can start to check the condition?

Edited May 20, 2015 by HuD 91gt

[HuD 91gt]

Out of place?

[Mark Maras]

Don't panic yet. The first thing to do is set the rocker clearance. Then you can do a cylinder leak down test instead of a compression test.

Out of place? Not to me. I once (back in the 70s) refreshed a 73 Z 4 speed in my apartment bedroom using a 4X8 sheet of plywood to (almost) protect the carpet. Trans. worked fine but the bedroom smelled like gear oil for a month.

[Zed Head]

How fast is "by hand"?  Wrench on the crankshaft bolt or two hands on the pulley?

 

I like the smell of gear oil.

[HuD 91gt]

Can I do leak down test with a portable air tank, or maybe even a large bicycle pump. I don't have a compressor in my living room.

Maybe I can rent a portable compressor. I also have one of those tiny air compressors but I doubt that would work?

I am turning the engine with a 18" breaker bar on the crank. To get it to compress, and feel some exhuast from the manifold I turn the crank 360 degrees twice, in 6-8 seconds.

[HuD 91gt]

Just went out to grab my tools for a valve adjust, and forgot the feeler gauges. Doh!  Apartment living

[madkaw]

I think it will be hard to tell by hand. My last ZX motor only showed 90lbs by hand on a compression test. Once apart I realized it was in very good shape. Leak down test for sure.

True motor head has an engine in the living room:)

[HuD 91gt]

Valves adjusted(They were pretty close), leak down tester rental search begins.   I'm thinking a car tire compressed to 60psi or so should work instead of a compressor.  Thoughts?

Edited May 21, 2015 by HuD 91gt

[Zed Head]

Brand new parts don't seal like used.  Rings have to seat.  The valve lash will affect spinning engine pressure numbers because it controls when the valves seal the chamber, but leak-down is a static operation.  So valve lash shouldn't have an effect on leak-down results.  But leak-down results will be suspect because the rings haven't worn-in.  

 

Not sure you'll be able to verify good parts and assembly by testing.  How unknown is it?  You knew " The head was apparently rebuilt, onto a block with about 30,000 miles."  There must be a little bit more.

 

Even if you took the head off, you'd only be able to check valve seats, and cylinder wall finish.  Might as well install, break it in and hope.  Aside from a complete tear-down with measurements, doesn't seem like there's much else you can do.

[HuD 91gt]

Here's a video of me turning the engine.

 

[HuD 91gt]

Zed Head, thats not what i wanted to hear. But the truth hurts. haha. Also, you talk about the rings not sealing.  The block was not rebuilt, it has a claimed 30,000miles, they should seal, no? This was direct from his email. "I also ported the intake runners, lapped all valves, checked the valves for straightness, checked the valve guides for excessive wear, and replaced the seals."

 

The block is the true unknown.  He said he ran it prior to redoing the head.  He was told it had that mileage although he could not confirm.  From the sludge I found in the oil pan I find 30,000 pretty hard to believe.  Perhaps 300,000.  Although going through his emails again he said he did a compression test prior to the rebuild and it had even compression across the board.  

Edited May 21, 2015 by HuD 91gt

[Zed Head]

I overlooked that 30,000 connection.  130,000 maybe?  So the rings should be well-seated by now.  Hopefully not worn out.  Sounds like the head wasn't even rebuilt.  Lapping used valves, no mention of valve seat replacement.  Not sure what that means.

 

The good news is that these engines last many, many miles.  Many more than the typical US domestic Chevy, Ford or Mopar engine.  Basically, it sounds like you have a used engine that has head the head gasket replaced and the intake runners ported.  Still not sure what you could do to feel more confident besides running it.  I've run engines in my garage, on the floor.  Actually just one engine.  A running engine in the living room - that video might go viral.