Crank case pressure

[makeitfit]

Hi learned ones, I'm popping back in for some much needed help.
I've rebuilt the Black Pearl engine again.
Timing is spot on now but not stock. Ended up tweaking pump and cam timing but it runs sweet as a nut now.
Good oil pressure and compression test shows 380 ( 4 chuffs) to 400 ( 5 to 6 chuffs) psi across the 4 consistently.
My issue is oil is bubbling up through the PCV valve drain pipe. I know there's some kind of restriction or one way valve in it but can anyone confirm this ?
IF this return pipe is blocked off I guess any crank pressure should vent through the rocker vent ?
What say you ?

 

[solarman216]

Thinking 400 is a bit low, have not looked up the stock pressure on a 2.7 but my 2.8 is 450 so that may explain your case pressure, how long has it run since re doing the bores etc, Rick

 

[makeitfit]

All of about half an hour . Had it running on test frame. Now in situ. Bore was still in nissan tolerance but on the lower end of the range as it had been honed before. New piston rings, gapped and clocked :thumb2
I expect some blow by thinking now about how to manage it ??
Ill open up the manual and check comp figures though

 

[makeitfit]

Just checked the manual
Min 356 psi
Max 427 psi

 

[Flying Torquewrench]

Did you de-glaze the piston bores before fitting the new piston rings?

 

[makeitfit]

Yep, I had the block cross hatch honed.
Apart from investigating what's in the oil return pipe, I think it is what it is now ��

 

[Flying Torquewrench]

In your previous post you mention that the block was just within limits as it had been previously honed. Does that mean that it is just in limits after the second hone?

Have you checked the bore for roundness? As they normally become egg shaped in the direction of piston throw.

 

[makeitfit]

In your previous post you mention that the block was just within limits as it had been previously honed. Does that mean that it is just in limits after the second hone?

Have you checked the bore for roundness? As they normally become egg shaped in the direction of piston throw.

Yes it is
Previously I had it honed at a local machinist; big mistake:doh
This time I took the block to a pro engine build company and furnished them with the Nissan spec.
The bores were still within spec and no ovality ( we assumed honed out last time). The previous build had only managed a few hundred miles before the rings wore out:doh
I think it's a fair comp considering its past

 

[Flying Torquewrench]

Yes, you are right. The compression figures seem to sit in the middle. Of course a bore that is close to the limit will always leak a bit more compared to a brand new bore.

Why did the rings wear out so quickly? From your post I assume that it was honed a bit agricultural shall we say? Or did he not clean everything out properly as that causes the same issue?

 

[makeitfit]

I think it the agricultural method
I cleaned it before building it up again.
I was amazed at the ring wear Live and learn though

 

[Flying Torquewrench]

Fingers crossed for this time. :thumbs

I found that the biggest issue with honing cylinders is that the wear on the 3 pronged honer is not even. The top of the stone can wear faster/slower compared to the bottom of the stone, hence creating a piston bore that doesn’t have the same shape all the way through. The more the honing stones are used the worse the uneven wear is. But you may assume that a pro engine build company checks the equipment before they use it compared to a machinist who just wants to make a quick buck.

You obviously spend some money on getting the engine done properly, so may I ask what sort of running in oil you are using?

 

[makeitfit]

Nothing special to run in. Just change oil at 500 miles.
Whole new thread on does and donts of running in oil ��
Suffice to say engine machinist said modern oil is fine. Better work the engine sensibly .

 

[solarman216]

Could never see the advantage of so called running in oils, just change it early to get rid of the metal that inevitably wears off pretty soonish, Rick

 

[macabethiel]

Running in oils

Could never see the advantage of so called running in oils, just change it early to get rid of the metal that inevitably wears off pretty soonish, Rick

Back in the early 1970's when I worked at an Audi dealership we had to use the running in oil that came with a new factory engine - the Audi engineer explained that it contained a mild abrasive to bed in the bores.

 

[solarman216]

Back in the early 1970's when I worked at an Audi dealership we had to use the running in oil that came with a new factory engine - the Audi engineer explained that it contained a mild abrasive to bed in the bores.

And that "mild abrasive" is also running round the big ends, mains, camshaft etc, no thank you very much, never did go along with all that rubbish, Rick