Miata Turbo Forum - Boost cars, acquire cats. - Engine Building Advice? (Noob)

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DNMakinson,

That kind of stuff makes me scared to build a motor. One little mistake and boom. Money down the drain :eek4:

Quote:

Originally Posted by c.buffm (Post 1587286)

Compression test results are in. Thankfully, looks like its valve stem seals:

Dry:
1: 150 spiked 160-165
2: 150 spiked 160-162
3: 162 spiked 165-170
4: 165 spiked 165-170

Wet:
1: 170
2: 150
3: 165
4: 170

My buddy said he thinks those are okay looking numbers and from what I have read that seems good (no more than a 5% difference on the dry test). He said on his gauge it spiked up and then dropped a little after I stopped cranking. Could this be due to some pressure escaping out of the valve stem seals if they are bad?

The check valve in your buddie's comp test set is getting old. The "spiking" then dropping is not a problem with your motor. The check valves LOOK like common Schrader valves but they are special low tension spring versions that cannot be swapped for normal ones.
The ONLY places that can leak compression are all in the cylinder and combustion chamber. Pistons, rings, head gasket, intake and exhaust valve to seat contact points. that's pretty much it. The stem seals WILL NOT show up on a comp test.
Your numbers look good to run.

Quote:

Originally Posted by technicalninja (Post 1587313)

Thanks for the clarification and explanation on that. In that situation then, would you go off of the numbers it spiked to or settled at?

Spiked at. That is what the motor made even if it didn't hold on the comp tester.
Your motor is "juicy" as it has had more oil than it needs on a regular basis.
This is why your dry and wet tests are so close. In my first post I mentioned this...

Next step is to change those pesky valve stem seals.
Read multiple threads regarding this before tearing into it yourself.

The pics of your turbo looked normal, no obvious signs of excessive oil there.

So, I wanted to update this thread as of where this situation is at now. The car has been in the garage for the most part since early December so I haven't really been able drive it recently.

I had a one way check valve properly setup in between by intake manifold and catch can to stop any possible pressure that might try and make its way into the head (I was following the Deezums catch can thread).
https://cimg4.ibsrv.net/gimg/www.mia...cc41a018d9.jpg

I took the valve out, tested it out with my mouth and found it to be restrictive in the direction it was supposed to flow. I ditched the check valve for the last week or so the car was on the road and during that time I did not see any blue smoke out of the tail pipe at all. I have not drove the car since so I haven't been able to do any further diagnostics or checks.

I am guessing that the check valve was restrictive and helped pressurized the valve cover which may have led to burning oil. I can update more once the salty roads clear off here in PA but I believe that may have been the issue.

I THINK the valve stem seals are fine (maybe they got messed up due to the valve cover pressurizing?) but I have a full new set to install if need be. Any input on the situation as it is now would be great! Thanks :)