VVT Bottom-End Rebuild / Refresh
#41
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I'm somewhat worried about this (hydrolock), there was a *decent* (maybe a cup, cup and half?) amount of coolant in there - rods *may* be on my list of purchases, just to be safe. Your tip about cleaning the crowns and measuring length is noted - thanks!
#42
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Potential for computer damage, via coil failure, is really just a product of how an ignition coil functions. Long story short, a short or partial short in the primary winding is what kills the ECU drivers. Total current flow of a straight piece of wire with zero effective resistance vs. the windings of the coil primary side is significant. If there is a short within the primary, current levels can be higher than expected, damaging the driver. Manufacturers and their engineers have finally gotten wise to this, I went to a FCA training event a few weeks ago and basically every driver on their new ECUs have current limiters which will disable the drivers if excess current flow is detected. I seriously doubt the miata ECU has current limiting drivers, but you never know. IMO if there is a concern of a damaged driver in the ECU, the driven component must be thoroughly inspected. Unless you have a lap-scope, there really isn't a good way to do this. Really I would only worry about the coil which was not being switched properly. If the other one worked fine, I wouldn't say it's required to be changed. Of course, coils aren't crazy expensive either.
This is the enjoyable aspect of my day-job, so I enjoy nerding out about it.![Party Kitty](https://www.miataturbo.net/images/smilies/birthday[1].gif)
Good luck with your exploratory surgery on the motor.
This is the enjoyable aspect of my day-job, so I enjoy nerding out about it.
![Party Kitty](https://www.miataturbo.net/images/smilies/birthday[1].gif)
Good luck with your exploratory surgery on the motor.
#43
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Slight Update:
Pulled the engine/trans. Disassembled the engine down to the bare block (notice the nasty, brownish looking oil - MAJOR coolant dilution):
![Name: POLeWK6.jpg
Views: 39
Size: 4.23 MB](https://www.miataturbo.net/attachments/engine-performance-56/227991d1683051425-vvt-bottom-end-rebuild-refresh-polewk6.jpg)
Looked over the whole thing in detail - some minor scoring on the cylinders, pistons/crank/bearings looked fine. No rods bent (a concern was hydro-lock from the coolant in the combustion chambers.) No cracks (visible or felt with fingernails - very 'high tech' analysis.) No worn-in ridge/ring at the top of the cylinders either.
In the process discovered this - beside the oil squirter for Cylinder #4:
![Name: 6aTOmdb.jpg
Views: 35
Size: 4.16 MB](https://www.miataturbo.net/attachments/engine-performance-56/227992d1683051425-vvt-bottom-end-rebuild-refresh-6atomdb.jpg)
Some of you know what this is - caught me MAJORLY off guard - those ragged edges looked so bad - I spent the night convinced I had grenaded my block. Turns out NOT to be a hole / casting defect, rather the oil return/drain passage for the head. PHEW.
Haven't gotten the any parts to a machinist for measurement - nothing within 3hrs of my location - will do this soon. The overall condition of the block/bore/crank/bearings seem promising - possibly just need a good cleaning, honing, rings/bearings/seal job?
I did take a look at my valve lash (thanks Greg Peters) - nearly HALF of my lifters don't fully close due to poor adjustment. It's possible this is where my compression test issues (look back a half-dozen posts) seem to have originated. Still doesn't explain my primary engine issues.
Pulled the engine/trans. Disassembled the engine down to the bare block (notice the nasty, brownish looking oil - MAJOR coolant dilution):
![Name: POLeWK6.jpg
Views: 39
Size: 4.23 MB](https://www.miataturbo.net/attachments/engine-performance-56/227991d1683051425-vvt-bottom-end-rebuild-refresh-polewk6.jpg)
Looked over the whole thing in detail - some minor scoring on the cylinders, pistons/crank/bearings looked fine. No rods bent (a concern was hydro-lock from the coolant in the combustion chambers.) No cracks (visible or felt with fingernails - very 'high tech' analysis.) No worn-in ridge/ring at the top of the cylinders either.
In the process discovered this - beside the oil squirter for Cylinder #4:
![Name: 6aTOmdb.jpg
Views: 35
Size: 4.16 MB](https://www.miataturbo.net/attachments/engine-performance-56/227992d1683051425-vvt-bottom-end-rebuild-refresh-6atomdb.jpg)
Some of you know what this is - caught me MAJORLY off guard - those ragged edges looked so bad - I spent the night convinced I had grenaded my block. Turns out NOT to be a hole / casting defect, rather the oil return/drain passage for the head. PHEW.
Haven't gotten the any parts to a machinist for measurement - nothing within 3hrs of my location - will do this soon. The overall condition of the block/bore/crank/bearings seem promising - possibly just need a good cleaning, honing, rings/bearings/seal job?
I did take a look at my valve lash (thanks Greg Peters) - nearly HALF of my lifters don't fully close due to poor adjustment. It's possible this is where my compression test issues (look back a half-dozen posts) seem to have originated. Still doesn't explain my primary engine issues.
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