Engine break-in issues?
 

Hey guys,

I believe I'm experiencing some issues with my freshly-built BP. I had a shop build the bottom end, clean the top end, and assemble the head to the block. Let me give you some more information about the build before explaining the "issue".

1994 1.8L BP swapped into a 1991 (1.6L B6 electronics w/ 1.8L BP injectors, etc.)
Manly forged H-beam rods
Stock pistons
New rings
ACL Race main and rod bearings
Boundary Engineering oil pump/gears
New head gasket

Head:
I had the head cleaned and decked (only to ensure a flat surface)
Valves were checked and seal great
New valve seals installed

Block:
Cylinder hone (ball hone)
Assembly with new parts

I've used the following break-in procedure as a guide:
Flyin' Miata : Tech : How to break in an engine

Using Pennzoil 10w30 Conventional (white bottle) oil.

What's happening is I am getting smoke when and after pulling vacuum under decel. The engine appears to be "healthy" as it has good power, but I've driven it roughly 150 miles and through 2 oil changes of the Pennzoil 10w-30 conventional oil and it is still smoking under the conditions mentioned above. I pull a max of around 28" vacuum and have about 20psi oil pressure at idle, 40-50 when driving.

Please help/explain what may be going on, and what I may be able to do to fix this.

Thank you!
Ryan

My guess would be valve guides. We change them in every single one of our motors.

I thought that was a possibility since it can really only be that, oil rings, or valve seals. BUT, I've ran this engine before the rebuild (same head) and didn't have this issue.

I will try to do a leak-down and compression test and report back. Feel free to chime in while I'm trying to get this information back to you guys. =)

Here are some shots of the plugs. The first one is a close-up of what they all basically look like. The ceramic looked tinted a bit tan, and there was a small layer of black soot on most of the metal portions. They honestly look fine to me but I could be wrong. Any of the odd looking silver on the bottom edge, threads, and washers is just silver anti-sieze. If anything the ceramic on plugs for cylinders 2 and 3 were very slightly darker.


Close-up:
https://www.miataturbo.net/attachmen...ine=1343178283

Group, 4, 3, 2, 1:
https://www.miataturbo.net/attachmen...ine=1343178283

Another shot in black and white since my lighting was kinda BS:
https://www.miataturbo.net/attachmen...ine=1343178283

Here is a video showing approx. 28" vacuum during rev-down and the smoke associated with it:

another member Rushin just went through pretty much exactly what you're talking about. he swapped to another head he had and that fixed his ish.


https://www.miataturbo.net/methanol-...e9/#post906024