Monday, January 20, 2020

Something's missing!

For those of you that followed our "If you plan it they will come" road trip you'll remember that somewhere between New Orleans and San Antonio the Festiva's engine developed a misfire. It ran a little rough under 3000rpm but seemed to smooth out a bit above that and we were able maintain highway speeds. Fuel consumption increase by about 25% for the remainder of the trip but there were no other apparent issues. We made it home safely and now it's time to figure out what's going on with the car.

Safely home after our "If you plan it they will come" road trip.
The first diagnostic step was to run a compression test. I discovered that there was something missing in cylinder number three.
That something was compression! Cylinders one, two and four were all up around 125psi with number three at 0! Possible causes are broken piston rings or burnt valve and the only way to tell will be to tear the engine down and have a look. I had been experiencing oil consumption issues even before we went on the road trip so figured it was time for a rebuild anyway.

Before embarking on this project I had to make room in the garage and clean things up a bit. My other project car was moved into the back yard and hidden away under a tarp for the duration to free up space. Cleaning up was mostly putting stuff away and giving the floor a sweep. That task completed I can now move the Festiva in and get to work. I started by removing the hood, bumper, grille and headlights.

Garage all cleaned up and ready to go.

Hood, bumper, grille and headlights removed.

Engine out and transmission put aside.
Once the engine and transmission were out of the car I separated them, put the transmission aside then pulled the clutch and flywheel so I could get the engine on its stand. Next I pulled the head, had a quick look but didn't see anything right away. Examined the block and checked for any damage in cylinder three. There was no scoring or other apparent damage and it turned over nice and smoothly. I had a closer look at the head and that's when I discovered the next missing piece!

I don't think it's supposed to look like that!
One of the exhaust valves missing a good chunk! That would explain the zero compression wouldn't it?! Fortunately there was no damage to the cylinder head itself. 

So now I had the problem figured out I had to come up with a solution. I acquired a large stock of Mazda B6T and B6D parts a few months ago and in that inventory was a number of spare valves and a few other bits that I would need. Also included was a short block B6D engine from an early, normally aspirated, Mazda Miata/MX-5. I learned that this particular block had only 125,000km / 78,000miles on it which is at least one third the mileage on the 323GT engine that came out of the car. In addition to the lower mileage the Miata block runs with 9.4:1 compression rather than the 7.9:1 in the 323GT engine.

7.9:1 piston on the left. 9.4:1 piston on the right
After consulting with a couple of fellow Festiva fanatics I decided to go with the Miata block and the higher compression pistons. In order to temper the increased compression a bit I decided to go with a 0.080"/2.0mm Cometic MLS head gasket which is double stock thickness. Other than that everything else will remain the same. The parts department at Stoney Trail Mazda here in Calgary has been extremely helpful in finding some of the parts I needed. In addition to the parts I needed for this job I've purchased several others, particularly some for the turbo oil feed and drains. Considering that this engine is over 30 years old I really appreciate their help.

New head gasket.
Timing belt, cam seals and oil pan gasket...
New crank bolt and key, water feed outlet and hose for the turbo from Stoney Trail Mazda.
The block was completely disassembled as was the head. Both were sent to Cetus Automotive here in Calgary, the block to get hot tanked, the head to get  cleaned up and resurfaced. They only had to take 0.004"/0.010mm off the head to get it nice and flat.

Honed, hot tanked and painted... ready for reassembly.

Head shaved by 0.004"

While the block and head were out at the shop I set about cleaning the pistons and rings. They came up really nice and I was able to reuse all but one ring. Once the  block came back it received a couple coats of a flat black engine paint. The crank and rod bearings appeared to be in really good shape. Clearances were checked using Plastigage and the were well within specs so I simply reused them.

Pistons all cleaned up and ready to go...
The engine was reassembled with a new water pump, timing belt, idler and tensioner pulleys, and gaskets. I made sure to clean the old parts that were going back on the engine. The oil pan was really straightforward but I was in for a surprise when I disassembled the valve cover.

Media blasting debris in the valve cover...

... even more...

After sharing these photos and video with the Festiva community we figured that it was the remains of blasting media that was used to prepare the cover for powder coating. This was done before I got it so had no idea this junk was hiding in there. Needless to say I was very happy to have discovered the mess before putting the cover back on the engine. It took quite a while to get the valve cover clean but the effort was well worth it. 

Oil pan all cleaned up and ready to go!
Things went fairly smoothly moving forward. The threads for miscellaneous brackets were cleaned, a new block heater installed, the knock sensor and oil cooler from the original block were transferred and it was starting to look more like an engine.

Cylinder head isn't bolted down but you can see how thick the head gasket is.

Making progress

With the engine bay empty I noticed that the steering rack boots were disintegrating so took the opportunity to replace them. While I was at it I cleaned up the bay as best I could... a lot easier to do both these tasks with no engine in the way.

All cleaned up and ready for the driveline.
Now that the long block is back together and the engine bay is cleaned up it was time to take the engine off the stand and mate it back up with the transmission before dropping it back in its home.

Engine and transmission reunited.
Back in the car!
While putting things back together I took the opportunity to clean everything up as much as possible, starting with the A/C compressor

A/C compressor all clean and shiny.

Exhaust manifold, turbo, heat shields and oil and water lines all hooked up
Now that the engine is back in its bay the ancillaries can be installed. A/C compressor, exhaust manifold, turbo with its oil and water lines, heat shields, starter, linkages and wiring harness... all got repaired where necessary, cleaned and reconnected. Hopefully there's nothing missing.

Next question... will it start?

There's a couple of things I've learned to appreciate over the course of the sixteen days it took to complete this job. First, this generation of Mazda engines is tough! We drove the car almost 3400km/2100 miles with a burnt exhaust valve! We were able to keep up to highway speeds, although it took us longer to get up to speed and we used more fuel doing so. Now that this one has been rebuilt I'm confident that will last for at least another 300,000km / 180,000 miles! And I'm sure that after a good check up and refresh the short block of the engine we took out of the car will live on.

The three cylinder portion of our trip!
The second thing we really appreciate is the Festiva community. There are a number of fellow fanatics who have provided advice, recommendations and even parts to help this latest project along.

What's the end result? We now have an engine in the car that is not burning or leaking oil and will last a long time. With the higher compression pistons there has been a jump in horsepower. The stock Mazda B6T engine is rated at 132hp, knowledgeable friends estimate that the added compression will boost that to over 150hp. Those numbers are at the crank... it would be interesting to get the car on a dyno and see what the power at the wheels might be.

First test drive... to the car wash!

All clean and shiny.
The car has been back on the road for about eight weeks and the added power is quite noticeable. There are still a couple of little things to sort out but all in all I'm very happy with the way this has turned out. 

Thank you for your continued interest in our little econobox and the adventures it takes us on. What can you expect from the Econobox Cafe moving forward? Show and shine season isn't that far off so you can expect a few posts on that topic, there'll be some road trip tips and tricks, we'll be featuring some econoboxes from Europe, perhaps a hot hatch or two, and lots of other 'stuff'. Let us know what you'd like to see in our blog in the comments section below.

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