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Mazda BT 50 & Pickup TrucksWhile Mazda may not be known for their trucks, they have always produced quality reliable trucks for both hauling cargo, or simply crusing. BT 50
2 very full days. My mentor and a friend that wants to learn came over last Friday.
We got the engine out. Was a bit of a struggle on some of the bell housing bolts and prying the crank off the spline.
We used a chain hoist instead of the backhoe, more control. We blocked the transmission up as well as left my jack under it.
Today, we (mentor and me) hung the engine on the stand and proceeded to tear it down. Manifolds, accessories (at this point only the alternator). We got the timing chain cover off and discovered that the slack adjuster on the oil pump chain was rather loose and would definitely be a source of the whine.
We had pulled the oil pan, loads of RTV schmutz on both sides of the gasket.
The strainer was in good shape. A few pine needles and small detritus. Probably not the source of the low oil pressure. We think perhaps the oil pump was cavitating. Also, there may be extra rtv in the oil channels.
The valves were chonky. A few spots in 2 & 3 that were obvious sources for lack on closing valves. The head gasket was relatively good. One or 2 spots that may’ve contributed to the low compression. Looks like I didn’t get a picture. I was quite eager to clean them. Do you guys know what the measurement is for the valve seat? I know it’s 45 degrees, but the width is eluding us.
The main bearing, crank bearing, and cam bearings are all nice.
The pistons were in decent shape, but several of their oil rings were seized. I’ll be ordering the rebuild kit without pistons.
Looking like I’ll be getting: rebuild kit, hose kit, water pump, possibly a clutch, and the weber-ish carb.
I’m planning to soak the chunks in diesel. My other concurrent project is a deuce and a half. She needs her fuel tank drained and cleaned. Seems I have a place and a need for a large quantity of gross diesel…
My mentor asked that I pose a question for the community. How does one tell if the hydraulic lash adjuster(s) are adjusted and functional?
We worked on cleaning more parts today. He showed me honing technique and I honed the cylinders. We fitted a new ring in the bore, nice and tight. Unfortunately, the ring was too large for the pistons. We think the rebuild kit I purchased the rings would’ve worked in the pistons that I left out of the order.
Anyhow, I need to measure the rings and determine if my pistons are oem or aftermarket.
Where I live I do t have cell signal at my house. I have to go to the county dock.
There are worse places for getting internet.
I am hoping to wrap up the rebuild before the end of June.
You are absolutely correct with this link. I tried the knockoff Amazon version and I’m sending it back. Looks like the Redline is a better bet.
Yes. There are still things you'll need to do: Most important: Make Weber adapters flat perfectly flat, sand them flat using wet/dry on a sheet of glass.
Use a thin coat of Permatex Aviation or similar (NOT RTV) used on all the gaskets for the adapters and bottom of carb
Torque the mounting screws and bolts correctly? Did you use blue Loctite on their threads?
Plug the electric choke of the Weber into the rear of the alternator. If the bi-metallic spring doesn't get heat from the choke heater to open up the choke butterfly, the fuel:air mixture will be richer than it should be for a warm engine.
Cap off all the vacuum ports capped off with GOOD quality caps (or pieces of vacuum tubing and golf tees) Get a stronger throttle return spring.
I used 14mm x 1.5mm wheel lugs from O'Reillys to plug the pair tube outlets coming out the upper manifold heat shield.
You don't need the PTC heater under the factory carburetor; but you might need shorter screws then than what are supplied in the kit. I got shorter screws for mine at Ace Hardware.
More time on this project today. I think all of the parts are here now, save a few fasteners that need replaced.
While cleaning the front of the block I discovered what looked like a sheared bolt. I don’t remember any breaks when taking the timing and oil pump chains off.
We removed the “bolt”, it was thread less (which could be from removing it), and it had a hole through it. It also goes into the oil gallery.
With the red circle.
What is this hole? An oil spray nozzle for the timing chain? Part of the timing chain guide attachment? Please let me know if I need to re-tap and heli coil it.
I have not rebuilt or pulled a Mitsu engine apart before, but I do know that the Mazda 2.6L engine out of the B2600i trucks has a small diameter roll pin that is located in a similar position on the engine and it is there to help keep the timing chain from falling away from the crank gear when the cylinder head or cam gear is replaced or removed. Here is a pic of it installed.....
05-30-2023, 09:49 PM
Out and diagnosed!
