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You are definitely on the right track with your rebuild. I have rebuilt several of the G6 [2600i] engines (as well as the FE [B2000] & F2 [B2200] engines) and every time, I just cleaned everything and installed new bearings (less the balance shaft bearings) and rings, gaskets, oil pump, etc.

I believe that the metal in these Mazda engine blocks is very good, and you hardly ever see a ridge at the top of the cylinders......if your piston skirts do not have deep vertical scoring (scuffs are fine) then you can actually re-use the factory pistons......I have done this and my engines are still going strong. My way of thinking is, if boring and new pistons are not really needed, then re-use the originals if in good shape.......you will still get plenty of miles out of the engine when rebuilding them like this......I can attest to that!!

You may want to spring for a new oil pump though, and unfortunately, they include the timing chain cover also, and therefore are quite expensive ($300.00 or so).......but good insurance for your new bearings!

I will post some pics of some of my G6 rebuilds soon.......gotta get some dinner right now! :)
 

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None of the bolts are Torque-to-Yield........clean them good and re-use them! They are already better than any replacement bolts that you can buy, save ARP or the like!

I use a 240 grit Flex Hone to cut the cylinder glazing.

FelPro or Mazda gaskets are the best bet......and you don't need a Oil Pan gasket! Mazda used silicone to seal the oil pans on all of these truck engines. I use the Ultra Grey silicone.
 

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Here is the engine in my first B2600i truck that I bought exactly 13 years ago today.....if I'm not mistaken!

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I bought this truck from a junkyard in town, after the previous Owner tried to replace the head and gasket and did not set up the timing chain correctly......proceeded to crank the engine after putting it together, and bent all 4 exhaust valves.......and 1 intake valve. Never crank one of these engines without turning the engine over by hand, to check for clearance issues!

Apparently, after realizing what he did, the P.O. towed it to the JY with only 83,516 miles on the ODO! I hit the B-Series Lotto that day! Out the door with Tag, Tax, & Title for $702.00 ....... cost me $125.00 for the machine shop to replace the valves......then about another $100.00 buying a new FelPro HG and misc. gaskets, etc.

All I did was cleaned it all up good, and re-assembled the engine......still driving the truck today! (Old pic below)

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Here is a G6 engine that I totally rebuilt......but still re-used the factory pistons, and kept it all standard sizes......no boring or crank conditioning.....other than my cleaning and polishing on it. All new crank & rod bearings, rings, seals, oil pump, gaskets, etc.
Sold it to a friend, he sold it to his Son, then his Grandson had a heater hose burst, and he kept driving it, all the way home! I had to replace the cylinder head, gasket and ALL hoses.......just to make sure he was good for a while!! He eventually sold the truck to someone, and I have not seen it again.

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I cleaned the block up, re-installed the balance shafts, and started to rebuild it.....

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The new Owner getting some sweat equity in.....

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Cleaning everything by hand is a chore, but rewarding in the end.....

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Do not use steel or brass cleaning brushes on the aluminum pistons......only plastic......takes a while, but no scratching going on.....

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Don't have many pics of me measuring the clearances, but that's what I'm doing here.......installing the bearings and then measuring the size, then subtracting the crank journal sizes.....

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Getting ready to drop in the crank....

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Yes.....I re-used my stock pistons and ordered std. sized rings for them. Clean them well inside of the ring grooves.....if needed, you can gently use a small/sharp "dental tool" to get to the inside corners of the ring grooves, to get that last little bit of carbon/crud removed.......just try not to add anymore scratches to the aluminum pistons......that's the goal.

You will want to order new Hydraulic Lash Adjusters (HLA's) and totally clean your original rocker arms & shafts......then install them into/with the NEW cylinder head cam caps. If you are uncomfortable taking the rocker arms & shafts apart and cleaning them, ask your machine shop if they could do it for you.......and provide them the new head, with the new cam caps, and your original camshaft.......BEFORE shipping the core (and it's cam caps) back to CCH.

Yes.....use RED Loctite to keep all of the studs in the new cylinder head. You can thread two nuts together, onto the non-head side of the studs, then tighten them against each other, to help tighten the studs into the new head.

Thanks for the kudos! I actually enjoy building these smaller 4 cyl. engines and have always taken a lot of pictures as I work on vehicles.......it really helps you later on, to be able to go back and see what you did a few years later! As we get older, it's hard to remember everything!! It is all looking good too!!
 

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Another thing to think about.......as you get further along with your engine, look into buying new Mazda coolant & bypass rubber hoses.......the new Mazda hoses will last another 20 years, and add some good insurance that the coolant system is in good shape for years to come.......none of the 4-cyl. engines like to overheat!
I've had replacement heater hoses split before, when only 5-6 years old......and they were NOT a Mazda hose!

Another thing......use a quality (not made in China or Taiwan) front oil seal......the one in the timing cover where the harmonic balancer mounts. I've had a Taiwan made front crankshaft oil seal "push out" of the factory timing cover on one of my B2600i trucks, years after it was installed, while driving down the road! Did not know it, but stopped at the grocery store and smelled burning oil when I got out of the truck to go into the store.......thought it was from a car that was parked next to me.....surely it couldn't be MY TRUCK! Well, heading back home from the grocery store, and my oil idiot light starts flashing on and off......I was just about to my driveway, so I shut the engine off and coasted into the drive.......got out and looked (it was night time of course!) and the whole underside of the truck was coated in oil. When I fixed it the next morning, I measured the outside diameter of the new, made in Japan seal, and the old Taiwan seal that I had bought from one of the box auto parts stores, and if I remember correctly, it was .019" smaller in diameter.......when measuring it with a Dial Caliper.

Here is the old Taiwan seal.....

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Also......you will need to check the crankshaft end play again......once you have new bearings installed, and the crankshaft installed and the caps torqued down. The #4 main "thrust" bearing will determine the end play value, as that is what the crankshaft hits when shifting it forward & backward to check the value.
 

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Straight forward dismantling process......you will find that some of the cam caps will get stuck a little as you try and slide them off of the rocker shafts......the holes in the rocker shafts that the cam cap attachment bolts go through, can be sharp and like to "snag" the soft aluminum cam caps, but you just oil it up some with WD-40 or the like and they will come off.

Oil flows through the rocker shafts (this is why it needs to be cleaned!) and there are a series of holes out of the bottom of the shafts......of course they need to be put back together exactly as they are assembled originally, so lay every part & piece out on a table, and just clean one part at a time......this way you are not going to get the items mixed up.

Pic to show how I do it.......and I'm glad you have decided to do it yourself! This is how you learn! Congrats!

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I installed new HLA's on this truck......hence why I was cleaning up the valvetrain.

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I would definitely add those to your new parts list, if you haven't already.......that old oil in them, and the worn condition of them would not be a good fit in a new engine!

You will need to prime them before you install them also.......a friend of mine had a video online of him doing this......I'll see if I can find it, and post a link here in your thread.

Your Son is getting some valuable mechanics lessons with this project......and he will love it I'm sure! I went through the same experience with my Dad.......so many years ago!
 

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Some more advice.......when re-installing those 12mm headed bolts for the valvetrain & cam caps.....use a torque wrench, set to the value in your FSM (they give you a range, and I go close to the max of the range) as they are hardened bolts and will snap off if you wrench them down too hard......and NOT an easy process to get the broken portion out of your cylinder head! I have seen trucks that are missing a couple of these bolts.......because part of the last bolt is still in the head!!!

As many of these trucks that I have worked on, it never ceases to amaze me what some people can do.......when they DON'T KNOW what they're doing!!

I pulled a B2200 engine apart that was making a noise.......supposedly, the engine had been rebuilt......I found out that it had indeed been "rebuilt".......by someone that never had a Haynes, Chiltons, or FSM to reference while they "rebuilt" it.

They put the Thrust bearing in the WRONG location! On a main bearing CAP also! When the motor started, it peeled the thrust surface on the thrust bearing......like an Onion!! It made me laugh real good, anyway! The crankshaft end play was around 3/8" if I remember correctly......after the thrust surface gay way, the crank was rubbing on the block while turning......hence the noise!
 

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Hell.......you gotta see this.......right?

:LOL:

The thrust bearing was on the #1 Main Cap.......and the crank was rubbing the back of the oil pump......

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This was the GOOD side of the thrust bearing....

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And the BAD side.....

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Backside of the oil pump.....

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In hindsight, I probably nasty-ed up your thread here.......if you want me to remove the nastiness, just say so!

:ROFLMAO:
 

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Good call on the bolts......I always use the factory bolts when possible......I trust them way more than "off the shelf" bolts that others may use and call it good.

Hard to tell what amount of scoring is on the rocker arm cam follower pads, from the pics......Are there any "flat" spots? They should be nice and rounded.....no flat areas. Most of the hardened "cam follower" pads that are bonded to the rocker arms will show some wear, but it should not be scored. If they are, then you may need a camshaft also.......because it will be worn as well.
 

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With the 2.6 engine, it might be best to look for a used cylinder head (usually the cylinder head is bad, but the cam and rockers could be good enough to re-use) in the junkyards, or through FB Marketplace, etc.

I looked for new or used rocker arms for the 2.6 engine, but couldn't find any online.......plenty for the 2.0 & 2.2 engines though.
 

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So, if you wind up just buying the 5 rocker arms that you need.....keep in mind that, according to the part numbers, there are 2 different rocker arms........so make sure you are getting what you actually need.

I can look to see what I have in my used parts......but it may be a few days before I can even look. Hopefully I can look on Sunday.
 
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