Engine 225 sharing parts on 231

[Apple]

FNG here on this forum. I have had a mostly stock 68 CJ5 with 225 V6 for a while now that I am currently swapping over to a 231 so I can take my time and rebuild the 225 and still have my Jeep running while I do it. This week is the first time in years my Jeep is down for repairs. My Jeep is a work horse and not a show queen. I started this swap process about four years ago and life had gotten in the way until now.

What I have is a 1975 231 odd fire that I have rebuilt. It is .030" overbore, crank ground .010", RV cam, stock style pistons, double roller timing chain, .090" shim lift on rocker shaft supports with new length push rods for proper rocker angles on valves. ...nothing special. I don't want to run the 231 intake as I don't have a carburetor for it and it has all the EGR on it. Also the front cover is trash on the 231 and has the wrong oil pump orientation. My plan is to run the like new cover that is currently on my 225 and swap the intake and flywheel as well. The front cover should be a direct swap over. The intake will not be a direct swap as the exhaust cross over ports are different and the 231 heads have a void near those ports at the mating surfaces that will not allow a good seal of the intake gasket around those ports with mismatched parts.

The 231 port gasket surface is a square with a clipped corner and the 225 gaskets are the full square. 225 gaskets leave a hole from that port into the void on the head and out to the air. The 231 gaskets will seal the port on the head side but leave an unsupported gasket into the exhaust port of the 225 intake so a leak will occur there as well.

What I have done to remedy this is block the ports in the head altogether. The 231 ports are a rounded hole about 5/8" diameter cast on an angle to the mating surface. I rounded the edges of the holes and drove freeze plugs into the holes and peened the casting to hold them in place. In my experience those exhaust ports always carbon over and plug up and I have never seen any adverse effects on my engines when they are plugged even with the butterfly valve still in the right side exhaust manifold. My 225 intake had carbon plugged ports and the 231 was plugged on one side.

My plan is to eliminate the butterfly valve in the right side exhaust manifold just to get rid of it as mine has a cracked housing and I'm unsure if it operates correctly anyway.

I want to keep the engine looking as close to a 225 as I can as it might be a while before that old 225 gets rebuilt again. My plan for it is to rebuild it with a cam and better fuel system. The current 225 was rebuilt not that many miles ago but many years ago by a crappy engine builder. It went to be rebuilt again after the oil pump was not changed on the first rebuild and had to go back a third time for the heads to get done again. All the years I have owned it the heads have been an issue as I believe the rocker arm to valve angle is way off pushing sideways on the valves and wearing the guides. I will be tearing into that engine soon and confirming what I am sure is happening. Plus I want to see what else is worn or incorrect from that last rebuild by the idiot shop. In a perfect world the bottom end will still be good and all I will have to do is the heads and update the cam. I run an Overdrive unit and the cam will help me with torque when traveling down the highway.

Has anyone else tried to morph the 225 and 231 together?

Skidding logs a few years ago...

Current 225 about to be pulled out....

231 with 225 intake installed..... I removed it again to swap gaskets and plug those ports. You can see those voids in the heads at the centers where the intake gasket is visible...the holes are now plugged waiting on the new gasket.


When the gasket gets here I will install the intake again and then I will pull the front cover off the 225 and clean it up, rebuild the oil pump, and attach it to the 231. I have a fairly new water pump on the cover already. Once all the easy parts are swapped over I will pull the 225 out of the Jeep and finish the swap. I am also going to rebuild the steering box and apply some ceramic coating on the firewall and floor boards to help slow heat transfer into the cab before setting the 231 in place.

 

[Manic Mechanic]

Welcome. I look forward to watching this build

 

[Belizean]

 

[Apple]

This 231 engine did not originally have a breather on any valve cover. It only has a PCV valve mounted at the back of the intake. The 225 has the PCV on the passenger side cover and a vent into the air cleaner on the drivers side. I drilled the 231's passenger side cover for the PCV and have been holding off drilling the drivers side for the vent. The 225 has a baffle inside to help keep oil out of the vent and the 231 may have a baffle there. I need to pull both covers off as I remember there being a baffle someplace on the rocker shafts. I need to see about that baffle and cutting a hole into the drivers side cover and installing the vent there. There is no embossed area for adding a hole so I will just cut one anyway. I'm not worried about messing up the 231's covers...I want to keep all the 225's parts intact though. Too bad the covers will not interchange.

I'm going to have to research how that 231 vented in the original 1975 Regal as not having a second way for gasses to escape had to make that engine a real oil leaker.

 

[Apple]

Well, the mistakes made rebuilding this engine years ago keep on growing. I took the front cover off today and what did I not find?.....the cam button and spring, the crankshaft oil slinger, and the timing chain tensioner (stock style chain). All missing, gone, forgotten.

The camshaft was free to float whatever amount the fuel pump arm and timing chain would let it move.

I got the front cover and water pump all cleaned up and will have to tackle the oil pump and all the cover bolts next. Everything is covered in a 1/4" of oil and sludge. The water pump and fuel pump are fairly new so I will reuse those. I have a rebuild kit for the oil pump.

I need to get the intake manifold on and button up that top end before I put the front cover on the 231. My gaskets should be here today for the intake.

 

[Apple]

I ran into a fitment issue with the front cover. The 225 and 231 share the same front cover, zero differences on the cover itself.

My 225 has an aftermarket front cover that I am putting on the 231. The 231 has an original cover that is wore out in the water pump area. I was able to confirm all key measurements are the same between them.

I upgraded my timing chain set to a double roller for longevity and deleting the tensioner. Both the 225 and the 231 had stock style timing sets. The front cover has an area the cam button rides on to keep the cam pushed into the block. Above that area is a small post that is there to act as a safety of sorts (I'm guessing) that will ride on the front face of the upper timing gear if the cam button were not there and possibly keep a loose chain from jumping off and getting between the gear and cover. The 231 original cover shows zero contact between the cam gear and this post.

The double roller timing set has a top gear that is wider than stock. Wide enough contact is happening between that post and the cam gear not allowing the cover to seat by at least 1/8". I was test fitting the parts when I discovered this. This double roller set was advertised to go into a 231.

My plan is to machine down that post until I have the same clearance as it would with a stock set of gears. I am going to machine it down until the cover fits flat without the gasket and take another .002" off the post. That post was keeping my cam in place on the 225 and has wear on the post so I have no idea how close it should be and it will be impossible to figure it out based on what is left of the gasket on the 225 to measure off of. What I do know is that post was untouched on the 231 with stock timing set.

Big takeaway is a double roller timing set will need modifications to the front cover to fit.

 

[Apple]

A little more progress today. I machined that cover and installed it. I got the fuel pump on, coil, alternator, intake, oil pan, carburetor, bypass water hose, and spark plugs all installed. I debated about painting the front cover as it was raw aluminum...paint won out. It feels good to finally have this block buttoned up after nearly four years since I assembled it.

I need to go shopping and get some oil and a few other odds and ends so I can prime the oil pump and prime the entire engine with oil. Once that is done I will drop the distributor in and put the front dampener and pulley on. I'm leaving the front dampener off until I get the distributer in place as the 231 engine is sitting at TDC on number one and I marked and pulled the distributor on number one in the 225. I should be dead on for timing when I stab it back in. Once that is done I don't care if the engine rolls over when I put that dampener and pulley on, until then it's not getting moved.



I need to keep this pace going and not stall out. I'm trying not to burn myself out and only working on it a little each day. I'm going to keep swapping parts off the 225 until I have everything off I can before I have to pull the engine out of the Jeep.

I did not have the original oil pan bolts and bought 14 bolts a few day ago.....14 of the wrong bolts!!! So, I dug through my nuts and bolts bins and found 14 bolts and washers that were perfect for it...they are not all the same bolt but I don't care about that on this build.

 

[Apple]

More progress today. I went and got oil and zinc additive and a few other supplies. I put on a new oil filter and filled it with oil. I built an oil pump drive that attached to my drill and primed the oil system until it was oiling all the rockers. I punched a hole in the drivers side valve cover and put a grommet in to attach to the original 225 vent with an adapter as I could not get the same sized (without paying $16 dollars shipping on a $3 part) grommet as the 225 has. I still need to pick up some matching hose clamps for that breather hose.

I stabbed the distributor and clocked it where I have room to move it both ways. I repaired a broken bolt on the front dampener and installed it with the pulley. I also installed the alternator and fan. I swapped out the plug wire holders and put the cap and wires on.

Next I need to try and get the dipstick and tube out of the 225. I may have to wait until I pull the engine to do that. I am at the point where I will need to pull the 225 out. I don't want to try and get the exhaust manifolds off in the Jeep and I need the motor mounts, flywheel, and starter too.

I want to get the 231 dressed as much as I can before it goes in the Jeep. I have had the engine out of the Jeep twice before for clutch work and I can pull the engine complete, minus only the starter and air cleaner. I plan on leaving the starter, air filter, fuel filter, and fuel lines off when it goes back in.

I did have to decide where I would quit painting things. I stopped painting at the pulleys, fan, dampener, fuel pump, air cleaner, and vent on valve cover. The rest of the Jeep is old and greasy and I had to stop someplace

My original plan was to not paint anything and let it all be raw and ugly and I talked myself out of that idea. I just could not talk myself into painting any more though.

 

[Apple]

I tried to not work on the engine today but I snuck in an hour pulling the drivers side exhaust manifold and dip stick. I found another issue with the 225, there was at least one heli-coil on the manifold to head bolts as the coil pulled out with the bolt. I know broken manifold bolts are common so not a big deal but still an issue to deal with when I rebuild those heads. I might just pop a new coil in it right away so I don't forget.

I got everything cleaned up and installed on the 231. The dipstick and tube fit perfectly. With 4.5 quarts in a dry engine it reads almost a quart low.

The passenger side manifold will be next if it does not fight me. I had two bolts fight me on the drivers side that required flexing back and forth before they started to move, and tiny back and forth motions to get them out without breaking them. I would rather spend an hour wiggling a bolt than removing a broken one. When I used to rebuild Model A Ford engines I would spend hours wiggling head studs out of blocks to not break them.

If I can get the other manifold off in the Jeep it will be the last item I can pull before getting under the Jeep to start removing the engine.

 

[Apple]

Today I pulled the passenger side exhaust manifold and that cast butterfly valve. I kept having exhaust leaks at that valve and lo and behold it was broken in two. I was going to delete it anyway but did want to use the casting as it mates between the flat flange and the flared pipe.

I ordered a new exhaust flange and machined myself a flared spacer that I will weld into the new flange. I may have to machine the part a little more once the flange gets here to insure a nice fit.

The machined part will slip inside the new flange and get welded inside and out. In the photo you can see the broken casting and my old gasket sitting under the machined part. The new flange will take the spot of the gasket to mimic the cast part.


Here is the 231 all complete except for the flywheel...

 

[Apple]

Here is my machined part and the flange I purchased. All I have to do is weld it up now. I'm really hoping I can bolt the new part on separately and then add the nuts for the exhaust pipe flare flange. I think that would be more secure than just letting the exhaust pipe flair flange sandwich it all together.