EJ25 Rebuild DIY

[cas5259]

I started a low oil pressure thread a few months ago on an EJ253 from a Baja. All bearings were pitted/worn. Root cause was a head gasket failure resulting in an overheat that was likely driven for an extended period of time. Aftermarket head gaskets fixed the leak, but the bearing damage was already done. My guess is that they continued wearing over time until the dash light started coming on. Anyways, here's a summary of what it takes to rebuild an EJ short block. This is part 1, part 2 will come sometime this week.

 

The key to assembling is cleanliness. Clean, and then clean some more until the rag/paper towel stays white. Be careful about debris getting on the bearing surfaces during final assembly.

 

Being a former production engineer, I made an assembly cheat sheet with specs and procedure so I wouldn't be fumbling through all-data during the rebuild. I have a ground crank and am reusing everything except for bearings and piston rings so measurement is critical. If you're using new parts, then you can probably skip some of the measuring.

 

Google Drive link to spec/assembly cheat sheet HERE

 

Parts back from the machine shop. Crank ground and measured, oversize bearings, block/pistons/rods cleaned, heads decked. It was worth it to have the shop clean everything. Sorry for the non rotated, photobucket apparently sucks big time now.

 

 

 

Clean the rod and cap surfaces and match them up. Clean/install bearings.

 

Place a piece of plastigage across #1 bearing surface. Make sure the letters are lined up on the same side and the swoosh is facing forward. Bolt rod and cap together, torque to spec. Remove cap and measure oil clearance. Repeat for all rods.

 

Clean plastigage off all surfaces. Apply assembly lube to bearings and reassemble like last time. 

 

Note how all the number side of the rods are matched and facing up when they are all pointed to the right.

 

Check side gap.

 

Clean/install main bearings. Note thrust bearing is on #5.

 

Install crank on one half. Check thrust clearance

 

Place a peice of plastigage across each main bearing. Drop other half on Torque bolts to spec - its a rather involved process outlined in the assembly attachment. Disassemble and measure oil clearance. 

 

Clean plastigage off all surfaces. Clean block mating surfaces. Apply assembly lube to main bearings on both halves and crank surfaces. Reinstall crank into left half of block. Install 4 o-rings.

 

Apply RTV to other half. Be careful around the bearings.

 

Drop RTV half onto the other half. Replace the metal/rubber washers on the bolts that go inside the water jacket, and apply RTV to bottom of washers. Oil all bolt threads and install/torque like before. You won't be able to get a torque wrench on the bolt inside the bell housing or the one inside the bottom part, so just go by feel.

 

Install rear main seal. I messed up and drove it too far in, so that's where I stopped today. Will continue with part 2 once I pick up the new RMS.

Edited September 12, 2016 by cas5259

[lmdew]

Thanks for all the extra work, I'm sure it will help another member out there.

[Rooster2]

Impressive work and photography. I am sure once assembled, the engine will run like it is brand new.

[cas5259]

Part 2:

 

Removed and replaced RMS...much better. Now to install pistons. Start gapping rings. Slide them in and use a piston to make sure they are sitting even in the bore. Then slide a feeler gauge in the gap. Repeat a lot.

 

Load pistons with rings. Follow manual for gap locations, side clearance, and piston size specs.

 

There are 5 rings total. Note bottom oil ring end sits in notch on piston side.

 

Clean all bores until the rag comes up clean. Confirm no debris, then lightly oil cylinder walls and the wrist pin holes on both rod and piston. Confirm ring gaps are in the right position. Apply piston ring compressor. Leave some skirt gap to get able to get it to line up. My compressor is utter crap, but worked with some curse words.

 

Set #1 to BDC. Oil wrist pin, install piston (tap it down gently, it should go in easy unless its not centered), line up wrist pin holes and insert wrist pin. Repeat. Make sure dots are towards front and the pistons go back in the same hole (there are A and B pistons with very slightly different sizes). Insert wrist pin circlip. Confirm it is fully seated.

 

There, done! Turn crank to ensure it is smooth. Insert access hole bolts and seal up the covers.

 

Get it back on the stand. Install baffle, oil pickup, pan, oil/water pumps, ect.

 

 

Install new head gaskets - make sure they are facing the right way. Coat head bolts with clean oil, then follow ridiculous procedure for torque spec. Install timing belt and everything else!

 

Drop it in and get everything else attached. Fill with fluids, turn crank by hand/starter a few times (with fuel pump fuse and spark plugs removed) to get oil circulating. Install spark plugs, insert fuel pump fuse and start her up! After a slight adjustment of the throttle and cruise control cables, it runs like new!

Edited September 28, 2016 by cas5259