My 3a engine rebuild notes

[xirdneh]

Toyota 3A Engine re-build
Block
1. Check rod bearings; remove cap, wipe journal dry, insert Plastigage strip (color green), install cap and torque to spec. (12mm nut 26-32ftlb or 14mm nut 36-42ftlb), Remove cap and use paper gage to determine if clearance is too large. If so, new bearings are needed. Also check bearing for deep scratches/gouging, if so replace them. If I replace the bearings with new I will do the plastigage test on at least one rod with new bearing to make sure the tolerance is good. Maximum .0031”, STD .0008-.0020”. I re-ringed (only) an engine once and reused the bearings that were about .0026” and it has over 150,000 added miles on those bearings.

Note 1: When removing rod caps or rods from engine, be sure to keep the rod caps in order. They have to be re-installed the same way they came off and cannot be used on another rod. I scratch the number of the cylinder on the bottom of the cap and on the rod. Scratching an arrow pointing to front of engine is a good way to keep caps from being rotated 180 degrees.
Note 2: If rod caps get mixed up you can look at the machine marks on the sides of the rod and cap to see if they match each other. It may take a while to get all four in the right place/position.
Note 3: There are two types of rods depending on model year, wide bearing and narrow bearing, also 12 or 14 mm nuts
2. Check crankshaft bearings; remove cap, wipe journal dry, insert Plastigage strip (color green), install cap and torque to spec. (40-47ftlb), Remove cap and use paper gage to determine if clearance is too large. If so, new bearings are needed. Also check bearing for deep scratches/gouging, if so replace them. If I replace the bearings with new I will do the plastigage test on at least one crank journal with new bearing to make sure the tolerance is good. Maximum .0031”, STD .0008-.0020”
Note 3: Crankshaft bearing caps must be installed correctly, caps are numbered 1,2,3,4,5 and have arrow pointing to front of block, in case they ever get mixed up. A sure sign you have them mixed up is the crankshaft is bound up and will not rotate. Also know that caps are not interchangeable between blocks.
3. Remove crankshaft and inspect bearing surfaces for excessive scratches. If you think it might be excessive take it to machine shop and have them look at it. If excessive the crank would have to be re-ground and new smaller bearings installed. Also check the keyway on front of crank to make sure its not enlarged, key should fit snug. If keyway is enlarged or beat up you will need to find a replacement crank, I think getting it fixed would be too expensive.
4. Remove oil pump, disassemble and check tolerances with feeler gage. If it exceeds tolerance toss it and get another one. I have taken apart several old oil pumps and measured them and never found a bad one.
5. Remove pistons and check cylinders for obvious gouging. If cylinders are gouged, they may need to be bored out for oversized pistons. Deep gouging may not be fixable and block will be scrap.
6. Clean head gasket residue off top of block and use straightedge to make sure its flat. If warped, a machine shop can mill it flat. You could do it yourself but you will need to watch a YouTube video to see how. I have never seen a 3A block that was not flat.
7. Take block with crank caps loosely installed to machine shop so they can measure bore to see if new STD pistons can be used. They can also tell you if old pistons can be re-used. Either way the bore still needs to be honed (de-glazed) so new piston rings will seat. I have done this my self using the three stone unit in a hand drill or drill press but lately have been letting the machine shop do it. If you do it yourself make sure you understand what the process is, mainly how to move (stroke) the hone up and down fast and full distance from bottom to top of cylinder, this is critical!! If cylinders are not honed (de-glazed) or not honed properly your engine will be blowing blue smoke within 300 miles.
Note 4: The last time I took a block and new pistons to machine shop (2021) they charged $168 to measure and hone cylinders, dip clean block and replace old pistons with new. If cylinders are worn too far you will have to have the cylinders bored out to fit new over sized pistons which will cost much more.
8. If you removed oil pump now is time to install with new gasket.
9. When installing crankshaft and bearing caps oil the bearing side surfaces first. The four crankshaft thrust shims need to be installed located at middle of block. They have oil grooves that are to be on forward and aft side facing the crank Not facing the block bearing cap. Cap bolt threads should be lightly oiled and torque to spec.
10. Before installing piston rings insert them into cylinder and check the gap to be sure it’s within tolerance. Install piston rings on pistons so gaps are staggered according to spec. Install pistons so indentation on top of piston is forward. Use a ring compressor or make one from a piece of thin aluminum sheet and large pipe band (the ones you tighten with screwdriver). Drop piston in cylinder with rod end lined up correctly to crankshaft and lightly tap top of piston with butt end of wooden hammer handle. It should go in easy, if you feel the need to hit it harder don’t. Remove and double check everything.
11. Line rod up with its spot on the crank and push piston down. Install cap and tighten bolts to spec.
12. Now you can install front and rear main crankshaft seals. I like to lube the seal lip with light grease and coat the outside with a light bit of non-hardening gasket compound, the black stuff usually called “#2”. I press the seal in with fingers as evenly as possible. You do not want it to be tilted. Then I use a piece of metal rod about ½” diameter to tap all around till its flush.
13. Install oil pan with gasket. I use non-hardening gasket stuff on both sides of gasket.
Torque 36-61 inch pounds.

Machine shop measure cylinders, hone (deglaze) cylinders, dip clean block and remove old pistons and install new pistons. 168.00 (in 2021) Oil Pan Gasket 000
Crank thrust shims 000 Oil Filter 000
Crank bearings 000 Oil 000
Crank front and rear seals 000 Distilled Water 000
Rod bearings 000 Anti Freeze 000
Pistons 000 Clutch Kit 000
Piston Rings 000 Throw out bearing 000
Head gasket 000 Clutch Disc 000
Exhaust/intake gasket 000 Pressure plate 000
Exhaust pipe/manifold gasket 000 Crank pilot bearing 000
Valve cover gasket 000 Timing belt 000
January 2023 total cost of all listed here 419.00

[NWMO]

Thanks for the great info Robert!

Chris

[boxy4bangerbabe]

Hey hey,

Nice notes.
You seem to be the right person to ask this:

I'm looking for the rocker arm gap specs for the 3a engine.

Thanks for the help!
-Sam

[NWMO]

boxy,

The FSM is available as a PDF. The info you are after is on page EM-33.

Chris

[boxy4bangerbabe]

oooo. yes.
Thank you!

[Dreaminvader]

These are great notes thank you! I love your YouTube videos also. You should totally make a YouTube video of this process next time you rebuild a 3a (if there is a next time?). Thanks for all that you do for our community!