[30ONA]

As the heading eludes, I was thinking about buying a second hand J20 and rebuilding it myself. I don't have a time frame to finish so thought I could slowly do it at home. Learning from it and hopefully saving on labor costs.

I have done plenty of mechanical repairs in the past but have never rebuilt an engine. I can find parts but don't know which brands to use. The goal would be just a fresh engine. If there are upgrades that can be done at the same time without additional cost I would like to do that to. ie if compression can be increased for more torque/power by using different pistons/rods etc but at the same cost.

Just wondering what people think about the idea. Obviously I'd be learning on the job and doing all the removal and fitments of parts where I can but would need to outsource machine work.

Is there a large array of special tools needed?
What are the most complex bits?
has anyone done it using the workshop manual? (I have one).
I'd probably send the head away to be done completely but hoping I could assemble everything else myself on an engine stand.

Tools I don't have that I think I would need (feel free to add to it or tell me if I don't need it). I have good sockets, spanners and torque wrench.
Bench and vice
Press (what size)

[Gwagensteve]

Bearing pullers, micrometers for bores, plasti-gauge, accurate torque wrench, ring compressor, cylinder hone (as a minimum) feeler gauges for ring gap etc. engine stand, there will be loads more stuff too. How much more will depend on how much modification you want to do. Increase compression with pistons etc? You’ll want to cc the chambers, check for piston/valve clearance, potentially clearance the block, and the. You’ll need to tune that motor once it’s in a car

It’s easy to pull a motor apart- takes minutes. It’s hard to put a motor back together properly.

If it’s for curiosity, start with something simple and cheap like a g13.

If you want a good outcome (or improvement over stock) pay someone to do it right.

As for brands I’d use SGP unless you’re looking for modifications, and then you’ll need to do lots of research. The J motor isn’t commonly tuned anywhere in the world.

[greyghost]

and don't expect it to be cheap

[30ONA]

greyghost wrote:

and don't expect it to be cheap

Assuming all stock I was guessing 3k.
1k send head for refurb
1k block work and machining, new Welch plugs etc
1k parts bits and maybe some professional assembly of bottom end.
Am I way off?

[Gwagensteve]

Depends on the condition of the motor and what you’re trying to achieve. If you’re trying to get meaningful increases in power that won’t cover the tuning and ancilliary costs

[VitNick]

Club SX4 has a fair few builds with big power J20a's which are newer but share enough in common with the older motors, but also probably way beyond your intentions for it. They also had some handy info for setting the timing chain correctly etc
an example build: http://clubsx4.com/forum/showthread.php?t=3152

[greyghost]

I'd say closer to 5K, as long as the crank doesn't need a grind, the cam is serviceable or the rods need re-sizing
as soon as you add any of this in closer to 6K

GOOD pistons alone are $1200,

if your going to rebuild an engine, do it correctly, its lots of pre-assembly, measure measure measure.

last engine I built was over 4 hours work just in gapping the rings, $2500 in machining the block alone, $1200 in pistons, another 2K in timing gear, oil pump, lifters etc..
and this was an old cast iron push rod engine, nearly 10 years ago.

if you've never rebuilt an engine before, start on a lawn mower, you'll learn the basics with the minimal of outlay. and all the theory and practical experience of rebuilding engines is exactly the same.

this is how I started, and I'm quite happy to pull apart any variable multi cam engine and rebuild it.

[30ONA]

Gwagensteve wrote:

Depends on the condition of the motor and what you’re trying to achieve. If you’re trying to get meaningful increases in power that won’t cover the tuning and ancilliary costs

Not looking for increases

[30ONA]

$1200!!! for pistons?

how about US$12 each? 0.5mm oversize (rock auto), I know you get what you pay for but thats a loooong way from $1200.

[30ONA]

Gwagensteve wrote:

If it’s for curiosity, start with something simple and cheap like a g13.
.

Why is a G13 simpler than a J20? apart from DOHC?

[Gwagensteve]

8v sohc, belt not chain, lower compression and correspondingly less critical tolerances (that’s a guess but I reckon I’m right)

I’m a bit confused about what you want to do though. In order for there to be any point in the exercise, you’d need to be rebuilding a worn motor to spec, the amount of work, cost and parts will be entirely dependent on the condition of the motor when disassembled, or trying to improve on a standard j20.

Unless the engine is in pretty good condition and has a specific, known problem, the cost of rebuild will exceed the cost of a take out motor from a wrecker, which will come with a three month warranty. (Which is three months more than you will get from an engine you’ve opened yourself)

I’m with greyghost. If you want to work out how an engine works start with a lawnmower. Much better than messing with a j20.

[30ONA]

I know how engines works and have replace engine parts and gaskets, done services, brakes, rocker covers, injectors etc but never opened an engine. I've worked on all my cars from quad cam V6, pushrod V8's and my current car (DOHC 4cyl).

I have a car with a healthy engine (175-180PSI all cylinders) but obviously it won't last forever (191k so far).

I've always wanted to rebuild an engine.

I figured why not start now on a future replacement for my GV. But my philosophy with all repairs is if I have to replace it why not upgrade at the same time if the cost is similar. But as you have all described this is not possible with an engine build.

I'm looking at a complete motor for that has low compression. So figured I'd strip it myself and research and rebuild, taking as long as I want rather than being left stranded should something happen to my current motor. In all honesty I expect I'll get it apart and then rely on builders to finish the job. But at my own pace rather than all at once.

[Gwagensteve]

Instead of burning all that money on a rebuild, why not take your time to find a low KM j20 in excellent condition and store it well (sealed, oil in cylinders etc) for use down the track.

Much much less heartache, unexpected bills, having the machinist blame the mechanic for some bit of the job that was done six months ago, having the crank rebuilder loose the crank because you told them not to hurry etc etc. either get a quality machine shop/rebuilder to tackle the whole job and expect a big bill or stay away.

There’s another factor here. By the time a j20 is worn out, the car it’s in is also likely to be worn out. Manufacturers are pretty good at this now- “lifeing” components by engineering the whole car to last about the same amount of time. Modern, lightweight engines aren’t all that responsive to a rebuild because they’re engineered much lighter than in the old days. That’s no more evident than in air filters, where filter housings are now garbage because if the engine would be dusted in 6 years instead of 20 it doesn’t matter because the rest of the car isn’t going to last 20 years anyway.

[30ONA]

Thanks for the discussion and input all.

[Angus Martin]

During year 12 school holidays I freshened up my G13, new rings, gaskets, etc. for $300 lol. Put another 10k of hard kms on it and then sold it. By no means was it a whole rebuild but I did what I could at the time (money wise). taught me a lot about it. specialist tools i used were feeler gauges, piston ring compressor and got it honed for $100 at a machine shop. hardest part was because I used the old pistons and didn't lay them out in order it took a lot of trial and error to match them back up correctly. almost put a new clutch in but that what make it $500 all up and that's just ridiculous aha. Anyway, that was the first time I had opened an engine and taught me heaps.
I say go for it if you're doing it because you want to learn, but it's not the most cost efficient solution if you're spending a bit of money doing it, replacement engines are cheap as mentioned above.

[shakes]

I'm with Angus, if your after a freshened up stock motor. It's simple enough, just expect that you may halve the life of it by missing a 'simple' assembly trick of process.

Cut it down into small chunks.... replacing valve train (easy enough) replacing timing gear (easy enough) replacing big end bearings (easy enough) replacing rings and pistons (easy enough)
Doing it cost effectively with the correct machining is the trickier bit, and it's very easy to miss that washer or cover an oil gallery with a bad gasket or misread a decimal to a fraction in the specs or a million other small things and have the whole thing lunch itself on first startup too.