So why do we spend big money on engines? Apart from increasing performance, most of the engine rebuilding equation involves risk taking and insurance. We have to weigh up the risks and decide whether we need to reduce a particular weak link by replacing that particular item with a slightly better component.
Fortunately for us, many of the modern-day four cylinder and rotary performance engines come fairly tough from the factory and only require an enthusiast to give them a bit of a stir-along in the performance stakes.
One of the more popular engines that enthusiasts seem to be going for today is the Nissan FJ-20. Datsun 1600s seem to have become the most popular home for these feisty pony producers, and until recently I'd always thought they were a little over-rated. That was, of course, until I went for a steer in one that NRG Automotives of 3/33 Nancarrow Avenue, Meadowbank, (61 2 9809 1037), had rebuilt and thrown a heap of boost into.
If smoking the tyres at 90kmh with your head planted firmly in the headrest is your type of fun, then read on, because this engine/turbo package provided just this sort of fun.
On the dyno the FJ-20 made 216hp at the rear wheels and 680 Newton metres of torque with very little encouragement. In this segment we run through a quick rebuild with a few do-it-yourself race improvements to achieve this sort of power. Don't get me wrong, these figures are fairly obtainable with the standard mill, but with a rebuild the power becomes reliable and more permanent.
Begin by removing the engine from the car and mounting it on an engine stand. Get yourself a few containers for nuts, bolts and engine parts and try to clear the area of other projects so parts don't get lost or mixed up with other bits and pieces. Begin by removing the head, timing gear, then roll the engine over and push the pistons out and finally the crank.
As you go, make a list of worn parts and accessories in your head. Once the engine is stripped have a good look at the block and the bores to see if the block will need reboring. If it does it will need to be sent out with the new pistons, crank, flywheel and balancer to the machine shop.
Inspect the crank for any scoring or damage and if you find any it will need to be reground. The whole bottom end needs to be rebalanced but before sending it out we are going to polish the conrods so that the engine can be revved harder without fear of breaking a conrod. (Fig. 8: Fj20_8.JPG)
Polishing conrods yourself will save you a lot of money and is an important performance bonus. This needs to be done before the bottom end is sent out for balancing and the steps on how to do it are pictured.
Send your head to the local machine shop for an overhaul and they will relap the valves, check the valve-guides, replace the valve-guide seals and give the head a quick skim.
Assemble all your new parts, which include rings, bearings, gaskets and possibly timing chain, oil pump, cams and anything else that looks like it really needs replacing .
After getting your parts back from the machine shop, thoroughly wash them down in thinners or petrol. Before washing down, however, it may pay you to polish the case with a die grinder to reduce friction. (Fig. 1: Fj20_1.JPG) and (Fig. 2: Fj20_2.JPG)
Blocks are best placed on the engine stand then hit with a high-pressure washer followed by a quick blow-off then oil-down.
Bearings should be washed in petrol then dried prior to fitting, as should any new parts.
Before building your engine be sure to thoroughly clean the workbench and lay out all the parts and tools you require. Clean all your tools so that you aren't getting bits of dirt on your hands after picking up tools and then putting the dirt on the new parts.
Once you are ready to go, begin by gapping your rings. Do this by placing a compression ring in the bore and pushing it down the bore with a piston that has an oil ring fitted to it. Doing this with a piston that has an oil ring fitted to it will ensure the ring is placed evenly in the bore.
Once positioned. measure the gap in the ring with a pair of feeler gauges. The rule of thumb is that you need four thousands of an inch gap for every inch of bore.
Your pistons and rods will be marked after coming back from the machine shop and this gapping process needs to be done for each bore. Don't gap all of the rings file and finish with some 1200 wet and dry (use dry or with a little oil) or a small oil stone. (Fig. 6: Fj20_6.JPG) and (Fig. 7: Fj20_7.JPG)
Once all the rings have been gapped and fitted to the pistons with rings pliers (these can be bought from most auto accessory shops for under $20) we are ready to begin.
Roll the block over and fit the main bearing shells to the block. Do not oil the underside of the shell and make sure the oil feed hole in the block corresponds with the hole in the bearing. (Fig. 3: Fj20_3.JPG)
With these in position, liberally oil the shells with some assembly lube - ACL Bearing Guard or Torco Assembly Lube. Lay the thoroughly cleaned crank into position and spin it over by hand to make sure it feels okay. (Fig. 4: Fj20_4.JPG)
Press the other half of the shells into the cap and sit into position. Before tensioning, be sure to oil the threads on the thru bolts as this will give more accurate tensioning.
Tension the caps in two stages, first at 40ft/lbs then at 61-72ft/lbs. Begin at the centre cap of the crank and then work in a circular motion outward from the centre cap through the other caps. (Fig. 5: Fj20_5.JPG)
Spin the crank over by hand to check that there aren't any tight spots. If it feels good, pull off the centre cap, wipe off the oil on the bearing and flexigauge the cap for bearing crush. Consult the workshop manual for the exact parameters, but you should be looking for crush of around two thou.
Wipe the flexigauge off the bearing before oiling and retensioning.
Roll the engine over and begin to fit the pistons. Prior to fitting you need to fit the bearing shell to the conrod and thoroughly lubricate the gudgeon pin piston and rings. (Fig. 9: Fj20_9.JPG) Be sure to align the rings as per the factory manual or basically make sure all the ring gaps aren't one on top of the other. (Fig. 10: Fj20_10.JPG)
Unbeknown to most, the rings actually rotate on the piston when the engine is running so the way you set them up on the piston before fitting will soon change.
If you slot a length of fuel hose (8cm) over the end of the conrod bolts prior to fitting, this will stop the rod from fouling on the crank when you lower the piston down into the bore. (Fig. 12: Fj20_12.JPG)
Fit the ring compressor to the piston and gently tap the piston down into the bore with a rubber/nylon hammer. (Fig. 11: Fj20_11.JPG) Do not force the piston if it doesn't want to go. Pull it back out and have another go at it.
Once in place, roll the block over and fit the bearing and cap to the conrod and tension in two settings to 43-47ft/lbs. Turn the engine over and make sure it feels good before finishing the other pistons. It's a good idea to flexigauge the conrods for bearing crush afterwards and remember to clean the flexigauge off the bearing and crank.
Assemble the oil pump and pickup and bolt the sump on using plenty of gasket sealer on the gasket. (Fig. 14: Fj20_14.JPG), (Fig. 15: Fj20_15.JPG) and (Fig. 17: Fj20_17.JPG)
Bolt the timing cover into position after placing the timing chain in location, and if you have managed to get an original timing chain (which isn't available in Australia but is available in Japan), setting up the timing later is going to be much easier. (Fig. 16: Fj20_16.JPG)
Wipe the oil off the top of the block with thinners and place the head gasket in location. (Fig. 18: Fj20_18.JPG) Be sure to check that the holes in the gasket correspond with those in the block.
Lower the reconditioned head into position (Fig. 19: Fj20_19.JPG) and with lightly oiled bolts begin to tension the head down in three successive torque settings beginning from the centre of the head and working out in a circular motion (25ft/lbs, 60ft/lbs, then a final torque setting of 87-94ft/lbs). (Fig. 20: Fj20_20.JPG)
Fit the cams to the head and then set up the timing of the engine. If you managed to get a factory chain it's simply a matter of TDC then aligning the shiny links on the chain to the dots on the can sprockets. Otherwise you really need to get a factory manual. I'll try to explain but it's quite complex. If you draw a line across the gasket face on the head, the centre line of the bolt hole should line up with the dowel pin centre on the cam sprockets at TDC (top dead centre). It sounds easy but I thoroughly recommend that you get a copy of the workshop manual to set this up.
Slip the harmonic in position and turn the engine over slowly by hand. If it jams do not force it! Back off and recheck your cam timing.
From here it's all downhill. Bolt on the remaining accessories including the intake and injection, rear main oil seal and turbo. (Fig. 21: Fj20_21.JPG)
This engine was treated to a high-flow turbo charger which accounted for the ease with which it made the power.
From a factory standard of approximately 175hp (approx. 120hp at the tyres) to 216 at the tyres, an 80-plus per cent increase in power is more than certain to put a smile on your face!
