Engine Rebuilding Tips

Contributed By: Rod Linnett

The things I learnt whilst rebuilding my AMC 360.

The project: to rebuild the motor to provide better performance running LPG, but maintaining a satisfactory performance on fuel as well.� I refer to performance in regards to power/ torque and economy. The plan is to build a strong reliable motor with minimal modifications other than those required to meet the objectives.

"Before"� Mileage was in the vicinity of 8-9mpg city (UK Gallon) and 10-11mpg highway.� General lack of power running LPG due to low compression, badly seated valves and 230,000km on the odometer.� Power was noticeably better running fuel, but economy still bad.

Goals:

• 200+ BHP and 350ft-lb torque or close.
• 15mpg on the highway.
• An overall improvement in performance.

What was done:

• Hi-Compression pistons approx 10-10.5:1.
• Slightly warm cam -� called and 'RV torquer' or 'LPG Cam' or 'Pre-pollution' cam.
• Remove fuel pump and install electric fuel pump.
• Rebuild oil pump.
• Super Heavy Duty Double Row Rollmaster timing
• chain with indexed cam gear.
• Holley 600 4 Barrel Carb with vacuum secondaries.
• Holley 'Street Dominator' alloy inlet manifold.
• New distributor cap, coil and ignition leads.
• Heads modified for better suitability for LPG -
• Stellite valve seats. (Note: for an LPG dedicated vehicle Stainless Steel valves are ideal, but expensive)

The rebuild:

When assembling the motor, follow the steps set out in the TSM for assembly.� But these are few things I learnt that wasn't in the manual.

Big End:

First blow out all the water jackets, even scrape out any debris, rust and scale etc.� Blow out all oil passages in the crankshaft and block. Once all that is done, work in a clean dust free area to install crankshaft, piston and rods avoiding any contamination from dirt and dust.� Always cover the block when left for any period of time.� Use a lint free cloth to oil each bore.

1. Use plenty of oil, even around the ring compressor and in the bore when knocking the pistons in.
2. Put little pieces of hose on the rod bolts so they don't damage the bore.
3. Put oil on each bearing surface before tightening up and torquing.
4. DON'T FORGET the oil gallery plugs !! at the back and the front of the block, one each side of the cam plug on the back and one each side of where the came comes out the front.� Put some 'Stag' jointing paste or equivalent on the thread to ensure they won't leak. Otherwise you will spend 3 days removing the transmission and transfer case like I did to get the back ones in and another day to remove and replace the timing case cover for the front - like I did.
5. Don't forget the oil pressure sender either.

Head Installation:

1. Place gasket on the block and put head down onto it.� Use a non hardening (permatex No.3) sealant on the block side of the gasket which helps keep it in place. Rest the head on the edge of the block (there are some small 'ledges' there which help) to aid placing the head down easily.
2. Put a squirt of oil under the head of each cap screw before tightening� and torquing down.
3. Put a squirt of oil under each washer (or rocker bridge if you have them) when tightening down the rocker arms.

General Assembly:

1. Use plenty of Silastic (RTV Silicone) on the front and rear main seals.
2. Use silastic to seal around the Timing Case Cover gasket. Once you have the Timing Case Cover bolted up to the block� - leave it for awhile before attaching the Alternator, Air Cond etc because the bolts go through the Cover and you could lose the seal.
3. When bolting up Alternator, Air Cond etc remove 1 bolt only at one time to maintain the seal to the engine block.
4. Triple check the Timing Gears are correct and then install distributor and check again before putting Timing Case Cover on.� If possible, block off the water inlet/outlets and hook up radiator (fill it with water) and pressure test the system and check for leaks.� It's easier to remove and replace the Timing Case Cover on the engine stand that in the engine bay, believe me� I've done it ! :-).
5. Put the distributor in before the oil pump.� It's easier to turn the oil pump shaft to� line up with the distributor than lining up the distributor to the oil pump driveshaft.
6. Use plenty of Silastic again for the front and rear seals on the inlet manifold.� Carefully and evenly tighten down to avoid the seal from being squeezed out the side.
7. Put exhaust manifolds on whilst engine is still on the stand, in fact put as much as possible while it's on the stand.
8. Put heater hose on water pump outlet before alternator and bracket etc go on.� I recommend doing this before the engine is back in the engine bay.
9. Work out how to put alternator, air cond and power steer brackets on while on the stand.
10. Once the engine is off the stand and on the hoist put on adaptor/ spacer before installing flex plate on and torque down to 105ft-lb.� The flex plate will only go on one way.

Installation:

1. Leave engine mounts off until the motor is in position and some of the bolts to the transmission are in with the engine still on the hoist.
2. Get someone to help, it's very heavy by now and there's alot of pushing, turning and twisting to get it lined up on the transmission.
3. Reconnect fuel, vacuum, heater hoses, radiator, thermostat etc etc.
4. You can use run-in lube to start up or run the oil pump with a long screwdriver on a drill before turning the motor for the first time.� I put the oil in about 5 mins before and then turned it over for about 20 -30 seconds before letting it fire.
5. Once it fires get the timing close� so it sounds right and don't let it idle too long or stay at the same revs for too long� - it will 'glaze' the bore.� You need to vary the revs from idle to 1500 or 2000rpm or so.
6. Run around feverishly looking for any oil/ water/ exhaust leaks.
7. It's probably a good idea to first hook up a mech oil pressure gauge for start up than rely on an electric one to make sure you have oil pressure.
8. If everything is OK, check the timing, get it to operating temp, fill up with water, put radiator cap on.
9. Tune up engine.

Run-in:

There are many varied opinions I have found out on how to run a motor, so I'm only going to outline my run-in plans.

1. Drive gently, varying revs up to 2,000rpm max 2,500rpm for the first 500km, max speed about 80km/h.
2. Change oil and filter at 500km
3. Drive with a larger rev range, up to 3,000rpm max, max speed about 100km/h for the next 1,000km.
4. Change oil and filter at 1,500km
5. Drive more 'normally' but still being considerate and only rev above 3,000rpm when completely warm.
6. Change oil and filter at 5,000km.� Do a final tune up for the Carb and LPG, measure Air:Fuel Ratios preferably whilst on a dyno under load.
7. Change oil every 5,000km, Oil/Air Filter every 10,000km.

Result: So far I can feel a difference in performance, even though I have not revved it over 2,500rpm.� There is a noticeable increase in response and power as well as torque, climbing some hills without changing gear or loosing RPM, on which it would have previously. It's still too early to detrmine any improvement in mileage though and besides I haven't been keeping a close eye anyway.

Rod Linnett
'79 Chero 360, TH 400, QT, D44's 
Wollongong, NSW,(Toyota Infested) Australia
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