Assembly and Running In

There's nothing out of the ordinary to consider as far as assembly goes but even so we'll briefly touch on a couple of points. The first is the use of engine build sheets. Basically these are just a record of every dimension and clearance in the engine. For example for every cylinder you would note the bore and piston diameters and the resulting clearance, and the ring gap for each ring. At the bottom end you would record the main tunnel diameters as well as the journal and bearing diameters, bearing clearances, rod and crank end float etc. Things like deck heights, chamber volumes and spring heights should also be noted; anything at all really that is normally measured and quantified during a build. It doesn't have to be anything flash; handwritten notes in an old exercise book are fine. There are a couple of reasons for doing this. One is that it can help prevent things being overlooked, something that can happen to anyone no matter how many engines you have built. The second is that it is sometimes handy to have a record of what parts (including over and undersizes) are in an engine for future work. It's also not a bad idea to mark each fastener with a paint marker pen after it has been fully torqued up. It might seem a childishly simple thing but even experienced engine builders have been known to overlook a critical bolt and the paint mark is cheap insurance against this.

I should also mention the use of special assembly lubes, and why you should avoid them like the plague. If the components are oiled with a good mineral oil during assembly, and the oiling system is primed before startup, then there will be no lubrication problems and no need for special assembly lubes at all. Why do we need to avoid them? A good ring seal is absolutely critical to getting the most from an engine, and any special "superlube" used during assembly will mix with the oil and potentially be very detrimental to getting the rings bedded in effectively. Moly grease on cam lobes is probably the worst offender. This stuff is often supplied with the cam, and some guys slop it on like a redhead slops on sunscreen. It does provide very good protection for the cam if oiling is inadequate, but it also washes off quickly and will end up embedded in the cylinder walls. Most cam grinders won't give any warranty if you don't use it, but they're more concerned with avoiding claims than with your ring seal (and fair enough too). It's really just to provide some lubrication until the oil starts to splash around, so if you're confident you will immediately have oil pressure you can safely leave the moly grease off. Of course this assumes you'll be using a good zinc rich oil. I generally just use a thin smear of conventional wheel bearing type grease (non-moly) to prevent dry running for those first few revs until the oil is being thrown around and have had no cam or lifter problems. Of course if you will be running high spring pressures you will need to run light springs or leave out the inners until the cam has been run in, regardless of whether or not you use the moly grease.

In the page on cooling systems we mentioned the importance of using a thermostat with a bleed hole. I bring this up again here because the lack of a bleed hole is sometimes a very big problem with a newly built engine. What occasionally happens is the proud owner or builder of the said engine quickly fills the radiator to the brim and then fires it up to run the cam in. Unfortunately for him the head and top part of the block are still bone dry because there is no way for the air to escape, thus allowing the water to fill the head. Because the thermostat is sitting in thin air it often remains closed until the engine is well cooked, and likewise the temperature gauge sender reports all as being well. Often the cooked engine is blamed on a faulty thermostat, when the real cause of course was a simple air lock. I've seen this happen more than once and in one case it cracked some expensive heads. At any rate it's something to be aware of.

Prior to the initial startup you should already have your ignition set up and timed so you don't have to stuff around with timing during the break-in process. Fill the engine with good mineral oil and water and check for leaks. Don't use coolant or anti-freeze just yet; you can add this later once you have confirmed everything is watertight. It's not possible to prime the oil pump with a drill like you would with a Chevy; it has to be cranked over. Leave the plugs out and the rockers off until you have oil pressure; if the pump is in good shape and it was oiled during assembly it will pick up the oil almost immediately. Once you have pressure keep cranking for a while to get all the air purged from the oilways. You can now fit the rockers, rocker cover and spark plugs and fire it up.

The first twenty minutes are absolutely critical for both cam life and ring seal. You need to be able to get the revs up to about 2000 straight away in order to get some oil on the cam. You also need to get some pretty heavy loading on the engine to bed in the rings. Don't let it idle; if there is a problem shut it off and fix it before restarting. The run-in period is probably the worst possible time to be setting up a new and untuned carburetor or ECU; if possible use a known good carb setup that will allow you to drive the engine under load immediately. You can always fit and tune the new setup later. Likewise make sure the ignition is ready to go before startup. A dyno is the best way to control the load, but if you can get on the road and load it fairly heavily that's okay too. Basically you want to accelerate the vehicle with at least 3/4 throttle for a few seconds at a time before closing the throttle and letting the car slow down before repeating the procedure. Use 2nd or 3rd gear at first, then later you can use higher gears and hold the load for longer. A properly built engine will tolerate full throttle and load right from the start without problems. After about twenty minutes of this you should have a very good ring seal and no further special treatment will be required though it certainly wouldn't hurt to give it another hour or so of limited revs before fitting the inners where this applies. Avoid idling even after the run-in procedure; it's hard on the cam at any stage of the engines life. It's not a bad idea to change the oil and filter after the run-in; also check the valve clearances again as a check on the health of the cam lobes and fit the inner springs if necessary.