Hi,
All the suggestions are good so far.
My opinionated 2 cents worth...
Be absolutely certain to *not* use a synthetic oil during break-in. It will prevent the rings from ever seating properly and the motor will always burn oil and never reach it's full potential due to less than optimal compression.
Any good quality 30 or 20W50 mineral based oil will be fine. Just be sure to change it promptly, after 300-600 break-in miles. A second change might be done at 2500-3000 miles. Be sure to change the filter at these intervals, too, since it's likely catching more stuff than usual as the engine is breaking in.
If the car is only occasionally driven, you might need to consider the length of time the oil is in the crankcase, instead of the actual mileage. Personally, I think 6 months is just about the max time any oil should be in the car, regardless of mileage.
At 6000 miles it's possible to change to a synthetic oil, if you wish, although some prefer to wait until 9000 miles. If you do choose to go with a synthetic, try to avoid high detergent varieties. These can often be identified by "extended use" ratings, but you might need to do some research and read a bunch of labels. (Personally, I might go to a 50/50 synth. "blend", but would more likely just stick with non-synthetic).
Dave is right. Lots of cam lube is important during assembly if a new or reground cam and new followers are being installed. The longer the engine is on the stand after a cam is installed, the more important it is to really slather the cam up with lube. It's a good idea to lube the crank journals in the same way, and even to put some inside the oil pump.
There are other considerations that effect break-in:
I think it helps to have a new or reground cam hardened, although some feel it will adequately self-harden during the initial break-in period. In my opinion, modern cam follower materials are such that it would be better to go the extra step and have the cam hardened. The hardening really is done mostly for the break-in period, after which the cam should enjoy a long and useful life.
Speaking of cam followers, you might already know they are also a key reason proper break-in is important. The TRactor engine design does not promote the followers to rotate as is usually done in more modern engines. This just wasn't a design factor at the time the TR engine was originally produced. Plus, there are good and bad cam followers. I'd probably not use the plain, stock variety without hardness testing. There are better, phosphated and drilled followers that provide some improvement to a stock or moderately tuned head, available from the usual sources. A more high performance solution is GT40 cam followers, which are a little smaller diameter and need a special sleeve to work in the Tractor engine. These have been proven to be about the most durable, but are more expensive. Some followers are actually too hard, and might too rapidly wear off cam lobes, especially if used with stronger valve springs
Speaking of springs, they should also be tested. There seem to be a lot of too-soft springs aroud. And, IMHO, stronger springs will only lead to faster cam wear. Stock spring strength or very slight upgrade is plenty to prevent "valve bounce" even with higher lift cams in these engines.
I don't believe in babying a motor very much during break-in. Sure, stay away from the red line during the first 500 2500 miles and avoid wide open throttle acceleration. But, I think it's more important to vary RPMs and the load on the engine, and to not just drone along at 3000 RPM on the freeway or get stuck in traffic idling. Just revving the engine without any load isn't much help, either.
My ideal break-in would be twisty windy back roads with some straightaways and little traffic, where I can take the motor up to modest RPMs, using 1/2 to 3/4 throttle occasionally, and giving frequent opportunities to decelerate on a closed throttle. This latter helps the rings form a better seal.
At the same time, I'm not a proponent of "driving it hard" right from the start with a street engine. This approach only makes sense with carefully blue-printed race engines. The reason is that a race engine may have half the allowable wear built into it, i.e. is actually built with looser fitting bearings than a street engine, simply because it will never get enough running time to enjoy a "normal" break-in. A street engine starts out tighter to give a longer service life and as a result needs a little bit more gradual break-in.
Another thing to watch out for is that the carbs are reasonably well-adjusted, not excessively lean or rich. Too lean might cause extra heat during a time when the engine will likely run a little hotter as parts bed in. Too rich might wash lubrication from the cylinder walls. Either extreme can even damage the engine.
Carb tuning changes are likely to be needed if any performance modifications have been done, such as adding headers, increasing compression with a milled head or installing a longer duration/higher lift cam. And, carbs will likely need to be re-tuned a bit once the engine starts to settle down, at 500 miles or so.
I've heard two schools of thought about hardening the crankshaft. Some feel it's beneficial helping it best bed in with new bearings. Others don't think it's necessary. I don't personally think it can do any harm, just adds some additional cost to the rebuild.
Cheers!
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
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