Finally got my lower end rebuilt, have questions

[Pir0San]

I finally got my lower end rebuilt! I decided to take the plunge and spend the money to get it done. The engine was a little worse off than I thought, it needed to have another crank installed because it was worn and the harmonic balancer messed up the woodruff key notches, and I needed to have the block bored. I ended up having them bore it .020 over, resize my rods, install another crank with oversize bearings, put in new freeze plugs, and pretty much put the lower end together. They ordered me a master rebuild kit with ITM pistons, a new oil pump, all gaskets, valve seals, new timing set, and pretty much the whole kit and caboodle.

The lower end is set up and ready to go, except for the timing stuff to be put on and the front cover to be installed. I had them also pressure test my head and resurface it to make sure it would be totally straight. The head came out great, with only a light surface.

I've got a problem though. When I bought the head, the machinist had punch marked the back of the rocker arms to indicate which cylinder they went to, but he marked both the intake and exhaust rocker with the same number of punch marks. The machine shop didn't separate the intake and exhaust rockers, so now I'm not sure which order to put the pairs in. From what I understand, the camshaft wears on each rocker differently, so if you swap rockers back and forth, it could mess up the grind on the camshaft. Is this something that I should worry about? I don't want to get everything together and just have to rip the head off again just to swap the cam and rockers.

Also, what process would you guys recommend to break in a new engine? I've read some of the threads here on breaking in a new engine, and there are mixed feelings on how to break in a new engine, and there were even mixed feelings when I asked the different guys at the machine shop. The guy who did my block recommended I take the car on a 100 mile trip or so when I get the engine running, and to vary the speed as I drive. I asked him about if it was bad to let the engine idle, and he really didn't say too much about it. He advised I stay out of stop and go traffic, and that I not jump on the engine too much, but to give it some throttle to help the rings to seat. He also advised I use engine braking, and not to lug the engine. After 500 miles, he advised me to change my oil, and to change it again at 1000 miles, and then every thousand up to 3000 miles. After that, he said it should be fully broken in.

One more thing, what is a good base adjustment for my carburetors? I know that they were running rich before I dismantled the engine, and it seems that the base setting is 2 - 2 1/2 turns. Any suggestion?

What would you guys recommend? I'm going to hopefully have the most part of the engine put together tonight, and I can't wait to hear it run.

Here's some pictures, I'll hot link to them so as to not slow this thread down.

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[d240zx2]

Hi, Jeremy.

The only thing I can respond to is that the valve height must be identical from front to rear and that the cam holes be line-bored for exact height above the valves. I don't know that the rockers are location dependent since the other stuff makes it all line up anyway.

[Pir0San]

I ended up using the old cam and rocker arms on another head that I had, that were in good condition.

Thanks!

[carrott]

on initial start up don't let engine idle for long only long enough to check timing there is very high friction omn the bore of a new engine .U

[beandip]

On first start up , keep the rpm up around 1500 rpm to keep good oil flow and lubrication going. I wouldn't rev the engine , however running it up while driving should not hurt any thing but don't do it quickly. In other words for the first few hundred miles , drive the car as you would normally . No racing . Taking the car on a 100 mile run is right on and varying the speed is also , watch the temp. If she starts to heat , slow down some. If the engine was running OK when you removed the carbs , leave them alone until you have some miles on the engine. If they are a little rich it wont hurt anything. I think changing the oil as the builder is cheep insurance, and I would do the same thing. Worse case scenario on the cam and rockers thing is the cam could be damaged and in need of replacement. But if so the work all can be done without pulling the head. Keeping the RPM up on a first start up is important, at idle the crank isn't spray/splashing oil like it is when the pressure is up. This is lubricating the cylinder walls which are tight and breaking in.

Gary