Cherockee

Over the past few months (yes, I'm slow and on a tight budget) I have completed my engine rebuild. Vehicle is a 1997 XJ, 4.0L motor is from a '95. I had a machine shop prep the block (all machine work and balancing) and ordered the kit for me. I did the assembly in my spare time over a week when time allowed. It's been a much longer road to get to this point than I ever imagined it would be, and I'm still not done.

So my questions: I've never did a break-in like this before, but I suspect all the smoke I saw when first started is normal. Once started I made a quick check of all it's vitals and then bumped it up to 2000 rpms for 20 minutes. Tempature was good, oil pressure started out at 60 and by the end of the 20 minutes it had dropped to 30 (@ 2K rpms). I am worried that when I left it idle the oil pressure dropped to around 15. I'm using a mechanical Sunpro gauge and I did notice some air bubbles had formed in the supply line. Why is my oil pressure so low when hot? what's causing the air bubbles and is that why it only reads 15psi? Shouldn't the gauge self-bleed?
Also, during the break-in the header got red hot. I'm thinking that may be because the computer it still "learning" to set proper fuel management, would this be the cause of the excessive heat at the exhaust manifold? Computer has been disconneted for several.... years... and I have changed some parts that are not stock '97 XJ. I'm running 703 fuel injectors, '99+ intake manifold, and a Banks header. Cat looked okay when I inspected it, and got a nod from a local exhaust expert that said it looked good to him too, besides- there was a ton of smoke pouring out of it so I know it's no clogged. Any thing I should worry about?
Only other trouble I ran into, beside finding out my alternator is bad, is that I've got a very small oil leak. Hard to believe since I took such extra care to install the gaskets just so this wouldn't happen. Looks like I'll be dropping the pan soon, but that brings me to my last question. When should I change out the "break-in" oil? Should I do that now, or should I wait a while? Problem is I won't be driving it for a while as I have many other things that need attention before I can license it for the road, so it will only be diven around my parents property. Any suggestions as to when I should change the oil?

Thanks for taking the time to read all that. I appreciated any help you can give.

UJSLOST

1. Smoke is normal after a rebuild, especially if you lubed the cylinders.
2. Oil pressure @ 15psi at Idle is normal
3. Air bubbles in the guage line is normal
4. Red header is a sign of a very very lean condition such as timing to low.
5. Id say remove break in oil between 500-1000 miles. What oil did you use? Did you put in a zinc additive for the break in? Some engine builders suggest it because conventional oil nowadays does not have zinc in it and the old flat hydraulic tappets need zinc to help break them and the cam in without rubbing a lobe off the cam during break in periods. And personally, I suggest break it in like you will drive it all the time. Dont bother babying it to death during break in period. Some folks say not to get over 55 mph during break in. I dont .

Cherockee

This is what I used:http://www.penngrade1.com/Products/H...ak-In-Oil.aspx

And I plan to use their 10W-30 for the next few changes and probably all of them after that.

So you're saying I should drive it for 500-1000 miles before I take out the break-in oil? Problem with that though is it's not street legal yet, so that might take a while. I may try to call Brad tomorrow and see what he suggest too.

Thanks for the quick reply!

DFlintstone

500 is good. I've herd it's good to try to use a range of RPM, don't just drive steady allot at the same...Sorry about the leak, hate that. Third times the charm?

Low Profile

I'd say the break-in before you change the oil kind of depends on how hot the engine got when you fired it up the first time. (What? No photos? Dude! ) A little smoke is normal until the rings seat. I'm assuming you did have a machine shop go through the head, to make sure you don't have any bad valve stem seals, etc. 500 miles is about right, unless the oil got "burnt". If it's dark and smells burnt, change it out and solve the lean problem.

I agree with UJSLOST, the red header is a worrisome problem, bigtime. Be careful not to burn a valve or melt a piston with it running that lean. I'm not much of an auto mechanic, most of my wrenching experience has been on Harleys, but the principles are similar. You aren't sucking air somewhere are you? If you've got an intake leak that allows atmospheric air to leak in it causes the same symptoms as running way too lean. On a Harley, it causes chrome exhaust pipes to turn blue near the cylinder because the exhaust gases are so hot. We usually checked that by letting the engine idle and spraying WD40 around areas where the leak might be. (Just keep it away from the intake.) If it's sucking air at idle, the WD40 causes the RPMs to increase abruptly, as if you had opened the throttle.

Cherockee

So what are some causes for it running too lean? Could it be the 703 injectors? The +99 intake manifold? What should I be checking or replacing? Nearly everything is new on the motor except for the throttle body sensors, they're all orginal. Would the AIT sensor cause this?

Keep in mind this is the very first time this engine has ever run. The computer has sat for a very long time with no power to it. I'm hoping the lean condition is just because the computer is still "learning". How can I be sure?

Yes everything inside the engine is new or reconditioned. The head was worked (new valve seals, valve grind, etc... it like a new head). The only thing orginal in the block is the crank and rods. Crank was polished and the rods were inspected. Block was bored 0.020 over and new pistons and rings were installed. All internals were then balanced.

Sorry about no pictures yet. Unfortunately I still don't know how to use my camera correctly and all the video is way too dark and sound was almost not existant. I should have tested it more. I will try to get some pics up soon, maybe start an actual build thread.

UJSLOST

Lots of things can cause a lean condition. O2 sensor, ECM, Mass air Meter, Intake leak, vacuum hose leak. Check it again today. Let us know if that header gets red hot again. Im new to the jeeps but not new to auto mechanics, so Im not sure if your year model has a distributor or distributor-less engine. If your is a 97 it should be OBD-II and there should be no "relearning". OBD-I is the EEC system that had to "relearn" crap all the time.