Engine Break In

The mechanic (who I trust ) that put my F134 together is pretty adamant about the break in procedure...
Fire it up and DRIVE it, up hills, down hills, low speed, higher speed, compression brake, etc...for 20 to 30 minutes.
I have always...and been told to... run the engine at varied RPMs for 20 to 30 minutes but never to actually take it out on the road.
I guess i can see the value of running it under load...but absolutely every component (brakes, steering, drive line, etc ) is completely untested.
I am just a little bit out about this...

I want the best for the CJ so if that's what it takes i will go for it...worst case ill fire it up and try...if it seems sketchy i will just let it run in the drive way and take my lumps...

Any thoughts?

 

When I rebuilt mine I primed the engine with a hand pump. The F134 doesn't have an oil pump that you can use a drill to do this. I ran it at 2K for 20 Min then changed the rpm. I think most rebuild books are pretty specific about this. Most important thing is to hook up a mechanical gauge and make sure you have oil pressure. The 20 min is to seat the rings which mean you are essentailly lapping the new rings in with the bore that should be properly honed. I didn't have my jeep ready to drive but if it was I would then drive it around at low rpms a few times then change the oil. You should have dipped the pistons in oil before installing and if it's been a while, put a little oil in each spark plug hole and cycle it through a few times by hand. You should have some oil in the bore for lapping. Use regular 10/30 or so motor oil. BTW, this is a very important step and your engine can burn oil if you don't follow procedures.

 

I woudn't worry about driving it around. Tackle one thing at a time and your main goal at this point is oil pressure, seating the rings and make sure the engine doesn't come appart. When you assembled the engine you should have cycled it a few times and that's where you would detect if something is bound up or not assembled right. You should put a pen mark on each bolt after you torque it then go through and verify your work. Don't drink beer when assembling an engine, wait until after.

 

I would wait until the vehicle is roadworthy to start engine. Camshaft companies generally recommend the 20 min start up procedure you mentioned. Then follow your mechanics instruction to seat rings. Not rocket science. Camshaft break in on a F-134 should be fairly uneventful. The instruction that your mechanic gave for seating rings has been around for about a hundred years . enjoy the new engine. mike

 

It's not rocket science but I would argure it's common sense that you don't want to start an engine that has no oil pressure and not properly prepped for start and broke in. Your mechanic left out some steps. The cam breaks in over a longer period of time. The first thing that happens is the ring seating and if you have no oil pressure shut it down. I've been through this and these pump sometimes don't pick up oil right away. There are steps you can take to minimize that problem. Also, if you don't know about your oil gauge, go buy a new one.

 

Just my personal bias, but I like to change the oil several times, like after the first few minutes, then a couple of times after an hour or two. Or maybe like at 5, 50, and 500 miles. "The more the better" seems like cheap insurance.

 

When you consider that lapping it literally the process of filing metal off your cylinder wall I don't blame you. The oil filter probably doesn't collect all of that and it's best to dump it out sooner rather than later.

 

Since you're dealing with tappets and not lifters, I'd do what your mechanic says.
Make sure Jeep is safe to drive, let it warm up, and go drive it.

 

fwiw I know more than one guy that builds engines they all say the same thing your mechanic did....

 

You want lots of mixed driving with a new engine... worst thing to do is take it on a long trip at constant RPM just to reach some benchmark of “miles”

 

Thanks for all the input!!!
I do trust my mechanic...best case scenario is i get to go for a spin as soon as i fire it up
worst case...dont want to think about it...
Im gonna shoot for road worthy and follow the mechanics advise...he happily offered to be here when that happens, i think he wants to go for a ride with the windshield down and some goggles

 

If u can't drive on road, u got a jeep, put in low range, drive around in yard or field.
Vary rpm, load and coast engine. This will mimic a road trip. Then one thing I always do is after maybe a couple hours total run time, drive it like u stole it a couple short burst!
I Also usually buy 3-4 oil filters and 2 oil changes. I like to change just the filter after 1st 20-30 min. I leave the cam break in oil in the first 2 hours or bout 50 miles, then do a oil change.
I Also add ptfe, or some kind of additive for older engines.
Good working oil and temp gauge a MUST.
I once had a customer come to pick up his fresh engine car. A 62 VW bug, 1835 big bore engine (1600 stock), I already had 2 hour run time on it in shop and fresh oil.
We warmed it up in shop, then hit the road, me behind the wheel, I turned 6000rpm through 1st,2nd,and 3rd, then let off, he was white as a ghost, his first words, that my 2 grand engine, why run it so hard, I replied what better time to find a problem than with your mechanic behind the wheel.

 

My buddy Doug hammers them hard from first start. Same story if it’s going to break let it happen then.