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Engine rebuild break in

chaynes12

Jr. Member
Joined
Feb 4, 2018
Messages
86
Just finished the engine rebuild. Curious what the recommended break in oil is for the first start up.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,353
Is this a flat tappet cam engine, or a newer roller cam type?

Paul
 

68ford

Bronco Guru
Joined
Dec 26, 2004
Messages
2,710
Joe Gibbs break in oil for recommended time, then any oil you want.
 

DirtDonk

Contributor
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Messages
47,353
Yep, good reputation. There are other brands of break-in oils too though, so plenty of choices.
Just make sure it's for flat-tappet cams and has lots of zinc/ZDDP in it.
In fact, same for your regular oil from now on I say. You can use the weight of your choice, but make sure it's for older engines with flat-tappet cams.

You familiar with the typical break-in procedures for a cam?
If not let us know and we'll run it down for you. There are lots of variations on the same theme now, based on whatever that particular person learned originally. In the old days it seemed they all said one thing. Run the engine at 2500-3000 rpm for 30 minutes with non-detergent 30wt oil in it, and change it after the break-in.
But nowadays that has been tweaked and modified using just about everything between 15 and 30 minutes, and 1500 to 2500 rpm, and every variation in between you can think of.
As often as not nowadays too, the oil recommendation is to use whatever you're going to use in it's every day life after the break in. Some say change it after, some say just run it.

Guess you have to make your own decision on it after getting some answers.
But the one thing that never changes is, DO NOT LET THE ENGINE IDLE during this time.
By the same token, don't let it crank excessively on the starter before firing up. If it won't fire immediately, stop cranking it and find out why.

good luck!

Paul
 

pennyduke

Sr. Member
Joined
Jul 18, 2010
Messages
377
Loc.
Stafford
Make sure to prime the Oil Pump. Spin the oil pump shaft ccw through the distributor hole with a priming tool until you see oil coming out of the rockers.
 

rmk57

Sr. Member
Joined
Feb 24, 2016
Messages
580
If it has a big camshaft (lots of valve spring pressure) I always remove the inner spring then put them back in after break in.

I here good things about Valvoline vr1.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
Instructions vary. My last cam stated 2 runs of 10 minutes at 2000 RPM with a complete cool down between. In the past I have done 20 minutes at 2000.
 

DirtDonk

Contributor
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Nov 3, 2003
Messages
47,353
That's good to hear. Glad some others are touting the multiple-sessions rule now too.
I've been doing it that way for years just to add an additional heating and cooling cycle into the mix, and give people a break too!

I've used 20 minutes as a minimum total time, and 30 minutes as my preferred time.
Not because I don't think 20min is sufficient. Just that I like to give it that extra bit just to be sure. And I have the time, so not afraid to waste it.

Paul
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
Newb question, why don’t you ever ever let it idle? What happens that is bad?

Engine break-in, the piston rings need to seat.
You don't want to hammer it hard and you don't want to baby it so much that it does not fully break-in either.
 

DirtDonk

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Not as much a newbie question anymore buster. I bet lots of younger pro-mechanics don't know about it either, since the last time a flat tappet cam came in a new engine was probably over 20 years ago now.

And in addition to what syk said, and more importantly in fact, it's all about the camshaft.
The reason for not idling when the engine is fired up for the first time is that the cam lobes, which are arguably the most highly stressed part of an engine, do not get pressurized oil fed to them. Only the cam bearings get that luxury.
The cam lobes and lifter bases are only oiled by "splash" lubrication. More of a combination of splash, drip and windage/vapor lubrication actually.
The only thing that could be considered pressurized oil delivery is the excess oil that squirts out the sides of the cam bearings, some of which finds it's way to the lobes.

Some of the oil that makes it up to the top of the engine makes it to the ports above the cam as it's draining it's way back to the oil pan. That drip goes straight to the cam lobes.
Since this and the other things are the only way to get oil to the cam lobes, and the initial start-up is the most critical time of parts bedding in, or mating up to their counterparts, we're trying to get as much oil to the cam as possible during the initial few critical minutes while those parts get to know each other while literally sliding and scuffing themselves silly together.
This is basically why you also never mix and match lifters and cams once they're broken in. If you remove the lifters, they need to go back into the same holes they came out of to get the best chance of finding a good mating surface to slide on.

All this is why, during initial startup, you don't want to crank it on the starter for extended periods, let it idle while you fiddle with carburetor and distributor settings, and stuff like that.
If you see an oil or gas leak, you shut if off. If you feel you want to adjust the timing, do so quickly. If you need to adjust points, shut it off. If you need to add more fluid, either do it at the higher speed, or shut it off. If it looks like you're having a cooling issue (temps over 220) shut it off until you find out what's going on.
It's important to make sure the ignition is working and timed at least close (you can tweak it while running at 2500 rpm to at least get it working), and that fuel is in the carburetor.

And that's why you don't idle the engine for the first 15 minutes. Or if you're like me, 30 minutes just to be safe because I don't want to do the job twice!

The speed can be varied, which does help the rings and things seat in more better, and will vary the temperature slightly as well. You can run down to 2000 rpm, or up to 3500 rpm. But not less than 2000 for at least the duration of the break-in.
As mentioned, I like to give everything and everyone a break and multiple heating and cooling cycles to get parts to work together better. So will often shut it down after the first 15 minutes or so. I have run it the full half hour before, because it was fine, the mufflers were installed, and I had nowhere else more important to be at the moment.
But shutting it down to let it cool off for awhile is not a bad thing.
The piston rings, pistons, bearings, and other things can actually handle idling down, but the camshaft can't.

So that's why you don't idle it...;)

Paul
 

661buster1963

Full Member
Joined
Feb 18, 2009
Messages
287
I have a flat tapper motor, rebuilt 2 years ago and sitting on the engine stand. Life changed and now I’m getting back to it. The engine has aftermarket steel heads, lunatic cam with torque in mind and a 10:1 compression he always assured me would run on pump gas. The engine builder was going to come over when time was right to light it up. Realistically the is still 12 months away, and my engine guy has relocated long way away. What resource can I look into to guide me through startup when the day comes.
 

Bronco Junkie

So Cal Broncos
Joined
Feb 29, 2012
Messages
3,232
In the past I have done 20 minutes at 2000.

This is what I have done with my past 2 flat tappet cam motors...including the one in my Bronco now.
 

Broncobowsher

Total hack
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Jun 4, 2002
Messages
34,835
Newb question, why don’t you ever ever let it idle? What happens that is bad?

The 2000 RPM idle moves a lot of oil. As the RPM goes up so does oil pump output. So you have a lot more oil moving around than at a low idle.
The fast idle also flings the oil around a lot more. Throws it up into the bottom of the pistons and all over the cylinder walls. Since the rings have not mated to the cylinder walls there is a lot of friction and (expected) wear as the parts seat in. Think of it more as a cutting oil, allows the rings to seat in without self destructing. Much like a machine tool will cut into a part without destroying it when lubed. So this fast idles break in is vital regardless of cam type.

Now a flat tappet cam needs to break in like the rings to the cylinder walls. Only this is the tappet to the cam lobe. There is some interesting metallurgy that goes on during this break in. Some of that zinc actually gets embedded into the metal surfaces. A broken in cam is more polished then the shiny new parts before break in. As part of that break in there needs to be plenty of oil so they gently mate and not destructively mate. The fast idle does a great job of tossing oil onto the cam lobes.

As for the 2000 RPM number, well it is a good RPM because it is fast enough to move a lot of oil, keeps the water pump and fan running at a fast enough speed (lot of extra heat from the friction of the parts breaking in). But not so fast that you are stressing bearings due to high RPM. Engines are typically pretty happy cruising for hours at a time at 2000 RPM going down the highway. I don't get too fussy about exactly 2000, I turn it up to a really fast idle and look to see if the tach is somewhere around the 2000 mark. Usually after the warm up you will gain a few hundred RPM as the friction in the engine drops.

You may have noticed I am looking for wear during break in. Therefor I don't go straight to the high grade oils. I will do a thin oil like a 5W30 so it can flow. Name brand non-synthetic whatever is on sale. I do want a detergent oil, I want the break in particles to be filtered. The thin oil will flow through the filter better and not back pressure opening the bypass.

The thermal cycles, that isn't just water temp. Oil temp is key to the thermal cycle. Oil warms up much slower than water. But that 2000 RPM will warm it up a lot quicker then a slow idle as well.
 

DirtDonk

Contributor
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I have a flat tapper motor, rebuilt 2 years ago and sitting on the engine stand...
...What resource can I look into to guide me through startup when the day comes.

Good question. Will you be trying to test-fire it on an engine stand first?
Presumably the engine will be in the vehicle when you first fire it up, but I figured I'd ask just to be sure.

Either way, we've kind of run down all the basics already. Are you going to be able to hook up all the peripheral systems yourself? If so, then you can likely do the startup yourself too.
Having a helper or three around just so they can be your eyes and ears while you're fiddling with the throttle adjustment and focusing on the things in front of you is a good thing.
They can lay underneath and look for fuel leaks, oil leaks, trans oil leaks if an automatic, and stuff like that.
And just as important as all that other stuff sometimes, at least one of them can be watching a timing light and where the marks are. One thing you don't want to do is run it at high rpm with retarded timing. Heats up the exhaust to an extremely high level. Some more than others, and this also has much to do with the cam profile, but they will heat up pretty good.
And this is especially important if you have new headers with a fancy coating on them. Be a bummer to overheat it and have your $300 coating start to flake off!

One of the best resources can be a factory service manual actually. Lots of stuff in there you may never use, but lots of stuff that you can file away in the brain's filing cabinet for that one time you need to know something in a pinch and it's there.

Otherwise, we're going to be here too.
And speaking of members here, have you hooked up with any local Central Valley members yet? Maybe a few of them would be overjoyed to join you on your startup day for some BBQ and cool ones.
Don't know about all the members, but personally I think a fire-up gathering is a blast! Lots of fun finding and fixing the little things that crop up, and being the "other guy" that just happens to remember something that was forgotten in the heat of battle.

Good way to make good friends too. And if you're going to be off-roading your Bronco, a good way to meet future trail-mates.

Worth thinking about anyway. Better than any book or YouTube video!

Paul
 

jagbucket

Full Member
Joined
Aug 9, 2013
Messages
251
ive always thought the 2000 rpm at 20minutes was the way also. until last week i watched professional engine builder on utube break in a customers motor by not leaving it steady at 2000 but varying the rpm on the dyno before making pulls actually bliping the throttle. but not letting it idle below 2k
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
ive always thought the 2000 rpm at 20minutes was the way also. until last week i watched professional engine builder on utube break in a customers motor by not leaving it steady at 2000 but varying the rpm on the dyno before making pulls actually bliping the throttle. but not letting it idle below 2k
That's good. Varied RPM is good.
 

661buster1963

Full Member
Joined
Feb 18, 2009
Messages
287
I know Ed, local bronco guy with a bunch of machine shop experience. I was going to break it in with cast iron exhaust. I have some long tube TBP headers for later. I’m not too worried. I will probably light it in the frame, with tub on. I’ve done a couple but, it was 30 year ago and my favorite uncle was always there to help. Sad to say he won’t be able to help. Worst thing is I really don’t want to pull a torched cam out later, just hate doing things twice.
 
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