The Stovebolt Site Forums The Shop Area Engine Shop Is a tach required to break-in an engine?

I understand that a rebuilt engine is supposed to run at 2000 rpms for 20 minutes upon start-up. However I don't have a tach.

Is a tach required, or can I just guess? Or is there some other way to judge 2000 rpms?

You will need a tachometer - or, good luck guessing rpms.

I could not find a 6v tach, or one that attached to an external 12v battery, so I bought one like this: tachometer

It's a matter of common sense, which is almost illegal these days. The whole point of a raised-RPM initial engine run is to prevent scuffing the camshaft lobes while the cam and lifters establish a running fit with each other. Roller cam engines don't need the cam break-in run at all. The only reason for the raised speed is to assure there's plenty of oil being thrown off the connecting rods to assure the cam lobes are flooded with lube. The specific speed is irrelevant, as long as the engine isn't revved up enough to start hammering those new rod bearings out of shape. 1800, 2000, 2200, 2500- - - -who cares? A raised RPM initial run does nothing to seat piston rings. That requires about 10 full throttle accelerations from 30 MPH to 50 MPH in high gear, so once the cam gets its run-in, head out on the road for a long straightaway. If your new engine never sees anything but a run stand, maybe you can rig up some kind of chain drive. Good luck steering and stopping!
Jerry

Great, thanks.

So for the piston rings,I just need to hit the highway about 10 times. When you say "full-throttle" do you mean pedal all the way to the floor?

Pedal to the floor from 30mph to 50mph ten times while in high gear. Sounds like fun to me. Get er done!

Just don't use enough throttle to make an automatic transmission downshift- - - - -the idea is to put some serious cylinder pressure behind the piston rings and scuff them into perfect contact with the cylinder walls. High speed isn't necessary, but as much constant load as possible on the ring/cylinder wall junction is. With a standard trans, just do a wide open throttle acceleration in direct drive 10 times from 30 to 50 MPH.
Jerry

To continue what Jerry has, when you get to fifty, let the weight of the truck slow you back down, this tends to load the bearings and rings a different way then the acceleration does.

I also agree on the rpm, actual reading doesn't matter, just get it up off idle and then a little more. Most fast idle settings are good enough with no load on the flywheel.

I run mine at 1800 then 2000 then a final 2200 for the last minute or two, but then my stand has a tach. You will know if it's to high or not, if you cringe slightly, it's about right!

Hmmm, none of this was mentioned in any owners manuals of any new vehicles I have bought over the decades. Nor is it mentioned in my 39's owners manual. I must have been lucky.

Rick

This is what GMC recommended for break in in 1958 on a dyno.

https://plus.google.com/u/0/1126369...0557413442&oid=112636930370126476644

A dynamometer was not included with my new vehicles. When engines are assembled at the factory, do they run them in? I know Uncle Henry did with his Model A engines, but what about Chevrolet with the stovebolts?

Rick

It's my understanding that most engines were either run after assembly, or "motored" over by a big electric motor for a certain time without actually being fired up, to break in the parts and check for proper oil pressure, etc. A lot of commercially rebuilt engines get the same treatment. By the time the engine gets installed in the vehicle, it's been spun over enough for any disastrous assembly errors to show up.
Jerry

Modern engine plant today..........they test run a small sample ( usually 1 out of 50) of the engines off line. The rest go directly to the assembly line ( or shipping ) and installed in the vehicle. The assemble cars or trucks are started and run off the line.

"Break in"..............is as debatable as oil threads.

Modern car might be started as few as 5 times before arriving at the dealer and as many as 50 depending on rail or truck transport, storage yards, distribution centers, inventory, in factory repairs and testing.

Modern cars have roller cams so there is no comparison there.

Depends on where "modern cars" start.

Another difference (apples and oranges in my opinion), is that we are comparing a new engine which has all new parts to a used engine which is more likely to have more issues with less than perfectly matching parts.
Carl

I have seen movies from the 1970 Pontiac assembly line where the engines were spun with electric motors. They were even balanced once most of the engine was put together. Last step in assembly was putting the covers on.

This is a cool 1936 Chevrolet film, there are four parts to it . The engine building part is the best. The guy tunes it using big old screw driver up to his ear.
https://archive.org/search.php?query=subject%3A%22Occupations%3A+Automotive%22


Break-in is just like oil choices, it's your money, do as you will.

Joe

So the OP says he rebuilt the engine to new specs.......lets say bored, new Pistons, rings, cam gear, crank ground all new bearing, complete valve job and reused the old cam............that is some how different than a new modern engine as far a break in.......???

Break-in is for camshafts only. That is, running at a set speed for a set amount of time, and then only for new camshafts and lifters with a flat bottom (flat tappet).

For a real radical cam for a high performance engine with flat tappet lifters, it is a must, and even then not a guarantee it will live. The mild stock replacement cams can get by with less. All this is due to oil formulas changing back in 2007(ish). Used cams with matching lifters, in the same location can be run as is, its still recommended to add some zinc additive for a while.

Normal driving back in the day was enough to break in piston rings and cylinder ways since most cars and trucks had manual transmissions which by their nature, run the engine up and down with reasonable loads.

Todays cars, even those 30 years ago, have much better materials in them with better oiling systems and better oils, can be driven right off the assembly line and live for what seems like forever. In about 1986, everything switched to roller cams which eliminate all the concern about camshaft wear and break-ins.

I would question the wisdom of re-using a cam and lifters in an otherwise completely reconditioned engine. If it needs all that other stuff, what's to keep the cam and lifters from being worn out- - - -and will they survive another 100K miles until the next rebuild?
Jerry

^^^^^^^^^^^ in " collector truck" run less 3000 miles per year......I think the cam might last if measured in with usable specs during the rebuild.

Hi all, I didn't mean to open a can of worms. Thanks to all for your help, I'm looking forward to running this engine in properly.

This engine is a 216, and I suppose some would question the wisdom of rebuilding a 216. The guy I bought it from was a farmer who had it done as a spare for his classic truck. However, after 10 years of sitting on his shop floor he realized it will go to waste if not installed. So I gave him $450 and he recovered some of his money for the rebuild.

It appears to be done properly. There is a tag on it telling me where the pistons came from, size of bore (0.040 over), and size of main bearings (0.030 over I think?). I would guess they replaced the cam and lifters.

I don't have a speedometer so I will have to guess at 50 mph. Like 2000 rpms, I suspect the speed isn't critical. From Jerry, I understand the intent is to get a load on it so the rings seat properly.

A can of worms is what we are all about!

No need for speedometer, just run it up with traffic then let out and go again. You just need to load the engine down and make it work without going to high or extremely hard.

I used to break my race motors in at the drag strip. On decent water burn out plus one half throttle pass. If it sounded OK, the next pass was flat out.

Joe

Back to tach. I also got the chance to call buddies to let them hear my 261 at 2000 RPM.

20 min at 2000 RPM.
.

Westach makes 6 volt tachs, they aren't really cheap, but they aren't ridiculous either. (I don't remember how much it actually cost to tell the truth) It seems like a fine unit though,
I have had it for about 3 years now.

Google inductive tach...........many choices that do not depend on the vehicle or engine for power.

Do you have access to a dwell meter? Most have a tach function, and most don't care about 6 or 12 Volt systems. Probably work for what you are attempting.

What is a brand and part number for a modern tach-dwell meter that works in 6v 6-cylinder tach mode?

Tim,

I have an old 1980's vintage dwell meter like the one below...tach function works fine for a 6v 6 cyl.

http://www.ebay.com/itm/Sears-Tach-Dwell-Voltmeter-Volt-Meter-RPM-Calibration-USA-MDL161-216500-/182192920432?hash=item2a6b8b5770:g:k9EAAOSweWVXeFkK&item=182192920432&vxp=mtr

Paul

Thanks, Paul,

I am hoping to find a modern electronic one if the tach feature can work on a 6v system (positive and negative ground would be nice, but negative ground would be OK).

I bought a Handheld Digital Laser Photo Tachometer that has a dry-cell 9v battery but uses a reflective strip (on the harmonic balancer).

I believe you can use a 12 volt tach if you power the tach off a 12 volt battery, and use the signal wire from you engine. I done this with timing lights and exhaust analyzer.

I;ve got an old Sears tuneup meter just like Paul WNC linked to. It works great on 4,6 and 8 cyl (has a selector) has a volt meter and dwell meter. It is also supposed to read amps and has a spearate hookup but I've never used that function.

I would really like to get my hands on an old Sun 1020 tester. The scope can help pinpoint all kinds of cyl ailments.

There's a Sun 1115 on Ebay right now- - - -working condition, for only $350.00- - - - -"local pick-up" in Maine! Ready for a road trip?
Jerry