Engine Break-in Procedure

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Posts: 295
Joined: Wed Apr 11, 2012 12:39 pm
First and Last Name: Ben Michaud
Location: Richmond, Ontario

Engine Break-in Procedure

Post by PTWannaHave »

Hi all,

I searched the forums quite a bit to find this info (that I'm pretty sure is here), without success. Should make a good How-To thread... I'm sure there is very useful collective experience out there to be added to what may have been printed in a manual...

In my case, I am getting ready to fire and break-in a total (stock) rebuild. Perhaps this thread can be split in two for 'total rebuild' and 'freshened'? (I.e.: If only connecting rod, piston and rings are changed, perhaps break-in procedure need not be as comprehensive...?) Might need a third section for non-stock (hopped-up) rebuilds?

Everyone seems to have their favourite oil recommendation, so I wasn't going to go there... (For the record, I am using Walmart SAE40 detergent-free oil.)

I seem to recall a procedure such as 'run 5mins while adjusting carb; change oil; re-torque head bolts; run 10mins fluctuating engine speed; change oil; run 10mins under load (driving around); re-torque head bolts'.

I torqued the head bolts to 25ft/lbs, and was planning to add 1-2 ft/lbs every time I re-torque... Bad idea? (Spec is 25-30ft/lbs.)

Thank-you in advance for your collective wisdom,

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Posts: 150
Joined: Mon Sep 06, 2010 9:24 am
First and Last Name: Dale Merkle
Location: Middle Point, Ohio 45863

Re: Engine Break-in Procedure

Post by Merk »

This is the way I break in a rebuilt engine ( Cub Cadets-Kohler engine).
I will vary the engine RPM for the first 25 to 30 minutes. I will leave the RPM at a the same speed for a minute. I will drain the engine oil and replace with new oil. The next 30 minutes I will drive the tractor around. The RPM will vary the same as the first 25 to 30 minutes. I will drain the engine oil and replace with new oil again. The next 3 to 5 hours I will put a load-work the engine. I will drain the engine oil and replace with new oil again. Them I will drive like a stole it......plow days are a good place to break in a rebuilt engine. I will retorque the head bolts around 25 hours run time at 30 ft/lbs. Break in procedure is the same for stock and modified engines.

Kohler manual says to use straight 30 weight oil with temps above 32 degrees and 10W-30 below 32 degrees. I use Kohler brand conventional oil. I'm not a fan of synthetic oil.
Kohler manual says to use a detergent oil.

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Posts: 320
Joined: Tue Sep 07, 2010 2:51 pm
First and Last Name: Charlie Zuck
Location: Elizabethtown, PA

Re: Engine Break-in Procedure

Post by chzuck »

Engine break in is a little like brands of oil -there are lots of them. I have always used a 30 wight non-detergent for the first 5 hours after a rebuild. I use Rotella 15w40 in all of my air cooled engines year round. I am not a fan of synthetic oils either. I am not saying my method is better or right. Merk's method seems like a whole lot of extra work for me. I am sure it has given him good results. One thing to consider - the science of lubrication and additives has come a long way since our beloved K motors were first made. Rotella 15w40 is a heavy duty oil, great for the summer heat and with a multi-viscosity oil I can use it year round. You will have to read what all posters say and decide which you think is best.
There is only ONE ROTOTILLER.
147 with 48" mower deck & 42" QA snow thrower
70 with 42" mower deck, 42" blade, & Brinly 10" plow

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Posts: 1296
Joined: Mon Sep 06, 2010 8:45 pm
First and Last Name: Mike Andrews
Location: Niles,Michigan

Re: Engine Break-in Procedure

Post by BigMike »

I have not done a scientific study of engine break in but it is very close to what Merk does. I feel that that the sooner you can flush the loose metal particles and assembly lube the better. Once that's done running under a good load will puts pressure and lots of oil on the rings and well seated rings = happy engine.
I have never run synthetic oil in my Cubs....just good ole Dino type :beer: . I figure they lasted 40+ yrs with conventional oil they will last the balance of my life.

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