Break-in procedure

Forum rules
Please do not start new topics here, but here: New Panhead and Flathead topics
Post Reply
Posts: 230
Joined: Tue Aug 10, 2004 5:11 pm
Location: Michigan, USA

Break-in procedure


Post by 57pan » Thu Jul 07, 2005 12:13 am

I tried doing a search on this topic but didn't seem to come up with much. I'm looking for some ideas on the best procedure for breaking in my engine. I have done a complete top end job on it but did not split the cases. So it has new pistons, rings, valve guides and a couple of new valves. After all this effort I don't want to mess it up now, so what's the best way to break it in properly?

Posts: 18
Joined: Tue Feb 03, 2004 5:34 pm

Re: Break-in procedure


Post by 57JOHND » Thu Jul 07, 2005 5:34 pm

57 Pan,

Methinks you will have LOTS of replies to help guide you on this board, so many in fact you will probably have to decide which (or combination thereof) to use. In turn you will develop your own. Heres mine. Since it appears that it is "done" I presume its already been fired up. Thats kinda when I "start" my break in procedure. On initial startup get it "settled down" where it will run and idle (Carb,Timing adjustments) Yes, they will change, simply by the fact that that the motor will now run better (hopefully) and that the carb was previously adjusted for the motor in its prior state.
I trust intake (leaks) have been checked via a pressure or vac method prior to start. Don't wanna kill those new pistons right off the bat.
OK- I warm the motor just like you usually would being careful not to let it purely idle but slightly vary the engine speed to sling some oil up on the walls. Once the heads warm to touch- shut it off. Let it FULLY cool to room temp (this can take quite a while in summer)
and recheck head bolts and base nuts. I do this twice.
Finally on the road. 500 Miles/50 mph/Boring. Vary engine speed as much as possible. dont get on the freeway and run all day trying to cover the miles. During the summer months this is best done during early morning and nite. Listen, Check, Doublecheck,
Change the oil and ride the hell out of it. Broke In. Done.

Good Luck


Posts: 789
Joined: Tue Mar 23, 2004 6:57 am
Been thanked: 1 time

Re: Break-in procedure


Post by Billy » Fri Jul 08, 2005 6:56 am

I agree with 57JOHND, That is thorough & effective, especially about running in the cooler parts of the day, & Re-Torquing twice after initial start-up. & varying the speeds below 50 mph, for 500mi. I also like to change the oil at 250mi. & again at 500mi. & then Have fun. ;D
Works for me, too. ;D
1 thing I would add, when you re-torque heads & base nuts, loosen the top motor mount so as not to pull the head thread inserts. In case it tightens down much.
Just being careful. $$$ don't grow on my trees. :o

Posts: 230
Joined: Tue Aug 10, 2004 5:11 pm
Location: Michigan, USA

Re: Break-in procedure


Post by 57pan » Fri Jul 08, 2005 8:02 pm

Thanks for the replies.
I was in the process of retroqueing the cylinder base nuts tonite when I busted my cheap Taiwan curved head bolt wrench >:( I ran out to PEP Boys 'cause they were about the only place still open but they didn't have anything like what I needed. Guess I'll have to check Napa or AutoZone tomorrow.
And, yes, I did remember to loosen the top motor mount - good tip though.

Posts: 86
Joined: Thu Apr 08, 2004 2:21 pm
Location: Burley Idaho

Re: Break-in procedure


Post by 57stroker » Fri Jul 08, 2005 10:41 pm

Needed a wrench for 12 mm jap base nuts last weekend. Took a cheap wrench and ground the open end until it fit 1/2". Used an adapter and a 3/8" torque wrench. Maybe you good make something like that. If you have a welder and a grinder, you could buy an extension or adapter and weld it to the end of the wrench.

Panhead Register Member
Posts: 802
Joined: Mon Aug 16, 2010 7:18 pm
Bikes: '46 Knuck. '57 Panhead, '59 Panhead
Location: Repop Hell
Been thanked: 1 time

Re: Break-in procedure


Post by VintageTwin » Sat Jul 09, 2005 1:54 pm

When you loosen the top motor mount, also loosen the exhaust headers and remove the pushrods or rotate the motor so there is not tension on either push rod. Hydraulic tappets you may not have to worry, but with solid lifters, you have the push rods pushing agains the head you're pulling down. Harley never had a spec for re-torquing the heads. Stett said we should remove it from our shop manual. That re-torquing the heads wasn't necessary if you torqued each head bolts to 65 ft. lbs. I left it in because it means something, but you have to remove all the tension first.
Get a Snap-On foot adapter (#FRDH181) and a Craftsman click wrench. The adapter reaches all the head bolts. Others don't believe in a click wrench, but it works for me and my chuffin' Pan.

Post Reply

Return to “Motor”