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  1. #1

    Default Breaking in a rebuilt engine

    What’s the best way in breaking in a newly rebuilt 81 shovelhead motor?

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    Be sure there is at least 8 oz. of oil in the flywheel cavity. If not, you can add it through the timing plug hole. Not sure? Add 8 oz. More is better than not enough. Be sure the oil pump is primed, and you have oil pressure.

    First start, run it at a fast idle (1500 - 1800 rpm) for 30 - 60 seconds, until you feel the cylinders getting warm. Shut down, let it cool, look for leaks, etc.
    Some recommend repeating this several times, but I get ready to ride at the second start. Go easy, no more than 2500 rpm for the first 50 miles. That's about 45 - 50 mph, depending on gearing. Do not let it sit and idle, in traffic for instance. Rural roads and light traffic is best.

    After 50 miles, increase the max rpm to 3000, or 55 - 60 mph for the next 50 miles. At the 100 mile mark, change the oil & filter.

    The above applies to fresh top ends as well as full rebuilds. The first 50 miles are critical for ring seating and to break in new pistons. (Modern rings in good slick bores will seat in as little as 10 miles.)

    You can get a little more liberal with the rpm and speed, but go easy for the balance of the first 1000 miles. After that, if it was built right, it should be good to go for many, many miles. Might want to change the oil & filter again at the 1000 mile mark.

    Enjoy!
    Jim

  3. #3

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    Thank you!!

  4. #4

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    I worked at a shop for a while, we rebuilt a few shovels.
    The main mechanic went over all this with one guy about like Jim recommended.
    He left the parking lot nice and calm and then we heard him blasting through the gears for the next half mile or so! We laughed our asses off and went inside.
    He was back a few weeks later because it wouldn't idle very well.
    The cylinders were scuffed to hell, the head guy told him straight up he screwed it up himself by running it like he did when he left the shop. He didn't even argue, just paid again.

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    I had the same thing with a sportster. The owner got 200 yards from the shop and did a burnout. When he came back I told him that black mark in the road was his warranty.

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    From Easyriders mag, Tips and Tricks Vol 1


  7. #7

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    Quote Originally Posted by JBinNC View Post
    Be sure there is at least 8 oz. of oil in the flywheel cavity. If not, you can add it through the timing plug hole. Not sure? Add 8 oz. More is better than not enough. Be sure the oil pump is primed, and you have oil pressure.

    First start, run it at a fast idle (1500 - 1800 rpm) for 30 - 60 seconds, until you feel the cylinders getting warm. Shut down, let it cool, look for leaks, etc.
    Some recommend repeating this several times, but I get ready to ride at the second start. Go easy, no more than 2500 rpm for the first 50 miles. That's about 45 - 50 mph, depending on gearing. Do not let it sit and idle, in traffic for instance. Rural roads and light traffic is best.

    After 50 miles, increase the max rpm to 3000, or 55 - 60 mph for the next 50 miles. At the 100 mile mark, change the oil & filter.

    The above applies to fresh top ends as well as full rebuilds. The first 50 miles are critical for ring seating and to break in new pistons. (Modern rings in good slick bores will seat in as little as 10 miles.)

    You can get a little more liberal with the rpm and speed, but go easy for the balance of the first 1000 miles. After that, if it was built right, it should be good to go for many, many miles. Might want to change the oil & filter again at the 1000 mile mark.

    Enjoy!
    Jim
    Jim when you mentioned “ modern rings and slick bores” were you refering to moly or rings and plateau finish on the bores?

  8. #8

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    Quote Originally Posted by Whoremonger View Post
    Jim when you mentioned “ modern rings and slick bores” were you refering to moly or rings and plateau finish on the bores?
    Modern cast or moly rings are made so accurately today that they require practically no seating time. And bore finishes with 240 grit stones (AN500) are the norm, whether plateau finished or not.

    One of my acquaintances built late model stock race motors and clued me in to this thirty years ago. They had instrumentation on the dyno to measure blow-by, and he said the rings sealed almost immediately on a fresh motor, and they could see the ring seal giving up before they had the motor tuned on the dyno. Just a slight increase in blow-by, but measurable.

    Jim

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    JB, do you recommend dino oil for break in?
    I've done a couple new engines and we always used dino oil for the first 500 miles (first oil change after 50 miles) then switched to Mobil 1....

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    Quote Originally Posted by golfish View Post
    JB, do you recommend dino oil for break in?
    I've done a couple new engines and we always used dino oil for the first 500 miles (first oil change after 50 miles) then switched to Mobil 1....
    Yes, yes, yes!

    The only time I ever glazed a cylinder wall was when I tried to break in a race motor on Mobil 1 (which we were gonna run in the motor). Conventional oil only for break-in.

    Jim

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    Quote Originally Posted by JBinNC View Post
    Yes, yes, yes!

    The only time I ever glazed a cylinder wall was when I tried to break in a race motor on Mobil 1 (which we were gonna run in the motor). Conventional oil only for break-in.

    Jim
    Jim, Have you ever used trans fluid on the rings rather than motor oil?????

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    Quote Originally Posted by Tattooo View Post
    Jim, Have you ever used trans fluid on the rings rather than motor oil?????
    If you mean, on assembly, I just use motor oil, but I know guys who insist on assembling the rings dry.

    Jim

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    Quote Originally Posted by JBinNC View Post
    If you mean, on assembly, I just use motor oil, but I know guys who insist on assembling the rings dry.

    Jim
    Yes on a new build on assembly....... I've done it for years they seem to seat faster......... Just wondering if you have ever heard of it or done it.......... I use to use motor oil also........... And still do from time to time............

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