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Old 05-05-2009, 01:34 PM
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Run a fresh engine easy or hard?

I have heard two different things, A mechanic told me that he runs a fresh engine crazy hard at first just to try checking for flaws. But another Mechanic told me that it's best to give the engine a few thousand miles going easy on it before you put it to the test. My natural thought would be to let it break in. I have a fresh 355 that I just installed. What is your opinion?

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Old 05-05-2009, 01:44 PM
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You'll get different opinions on this but here's what I do.
first gear rolling start Full Throttle till about 30 mph. Let off gas, let the tranny pull the engine down to about 5-10 mph, repeat I do this about 10 times then use second gear form 30 to 55/60 about 10/12 times.

You want the increased cylinder pressure to push the rings out against the cylinder. If you baby it there's a chance you could glaze the cylinders. There's probably someone on hear that can give a better explanation than me but this has worked for me.
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Old 05-05-2009, 01:49 PM
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If it's got a fresh flat-tappet cam, you've got to break that in before doing anything else. There's been so much discussion on that here that I'll leave the details to the search function.

Matt
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Old 05-05-2009, 01:51 PM
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Hi,
I do about the same as 6426yy.
Rich
This is after the half hour or so running the cam in
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Old 05-05-2009, 01:52 PM
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re.

After we installed it we let it sit at 2200 rpm for 25 minutes. A good friend of mine who is a proffessional, said to set the rpm at the rate it would normally be at going 55 mph, so we set it at 2200 for 25 minutes. Since then, the rockers have needed adjusting. A certain family member of mine isnt convinced that it is ready to take to the dragway for some fun. I should have explained by fresh engine, I meant relitively fresh.
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Old 05-05-2009, 01:58 PM
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for the cam run in you should varry the engine speed, like 1,500
then up to 2,200 or so & keep doing that for the half hour or so
your breaking in the cam.
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Old 05-05-2009, 02:06 PM
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re.

It has been driven probably about 120 miles. So should I still do this? Or is it to late. The rockers are getting adjusted this week, and the engine is getting fine tuned. So should I still to that? Sorry im acting like i'm incompetant, I'm just a new guy the the engine building world.
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Old 05-05-2009, 02:14 PM
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I'd agree w/richard stewart 3rd on varying the speed, keeping at or above about 2000 RPM.

The reason is, the cam is relying on oil being thrown from the rod journals for much of the lube it receives (along w/windage, lifter bores and the drain-back from the top end).

There will be varying amounts thrown around at different speeds. I believe by varying the RPM, the cam will be lubed more evenly on average. At just one speed, the cam might not be as evenly lubricated.

Once the cam's broken in and the oil and filter changed, I run the engine hard up to the torque peak, deaccelerating using engine braking. I don't "cruise" the engine- the RPM's are always varying for the most part.

Once I have a couple hundred miles on it and the second oil change behind me, only then will I run it up to redline, again varying the engine speed often.

The idea of redlining an engine w/20 minutes on it doesn't sit well w/me- but that's me.
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Old 05-05-2009, 02:15 PM
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just adjust them & keep driving
when you have it all tuned, go racing
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Old 05-05-2009, 02:31 PM
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I myself am a mechanic I build race motors for people all the time and yes like a few others have already said you need to break in a brand new cam but they do it way differant that i do i have it sit at 2000rpm for 20 min and i tell the people when they come pick it up to go easy on it for about 500 miles not baby it you can romp on it here and there just dont do it all the time and you should be fine but once you pass that 500 mile mark do whatever you want with it and ive never had anyone come back with problems but its just really if your engine was put together right mainly
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Old 05-05-2009, 02:56 PM
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Quote:
Originally Posted by jb63vet
I myself am a mechanic I build race motors for people all the time and yes like a few others have already said you need to break in a brand new cam but they do it way differant that i do i have it sit at 2000rpm for 20 min and i tell the people when they come pick it up to go easy on it for about 500 miles not baby it you can romp on it here and there just dont do it all the time and you should be fine but once you pass that 500 mile mark do whatever you want with it and ive never had anyone come back with problems but its just really if your engine was put together right mainly
HMMMM, a 19 year old race motor mechanic.
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Old 05-05-2009, 03:09 PM
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Quote:
Originally Posted by S10 Racer
HMMMM, a 19 year old race motor mechanic.


yeah i live a quarter mile at a time and it only takes 11.5 sec or less and its all over and i graduated top of my class at lincoln tech they got me this job actually
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Old 05-05-2009, 03:12 PM
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Hey, I don't doubt he is, I'm just a youngun myself and I built my first engine before I had my license (in my '72 Cutlass). He's not an experienced pro by any means, but may very well be a competent engine builder/machinist.

Then again there are a lot of posers.
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Old 05-05-2009, 03:20 PM
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Quote:
Originally Posted by ap72
Hey, I don't doubt he is, I'm just a youngun myself and I built my first engine before I had my license (in my '72 Cutlass). He's not an experienced pro by any means, but may very well be a competent engine builder/machinist.

Then again there are a lot of posers.



hey i never said i was a pro but i grew up at the race track and im still there almost every weekend my showed me how to build my first engine when i was 9 years old granite the first one i did on my own wasnt until i was 14 but it ran and ran good until i sold the car 3 years later and now i build them for a living
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Old 05-05-2009, 07:24 PM
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i built my first engine by myself last year (13) and its still running strong
ive helped my dad build a few of them over the years
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