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Author Topic: Breaking-in of Race engines?  (Read 412 times)
Trans m
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« on: August 25, 2014, 12:12:29 AM »

First off, I've only rebuilt one engine, and assembled one other. I have had quite a few years since then to read and ask mentors and learn about building engines and I always recollect the essence of breaking in an engine. NOTE:"Full" rebuild done in well equipped machine shop at local college--did any/all required machining myself. Very neat experience, indeed.

I have come to understand--either correctly or incorrectly--that camshaft break-in is tantamount. There is also a method for "setting" piston rings. These two methods are done upon immediately firing the engine and immediately driving the car, respectively.


However, there seems also to be one more step of break-in, more of a rule-of-thumb "grace period" type break-in for the engine as a whole unit.  Typically it goes something like, "drive 500 miles, then replace oil/filter--do not exceed 3/4/5000 RPM;limit/avoid use of Wide Open Throttle" That is a pretty general description.

So here we have a minimum mileage requirement(most say 500-1000 miles), AND we have a performance limitation: most tell you to not push engine hard, and keep RPMs low for duration of initial break-in mileage.



So what did race teams do when they needed to race their engine like mad men the next day? I don't care if Traco or Bartz built your engine, or if it was Al Richards and his buddies Grin


What was the procedure to keep engines alive? I have a funny feeling Donohue didn't exactly take the Penske Camaros out for a 500 mile stroll the day before a big race with a new engine, nor did Traco do it for them.

So then what??


Did Traco/Bartz/independents just not care? I remember an article stating Penske engines were only used for a couple races before a complete teardown. Did they just break in the cam and then send it off to be spun at 7500 for eight hours and just say "screw it" to engine break-in? Is engine breaki-in only important to ignorant little kids like me who only drive on the street?  Huh  Grin



Thank you to anyone who may have insight, and apologies for my long-winded-ness.
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69Z28-RS
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« Reply #1 on: August 25, 2014, 06:16:49 AM »

This isn't specific to 'race engines' but it should be applicable as it's based on information I gleaned from a TransAm independent racer long ago.  I'm very interested if any other old racers follow any procedures drastically different than this...
- - -
I've rebuilt a number of engines over the last 40-45 years of my life, and based on that history, I have some opinions myself, although I consider myself still open minded to a different view as long as it's supported by some theory, logic, or fact..   My history includes:

o  assisting friends, as a 'helper', rebuild several engines in my early 20's, ranging from VW 4 bangers to 426 hemis, but with concentration on erly small block chevys.
o  When in engineering school in the early 70's, I met a Trans-AM, IMSA GT car owner, builder, driver (Robert A Christiansen) when he was asked to give a talk on 'engineering materials used in auto racing.   As a result of that, I ended up hanging around his shop, helping him on weekends and evenings, and generally trying to learn as much as I could from him, as he was one of the most 'practical mechanical engineers' I'd ever known, even to today.   He was an IBM engineer/manager at that time; a part-time racer, and ultimately retired from IBM.
o  in 1974 I bought a '68 Z28.. worked on it and drove it daily until '76 when I traded it for my present 69 Z28, which needed an engine rebuild, so naturally I asked Robert (Bob) for assistance.   He let me rebuild the engine in his shop; he told me what to purchase, he went to the machine shop with me and provided guidance to the machinist, but did not do any of the hands on work, instead he told me at each step what I needed to be doing and why..  so that experience formed the basis for most of my opinions on engine rebuilding.   I've rebuilt several (10 to 12 small blocks, and 1 BB 454) for friends since then, and a few of my own all using what I learned from that experience with Bob.

Things I learned from him were:
1.  For 'racing' build your engine on the 'loose' end of the tolerances ie. piston to wall and bearing clearances; basically it gives your engine a head start on the break in and reduces internal friction, and you're not looking for 100,000 miles of wear out of such an engine.
2.  Ensure that the oil returns are opened up; small block chevy oil returns typically have casting flash which restricts oil return.   Grind all those out in the ends of the heads and the lifter galley after tear down.
3.  CLEAN CLEAN CLEAN.   Hot tank is not enough.  You'll be amazed the first time you get an engine block back from the hot tank if you use a hot water pressure blaster to blast out all the water jackets..  you'll see metal chunks, rocks, etc..  come out!   USe hot water, detergent, and properly sized engine brushes to clean all surfaces of the engine block.   Obviously you should chase all the bolt hole threads before cleaning also.   After the cleaning and drying, coat the cylinder walls and lifter holes with oil or grease to protect against corrosion, and PAINT all the cast surfaces in the lifter galley, under the timing cover, etc..   in order to capture/hold any residual grit/sand/etc from the factory casting process.   I've always used Rustoleum (qt can will do many engines).  I use black or red so that any bearing material will show up 'silvery' against those colors.
4.  During assembly, liberal use of Molybdenum Disulfide on all 'metal to metal' friction surfaces such as lifters to cam, rocker balls/rockers, etc..  ie. high load, high speed, steel on steel surfaces (not bearings).  I also disassemble the oil pump, and polish all the frictional surfaces on the moving parts, and also use the moly on reassembly.  Lock tite or safety wire the fasteners; braize the pickup tube in the pump cover plate, after setting proper gap to the pan.
5.  Use plastigage on all the bearings with one drop of oil to hold it in place, torque down, disassemble and record each value.  Ensure consistency in the values and measures you get across all the same type bearings.
6.  Pre-adjust valves by your favorite technique.   IT should be good thru the initial startup period.  
7.  Before initial startup, ensure a KNOWN GOOD distributor and carburetor are used - you don't want a malfunctioning, mal adjusted distributor or carb during first fire up or break in.   you have to ensure proper timing and fuel mix during this time.   Also before startup, use an external device to pump oil to all the bearings, and after this, I ilke to actually spin the motor a few times with the starter (NO plugs/fire) to circulate the oil and get pressure up.   Verify proper oil levels and water levels (hopefully you're using a known good water pump as well).   Ensure that you have a working oil pressure and water temp gauge before startup and AND NO LEAKS.

Prior to start up, clean/gap and install plugs.   Set initial timing so the engine will start immediately (this is easy to do - ask if you don't know how).
Prepare to monitor the engine speed, oil pressure, water temp during the initial 30 min run.   Don't do this in a closed up shop...  Smiley   best is outside, because most of us don't have exhaust hookups to the outside.   Start the engine and run it for 30 min at 3000 rpm..  don't let it die..  if it's trying to, then increase rpm.    if you are using a known good distributor and carburetor, you should not have to be doing any significant adjustments during this time, but if everything looks/runs good, and you want to fine tune the timing or carb then do so, but don't neglect the monitoring of the water temp and oil pressure.

After the initial run it, take the car out and put some load on the engine.   I've always followed the 'break it in like you are going to run it' rule.. Smiley
When I took the '69 Z28 out back in '76, Bob went with me.. and I was 'babying it' ..   he said RUN IT!@!   so I did.. Smiley  up to 7000 or so but not in a high gear.   Load increases as the gear increases, so running your engine in low or second is not as heavy a load at a given rpm as it would be in a higher gear.   Main thing during the break in period to to not run it as a constant speed or load.  Vary the load and rpm during the first 500-1000 miles.    Change the oil and drive it... Smiley
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
Trans m
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« Reply #2 on: August 25, 2014, 11:14:47 AM »

Wow, that is very extensive and useful information! Thank you very much Gary!
Do you know how long Bob ran his engines before he ordered a rebuild? Because he was an independent driver, he might have just ran them until they died, rather than have them on a schedule for teardown like a heavily funded factory team.

That would obviously be the way I'd have to do it as well, not to mention the fact that any engine/car I would run would only be tracked once ever month or so, and street driven the rest of the time.

Again, thank you very much.
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69Z28-RS
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« Reply #3 on: August 25, 2014, 01:19:54 PM »

No, I don't recall that if I ever knew it.   He built his engines 'conservatively', since he was an independent and had to fund his own car (with some assistance from local businesses here).   When he was running IMSA GT in the mid70's, he had both a BB (427) and the 302 which he switched depending on the track he was running, and I recall at one time he switched in the 427 from his tow vehicle when he broke the one in the car.. Smiley 
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
satman
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« Reply #4 on: August 25, 2014, 09:55:51 PM »

In my opinion the single most important thing you can do when building a race engine is find yourself the best machine shop that you possibly can and preferably one that specializes race engines only........... Have them line bore your block, mill the deck then hone the block with a torque plate attached ........The other important item in your build is the crankshaft we had ours custom ground to assure we had the correct  clearance for our Clevite bearings then we would send the crank out for nitride treatment. For our engines camshafts wear was not a big issue so we used a heavy weight oil on the journals and lobes but the one thing we always always did was to prime the oil pump with a drill before we fired it up.

  AL
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Trans m
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« Reply #5 on: August 25, 2014, 11:36:01 PM »

Thank you both Gary and Al, very cool especially coming from two people with "independent" backgrounds. Much more practical info for me and most others in the future.
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