Engine Break In Procedure?

[Jimmy74]

Hi all:

I'm just rebuilding a 1275 with .30 over pistons, new tappets and all bearings (standard size no regrind of crank, or cam shaft). Head and deck skimmed.

Can I get your advice on specific break in procedures? In this case both carb settings and distributor timing require setting as no reference points from prior to the tear down are available.

Your advice is appreciated!

 

[jlaird]

Set it right by the book for starters.

 

[regularman]

Drive it easy for the 1st 500 miles or so to break the bearings in good, then change the oil and drive it normally.

 

[Sarastro]

Probably can't go wrong with the standard admonitions: don't let it rev too high, don't let it labor, and vary the engine speed a lot. Generally, go easy on it but not too easy. And, yes, change the oil around 500 miles.

My 948 didn't start feeling really broken in until about 1500-2000 miles.

 

[jlaird]

Break in oil in a new race engine is one race then change it and treat as normal. Ahh, the first race RPM wise is not a prob. Engine should be broken in after a few laps in the heats or practice sessions.

Modern engine rebuilds are such close tolarances that a long break in is not necessary.

For example, I suggest you take it out on the street after a good tune and warm up in the driveway (2000 RPM)checking for oil and water leaks. Then run on the street for maybe 30 min. Change the oil. then run to about 500 miles and change again then go to usual maintance schedule of every 3K miles or so or twice a year.

I know, I know, everyone has their own idea but this has worked for me for over 40 years.

 

[spritenut]

I fire up a fresh engine, let it warm up, make sure I have oil pressure, make any adjustments, tach it up a few times, set the idle at 2000 for a few minutes, 3500 for a few more minutes, and red line it a few times while it's idling high.
reset the idle to normal, shut it off, change the oil and filter.
All this is 20 minutes.
If it didn't break, it will not.
Drive like you normally do and change the oil and filter again at 500 miles. Retorque the head and adjust the valves @ 500 miles.

 

[Jimmy74]

Thanks for your responses. I'm mostly focussed on the first 20 minutes. I've read 20 minutes over 2000 rpm, with varying bursts, to ensure the rings don't polish the cylinder walls. My quandry is how to get the timing set, and get the right carb adjustments, while at the same time meeting a presumed requirement to ensure fast to really fast idle speeds for the 1st 20 minutes.

I understand an excessively rich mixture will wash down oil off the cylinder walls and may lead to scuffing. The carb settings were super rich prior to the tear down resulting in loads of deposits and piston skirt scuffing. So i need to get these carbs set asap while maintaining high rpms in the 1st 20 minutes.

For the carbs setting how many turns out from fully seated would be appropriate?

I'm thinking, start the engine, time it quickly, go to 2000 RPM with some regular bursts to 3000 or so, run for 3 to 5 minutes. Stop, inspect the plugs, adjust carbs accordingly, start run at over 2000, again with bursts, stop again after 5 minutes, recheck plug color, adjust as needed, and so on until 20 minutes have elapsed. All this in the garage.

Then out on the road the usual program. No steady RPMS for the 1st 500 miles, intermittent and frequent 1/2 to 3/4 throttle bursts, with throttling back using the tranny to allow coasting back to slower speeds. No full throttle ever, no lugging in teh 1st 500 miles.

That about do it?

 

[jlaird]

I would bet that will work just fine.

 

[regularman]

You got two competing things going on here. You want to break in the bearings easy and you want to rev it high to get the rings to wear in good.

 

[Ed Kaler]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The carb settings were super rich prior to the tear down...[/QUOTE]

Now THAT bothers me BIG time, Jimmy!! :hammer: Have you ever had them PROFESSIONALLY rebuilt?? I would STRONGLY suggest you do!!

Timing may be your standard static setting. GOOD carbs could be standard settings. Do NOT do that up and down revs. Let motor run at 2000-2500 for 15-20 mts. Done. Then do the 500-1000 miles, change oil & filter and re-torque head. Drive it like you stole it :lol:

I am curious tho, why not a new cam??


Ed

 

[Jimmy74]

Thanks Ed;

If fact the only problem with the motor was corrosion in the number 3 jug. Engine was rebuilt by a PO to .020 over. It had likely been stored with that intake valve open for a long time. Compressions was 175-175-150-168 and it was a pain to get it to idle without popping and drive untill well warmed up. Bearings and cam were all good, tappets a bit pitted. I decided to just change all the inexpesive stuff while in there but hold the rebuild costs down where possible.

It isn't back together yet so I'm still in the market for advice!

 

[MTribe]

Jimmy74, how'd the break in go? Hoping to fire mine up tonight.

Great thread--thanks everyone.

 

[Hap Waldrop]

From reading your post, I guessing you reuse the stock, which is fine along as all the lobes looked good and replaced the lifters. I would use a oil that has zince in it, since the lifter are new you need to do this, very important, use Vavoline VR1 Racing 20/50, you find it at your local parts store. Wehh you first crank the engine keep at 2000 with a few plips of the throttle, check your timing at this poit and set it, if and when the vehicle reaches 180 on water, shut it down and let it cool off. I would after the first or second running of the engine then retorque the head and adjust the valves. I run the car first on short trip keeping the RPMs say 4000-4500 or under, but don't lug the motor. You can change the oil anytime after a couple of hubdred miles, on a fresh rebuild, there going to be some debris in the motor, ring material, silicone, lint, etc, change the filter and put fresh oil in, then drive it like you stole it.