L31 break-in

[Quikshft]

Well today I got everything together, primed the oil system and got if running for a few seconds. Had good oil pressure, but the exhaust gasket on the center two ports on the passenger side was miss-aligned. Fixed that and started it again for 10 seconds or so with no obvious issues. So tomorrow I'll add the upper radiator hose and fan/shroud and top off the coolant and get ready for a street test.

Now, with a roller cam I'm understanding that the typical cam break in isn't required. Do I also understand that these engines have moly rings that don't require a break in - accelerating/loading the engine and then decelerating and repeating some number of times. What works? What about oil changes for the first 300 to 400 miles?

Thanks!
Jeff

[Kudzupatch]

Not trying to be smart alek but don't they give that info somewhere? I am going to buy one and swap mine out soon.

[AussieinNC]

Temp sender will not provide accurate temp readings where you have it installed....it wont be immersed in hot water until after the thermostat has opened....
and....that plastic fuel filter will harden pretty quick in that hot under hood area...suggest metal body fuel filter...

Is that rubber hose going to the brake booster actually vac hose of fuel hose?
Needs to be vac hose...

Fill the cooling system with coolant, make sure timing is to spec....if an automatic trans, make sure trans has sufficient oil in it so it doesnt run dry...

Start engine and keep at fast idle...1500 rpm for at least ten minutes...check oil pressure....

Do not let it idle....under no circumstances let it idle...

Once up to temp, check for coolant leaks and oil leaks....check trans oil level if its an auto....tighten every clamp again....they will take a set and loosen up in first run session.

Better actually if you put the rear axle up on stands with wheels off the ground and run the engine for about half an hour so that the speedometer sits around 45 mph....

Check constantly for leaks and oil pressure.

After 30 minutes of running, dump engine oil out hot, change oil filter...add new oil and restart...check for leaks, then set idle and final timing etc...then drive it....

Why run it on stands? Saves ya walking back home and towing it back if something isnt right...

Enjoy....

BTW...Most engines nowadays do not come with informative break in procedures...sometime these instructions are on a generic web page somewhere...

[trac209]

One piece of advise is get rid of the plastic fuel filter and get a metal one.

[AussieinNC]

Second again on fuel filter...

[truckster]

https://paceperformance.com/p-3978-e...procedure.html

There's no problem with letting the L31 idle - it has a roller cam, which needs no break-in.

[garyd1961]

I just cranked mine up and kept it at a fast idle for a few minutes, checked gauges, checked for leaks, took it down the road. I changed the oil at 500 miles but I'm pretty sure they didn't change the oil in the trucks that these motors came in until 3000. New cars at work go 10,000 now before an oil change.

[406flyfish]

I’ve put a bunch of these in. Gm has no break in process for the engine. It has a roller cam so no 1500rpm cam run in. I usually run it long enough for the thermostat to open and make sure it’s full of coolant set the timing and go for a drive.

[clay68c10]

Get it warm, check for leaks, go cruise.

[Quikshft]

Originally Posted by Kudzupatch

Not trying to be smart alek but don't they give that info somewhere? I am going to buy one and swap mine out soon.

As a couple others noted there were no instructions included with the crate other than how to return your core, which I don't have so no worries there.

[Quikshft]

Originally Posted by truckster

https://paceperformance.com/p-3978-e...procedure.html

There's no problem with letting the L31 idle - it has a roller cam, which needs no break-in.

This procedure seems reasonable, probably will go with it.

Thanks for the pointers on my underhood weaknesses like the fuel filter. Most of what you see is the set up from the previous 350, but will address and correct items pointed out.

[dfosh]

Keep us informed on what you think of the l31 . Power ,torque ect.

[dfosh]

What did you do for timing cover to oil pan gasket ? Did you change oil pan gasket ? Sorry for so many questions but several people seem to be doing this swap including my self . The L31 I got had all the timing cover and dowel holes drilled . Thanks for the info.

[A1971Blazer]

If you want a stock type temperature sender that will fit in the vortec head....
http://67-72chevytrucks.com/vboard/s...d.php?t=726700

[Quikshft]

Originally Posted by dfosh

What did you do for timing cover to oil pan gasket ? Did you change oil pan gasket ? Sorry for so many questions but several people seem to be doing this swap including my self . The L31 I got had all the timing cover and dowel holes drilled . Thanks for the info.

I did not change out the gasket, though I did pop the pan loose to add the timing cover. Interesting that my block had the dowel holes drilled. It also had the hole for the clutch cross-shaft pivot ball drilled and tapped. I had been under the impression that I was going to have to add all these. Guess its the luck of the draw.

[AussieinNC]

Originally Posted by truckster

https://paceperformance.com/p-3978-e...procedure.html

There's no problem with letting the L31 idle - it has a roller cam, which needs no break-in.

Personal preference to run at 1500 for a while...not really for cam as yes, it is a roller, but more to get the engine up to temp quicker than just letting it idle....

Running it at 1500 also ensure there is plenty of oil flow across the crank and rods and wrist pins....

Have done it this way for 48 years....bit hard to change now...