Thread: break in on chevy 350

Tweet

hello, i have a chevy 350 bored and stroked to 385. it was just recently built by my dad and i and i am still breaking it in and tweaking on it. It has fully balanced bottom end and some double hump heads that have had 3 angle valve job, ported, everything with around 12.9 to 1 comp. Went with the comp XR292R Mechanical Roller cam, 830 holley double pump, 3500 stall, and 4:10 gears, full msd so i know its getting good spark and pretty much anything you could think of (nothing spared) My question is what is your suggestions for breaking it in. I have already drivin it about 50 miles and not got on it very good yet just little revs here and there. Its smoking a little and oil on the plugs i just wasn't sure if the carb was washing the rings for being a little too big or if it was just going to take a little more driving to seat them. I am just worried because we honed the cylinders and put that dry seat film on it with the total seal rings. I didnt think it would take that long to seat the rings and it seems like its worse now than when started the first time, any advice on something im not doing? Not sure if higher horsepower motor needed something different to break in? thanks

Mine puffed a little smoke too for a little while after initially starting it. In fact, on the trip to Daytona I used about a quart of oil. Now that seems to have stopped. It takes a while to seat the rings it seems.

Since you and I have roller cams we don't have to do the traditional 2500 rpm breakin for 1/2 hour, but you will want to vary the speeds while driving for a while. Drive at like 45 for a little while, then drop to 35, then go up to 50, etc. Not sure what this does exactly, but it is the procedure every marine engine manufacturer recommends for new inboard boat motors, and I have also heard that is recommended for fresh car engines too.

BTW, you aren't running synthetic oil yet, are you? Also, one of our engine experts may say otherwise, but I think you are a little overcarbed. All this is assuming of course that something goofy like breaking a ring on installation or something otherwise wrong is not the culprit.

Don

To seat the rings you want to put some load with it. My ZZ502 manual says to do 4-5 half throttle runs from 30 to 60 letting off in gear each time back down to 30 and repeat using 3/4 throttle. Then drive normally for 500 miles, this establishes the proper wear patterns.

Kitz

no synthetic. used sae 30 for the 50 miles then changed oil and went with 10w 30. thanks for all of your help ill just continue to drive it and im sure over time it will be fine. The 104 im running at 5.50 a gallon kind hurts the checkbook tho. The carb is a little bigger than i need i think except for under full throttle I've heard its ok, I need like a 750 i think, but cant spend the money for another new carb just yet.

Should non-detergent be used?

I have a rebuilt 283 (stock w/mild cam) that has 0 miles on it. I'd like to know what oil(s) to use....

Rings should seat pretty quick mainly on the decel. As was said before, varying speed is key. Mine were bedded in within 15 miles from the shop to the house. Sounds to me you may be running overly rich? Blue smoke or gray? Might just need to dial in the A/F...

Something to think about...

-Chris