i just got done rebuilding a 4.2 how do you break it in and to seat the rings the right way and such

 

technically 3 warm up periods and the rings should have expanded and contracted enough to seat in. but to set the wear patterns that will take many many miles.. but id suggest some highways trips and set cruise

 

I've read conflicting materials on this. I read somewhere how some people did some study that showed it's best to do several WOT runs to break in a motor....I'll see if I can find it.

 

i have broken in many of my race mx bikes, and also a couple motocycles now and well differant machinces i believe the break in is the same. it takes a couple drives of varying speed. not constant 55 and also dont keep the engine or rpm in any extremes. i would say drive faster then 30 mph ( except where law prohibits of course but try not to stay in the city for a long time) and less then 75mph. dont run at highway speeds the whole time. and when u take off from say a stop light by all means dont baby it! but also dont redline it either. i would say 4k max personally i would try to keep it around 2500-3000 while accelerating on my break in period, after about 3000 miles or 3 months which ever comes first (unless u put on 20 miles in 3 months be reasonable, that ur truck is broken in. if ur going to drive it hard i would still not shert can it everywhere until 8k-10k. i wouldnt haul anything like a decent sized boat til after 5k. my 2 cents from expeirence.

 

Get out there and floor it! The way to get the rings to seal properly and not burnish the bores is to load the engine down, and the way to do that is to get on it. Babying the engine during breakin is of no value. If something is not right with the engine assembly, babying it will only prolong a bad situation. If it's gonna break, it's gonna break, whether you baby it or not.
Now don't abuse it, but don't be afraid to floor it either.
For more info on breakin procedure and why it is important to load the engine, go to mototuneusa.com, or if that is not the correct site, do a search for that site.
Later, and good luck.

 

we did a 302 and they told us to pull the crap out of it... worked pretty well

 

Had a new crate engine installed on a Buick Regal SC once, I was told by the dealer to drive it in town for a day or two before taking it on the highway, and accelerate hard from dead stops whenever possible.

 

Ever see an engine shop build and engine. They throw it together, put it on the dyno and make about three WOT passes. I guess what ever floats your boat. Mine I use a moderate load, vary the RPM and use regular engine oil for the first few oil changes.

 

just ask neal lol he took it racing the day he gets it lol and hes only had to rebuild it 3 times now due to faulure:-p

 

From what I've heard according to Ford, you should vary the RPMs while driving it for the first 1000 miles, (for example: not keeping the RPMs at a constant level for long trips). It also isn't recommended to drive it near redline for at least the first 500 miles.

 

we put a rebuilt 390 in a '74 F-100 way back then...
live in mass...
started it up on sat morning hooked up the trailer...
changed the break in oil when we got to oxford planes dragway in maine...

after towing the race car and gear all that way with zero miles on it...


just go for it!

(after all its under warranty)


...zap!

 

Yeah, definately run it hard (not too hard, mind you), and I personally would run through a semi-urban area with stoplights but a 55MPH seppd limit. That allows you to get in ur stops & Goes, yet allows you to get up to around 60 MPH with no police worries...That's what I've done with my 2 bikes, and they run fantastically.