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freshing up a 4.0

POLAR_JEEP_04

POLAR_JEEP_04

NAXJA Forum User
Location
Ohio
ok so im freshing up my 97 4.0 next weekend (rebuilt head, rings, rod bearing, oil pump, gaskits.) and was wonder what kind of "break in" would i have to do if any?
 
just take it easy, the most critical item is piston rings. you can do a google search for seating piston rings and find as many passionate opinions as you would in choice of oils. the point is to avoid micro welding (google again :) but, otherwise, just be easy, and choose your best plan based on what you learn, most folks, just avoid Xmph until X miles on the clock, there is no ONE safe formula, it's a seat of the pants thing, but do a little research and find what'll work best for you, as for the head and such, there's not that much to worry about, the biggest factors in engine wear in or break in is the piston rings and bearings. Oil being the most important factor, keep it full, and keep it clean
 
drive very easy for the first 500mi, no hard launches, or abrupt rpm increases. Then Change the oil, after that you can start getting on it but take it easy till you hit 1500 miles. Change the oil again and drive normally. Run Dino oil till you get up to 4k mi or so then switch to synthetic if you want.

I would run a ZDDP additive like the STP oil additive or the mopar junk. Lucas also just came out with a Zinc additive as well.

When I first started my stroker I let it idle for about 30 min. Then held the throttle at 2000rpm for 5 minute intervals for about an hour. It seemed to help the rings seat nice and easy.
 
Build it with good parts,use good engine oil (As mentioned), and stay off the skinny pedal (like me):D

A vid of my 4.0 first hour of operation
http://www.youtube.com/watch?v=n35bAOP4qHA

Drove it to winterfest last year with less than 500 miles on the engine wheeled the heck out of it there and ever since.(4000 miles and counting)

Good Luck

Nick
 
I'm doing the work next Saturday and Sunday and have a good trip planed for Nov 7th and 8th so hopefully all goes well! hana care to hit wellsville the 7th and/or 8th? :)
 
ZDDP is an abbreviation for a zinc compound. Under operating temps basically what it does is combine with moving surfaces, ie bearings and the came lobe lifter interface, and form a sort of hardened patina that protects those parts.

As far as a break in oil goes, there are a lot of suggestions out there, I used castrol 15w40 diesel oil for the first portion, and 30w diesel for the second. Then I moved to a standard Castrol 10w30 with a zddp additive till I got enough miles to feel comfortable running a synthetic. Currently I am running MOBILE1 EP with the lucas ZDDP additive, but I may switch to Royal Purple with the same additive next time around.
 
wolfpackjeeper said:
.

As far as a break in oil goes, there are a lot of suggestions out there, I used castrol 15w40 diesel oil for the first portion, and 30w diesel for the second. Then I moved to a standard Castrol 10w30 with a zddp additive till I got enough miles to feel comfortable running a synthetic.
Click to expand...

so no ZDDP with the diesel oil or do you even run it with that?
 
I would consider it now, I was running my break in before they lowered the sulfur and zinc content of the diesel oils. During the initial break in is when the engine gains the most benefit.

I am sure 5-90 or someone will chime in soon, but the main reason I used the diesel oil was the extra detergents and the extra zinc. Now that they lowered the levels there may be no real advantage as long as you use the additive. The heavier weight is nice though. Sorry, I just got off a 12 hour watch so my thoughts are a tad jumbled.
 
a normal melling from any auto parts store will work just fine, no need for anything special. you will however either need to:

A: Buy a dizzy prime tool
B: Grab an old dizzy from the JY and cut it up to make a prime tool
c: Find a screwdriver that works and make a prime tool.
basically it is just a tool that slides down the dizzy hole to mate up with and spin the oil pump. I made one from an old dizzy.

after you get the new pump in and are ready to start the motor, use a power drill to spin the oil pump via the priming tool to get oil up into the passages.
 
So do I understand you are not boring and putting in new pistons? Who is doing the work?

In the "old days" a mechanic might use a tool to cut down what is called the piston land with what is called a ridge reamer. The land is the top 1/4" inch or so of the cylinder that the rings don't run on, then hone the cylinder and install a new set of rings. This isn't very common any more. Most just rebore the cylinder oversized and add new pistons and rings.

Which are you having done?
 
As old_man is saying (I think) is that you need to make sure to put a cross hatch pattern into the cylinder walls to seat the new rings. And use a ridge reamer to take the unworn edge at the end of the old ring travel or the lead edge of the new ring could break off. If you do it "old days" style (like me).
 
well ended up having the wrong rings. i kinda need to have it on the road by monday morning. i have a 95 long block in my garage and the new ring i bought will fit the pistons that are in that block. my question is can i take the pistons out of that block install the new rings on those and then put them in my 97 block? if not im going to have to wait until tuesday to get the right rings. hmm... ???
 
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