Jeep Strokers

Hi all , I'm new to the forum, but have been doing alot of reading here for sometime. I have 2000 grand cherokee 4.0 with about 85k. The motor did as what seems most do......starts using coolant, then the oil pump went. I am now at the stage I have my engine in pieces getting ready to do a rebuild. My crankshaft is toast with bearings shot, cam seems worn, #6 piston and connecting rod broken & oil pump shot,etc. I have the 0331 head can't see a crack with naked eye and the gasket didn't seem cracked. So my question is when I take the head to have valves redone will the shop find the crack? If not am I safe to say that it does not have a crack? I am looking at building a stoker and in the process of gathering some parts. Thanks for the help!

You can have it pressure tested, magna fluxed etc to look for cracks.
John

The machine shop can check for cracks. I'm not sure I would use that head on a new engine, with it being prone to cracking. I have seen post about an 0331 Alabama cylinder head thats been recast to fix the cracking problem.

Any idea what caused the #6 rod to break?

Not sure exactly why #6 went , but step son was driving down highway and lost oil pressure after trailering it home we couldn't get it to turn over at all. Crank was pretty dry after tearing it down.

What did the oil look like that came out of the crankcase, also the valve cover, water often condenses with a tell tale state there.
John

I think the previous owner did not take care of this motor(DUH) I'm pretty PO'ed since I've only had it a year .Oil came out black with metal flake( was just coming up on a change). Not milky at all. I took head in to the shop they are going to check it out he said $18 to magnaflux it and $60 for valve job. Since I'm stroking this motor I think a strong spring would be in order. He is also going to bore my block $16 hole and $35 for acid dip. Big question is since this is my wifes ride & she will be driving daily what is the reliability of stroking this 4.0? I don't want to hear her if i am going to have alot of often adjustments. What kind of longevity will I get?

Longevity if you build for reliability instead of max power, should be the same as any fuel injected 4.0, i.e. well over 100,000 miles with no special maintenance, and probably well over 200,000 miles with diligent maintenance.

Theoretically speaking there's no realistic reason why a rebuilt 4.0 with a 258 crank wont last as long as a garden variety 4.0... Practically speaking though a lot of machine shops wont get the engine as accurately machined as the original plant did, and they wont put the engine together as consistently, and in as clean an environment. With less quality control and less strict standards for parts and techniques. That coupled with the owner probably beating on it more...

The only mechanical reasons why a stroker might not last quite as long are the lesser "journal overlap" of the 258 crank and the potential for increased ring wear due to the longer stroke. Less Journal overlap is just a way of saying that the main and rod journals are more far flung from each other which means more mechanical stress when its rotating and more possiblity of flexing leading to increased wear from things not being as perfectly in alignment as they might be with less flexation...

Practically speaking no one has shown these to actually decrease the effective life of a Stroker. The truth is that Strokers have only been around for relatively short time and they tend to be performance or off-road builds so there's not too many daily driver commuter strokers out there... I think Mine is one of only a handful that have over 50k miles. And mine was a trail rig build that got interrupted and morphed into a daily driver due to necessity... and now is back to being a fun rig that doesn't get lots of miles.

I'm with others who suggest going through the trouble of converting your engine over to the 0630 or 7120 head casting... Under no circumstances would I put the 0331 into a daily use vehicle that needs to be reliable and not constantly checked for coolant in the oil.

I would put a 0331 on a racing build in a heart beat to see if they would last a few races (like a Jeepspeed build) anything that would be torn down and inspected regularly... So the coolant contamination would never get bad enough to cause a thrown rod or worn bearings.

Thanks for the info. I have been told that the 7120 head will not work & and that the newer 0331 castings are of no problem. I will be putting my own motor together after having the machine shop do head & block.

What reason were you given that the 7120/0630 head won't work?

That it needed studs for the rail

You can make small straps that go from the head bolts to the coil rail. Also, I have heard that aftermarket headers for the 0331 head will work on the 0630/7120 head.

SilverXJ wrote: I have heard that aftermarket headers for the 0331 head will work on the 0630/7120 head.

Has anyone tried this yet.

I believe someone on Naxja has. Might want to search there. IIRC they used a rugged ridge header.

Still looking for a head may have one. Now I am thinking of reusing 5 good pistons( after clean up) & just replacing the rings any opines? Alot of times I go to Advance auto web page & check different year model to see what is interchangeable, I have been wondering for sure if the header from a 99 is gonna fit my 2000 for sure. Time to sh*t or get off the pot I guess. Also still undecided about which cam........hmmmmmmmmm.

Maddawg wrote:Still looking for a head may have one. Now I am thinking of reusing 5 good pistons( after clean up) & just replacing the rings any opines? Alot of times I go to Advance auto web page & check different year model to see what is interchangeable, I have been wondering for sure if the header from a 99 is gonna fit my 2000 for sure. Time to sh*t or get off the pot I guess. Also still undecided about which cam........hmmmmmmmmm.

Pistons are cheap and I wouldn't reuse them. As for the header from a 99 fitting.. are you taking about putting it on the 0331 head? It might work for teh same reason an after market 0331 header should work on a 0630 head.. larger ports. Any how,m that is for teh head.. you also have to be concerned about the rest of the exhaust. Do you have the cali emissions package (two precats, one larger cat, and 4 O2 sensors)?