84 cj-7 258 rod knocking questions

Had to pull a guy out of the river last week and to make a long story short when we were done a rod was knocking. My questions are can the bearing be changed with engine in the jeep Ie is there enough room to drop the pan? The jeep has a 4 inch lift. If the rod journal is not totaly trashed can it be buffed with emery cloth. Or if the rod is bad can you get the piston out without pulling the head. The engine does not burn any oil and no other issues have shown up other than the rod knock. So what is the best way to get by until I can drop a reman in or go thru this one depending on the crank. Jim

 

Piston will only come out up thru the top, which means removing the head.
First step would be to figure out which cylinder by pulling the spark plug wire off while idling; when it goes quiet, you possibly have found the culprit.
Drop the pan and check the bearings; the other questions can't be answered until further inspection.

 

Ok Thanks will try asap and let you know what I find. Jim

 

was the Jeep a submarine ?
this year and era were also known for carbon knock
when shut off, engine was running fine
when restarted, can scare you it's so loud
don't know the particulars in this case, but something to be aware of

 

Jeep was never in more than 1 ft water on day in question. But before I got it ? I am 100% shure it is a rod, quiet at idol gets louder as the rpm's come up goes back to quiet at idol

 

If you're sure it's a noisy rod bearing, there's not much you can do other than replace the crank. Cast crankshafts are soft enough that the bearing will damage the crank if there is metal-to-metal contact. Very unlikely you can clean it up enough with emery cloth - that's an old-school approach that works sometimes with a forged crank, but not with a cast crank.

I might follow Jim's advice (jpflat2a) and isolate the cylinder... or I might just pull the pan and start inspecting the rod bearings.

Another possibility is to look around for a replacement 258 or a 4.0L. There are a lots of 4.0Ls out there, and 258s are fairly cheap on the used market when you find them.

 

Thanks!! On most reman sights they ask for a engine code from the vin and I think mine is a c code, what are the differences in the engines according to the vin code? Is one more desireable than the the others?

 

There's both a build date code on the engine, and an engine character in the VIN. Both will be "C" for the 258 2V. Other codes are other displacements - not applicable.

This information is in the TSM.

 

I don't know....given the KISS theory and the way you describe it...sometimes a malfunctioning rod can sound a heck of a lot like an exhaust leak. Since you were in water, you took very hot metal and splashed very cold water on it, possibly changing its shape enough to give you a slight leak between one of the gaskets....JMO.

 

Thanks!! but it was knocking before I drove in the water, we were pulling from a sand bar when it started to knock. After we got him out of the deep part of the river I went in to jump his truck so he could help get himself the rest of the wayout

 

Another possibility is to look around for a replacement 258 or a 4.0L. There are a lots of 4.0Ls out there, and 258s are fairly cheap on the used market when you find them.[/QUOTE]

Ok found a 95 4.0 in the 120,000 mile range with everything but computer, the seller is from a small town and he knows the guy who had the engine and it is supposed to be in great condition.The local mechanic and hot shoe will testify to how it ran before pulled. The seller seems straight up. I am at 300.00 he is at 400.00 so prob 350.00 will get it bought.
Now is where I need some help. My 7 has a four speed will this bolt up with out any problems the 4.0 is a standard also.
Will the motor mounts work or have to modify.
What all will I need for the conversion ie computer, fuel pump, wireing harness.
What do you do about the serpentine setup since I dont have ps or ac.
And last for now I found a .010-.010 258 crank for cheap and am thinking about stroking this engine, what is your opinions on strokers?
any way should be able to do a good upgrade and stay under 1000.00 Jim

 

Can you feel the "knock" through the clutch pedal?
I had a CJ that started knocking while trying to unstick someone.
After wheeling back out of the area, the knock went away. A couple weeks later, my throwout bearing died and I did a full clutch system refurbish and I could see where something was touching the pressure plate housing for a while. Also replaced all the broke motor mounts as I thought that may have contributed to the misaligning of clutch system components.
I just recently had the same knock come out of nowhere after replacing my 74's motor mounts and firing it up for the first time. I could feel it through the pedal. I loosened the mounts, drove around the block and drove over some curbs in and out of our greenbelt/water catchment and the knock went away.
Just a thought.

 

Thanks but no you cant feel it in the clutch it is in the engine.

 

This is quite a lot to ask for in a single reply.

There used to be a forum at CJOffroad.com that covered the 4.0L swap. Unfortunately, it's been gone for about a year now.

Second best is likely jeepstrokers.com

I have not done this swap, but I believe that the 4.0L will just drop in. Certainly the bell will bolt up, and either the 4.0L or the 258 flywheel will work. You can go carburetor or the 4.0L TBI. The 4.0L block does not have a provision for a mechanical fuel pump, so you'll need an electric pump regardless.

The serpentine issue ... not sure. I think the 4.0L crank sticks out further, so the alignment for the pulleys won't be right is you try to use the v-belt stuff. I'd avoid the question by converting to power steering. The AC compressor can be kept, and turned into an air compressor.

 

Ok Thanks Tim, any opinion on pros and cons of stroking it?

 

My understanding - the main issue with a stroker is matching the pistons and picking a deck height. This is simply a side effect of changing the stroke. If you adjust the deck to work with 4.0L pistons, you will have too high a CR. If you keep the deck height, then your quench is not ideal. You can get around this issue by buying new pistons made for this application by Keith Black, or custom pistons (but this will blow your budget). Choice of camshaft is also important, as this affects CR.

If you've never built an engine before, I expect this would be a challenging project. However, I'm sure you can do it if you put in the time and effort to understand the issues.

 

Thanks Tim, I was on a IMCA team and did alot of sbc builds. Is there a good manual like Smokey Yunicks power secrets or the old Chevy power for Jeep engines? Also got the 4.0 today for 350.00. I checked on the KB pistons they are 425.00, so will have to see about about the stroker build. Thanks again Jim

 

Yes there is.
Its called MOPAR Jeep Engines (speed secrets and race modifications for jeep-built 4,6,and V8 engines)
Its Mopar part # is P4529529
It's a little hard to come by but should pop up on e-bay

http://www.amazon.com/MOPAR-Jeep-Engines-Modifications-Jeep-Built/dp/B000TMSD4Y

 

Thank you found one on ebay got it on the way.

 

In my experience once you have noise it's to far gone to just replace the bearing. That said, they do make .001 oversize bearings for many applications. A rod bearing is cheep so it might be worth a try.