Jeep Strokers

This site has a lot of great info and will be a valuable resource in the near future.

This is nowhere near my first stroker build but the first on a 4.0l. I own a 540" Mopar B-1 and used to own the machine shop I will be doing all the work on this 4.0l engine at. I originally realized you could do this build about 10 years ago when I had the two cranks sitting side by side to be ground and then looked up the bearings and said ah hah! Well U guys have done a fine job of doing ur homework and I'm going to tap into some of ur knowledge for this. I have read all the FAQ's and have a couple questions regarding the build.

The vehicle this is going in is an '89 2 door XJ W/auto trans that i have owned since new. It is my wife's driver and has a 3.5" lift runs 31.5's with a 4.10 gear w/sure grip. Just for the record (in case it helps someone) the rear end is out of my '65 Dodge Coronet that the 540" motor is in. I put a Dana 60 in the car and had this perfectly good locked 4.10 rear end sitting around that had the same bolt pattern as the jeep and was 1/4" difference in width so it didn't take a genius to weld some perches on it and call it a jeep rear end. Bonus was bigger rear brakes and a rear end that it is unlikely any straight 6 will ever break. But I digress....

I have a couple questions....

Block...for my application do I care about going and looking for the newer block with the stud girdle and more main web? This is a 99% driver and once in a while I take it out and put a dent in it for her. I understand the vibration thing and if it's a signficant difference I will hunt one down.

Pistons...KB is across the street from my old shop so I guess that's the deal

Crankshaft...I'll look for the 12 weight one and I'm definitely gonna machine the end off...from what I gathered crank key location, size, and snout diameter are all the same correct?

Rods...looks like we'll be using the 4.0's with that piston

Cylinder head....this is where I intend to draw on your guys' experience and knowledge. I would like to go to the HO head and probably will. My only thoughts are that smaller ports produce more torque and I live at 4500 feet so there is no air here anyway...just my thoughts In addition, I already have a borla header on the jeep and it would be a simple in/out motor swap. My understanding is that all that is required is to change to the ho head and manifold the fuel inlet hose, the throttle cable, and reroute some wiring, and swap TPS...is this correct? Do I really care about the HO head? Also, if I do swap heads that means I'll have a borla header for the 89 if anyone needs one....

Well thanks guys...U'll be hearin from me a bit in the next few weeks...We'll be off to the shop tomorrow with some parts and pieces and figure out where to go based on your input...

One question before I head down to the shop.....do U need to clearance the block for any of these combinations? Not that it is a problem, but it would be real nice to know while it's on the machines and before we start to put it together....

I haven't heard of anybody needing to clearance the block or the girdle for the longer stroke. i'd say to not be concerned about it

There is no block to crank issue that i have heard of..........But i have, for the lower reinforcement.
Minor clearance (grinding) was the fix?????


Flash.

The clearancing I was wondering about was rod to bottom of the bore clearancing but if nobody has had to do it then I will just check it on assembly. Does anybody have any comments on whether it is a big deal to go looking for one of the later blocks that has the main cap girdle or can I just use the one I have and and move on....remember this is my wife's driver and am not looking to set any records with it. I'm guessing that they only made these motors for what 30 years before they made that mod so it'll probably be ok, but just wondering what Ur guys feelings are.

OK I'm at the machine shop....they have a 10/10 12 counterweight crank and both a stock 89 head and a high output head...my block and rods are usable so at this point I really need to know if the HO head is worth the additional effort....Somebody, Anybody please?

not sure the HO head is extra work?? but it is a better head than the Renix's and i think ive seen a few guys have put a couple washers on to space out the mains girdle (if you have it)

Whats the casting # on the head? If its 0331 don't use it. They are prone to cracking.
If its the 7120 or the 0630 then use it. These are considered the strongest castings.
The 89 head should be a 2686 casting. That will work fine as well

They have several 7120 heads. As best my internet search can tell me the Renix motors were rated at 173-178 HP and the HO at 190. My understanding from this site is that I can put the HO head on and will have to use the HO intake and throttle body retrofitted with my renix TPS. I believe I will also have to ditch my Borla header and buy a new one to fit the HO head. Is this correct? Other than power gains what are the advantages and/or disadvantages of using the HO head?

Only advantage of using the HO head is power.

In terms of parts, the HO motor was in production far longer then the Renix motor was, i'm not sure if that may eventually play into the cost of parts for items like sensors or throttle body components or anything else you may need.

gonridnu wrote:They have several 7120 heads. As best my internet search can tell me the Renix motors were rated at 173-178 HP and the HO at 190. My understanding from this site is that I can put the HO head on and will have to use the HO intake and throttle body retrofitted with my renix TPS. I believe I will also have to ditch my Borla header and buy a new one to fit the HO head. Is this correct? Other than power gains what are the advantages and/or disadvantages of using the HO head?

The HP gains were mainly from the redesign of the head allowing for a better shot from the intake runners. That, and the ECU change were probably the biggest contributers to the gain in HP numbers between the RENIX and HO. However there are some people out there (myself included) that feel the RENIX is a better set-up computer wise. It was VERY advanced for its time. I also personally feel the RENIX has more "get up and go" power. I know my 90 puts my ass in my chair better than any HO i have ever been in.... and i havent even stroked it yet (granted its well taken care of, and has some bolt ons).

Mgardiner1 wrote:Only advantage of using the HO head is power.

In terms of parts, the HO motor was in production far longer then the Renix motor was, i'm not sure if that may eventually play into the cost of parts for items like sensors or throttle body components or anything else you may need.

If you put the HO head in a RENIX set-up, then your more likely then not going to be using all the RENIX sensors etc. Unless you swap out the whole harness, ECU etc... which i doubt many people will do due to what is involved.

IIRC all that is needed is a TPS adapter, and use all the cabling for the transmission and throttle body from a donor 91-95 (if using the 7120 head for example). Use the TB, Intake and Exhaust manifolds from the donor vehicle also. Everything else matches up just fine.

I think i read that you can use a RENIX exhaust manifold on the later model heads, but i havent confimed this. Its not something i would advise doing anyway as the later model design is better just as the later design of the head is better. You can get a APN header for the later heads for cheap, and they are basically a banks knockoff.

This vehicle does not have any trans cables other than the shifter cable...it does however have cruise control with a fairly elaborate cable and bracket system...does that change as well....it's starting to sound like keeping the Renix head would be a whole bunch less trouble and possibly not a lot less horsepower...If need be I can do some port work to make up the difference and probably have less time in it than messing around with brackets.cables and manifolds...not to mention keeping my Borla header

I did have to clearance the girdle from the 258 crank's longer throws--2 washers per stud. You should use the newer head(0630 or 7120) and adapt the renix tb to mount on it(get it bored to it's 60mm max). Downside is the borla might not line up. If not, you might be able to trade it straight up for a newer borla--your's is rarer and worth $300+.

The Mopar Jeep Engines (3rd ed.) book that covers the 4.0 mentions notching the cylinder bore for rod clearance when using a 4.2 crank (pg 135). However I can't recall seeing pictures or reading that anyone had to do so.

I believe I asked about the main girdle on the yahoo strokers group and was told that spacing it could interfere with the oil pan. That was a number of months ago and it's possible I've remembered wrong.

You are right, the Renix head would be much easier to preserve everything in its stock form, especially the cruise control. IIRC the Renix throttle is facing the rear of the engine, and the HO is on the front side.

That being said, i think with the exception of the TPS, the rest of the sensors shouldn't be a problem. I think you just wouldn't use the coolant temp sensor in the thermostat housing, as the Renix should have one in the side of the block for that.