Subject Vehicle is a 1990 Jeep Cherokee
My brothers original stroker conversion to 4.7 liter from a Renix 1990 4.0 yielded an honest dyno proven 51% increase in Horsepower and just over 60% more rear wheel torque. Note, our stroker conversion deviated from the normal in that we chose not to use the stock 258 rods, but follow one line of thinking around the popular Chevy (With their measly ¼ stoker crank verses the ½” of the 258 stroker crank) and go with the 4.0 rods, which are almost ¼” longer than the 258 rods. The theory goes that due to the better angle imparted toward the crankshaft, the longer rods should create more torque and less sidewall stress on the pistons. (I am NOT going to get into discussions on this subject, but only report what we chose for my conversion) Naturally, this created the need for special pistons, but then nothing is easy! It would be no fun then! We used a special modified Renix intake manifold, by Accurate Power, to allow the Renix system to be used on the H.O. head with minimal modifications. Ok Ok, We did have the stock throttle body bored to 58mm, and the Chevrolet 2.02 and 1.60 valves installed after six troublesome hours of porting and polishing the heads. We also modified the HO exhaust manifold to keep the EGR valve system, but wanted the better flow of the later manifold. That was not fun to do, but it worked well.
This set up is reflected in the head flow curves shown in the other intake manifold intake swap with dyno numbers at http://www.jeepsunlimited.com/forums...d.php?t=693034.
There are now have around 18,000 miles on this set up and usually get, when one keeps one’s foot out of I, and the grin off my face, around 17 MPG on the highway.
Recently, I changed to in later model intake manifold as detailed above. With those improvements, we decided that we also needed the later intake manifold on the stroker, but why stop there!
We installed a vacuum gauge on the intake manifold my stock engine, with only a bored out (Meaning lower lip removed) throttle body to 60mm and the large intake valves, to watch what happens at full throttle and maximum RPM. Nothing. The intake vacuum remained at 0in Hg, so I assume that the throttle body is of sufficient size to feed the 4.0 engine. I tried the same thing on the stroker, but at 4.7 liter and a modified 58mm Renix. With the intake disconnected from the air cleaner, so that any air cleaner restrictions could not come into play, I found the intake vacuum increasing to 2.5in HG at 5000 RPM. Now I reason that we HAVE to do something besides just change the intake manifold. The bored Renix throttle body is not large enough for this size engine!
Renix Power Steering Change
The installed power steering system as detailed in my previously mentioned write up. The only difference is to use a belt of 1000 mm length. I used the Goodyear Gatorback part number 4061000. This is 25mm shorter than original and a new belt layout is used. Warning, watch out for the timing assembly cast into the timing cover. It may rub the belt and will have to be ground down for clearance.
The new fan belt routing for the Renix exchange using the routing from the 00 XJ.
A lucky find at the local “Pick A Part” yielded a Borla header system. I could not let that go without installation! FYI…$29.99 plus tax!!
What we did not like is that the outlet of the Borla and also the Banks headers are only 2.25” in diameter. While the stock system is only 2.0”, we were not satisfied with this set up. This Jeep Cherokee is equipped with a 2.5” exhaust system now, but during the dyno runs, I noted an “After Burner Velocity” exhaust flow, which bothered us. Too much flow through that 2.5” pipe! The Borla header is designed as 3 pipes into two 1.875” pipes into the final collector outlet of 2.25”. If I assume the ID of the 1.875” pipes is 1.75”, this yields a total flow area of 4.808 square inches going into the final collector, which exits at 2.25” ID, or 3.975 square inches in area. Here is still a restriction to exhaust gases, but not as bad as the factory 2” outlet. If we go to an ID of 2.5”, we get 4.906 square inches, which is more realistic. No one, that I know of, makes such a header, so what to do? Not only that, but pushing that much flow around 10’, to the rear of the Cherokee will create flow restrictions in itself, even with 2.5” pipes.
This WILL void your warranty on the header. Make sure your welder is competent to weld to stainless steel. Now, before someone starts spouting off about loss of low-end torque, FORGET IT! IT DID NOT noticeably HAPPEN! My ONLY problem is lack of traction off the line. Can never have too much power.
We cut off the last collector back to the length that a flattened piece of 3” pipe would just slip over the remaining end, and welded it to the last collector.
Here is the modified header 3”outlet belled to accept further 3” pipes
Here is the crossover set up set behind the bell housing as factory. Note this also takes into consideration the ability to remove the transmission pan and engine oil pan. (The ability to easily remove the transmission pan can in handy later in this report). Later we added an additional brace from the lower bell-housing bolt, shown just above the elbow above, to the crossover pipe to assist supporting the weight of the 3” system. I do not want to crack that header!
The three-inch pipe easily clears the transmission cross member, but take care, this area is tight.
Just to keep the “Tree Huggers” happy, yes, it does have a new OBD II 3” Carsound converter, going into the new Flow Master “Super 40” series muffler. Now there is not sane way to get a 3” pipe out the side of a Cherokee, so I went with a 3” inlet and dual 2.25” outlets. Note again, the large case size of the Super 40 puts it close to the floorboard of the passenger compartment. I fabricated and bolted a light sheet metal heat shield between the muffler and the floor and bolted in place using muffler clamps. I had done this in the past and was very satisfied with the reduction in radiated heat to the floor in the passenger compartment.
Let’s once again do the math. 3” ID yields a total area of 7.065 square inches. Two 2.25 ID pipes is a total area of 7.95 square inches, so no restrictions here. Yes, I will have dual outlets on this Cherokee!! Sweet. Note- I was VERY pleased with the new exhaust note, verses the original flow- master 40 series with 2.5 inlet and outlet. We were very concerned about noise with the 3” pipes, but the new exhaust note is much deeper and the interior resonance was actually reduced. The individual power pulses now seem evident. Make sure you keep the driver side exhaust pipe as far away from the fuel tank as possible. One other note is if you “get on it”, big blocks and V-8s beware! It is deep and throaty. Eat your heart out rice rockets!!!
Dual 2.25” Exhaust and yes, with Chrome tips!
If a 4.0 with headers and large valve head, as mentioned in the above write up, can get almost 28 HP, WE NEED this new manifold on stroker with the same head!! Nothing is easy!!
If you followed the porting job on the intake manifold, bracket changes, and power steering changes as posted at http://www.jeepsunlimited.com/forums...d.php?t=693034, the intake change is basically the same. I did manage to get a little better flow opening on the intake ports when grinding this manifold than the first time on my ZJ, but practice makes perfect. I did open up the intake mount for the throttle body to 70mm. Oh yes, the dip stick cap for the 1990 power steering pump will not fit the required 1996-98 power steering pump. You need the later cap.
Here is the intake mounted with the HO fuel rail and new 1996 power steering pump. Now it gets “interesting”. The Renix fuel rail has the inlet line mounted near the firewall. Not so on the HO system. Solution-Back to “Pick a Part” for the complete fuel lines from the fuel tank to the fuel rail at the intake from a HO Cherokee. Note, this is not as bad as it might seem, as the fuel lines clip into the side of the main frame and snap out and in. Make sure there are no leaks with the new fuel lines!!! Good time to change fuel filter and old fuel lines at the tank.
The Renix throttle body has the sensors mounted to the front of the throttle body. Not so on the HO. Solution, extend the wires to the rear of the throttle body and modify the throttle position sensor-mounting bracket to allow it to mount and be controlled by the new throttle body. It IS NOT like the HO sensor, in that it also controls the transmission. The throttle cable must be replaced due to a different hook up from rear to front on the throttle body. If that was not bad enough…guess what? The transmission control cable for the Renix system will not fit on the HO system. It is 6” too short. Back to the junkyard for an HO transmission control cable. Drop the transmission pan, pull the original cable and reinstall the new.
We are having fun…Right?? One good thing, the previously installed 24# injectors for the stroker engine will interchange with the new manifold and fuel rail.
Dodge 4.7 Throttle Body Installation
I wanted to be absolutely sure that there would no longer be any intake restrictions, so merely going from 58mm (bored out Renix) to 60mm (HO- lip removed), by using the HO throttle body seemed risky…and, as it turns out-far too easy!!
Being impressionable and the excellent write up at http://126.96.36.199/forums/showthread.php?t=684664 on this subject, I decided to go for it with a Dodge 4.7 throttle body conversion. This, as stated in the write up, is MUCH Cheaper than buying a custom make after market throttle body.
Interestingly the Dodge 68mm throttle body (I reinforce the above story by stating that there is a 65mm and a 68mm version of this throttle body.) Go for the 68mm version.
One of the pictures in that excellent write up shows the adapter plate going to the rear with a bolt in it from the intake manifold. DO NOT DO THAT. That bolt is for the throttle cable-mounting bracket.
One “Small Problem”
I did find one “small item” that the article does not go into. The throttle linkage and transmission linkage WILL NOT CONNECT!!!!! The Dodge system uses the throttle body in the horizontal position (and a cam system for the throttle cable), verses vertical in our use. It is necessary to get a throttle arm from an HO throttle body and weld it to the arm of the Dodge system. The metal is so hard on the linkage, that drill and taping was not deemed practical. You also need to carefully use a Dremal tool to remove the throttle-mounting stud from one side of the arm to the other side, or it interferes with the Dodge linkage and you cannot reinstall the new arm or connect to the throttle cable.
Here you can see the HO linkage welded to the original Dodge throttle linkage. Also note the stud for the throttle linkage has been turned around and rewelded in place. Caution note here. I did not remove the butterfly shaft from the throttle body. This is risky due to possible high heat damaging the aluminum throttle body. Also DO NOT ground to the throttle body or damage to the body WILL result from current flowing through the various joints. You MUST ground to the work and cool the arm after every short weld!
Following this procedure, the modification worked well. You do need to grind off the original plastic cam assembly on the Dodge arm. I also found a lip at the bottom of the Throttle body bore, similar to the lip in the HO throttle bodies. I ground it away for the full 68mm.
Here is the installed Dodge 68mm throttle body with modified arm, relocated air temperature sensor, (Note the inlet air temperature sensor is now mounted in front.) modified TPS sensor, rerouted vacuum lines, and original IAC motor installed.
Wiring made to be moved around also. I did end up with a slight angularity on the transmission cable, but will modify the cable bracket later. It is very important that the original distance from the throttle body arm to the mounting bracket for the transmission cable is EXACTLY THE SAME or the transmission will not perform correctly. There are two different types of bracket for the throttle cable and transmission control cable. One for the later engines only has two mounting bolts and one has three for the earlier engines. You want the earlier with three bolts, as the distance to the throttle body is correct for the 1990 and 1993 cables.
The original cover for the Renix air cleaner mounts the outlet slightly farther to the front making installation of ducting for the intake difficult. Back to the junkyard for an HO air filter case cover, shown with a more rearward outlet. Note, you will also have to come up with a new elbow (Junk Yard) as SHORT in height as possible to get the air into the throttle body. You cannot use the stock intake hose, as the Dodge 4.7 throttle body is MUCH larger in diameter. I cut the HO intake hose to connect to the elbow I found for the throttle body. The hood clearance is very low, so make sure you keep the elbow short.
TIME TO START IT!
This vehicle is strong anyway with the stroker, but it is NOTICEABLY MUCH stronger now. Throttle response is MUCH better, to the point that is takes some getting used to.
The exhaust sound, as previously noted, is outstanding, without the interior resonance.
From a rolling start and “punching it” at like 10 MPH the tires are definitely having a problem with traction using 235x75 BFG All Terrains…unless I use 4-wheel drive…Ha Ha! I can live with that!