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Renix To Ho Head Swap.


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I have a '87 MJ with the 4.0 .  Recently, I have been losing coolant and gaining in crankcase volume.

Guess I'm looking at replacing a head gasket.  I also have a 4.0, HO head residing in my garage.  Would 

there be any advantage to be gained by swapping the in the HO head?

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Better flow.  The Renix head intake ports sit lower than the HO heads.  You can reuse your Renix intake manifold, but I can't remember if you have to use the Renix manifold gasket or the HO gasket... Just wait a bit, Cruiser will be see this thread and share his vast knowledge on the subject. :bowdown:

 

Also, you could change over to the HO intake manifold while you're at it, get the best flow possible.

 

Edit: I just noticed you're in North Carolina.  Where in NC?

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I would use the Google search......something in my memory says the openings for the water jacket are different.....seem to remember an article about somebody putting foam peanuts in them and plugging them with JB weld?

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I would use the Google search......something in my memory says the openings for the water jacket are different.....seem to remember an article about somebody putting foam peanuts in them and plugging them with JB weld?

Nah. That sounds like when you use a 4.0 head on a 258.......

 

If not, I've screwed up on a fair number of HO head to Renix block swaps.

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cruiser...you mean there are people that don't have Dremel's???

 

onlyinajeep.... Ever heard of Cove City?  Halfway between New Bern and Kinston on US 70.  About 45 minutes from the ocean.

Actually I don't have one. I have an air powered version.

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cruiser...you mean there are people that don't have Dremel's???

 

onlyinajeep.... Ever heard of Cove City?  Halfway between New Bern and Kinston on US 70.  About 45 minutes from the ocean.

Actually I don't have one. I have an air powered version.

 

I have those too.  Straight and right angle.  I just use the Dremels for tight spots.

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There was a big discussion on the strokers board about the swap some time ago. Some folks thought they got 75 HP boost from the swap, then they were unhappy when it didn't happen. All the magic in the HO system isn't in the head, you see. Alone it is worth about 15 HP. Add the better flowing intake for a bit more (especially the '01 up) but the big kick is the HO injectors. Right about here is when the ping monster rears it's head. Mopar dealt with that by retarding the cam and cutting back on the engine timing curve so they could do away with the EGR valve.

 

If you are expecting massive power increase, unless you do pretty much the whole swap, it will be somewhat disappointing.

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There was a big discussion on the strokers board about the swap some time ago. Some folks thought they got 75 HP boost from the swap, then they were unhappy when it didn't happen. All the magic in the HO system isn't in the head, you see. Alone it is worth about 15 HP. Add the better flowing intake for a bit more (especially the '01 up) but the big kick is the HO injectors. Right about here is when the ping monster rears it's head. Mopar dealt with that by retarding the cam and cutting back on the engine timing curve so they could do away with the EGR valve.

 

If you are expecting massive power increase, unless you do pretty much the whole swap, it will be somewhat disappointing.

Really? 15 horsepower? Then why is a 90 Renix 182 horsepower and a 91 HO  190?

 

8 HP difference total, all at the upper revs.

 

HO had a better exhaust manifold and a 58 mm throttle body versus the Renix 52mm body. That was a good portion of the 8 frickin horsepower!!!

 

You wonder why I' get angry with you? It's because I spend my valuable time correcting your shoot from the hip bull$#!&.

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WTF dude? I said you will NOT get a big boost out of the HO head swap. Not shooting from the hip as solidly proven below, but I should have said "Max increase 15 HP". 173 or 177 HP to 190 is 17 to 13 HP increase and I was saying it's NOT all in the head. The HO injectors are bigger and give more kick in the pants in the Renix setup than swapping the head does, but fuel economy goes in the crapper.


    The HO spark curve was cut down which cut the NOx produced. Less advance = less ping. By retarding the cam they don't fill the cylinders quite as efficiently and the power band is moved higher because of the timing change. Other companies did that in the early 70s to cut emissions as well.


 


The 1987 RENIX 4.0 made 173 hp (129 kW; 175 PS) and 220 lb·ft (300 N·m). In 1988, the 4.0 received higher flowing fuel injectors, raising output to 177 hp (132 kW; 179 PS) and 224 lb·ft (304 N·m)—more power than some configurations of theFord 302Chevrolet 305, and Chrysler 318 8-cylinder engines, and more than any of the Japanese 6-cylinder truck engines, but with comparable or superior fuel economy.[21]


In 1991, a Chrysler fuel injection system replaced the RENIX system, and the intake ports were raised approximately .125 in (3.2 mm) for a better entry radius. Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for more efficiency, and the fuel injectors were replaced with higher flow units. Camshaft timing was also changed. The net result was an engine that made 190 hp (142 kW; 193 PS) and 225 lb·ft (305 N·m). Badging on most Jeeps equipped with this engine read "4.0 Litre HIGH OUTPUT." The new cam profile combined with altered computer programming eliminated the need for an EGR valve and knock sensor, but made the engine more sensitive to alterations, especially where emissions are concerned.[citation needed]



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Wrong again.

 

The HO injectors work very well in the Renix. Mileage is fine. I've done it more than once. The ECU controls the flow quite nicely. The flow rate on the injectors is about the same. Where do you come up with this stuff? 

 

Wikipedia is wrong about the horsepower numbers. They left out 89 and 90 which were 182.

I worked at the dealership back then as Service Manager. 1980 til 1992. 

 

Wiki is wrong again. The HO used the SAME cam as the renix through at least 1995.

Stock Cam Specs

The stock '87-'95 Jeep 4.0 camshaft is a single pattern cam with the following specs:

Advertised duration int./exh.: 270.0/270.0 deg
Duration @ 0.050" lift int./exh.: 197.0/197.0 deg
Valve lift int./exh.: 0.424"/0.424"
Lobe separation angle: 112 deg
Intake centerline angle: 110.5 deg
Valve overlap: 46 deg
IVO: 12 deg ATDC (0.050" lift)
IVC: 29 deg ABDC
EVO: 32 deg BBDC
EVC: 15 deg BTDC

Same profile. POSSIBLY different cam timing but I'm not 100% on tht. If they use the same cam and crank gears, I would assume no. 

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Wikipedia is wrong about the horsepower numbers. They left out 89 and 90 which were 182.

 

Cruiser, does this have anything to do with the elimination of that pesky C101 connector?  My curious mind wishes to know. :)

 

Not really. The 89 and 90s had a more agressive fuel and timing curve programmed into them. That said, eliminating the C101 is NEVER a bad idea!!

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