h/o block and head on 87 xj but keep my accecories???please help
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Junior Member
Joined: Mar 2010
Posts: 69
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From: redwood city/ modesto
Model: Cherokee
Engine: 4.0
Because it's different depending on what year HO you get.
Forget anything later than 2000.
Use your Renix flywheel/flexplate, distributor, intake and exhaust manifolds, valve cover and all sensors. There is a place on the HO block for the knock sensor,most times already threaded.
Remove the furthest forward threaded block plug on the HO so you can screw your Coolant Temp SENSOR into the HO block before installation. It's a 5/16" square drive.
Be sure to use the intake/exhaust gasket for the Renix motor.
Some later HO motors do not have the provision in the back of the head for the temp SENDING unit. If that's the case, use the HO thermostat housing, put your sender in the threaded hole and extend the wiring up to it.
How's that? Maybe a mod will make it a sticky?
Forget anything later than 2000.
Use your Renix flywheel/flexplate, distributor, intake and exhaust manifolds, valve cover and all sensors. There is a place on the HO block for the knock sensor,most times already threaded.
Remove the furthest forward threaded block plug on the HO so you can screw your Coolant Temp SENSOR into the HO block before installation. It's a 5/16" square drive.
Be sure to use the intake/exhaust gasket for the Renix motor.
Some later HO motors do not have the provision in the back of the head for the temp SENDING unit. If that's the case, use the HO thermostat housing, put your sender in the threaded hole and extend the wiring up to it.
How's that? Maybe a mod will make it a sticky?
dam thanks bro
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Joined: Aug 2011
Posts: 43,971
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I've done 2 of these and match ported the head and manifolds. Both run very well.
Keep this in mind also. The HO isn't magic by any means when compared to the Renix. It was a great marketing ploy by Chrysler in 1991 and it's still working!!
1987 the 4.0 had 173 HP.
1988 the 4.0 had 177 HP.
1989 and 1990 the HO had 182 HP
These figures changed from year to year because the ECU had changes made to it. Nothing else. Grab an ECU out of an 89 or 90 Renix XJ or MJ and feel the difference. The last three numbers of the ECU are 428.
1991 the HO has 190 HP.
Therefore the net gain from the most powerful Renix to HO is 8 HP and it's all in the higher RPM ranges. Torque is the same between the two.
What really made the HP gain in 1991? Cam? Nope, it's the same.
Two things made the HP increase. The exhaust manifold was improved and made more free flowing.
The throttle body size was increased from 52MM to 58MM.
The bore of the intake manifold on a Renix is 60MM, even though they only used a 52MM throttle body.
Get a 60MM bored throttle body with a correspondingly larger butterfly from www.strokedjeep.com for $90 exchange and you're up there in HO HP territory. Add an exhaust mod or two and you can go beyond that.
CF Veteran
Joined: Sep 2010
Posts: 21,168
Likes: 5
From: Milwaukee, WI
Year: 1987
Engine: Check
Just do what I posted earlier for the conversion, being sure to use the Renix intake/exhaust gasket.
I've done 2 of these and match ported the head and manifolds. Both run very well.
Keep this in mind also. The HO isn't magic by any means when compared to the Renix in the higher RPM ranges. Torque is the same between the two.
What really made the HP gain in 1991? Cam? Nope, it's the same.
Two things made the HP increase. The exhaust manifold was improved and made more free flowing.
The throttle body size was increased from 52MM to 58MM.
The bore of the intake manifold on a Renix is 60MM, even though they only used a 52MM throttle body.
Get a 60MM bored throttle body with a correspondingly larger butterfly from www.strokedjeep.com for $90 exchange and you're up there in HO HP territory. Add an exhaust mod or two and you can go beyond that.
I've done 2 of these and match ported the head and manifolds. Both run very well.
Keep this in mind also. The HO isn't magic by any means when compared to the Renix in the higher RPM ranges. Torque is the same between the two.
What really made the HP gain in 1991? Cam? Nope, it's the same.
Two things made the HP increase. The exhaust manifold was improved and made more free flowing.
The throttle body size was increased from 52MM to 58MM.
The bore of the intake manifold on a Renix is 60MM, even though they only used a 52MM throttle body.
Get a 60MM bored throttle body with a correspondingly larger butterfly from www.strokedjeep.com for $90 exchange and you're up there in HO HP territory. Add an exhaust mod or two and you can go beyond that.
I really just want to open up the flow as much as possible. I just want to see what I can do with the 4.0.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
One thing that can be done easily is to eliminate the "crush" area in the downpipe right after the exhaust manifold. It's probably restricted about 30%.
This can be done by any good muffler shop. Your original Renix exhaust manifold comes straight dwon and the makes a 90* bend to the rear. It's very close to the front driveshaft. Have the shop make you one without the "crush" using two 45* bends so it will clear the driveshaft. You will feel the difference in the old butt dyno.
This can be done by any good muffler shop. Your original Renix exhaust manifold comes straight dwon and the makes a 90* bend to the rear. It's very close to the front driveshaft. Have the shop make you one without the "crush" using two 45* bends so it will clear the driveshaft. You will feel the difference in the old butt dyno.
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