4.0 Intake / Exhaust Upgrade - JeepForum.com
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post #1 of 27 Old 01-03-2020, 01:28 PM Thread Starter
1996maroonzjf
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4.0 Intake / Exhaust Upgrade

I've decided to do a little pre-stroker upgrade to the intake / exhaust on my 4.0 since the stroker is probably a year out from being done (still only doing research and collecting parts) and I planned on doing these things for the stroker anyway.

So hopefully allowing the 4.0 to breathe a little easier will help a bit in the mountains when towing my camper. I'm not expecting a miracle, but anything will help especially in the higher RPM range. I usually have to run in the 3000 - 4000 RPM area to keep up with traffic on the steep sections of I-70.

Parts ordered / pulled from the JY -

-WJ Horseshoe intake manifold
-62 mm bored throttle body
-62 mm throttle body spacer
-Bosch 12 hole fuel injectors and EV1 adapters - Flow matched to 1%
-Insulation kit for under the manifold / fuel rail and injectors
-Doug Thorley Tri-Y header - on back order until the end of January.

I also have installed a 3” stainless Kolak exhaust, but retained a non-mandrel bent walker stock like replacement down tube to help add some back pressure before I install the stroker. I will be installing a custom mandrel bent down tube with the stoker.

I have done quite a bit of research on air filters / cold air set ups and decided to keep the stock air box because of the excellent filtration. Cold air intakes look pretty, but they just do not filter well. I use A/C Delco paper filters which test show filter the best and for the longest.

I would like to add a smooth intake tube from the air box to the throttle body. Has someone found one that fits? Or can point me to a resource where I can get one?

I also plan on adding insulation to the stock air box and intake tube.


-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #2 of 27 Old 01-04-2020, 10:03 AM
tetatdo
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Quote:
Originally Posted by 1996maroonzjf View Post
I've decided to do a little pre-stroker upgrade to the intake / exhaust on my 4.0 since the stroker is probably a year out from being done (still only doing research and collecting parts) and I planned on doing these things for the stroker anyway.

So hopefully allowing the 4.0 to breathe a little easier will help a bit in the mountains when towing my camper. I'm not expecting a miracle, but anything will help especially in the higher RPM range. I usually have to run in the 3000 - 4000 RPM area to keep up with traffic on the steep sections of I-70.

Parts ordered / pulled from the JY -

-WJ Horseshoe intake manifold
-62 mm bored throttle body
-62 mm throttle body spacer
-Bosch 12 hole fuel injectors and EV1 adapters - Flow matched to 1%
-Insulation kit for under the manifold / fuel rail and injectors
-Doug Thorley Tri-Y header - on back order until the end of January.

I also have installed a 3” stainless Kolak exhaust, but retained a non-mandrel bent walker stock like replacement down tube to help add some back pressure before I install the stroker. I will be installing a custom mandrel bent down tube with the stoker.

I have done quite a bit of research on air filters / cold air set ups and decided to keep the stock air box because of the excellent filtration. Cold air intakes look pretty, but they just do not filter well. I use A/C Delco paper filters which test show filter the best and for the longest.

I would like to add a smooth intake tube from the air box to the throttle body. Has someone found one that fits? Or can point me to a resource where I can get one?

I also plan on adding insulation to the stock air box and intake tube.
I have all these upgrades you are planning except the doug thorley header, I also have the K&N FIPK and the 2.5" kolak exhaust. They do help, but definitely dont expect any miracles. I would say that a tune on top of all that stuff helped the most. The 4.0, not having a knock sensor has quite a bit of safety margin built in. If you ran 91 and got a tune, you'll see a pretty noticeable difference.
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Tetatdo
94 ZJ 4.0L/NV242 WJ Manifold, 63mm TB, Kolak 2.5" Exhaust, 703 Injectors, SBEC-II Tune
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post #3 of 27 Old 01-06-2020, 08:54 AM
zjosh93
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Seems like a good plan.

Did you grab the power steering pump bracket with the manifold? Before I did the manifold swap on my 93 I looked at the options regarding the power steering pump and decided that converting to the later pump, bracket, and tensioner set up was the way to go. Much better tensioner system. Bolts right up to the new manifold. You will need to get the later model pump but it's fairly cheap and the hoses are the same. Not sure about the pulley, I think I reused my old one. If you do that swap the belt routing changes and the idler pulleys move. On some early ZJs there is a boss on the timing cover that will hit the belt. It's not used so you just have to grind or cut it off.

Some info from my swap here:
https://www.jeepforum.com/forum/f13/...ds-up-3077377/
https://www.jeepforum.com/forum/f13/...ution-1867410/
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post #4 of 27 Old 01-06-2020, 09:07 AM Thread Starter
1996maroonzjf
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Quote:
Originally Posted by zjosh93 View Post
Seems like a good plan.

Did you grab the power steering pump bracket with the manifold? Before I did the manifold swap on my 93 I looked at the options regarding the power steering pump and decided that converting to the later pump, bracket, and tensioner set up was the way to go. Much better tensioner system. Bolts right up to the new manifold. You will need to get the later model pump but it's fairly cheap and the hoses are the same. Not sure about the pulley, I think I reused my old one. If you do that swap the belt routing changes and the idler pulleys move. On some early ZJs there is a boss on the timing cover that will hit the belt. It's not used so you just have to grind or cut it off.

Some info from my swap here:
https://www.jeepforum.com/forum/f13/...ds-up-3077377/
https://www.jeepforum.com/forum/f13/...ution-1867410/
Thanks for the reply. Correct me if Iím wrong, but I believe my 96 already has the compatible pump, bracket, and tensioner. I compared the horseshoe intake to the log style on my spare engine / future stroker, and they both have the 3 holes for the PS pump in the exact same spot. I will post a side by side picture this evening.

Thatís for the links as well. I will dig into them when I have a minute.
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C65FB6D2-41A0-4626-9337-A8BB8E67B37E.jpg  

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #5 of 27 Old 01-06-2020, 09:45 AM
zjosh93
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Oh, yes, I think your stock setup is fine. I think I saw the 1994 in tetatdo's info and thought you had a 94.
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post #6 of 27 Old 01-06-2020, 11:16 AM Thread Starter
1996maroonzjf
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Does anyone have any input on retaining the stock air box? Is there really any added performance from a cone type filter? Enough to outweigh the sub par filtration?

Edit: I guess it should also be noted that I am often towing my camper at or above 10,000 feet of elevation at +/- 4000 RPM for extended periods. And often in dry dusty conditions.
Attached Thumbnails
EB2F88C1-39A9-46DB-A954-AD905223EB57.jpg  

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #7 of 27 Old 01-06-2020, 11:58 AM
MaintMech
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Ratmonkey (RIP) always said the stock airbox for the 4.0 was just fine for pretty much any stockish application. IMHO I agree with him.
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post #8 of 27 Old 01-11-2020, 08:51 PM Thread Starter
1996maroonzjf
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Quote:
Originally Posted by tetatdo View Post
I have all these upgrades you are planning except the doug thorley header, I also have the K&N FIPK and the 2.5" kolak exhaust. They do help, but definitely dont expect any miracles. I would say that a tune on top of all that stuff helped the most. The 4.0, not having a knock sensor has quite a bit of safety margin built in. If you ran 91 and got a tune, you'll see a pretty noticeable difference.
Thanks for the input. I will be getting a tune once I install the stroker.

Can you elaborate on how not having a knock sensor has quite a bit of safety margin built in? I would expect the opposite?

I run 85 octane gas (regular unleaded here) since I live at about 5,400 feet and drive up to over 11,000 feet regularly. I’ve never noticed any pinging but I’m debating trying a few tanks of 87 or 89 just to see what happens.

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #9 of 27 Old 01-12-2020, 02:16 AM
Timo_90xj
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If there was a knock sensor, engine could be built with higher CR and engine management could use more aggressive timing. Knock sensor detects engine knock/ ping, at which point it adjusts spark timing/ fuel management to prevent knocking. You could also use lower octane fuel without the fear of engine knock - with negative effect of slightly reduced power output.

Without a knock sensor, options are to build the engine with slightly lower CR, a must-use of higher octane fuel, or setup the engine management to have enough safe room on timing to prevent knock/ ping from happening.

HO 4.0s are built with a lowish CR and fairly conservative spark timing, as are 5.2 magnums. 5.9 ZJs and later Dodge 5.9s use fairly aggressive timing, which causes the need for premium fuel. There was the "death flash" for 87 octane fuel, but that pretty much killed the performance of the niner.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #10 of 27 Old 01-17-2020, 05:44 PM
tetatdo
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Timo_90xj nailed it.

The tuner put something like 8 degrees of total advance in my tune with 91 and the 4.0 took it like a champ. I've had 0 knocking issues and a noticeable increase in response.
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Tetatdo
94 ZJ 4.0L/NV242 WJ Manifold, 63mm TB, Kolak 2.5" Exhaust, 703 Injectors, SBEC-II Tune
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post #11 of 27 Old 06-03-2020, 05:43 PM Thread Starter
1996maroonzjf
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After a 6 month wait the Doug Thorley header has arrived.

I did a quick mock up on my spare 4.0 - much more to follow.
Attached Thumbnails
5BC6C804-729C-41E9-A64E-6B11C2D8CE67_1591227899674.jpg  
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-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #12 of 27 Old 06-03-2020, 08:45 PM
jeepjeepster
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wow, thats a beautiful sight there!

Wonder if those are prone to cracking like most 4.0 headers.

1994 ZJ-I6 w/270,000 mi
1998 ZJ 5.9 w/66,000 mi Slate Black
2004 KJ w/108,000 mi
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post #13 of 27 Old 06-04-2020, 09:58 AM Thread Starter
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Quote:
Originally Posted by jeepjeepster View Post
wow, thats a beautiful sight there!

Wonder if those are prone to cracking like most 4.0 headers.
Yes I agree. I did not get the header for the bling factor, but it does look nice.

Thorley claims that the use the thickest gauge stainless of any header manufacturer (14 ga.). It also has a super beefy 1/2” flange. Much thicker than any aftermarket manifold. I have yet to get a caliper on it, but on the test fit it was the same thickness as the intake manifold mounting ears and looked very stout.

From Thorleys site-

“We have also manufactured this header from T304 stainless steel so that we can offer you the highest quality header on the market, and cracked manifolds will never be an issue for you again. All of this 100% American made, and backed by our lifetime warranty!”

-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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post #14 of 27 Old 06-04-2020, 06:30 PM
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I'll be curious how they hold up. While not as thick, my brother has gibson headers that are ceramic coated 409 stainless. Lifetime warranty and he is on his second set. Cracked at the weld at the collector like all other 4.0 headers do. His are 16 gauge with 3/8" flange though. Not sure if thickness keeps the weld from cracking though.

Ive had the factory replacement manifold that has the accordion looking expansion piece in it. Been fine for over 15 years.

1994 ZJ-I6 w/270,000 mi
1998 ZJ 5.9 w/66,000 mi Slate Black
2004 KJ w/108,000 mi
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post #15 of 27 Old 06-04-2020, 07:15 PM Thread Starter
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Side by side comparison-
Attached Thumbnails
0A020034-164A-41B4-8E10-DD66F73B40D1.jpg   129A784F-C3CD-47BD-AD65-9633EB6016E3.jpg   873DB5EB-B843-45D8-A1A4-70ECC3D03F6E.jpg  
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-Tim
(2) '96 4.0s
#1-'10-'18
#2- HP30/Ford 8.8 - 4.56, OME HDs, 5100's, IRO Adj Arms/Track Bars
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