4.0L build advice
Posted: March 6th, 2016, 3:32 pm
Hello all, I need some help with my engine build plans. 2000 TJ 4.0L 5-speed. 175k miles. Original 0331 head, thankfully not cracked yet. First let me say I do not plan to stroke it. I'm asking here though because this community seems to have the most knowledge about internal engine work. Here's what I'm trying to accomplish:
1. Increase overall efficiency and durability
2. Increase low- to mid-range power and torque (I don't want to move power higher up the rpm range)
3. Prepare for future supercharger install
Here's what I'm looking at so far. I've purchased a used 0331 TUPY head (has valves and springs, but no rockers). As I said my factory head has not cracked yet, but since I plan to eventually S/C it, I wanted to swap it for the improved head before I do. Having the extra head also gives me time to port/polish and do any other machine work I want before swapping it in. Since I have to buy rockers for it (I don't plan on re-using the 175k mile ones from my stock head), I was planning to put roller rockers in it (more considerations on that idea later). I will also probably buy new pushrods at a minimum. I also bought an extra horseshoe-style manifold, so I can do port matching work to it before it goes into the Jeep. My Jeep has the 2-piece exhaust manifolds but no pre-cats. Right now I'm looking at a Pacesetter 70-1129 header (says its for '99 or before, but since I don't have pre-cats it should work fine for me).
I also have an Eaton gen 3 M90 supercharger off of a GM L67 3.8L V6, as well as the fuel injectors from a supercharged 3.8 and a Unichip piggyback controller. My plan is to build a custom setup similar to the Avenger (with the blower mounted directly to the manifold). My goal is to produce only a few pounds of boost. I'm not building a drag racer, I really want to gain just a bit more power when I need it, and overcome the affects of altitude (currently live in Colorado and driving in the mountains takes its toll).
So, my goal is to increase airflow through the head, first to maximize power and efficiency of the 4.0L at stock displacement. And secondly to increase airflow and durability to stand up to the eventual S/C install. I was originally just going to port/polish and buy a set of roller rockers. However, after much research here are some of the factors that I am now considering:
1. Porting/polising:
(a) I understand that you don't want to do a full "port match" or "gasket match" on the head. It is OK to have a "step" to a larger diameter on the downstream side of the flow, and a step in the exhaust can help reduce reversion. Just remove casting flaws on the intake, and mirror polish the chamber and exhaust ports.
(b) The exhaust ports on the 0331 head are intentionally smaller than previous heads, which increases exhaust velocity. Also the raised floor is a more efficient design. Some places claim that higher exhaust velocity is better for low-end torque. Dino's site claims the smaller ports were intended to warm up the pre-cats faster.
(c) Since I don't have the pre-cats and want to improve airflow, should I open up the exhaust ports a bit? Or would that actually hurt low-end torque?
2. Valves
(a) I'm considering putting in a nice set of stainless valves, to increase durability with the future forced induction.
(b) Since I should take the used head to a shop to be checked anyway, I'm also considering having a multi-angle valve job done to improve flow.
(c) If I'm buying valves and paying for a valve job, that opens up the possibility of putting in larger valves at the same time (more on this option later).
3. Rockers
(a) I was planning on buying a set of roller rockers. However, I don't need adjustable ones, and reading the post in the FAQ makes me think now I won't actually see much benefit from them. And I'm worried about durability with aluminum rockers, particularly if I go with higher lift or see higher chamber pressure after the supercharger install
(b) I may go with rollers for a 1.7 ratio rocker (more on that later)
(c) I like the idea of the Crower steel rollers, however I understand that will require machining. If I stay with 1.6 ratio I'm considering the Hesco high performance stamped ones
4. Cam
(a) I wasn't planning on replacing the cam. However, at 175k miles I think it may be good to replace it anyway. And after some research, I'm thinking a different cam might be needed, both for my N/A plans and to get the most out of F/I.
(b) I like the idea of a roller cam, with the lower friction and faster ramp rates. I was considering dropping the $1200 on 505's least aggressive cam kit, until I started reading on here about the quality and longevity issues.
(c) I've also been reading that for a S/C, you want a cam with shorter intake, longer exhaust, and less overlap.
5. Compression ratio
(a) I don't want to increase compression ratio. I know some F/I setups actually use a lower SCR than their N/A counterparts. However, since I only plan to run a few pounds of boost, and I don't want to lower power before I get the S/C installed, I plan to keep the ratio the same.
6. Timing chain
(a) I was looking at replacing my timing chain (175k miles on my stock one). I wanted to go with a double roller setup, but I understand that my '00 cam won't work with them, unless I replace the cam.
(b) I read a few threads on here that seemed to suggest the OEM chain setup was just as good as a double roller?
Right now I'm trying to decide what the best course is to increase performance for a N/A and later F/I 4.0:
Option A (mostly stock valvetrain)
-stock cam (If I keep my stock cam, would it be a good idea to at least put in new lifters?)
-stock size stainless valves with multi-angle valve job
-1.6 rockers (stock or roller)
Option B (more lift)
-Stock size stainless valves with multi-angle valve job
-Stock cam
-1.7 rockers (roller required)
-New valve springs required?
Option C (larger valves)
-Larger stainless valves (valve job required)
-Stock cam
-1.6 rockers (stock or roller)
-Stock springs? (upgrade better?)
Option D (more lift and duration)
-New cam
-Stock size stainless valves with multi-angle valve job
-1.6 rockers (stock or roller)
Or some combination of the above? Without the increased displacement of a stroker I don't think I need the combined effects of a cam, larger valves, and 1.7 rockers. But what is the most efficient way to get more air through a 4.0 both N/A and F/I? Are there other factors I'm not considering.
Thanks in advance for your input.
1. Increase overall efficiency and durability
2. Increase low- to mid-range power and torque (I don't want to move power higher up the rpm range)
3. Prepare for future supercharger install
Here's what I'm looking at so far. I've purchased a used 0331 TUPY head (has valves and springs, but no rockers). As I said my factory head has not cracked yet, but since I plan to eventually S/C it, I wanted to swap it for the improved head before I do. Having the extra head also gives me time to port/polish and do any other machine work I want before swapping it in. Since I have to buy rockers for it (I don't plan on re-using the 175k mile ones from my stock head), I was planning to put roller rockers in it (more considerations on that idea later). I will also probably buy new pushrods at a minimum. I also bought an extra horseshoe-style manifold, so I can do port matching work to it before it goes into the Jeep. My Jeep has the 2-piece exhaust manifolds but no pre-cats. Right now I'm looking at a Pacesetter 70-1129 header (says its for '99 or before, but since I don't have pre-cats it should work fine for me).
I also have an Eaton gen 3 M90 supercharger off of a GM L67 3.8L V6, as well as the fuel injectors from a supercharged 3.8 and a Unichip piggyback controller. My plan is to build a custom setup similar to the Avenger (with the blower mounted directly to the manifold). My goal is to produce only a few pounds of boost. I'm not building a drag racer, I really want to gain just a bit more power when I need it, and overcome the affects of altitude (currently live in Colorado and driving in the mountains takes its toll).
So, my goal is to increase airflow through the head, first to maximize power and efficiency of the 4.0L at stock displacement. And secondly to increase airflow and durability to stand up to the eventual S/C install. I was originally just going to port/polish and buy a set of roller rockers. However, after much research here are some of the factors that I am now considering:
1. Porting/polising:
(a) I understand that you don't want to do a full "port match" or "gasket match" on the head. It is OK to have a "step" to a larger diameter on the downstream side of the flow, and a step in the exhaust can help reduce reversion. Just remove casting flaws on the intake, and mirror polish the chamber and exhaust ports.
(b) The exhaust ports on the 0331 head are intentionally smaller than previous heads, which increases exhaust velocity. Also the raised floor is a more efficient design. Some places claim that higher exhaust velocity is better for low-end torque. Dino's site claims the smaller ports were intended to warm up the pre-cats faster.
(c) Since I don't have the pre-cats and want to improve airflow, should I open up the exhaust ports a bit? Or would that actually hurt low-end torque?
2. Valves
(a) I'm considering putting in a nice set of stainless valves, to increase durability with the future forced induction.
(b) Since I should take the used head to a shop to be checked anyway, I'm also considering having a multi-angle valve job done to improve flow.
(c) If I'm buying valves and paying for a valve job, that opens up the possibility of putting in larger valves at the same time (more on this option later).
3. Rockers
(a) I was planning on buying a set of roller rockers. However, I don't need adjustable ones, and reading the post in the FAQ makes me think now I won't actually see much benefit from them. And I'm worried about durability with aluminum rockers, particularly if I go with higher lift or see higher chamber pressure after the supercharger install
(b) I may go with rollers for a 1.7 ratio rocker (more on that later)
(c) I like the idea of the Crower steel rollers, however I understand that will require machining. If I stay with 1.6 ratio I'm considering the Hesco high performance stamped ones
4. Cam
(a) I wasn't planning on replacing the cam. However, at 175k miles I think it may be good to replace it anyway. And after some research, I'm thinking a different cam might be needed, both for my N/A plans and to get the most out of F/I.
(b) I like the idea of a roller cam, with the lower friction and faster ramp rates. I was considering dropping the $1200 on 505's least aggressive cam kit, until I started reading on here about the quality and longevity issues.
(c) I've also been reading that for a S/C, you want a cam with shorter intake, longer exhaust, and less overlap.
5. Compression ratio
(a) I don't want to increase compression ratio. I know some F/I setups actually use a lower SCR than their N/A counterparts. However, since I only plan to run a few pounds of boost, and I don't want to lower power before I get the S/C installed, I plan to keep the ratio the same.
6. Timing chain
(a) I was looking at replacing my timing chain (175k miles on my stock one). I wanted to go with a double roller setup, but I understand that my '00 cam won't work with them, unless I replace the cam.
(b) I read a few threads on here that seemed to suggest the OEM chain setup was just as good as a double roller?
Right now I'm trying to decide what the best course is to increase performance for a N/A and later F/I 4.0:
Option A (mostly stock valvetrain)
-stock cam (If I keep my stock cam, would it be a good idea to at least put in new lifters?)
-stock size stainless valves with multi-angle valve job
-1.6 rockers (stock or roller)
Option B (more lift)
-Stock size stainless valves with multi-angle valve job
-Stock cam
-1.7 rockers (roller required)
-New valve springs required?
Option C (larger valves)
-Larger stainless valves (valve job required)
-Stock cam
-1.6 rockers (stock or roller)
-Stock springs? (upgrade better?)
Option D (more lift and duration)
-New cam
-Stock size stainless valves with multi-angle valve job
-1.6 rockers (stock or roller)
Or some combination of the above? Without the increased displacement of a stroker I don't think I need the combined effects of a cam, larger valves, and 1.7 rockers. But what is the most efficient way to get more air through a 4.0 both N/A and F/I? Are there other factors I'm not considering.
Thanks in advance for your input.