Camshaft Swap

[1lowryd]

need to rebuild my 89 4.0 comanche engine. want to get some more tourque too, are you guys swapping out stock camshafts? I want to keep everything stock with the computer and I'm not wanting anything crazy. just seenig what you guys are using

[Akula69]

Comp cams offers three different options. I decided to stay with the stock cam.

[tubpilot]

If you swap to a crankshaft from a 258 it turns the 4.0 to a 4.6 and the only other change is bigger injectors. It really won't add much to the total cost of an engine build, parts and machine work all the same, just injectors and a crank. You should be able to get a 258 from an AMC car for free or close. A friend built one for a Grand Cherokee and it performed like a 5.2 grand. You'll be quite happy with the engine.

[HOrnbrod]

If you swap to a crankshaft from a 258 it turns the 4.0 to a 4.6 and the only other change is bigger injectors. It really won't add much to the total cost of an engine build, parts and machine work all the same, just injectors and a crank. You should be able to get a 258 from an AMC car for free or close. A friend built one for a Grand Cherokee and it performed like a 5.2 grand. You'll be quite happy with the engine.

 

Hmm. So you just swap in a 4.2 crank into a 4.0 and automatically you have a 4.6L engine? What do you do about the increased stroke? Just add injectors?

[earl*t]

Say what?

[Geonovast]

Building a stroker involves A LOT to do it correctly, and it's not cheap. It's one of those "do it right or don't do it at all" things.

 

You should be fine just throwing in a mild cam with rebuilding the engine. Don't expect too much extra though, without adding other mods. But, if you do other mods down the road, the cam will already be in there.

[cruiser54]

Ain't worth the money on a stock motor.

[jpnjim]

The biggest problem with just machining a 258 crank & rods to use in a 4.0L,

especially with aftermarket (4.0L) pistons

is the pistons end up pretty far below the deck without decking the block.

 

Then you get a low compression engine that still needs mid grade fuel, or it will knock.

 

No sense getting custom taller compression distance pistons made,

if you are going to go to the trouble of ordering custom pistons,

might as well get them with a much shorter CD,

to work with the longer, stronger & lighter 4.0L rods.

 

^^^slippery slope, cheap stroker turns into expensive stroker fast.

 

Maybe someone has finally come up with good off the shelf pistons that work well with a stroker,

but last time I looked, the aftermarket 4.0L pistons all reduced CD slightly from stock (in anticipation of having to deck the stock block during the rebuild), and that's a step in the wrong direction for using the 258 crank & rods.

 

I haven't dealt with the engine management issues,

I'll leave that discussion for the guys who are on the Stroker Board,

and have been down that road 100 times already.

:)

[Alexia]

Lets get back on topic. He said CAMshaft, not CRANKshaft.

 

MOPAR sells several performance camshafts for various applications. The P4529229AC has slightly more lift than stock and pushes the top end just slightly.

 

Note, older revision part numbers in the scan. Just substitute AC for AB.

[jpnjim]

The problem with swapping cams in a Renix is they're already running a pretty big cam for the amount of head flow they have.

 

Proof of that is when Chrysler improved the intake head & exhaust in 91 they didn't touch the cam.

It was already more than enough to supply the new set up.

 

As a mater of fact, even with the high flow intake-head-exhaust they downsized the cam in 96' to better compliment the induction, and give back some low end torque.

 

That tells me that the Renix setup was the limiting factor, not the cam.

And once they got the improved HO ports,

they realised they still had too much cam, and backed it off.

 

So if your cam works best 2500-5500

and the intake-exhaust-head's sweet spot is 1800-4800,

the answer isn't a bigger cam :)

[mountainman]

Let me complicate things here for ya.... :yes:

 

http://www.angelfire.com/my/fan/Jeep4.0Camshafts.htm

 

http://www.hrracecar.com/tech_help/cams/AMC/_AMC.htm

 

It all depends on what you want from it. for sure the exhaust ports need work. They are the lowest flowing part of the equation. You can go as simple as some mild port work, a diff cam and header and cold air intake. And the factory ECU will prob JUST accept that. (20-25 hp gain MAX)

Or you can go all out and match up a bigger cam, increase the compression to match the cam, admit to yourself youll need to run 91 all the time, big head work with header and nice exhaust, a cold air,maybe a tad more injector, stand alone ECU and a new tune. The truck will certainly haul @$$ then... lol.

 

jpnjim did say it right though. The stock cam may be juuuust right. Look at what hesco offers... smaller in many ways. prob makes more torque all around. I have already stared at this for HOURS.

All i personally want to do is port the exhaust and pop in a cam on the stock motor and gain a tiny bit. I basically love the stock motor. With that i will say... I'm still not set on a cam yet. but my fav so far is.... erson's

E720111

[Stacks]

I did a rebuild on my '89 MJ 4.0 a year ago. .030 over bore and went with the CompCams 68-232-4 cam. There is a noticeable improvment in low end and pulls strong all the way to 5500. Running a cold air intake, 18" glasspack to dual stacks. I just received a set of the Clifford dual outlet headers and will take it to a muffler shop and get the pipes installed for true dual stacks. It runs very well but a little too lean so an adjustable MAP sensor will be added to richen it up a bit. Using the 21lb injectors from a '91-93 4.0. (#33007127) Mileage on the open road is 18-19 mpg running at 2700 in 4th. Even with 3.55's 5th isn't useable, vacuum is only 8-9" while in 4th it is 13-14". Hope that helps.

 

Larry

[HOrnbrod]

I did a rebuild on my '89 MJ 4.0 a year ago. .030 over bore and went with the CompCams 68-232-4 cam. There is a noticeable improvment in low end and pulls strong all the way to 5500. Running a cold air intake, 18" glasspack to dual stacks. I just received a set of the Clifford dual outlet headers and will take it to a muffler shop and get the pipes installed for true dual stacks. It runs very well but a little too lean so an adjustable MAP sensor will be added to richen it up a bit. Using the 21lb injectors from a '91-93 4.0. (#33007127) Mileage on the open road is 18-19 mpg running at 2700 in 4th. Even with 3.55's 5th isn't useable, vacuum is only 8-9" while in 4th it is 13-14". Hope that helps. Larry

 

Larry, I've found the adj. MAP is really only effective from 80% throttle opening to WOT when the ECU is in open loop mode. Below that the ECU will keep the A/F mixture right around stoichiometric (14.7 on the meter) no matter what voltage the MAP is sending to the ECU. I've verified this with my A/F meter and on the dyno. If it's running that lean I'd suggest larger injectors with an adjustable fuel pressure regulator to fine tune it across the entire power band. Especially with the Clifford headers.

[cz777]

wow on them bump sticks ! ok do me a flavor get 2 roller arm for a ford 300-L6 put them on no.1 and look at the lift of stock vs. this mod -its a bit more lift ..... its a low cost help

[Stacks]

Larry, I've found the adj. MAP is really only effective from 80% throttle opening to WOT when the ECU is in open loop mode. Below that the ECU will keep the A/F mixture right around stoichiometric (14.7 on the meter) no matter what voltage the MAP is sending to the ECU. I've verified this with my A/F meter and on the dyno. If it's running that lean I'd suggest larger injectors with an adjustable fuel pressure regulator to fine tune it across the entire power band. Especially with the Clifford headers.

 

Hornbrod... Thank you for that info!! On the suggestion of the adjustable regulator, would it HAVE to be one with a vacuum port? Also, perhaps a dumb question/comment, am I correct in my thinking that less vacuum to the stock regulator results in more pressure in the fuel rail? Could an adjustable fuel pressure regulator without a vacuum port be used? That could be a compromise though because you may need to set the static pressure higher than appropriate for idle/low load than for heavy/WOT. Was looking at other than a Hesco regulator. Not a fan of their's for some reason. ($$$$)

 

Thank you!

 

Larry

[HOrnbrod]

I've not used a non-vacuum FPR so really can't comment. Although I use a Hesco AFPR with good results, there are other aftermarket vendors that are cheaper, like here: http://www.strokedje.../regulator.html

 

Another cheaper option is to use a non-adjustable FPR that operates at a higher pressure than the stock 31/39 PSI, like the Chrysler #4418850, 5277829 or 5277864 regulators, called PR211 by aftermarketeers. These regulators will bump the pressure up to 40 idle and 48PSI at WOT and are a direct replacement on the HO fuel rail, if that's what you have. When/if my Hesco AFPR craps out, I will replace it with one of these fixed regulators since that's about the pressure I run now. And they only cost about $40 too. :yes:

[dasbulliwagen]

wow on them bump sticks ! ok do me a flavor get 2 roller arm for a ford 300-L6 put them on no.1 and look at the lift of stock vs. this mod -its a bit more lift ..... its a low cost help

 

I read about this before, it may have even been from you, but I'm waiting for someone to try this to see if it actually works. Adding higher ratio rockers was a common bolt on performance adder for the air cooled VW's I used to work on. I don't see whay it wouldnt work for these as well, but considering the airflow logic already posted, higher ratio rockers might not even make a difference, without other supporting flow improvements as well.

[cz777]

I read about this before, it may have even been from you, but I'm waiting for someone to try this to see if it actually works. Adding higher ratio rockers was a common bolt on performance adder for the air cooled VW's I used to work on. I don't see whay it wouldnt work for these as well, but considering the airflow logic already posted, higher ratio rockers might not even make a difference, without other supporting flow improvements as well.

my 2.5 and a friend's 4 liter have the 300 l-6 rocker arms so far no trouble ....on both run better than stock ....its not a race set up but volume efficiency is greater which helps out - a low lift cam with greater duration -this works great ...always remember will's law mod one thing ,the rest will must be moded too will is my old boss and friend who was in road racing years ago ,who knew old smokey ...

[dasbulliwagen]

Ill have to look into these then. Ive done a few mods already, this might just top those off. Ive gutted and sleeved the converter, added a Flowmaster 50 series muffler, "cold" air intake, electric fan mod. Rockers may just be just what I need for the next step before a full rebuild. Thanks.

[MJ_Milam]

Hmm. So you just swap in a 4.2 crank into a 4.0 and automatically you have a 4.6L engine? What do you do about the increased stroke? Just add injectors?

 

you have to use ford 24lbs injectors and adjustable fuel pressure regulator. there's a lot other things you have to do but that covers the fuel management issues

[HOrnbrod]

you have to use ford 24lbs injectors and adjustable fuel pressure regulator. there's a lot other things you have to do but that covers the fuel management issues

 

No, you don't have to use Ford 24# injectors. Unless you want to waste fuel w/o tuning first.