4.5 -4.6- 4.7 STROKER MOTORS

[SUPER_NOVA_71]

If I was looking to purchase a Cherokee. What year would be the "stroker friendly" year. Meaning which would be the easiest to adapt the stroker too. I talking about all the electronic stuff, computer, injectors, sensors. you know what i mean.

Aaron

 

[5-90]

That's sort of a "wide open" question, isn't it?

Considering strokers are going to based upon the OEMR AMC242 (4.0L) block using, probably, AMC258 (4.2L) crankshaft and rods, anything you can wedge the 4.0 into you can wedge the stroker into. As I recall, the difference between the three displacements you're listing is simply how far the cylinders are bored over, if at all.

Sensors and electronics don't really change - you just need to "upsize" the fuel injectors a bit to accommodate the greater displacement. OEMR units are 19#/hour, and I typically hear of people going to 21#/hr-23#/hr units, depending upon final displacement (I've probably got the optimax for everything worked out somewhere, but it's not handy. I'll either have to find that notebook or just break down and DO it again...)

Strokers have been done in every year of XJ that featured the 4.0 (1987-2001,) pretty much all years of ZJ/WJ, most TJ/YJ years, and even AMC/Eagle wagons! The control system really doesn't change - neither do the sensors, if the engine is still NA (if you supercharge/turbocharge, you'll want to think about installing a 2-bar or 3-bar MAP sensor at least, and probably a charge air cooler if you go past about 1/3 to 1/2 ATM of boost.)

Having read all of that, can you nail down your question a little better? It's not that we don't want to help, but your question was really a little vague, and it's difficult to give a better answer to the question as posed...

5-90

 

[XJJack]

If you go with the later model, 96+ You don't have to worry about the adjustable MAP sesor that I hear some people have to play with.

 

[Blue XJ]

91 - 95 heads flow the best, and the 97? and up blocks have the bearing cap girdles. I would go with a higher flowing head.

 

[SCW]

If you go with a RENIX (90 and older) you get a knock sensor and won't have as much pinging problems with lower octane gas (I've read, don't know for myself)

 

[CRASH]

If you go with a RENIX (90 and older) you get a knock sensor and won't have as much pinging problems with lower octane gas (I've read, don't know for myself)

Exactly. I think the best stroker combo around is a 87-90 Renix control system with a 91-95 head and a 99+ intake manifold. the knock sensor makes my 9.5 to 1 stroker work well with 87 octane.

 

[Cjmartz2k]

If you go with the later model, 96+ You don't have to worry about the adjustable MAP sesor that I hear some people have to play with.

How do you figure? I've got an adjustable MAP sensor on my '98 TJ and it works just fine.

 

[Dr. Dyno]

If I was looking to purchase a Cherokee. What year would be the "stroker friendly" year. Meaning which would be the easiest to adapt the stroker too. I talking about all the electronic stuff, computer, injectors, sensors. you know what i mean.

Aaron

The stock computer will work fine on any year of XJ with a stroker. Depending on the stroker specs, most will need at least 10% larger injectors and some may need 20% larger injectors than stock.
Sensors remain unchanged except for the MAP sensor which might need a MAP sensor voltage adjuster (or MAP adjuster) to alter the injector duty cycle and fine tune the air/fuel mixture.
Probably the best years of 4.0 engine that you could use to build a stroker are the '96-'99.5 versions in the XJ. They have stiffer blocks with a main bearing cap brace and the 0630 head casting which is as good as the '91-'95 7120 casting in terms of flow. You could swap the newer curved runner intake manifold from a '99+ WJ or '99.5+ XJ/TJ to gain a little more torque at lower rpm.
The Renix engine controller from the '87-'90 models has a knock sensor that retards timing when it detects pinging and this allows a stroker with ~9.5:1 CR to run on 87 octane, but the penalty is reduced performance if you run this grade of fuel.

 

[Grifter144]

sweet...the info stated here really makes me happy....seeing as i have a complete 94 4.0 liter in the garage..one set of 258 crank and rods(year unknown), and the currently running but knocking 2000 4.0 that powers my xj at the moment...

in my effort to keep it cheap i am unclear on a couple things...

1)do i need to buy a new camshaft? all of the buildups i have read suggest it...is it necessary..
2) new pistons or can i just reuse the ones currently in the xj just on top of the 258 rods.

Grifter

hmm motor internal stupid am i...

 

[SUPER_NOVA_71]

Thanks guys, You have answered all my questions.
I guess i was worried about the adjustable map sensor- and the knock sensor.

Thanks all!!
Aaron

 

[Cjmartz2k]

Just to be clear, "having to worry" about an adjustable MAP sensor has nothing to do with what year you have. Either your A/F ratio is already correct, or it's off, and you need to get a MAP adjuster or something else to tweek the fuel to get the A/F ratio right. With bigger injectors and a lot more hp, I'm betting it will be off, but you'll have to get it on a dyno or use a wideband 02 after the install and see. Having the knock sensor is a good thing also--I wish my HO setup had one.

 

[SUPER_NOVA_71]

OK, I can get a 1990 Cherokee
91 to 95 head
99+ intake

Has anyone put larger valves in the head (intake)

Has anyone had a custom cam ground?

 

[CRASH]

OK, I can get a 1990 Cherokee
91 to 95 head
99+ intake

Has anyone put larger valves in the head (intake)

Has anyone had a custom cam ground?

1. Good start. You can plug the knock sensor into a late model block, so the stiffer block and main girdle is desirable.

2. Yes, Hesco, Accurate Performance (no longer in bus.)

3. Why? Tons of cams available, just find the one that fits your needs.

 

[SUPER_NOVA_71]

1. Good start. You can plug the knock sensor into a late model block, so the stiffer block and main girdle is desirable.

2. Yes, Hesco, Accurate Performance (no longer in bus.)

3. Why? Tons of cams available, just find the one that fits your needs.

On the custom cam:

In one of the posts above they mentioned the knock sensor, and knocking with 87 gas ans 9.5:1 compression. I know plenty of chevy small block and big blocks that run on 87 gas with 10:1 compression. I know that timming is and issue, but what about duration and cam center line, oh ya and match that to the flow numbers of the head. Just a thought.
Any one have any flow numbers on the 4.0 heads?

Aaron

 

[5-90]

On the custom cam:

In one of the posts above they mentioned the knock sensor, and knocking with 87 gas ans 9.5:1 compression. I know plenty of chevy small block and big blocks that run on 87 gas with 10:1 compression. I know that timming is and issue, but what about duration and cam center line, oh ya and match that to the flow numbers of the head. Just a thought.
Any one have any flow numbers on the 4.0 heads?

Aaron

There are actually a couple compression issues that will govern the use of "pump gas" (which is typically taken as 90 octane or less.)

"Compression Ratio" isn't as important as everyone thinks it is - since it's a "static" number and doesn't take into account a critical variable - the time the intake valve closes.

"Effective" or "Dynamic" Compression Ratio is a larger issue - and that is governed by when the intake valve closes and compression actually begins. Since the intake valve typically closes after BDC, DCR will be lower than CR - but has a much greater effect on what fuel you need. CR will not change without changing damn near ALL engine components, while DCR will change if you change the camshaft, or "degree" it to have it advanced or retarded.

"Quench" refers to the distance between the piston deck and cylinder head surface at TDC, and it is generally considered that .040"-.060" is "ideal." This reduced clearance causes an "eversion" of the compressed air/fuel charge, which gets it away from any "hot spots" that remain in the cylinder from the last firing event. This has a cooling effect on the engine internals (not significant enough to show a change in operating temperature, but it will help prevent preignition and detonation!) and usually results in smoother advancement of the flame front. Proper "quench" clearance can actually REDUCE the octane normally required by a compression ratio by a step, if you've got everything else dialled in. As I recall, our pistons and heads are designed to be "quench-compliant," so you'll just need to watch clearances as you assemble (and, hopefully, check them.)

I'll have to look up the formulae needed to determine "head milling to increase compression" and for figuring DCR, since I don't have them to hand. They can also be found online with a little Googling, or can be found in automotive performance books as well.

5-90

 

[CRASH]

You really need to consider quench height to control detonation as well. If you are in the 9.4/5/6 compression, a good quench height can put you in the 87 octane range, whereas if it's screwy, you'd be solidly into 91 octane.

Edit, Jon beat me by seconds!

 

[5-90]

You really need to consider quench height to control detonation as well. If you are in the 9.4/5/6 compression, a good quench height can put you in the 87 octane range, whereas if it's screwy, you'd be solidly into 91 octane.

Edit, Jon beat me by seconds!

:laugh3: :twak:

It's taken me 22 years or so to learn to type - since that's offset by my tendency to give explanations to my answers, I'm mildly surprised I managed to beat you out at all...

Oh - there are sections in my book (this is for everyone else...) that cover engine math, camshaft specifications, and even flow data on OEM cylinder heads! CRASH, you've seen it - up at JT's...

5-90

 

[Dr. Dyno]

sweet...the info stated here really makes me happy....seeing as i have a complete 94 4.0 liter in the garage..one set of 258 crank and rods(year unknown), and the currently running but knocking 2000 4.0 that powers my xj at the moment...

in my effort to keep it cheap i am unclear on a couple things...

1)do i need to buy a new camshaft? all of the buildups i have read suggest it...is it necessary..
2) new pistons or can i just reuse the ones currently in the xj just on top of the 258 rods.

Grifter

hmm motor internal stupid am i...

If it's the '94 engine that you're going to rebuild into a stroker, the cylinders will most likely have a very small amount of taper and be a fraction out of round. After you've torn it down, take the block to a machine shop and ask them to measure the cylinder bores. They can advise whether it's worth reusing the stock pistons with a cylinder rehone.
You don't HAVE to buy a new camshaft but since the object of building a stroker is to get as much HP/TQ as possible out of it, it makes a lot more sense to add a performance cam as well.
Here's my stroker combo:

http://www.angelfire.com/my/fan/stroker.html

To let the engine breathe as well as possible and get the most out of it, ancillary performance mods like the ones that I've done become necessary.

 

[Grifter144]

Dr. dyno..thanks for the response...i know this sounds screwy, but at the moment i am considering taking the 94 apart(to figure out whats wrong with it, it was a freebie) and if possible doing a cheap rebuild on it as i would rather build the stroker out of the 00' block, this would allow me to hopefully temporarily eliminate the current knocking 00' 4.0 liter with the older motor and then use the stiffer 00' block for the base of my stroker build...however that obviously will cost extra cash, and in staying with the cheap i will probably stroke the 94 and just use the 00's head and intake...until i can get the 94 head ported and the 94 throttle body bored out...all money dep. of course...thanks for the input...i already run a beefed up 2.5 inch flowmaster catless exhaust, less the header option....which i hope to change soon..as well as a freeflow k/n intake on a rustys air tube...so she breathes pretty well....

as usual i am open to thoughts and pointers.....

unfortunatly when i am reading most of these stroker writeups i get lost in some of the motor speak...and have to flail around trying to figure out what will work for me and what i have to do...to have a proerly running motor..

thanks again...

Grifter

 

[Dr. Dyno]

I suggest you use the '94 block as the basis for your stroker because you already have it readily available. I also suggest you use the '94 head 'cause the '00 head is prone to cracking. You can either port it during the stroker build or do it later on.
You said your 2000 engine is knocking. Are you losing coolant? It has been known for the 2000 head to crack causing slow coolant loss into the crankcase contaminating the oil, resulting in accelerated rod/main/cam bearing wear. Remove the oil filler cap and peer under the valve cover. If you see a light brown emulsion between the valve springs of no.3 and 4 cylinders, the head is cracked.