new to the stroker world and some ???'s...my plan

[JeepCoMJ]

So I'm new here and happy to be on the forum...and guess what?! I'm looking to build a stroker motor for my 87 comanche. the truck is a shortbed, lifted 6.5", automatic aw4 with a 4.0, np231 with SYE, dana 44 rear and 4.10 gears
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here's what I'm looking for...high power and torque, with the ability to get great gas mileage. i know if you're light-footed on a 4.0 stroker you can get upwards of 25mpg, and that's what I would like to achieve.

basically here are my options...

I've got a 1989 4.0 with 150k miles, an 88 4.0 with 101k miles, and a 2001 4.0 with who knows miles but a cracked piston.

one 93 H.O. head and intake, and a borla exhaust manifold for that.

I'm trying to figure out what all I will need to build a stroker motor. I know i will need a YJ crank and have it machined to fit the 4.0 harmonic balancer (unless it's from a serpentine equipped YJ). I'm intending to use the 4.0 connecting rods with some performance pistons (shorter) to make up the length difference.

not sure on what bore... thinking .030 or so.

any opinions on cams?

opinions on which motor to base this off of? I don't want to deal with wiring swaps right now, as this engine will need to be built dropped in then running within a day or two of yanking the old motor.
kind of thinking that a renix block with the H.O. 93 head and borla and a 99+ intake all ported to match would be the way to go...i like renix, but want more power (obviously )

also, any changes that would need to be made to the computer? do I need an adjustable MAP sensor or any alterations to any sensors?

the project will be a fall/winter project then dropped into the truck, and the budget is less than $1500

thanks guys
-Pat

[seanyb505]

A couple ideas....

How badly was the 01 block damaged by the piston? I would use that block if it hasnt overheated or been damaged to the point you need to bore over .060. After that I would go with the 88. The 01 has NVH treatment, but Ive heard the renix blocks are quite strong. Also Im not sure what kind of electrical issues there will be going from an 87 block to an 01 block.

I would look for a crank from a YJ; 87-89 I believe. You are correct that they will not need the snout machined. I picked up mine from O'reilleys for $236 with free shipping. Im not sure if they made the 4.2 in 90 or not but it wouldnt hurt to look it up. Get used to research lol

If you use the 4.0 rods I think the cheapest piston you're looking at is the KB944; somewhere around 500 shipped I think. I could be wrong, but not by much. If you use the 4.2 rods you will have a wider selection of pistons which will also be cheaper, but figure in what you will pay for purchasing the rods to at least 130ish for pistons, and dont forget if you want the pistons dished or not.

Cam choice will be up to you. Define what you want the engine to do and find a cam that does it. I went with the Isky 133125/26 because it had a dual pattern and mildly more lift than stock. I didnt like who I talked to at Crane or what I was told or the reputation theyve gained with the Jeep strokers so I avoided them. Having said that, the Crane 753905 has been a popular choice.

Im sure you've heard that you can have two or these three: fast, reliable, and cheap, but not all three. Pick which one you want to leave out. I wanted to finish my stroker with under 2000 but it has soared to over 3000 just so I will have some peace that it wont break soon.

[SilverXJ]

You don't want a 2000+ block as some accessory mounts and engine mounts are different.

[oletshot]

You'll have to work on the power steering mount with the 99+ intake and adapt the HO throttle body to renix. 2001 block won't have the knock sensor hole and may have different mounting holes for the engine mounts.

[JeepCoMJ]

You'll have to work on the power steering mount with the 99+ intake and adapt the HO throttle body to renix. 2001 block won't have the knock sensor hole and may have different mounting holes for the engine mounts.

yeah. I have looked at that and they're very similar...just need to drill out the threaded portion on the old unit, or upgrade pumps to anything H.O. (you can drill out the H.O. power steering pump and bolt it right in place from what I've looked at). thinking of actually adapting the renix throttle body to the H.O. head, but boring it of course.

[oletshot]

I made a throttle body spacer/adapter for my renix TB to bolt to a HO intake. I never used it, decided to go with HO ECM.

[Reelm n Rubi]

If your building a stroker there is no reason to go less than .060 in my opinion. 4.0 blocks are a dime a dozen, so go BIG!!

[JeepCoMJ]

If your building a stroker there is no reason to go less than .060 in my opinion. 4.0 blocks are a dime a dozen, so go BIG!!

but money and time are the real issue here. those are what I'm short of...i've GOT plenty of 4.0 blocks

[1bolt]

Welcome to the strokers forum Jeepcomj, what happened to late model Camaro V6's man?

Just my personal opinion but with those stats you should more realistically set your MPG goals on 20 MPG hiway and be pretty happy if you hit that. The lift, and tires are really going to lower your fuel efficiency drastically... Depending on your tire size the 4.10's may not be enough which will put you off peak torque at cruising speed. At 6.5" of lift I'm almost willing to put money on your tires being too big for 4.10's, I've got 4.56's on My XJ and it's only on 33/10.5's with 3.5 inches of lift. 4.56's are dead on perfect for 33"s in terms of highway RPM's and peake torque... As a consequence I can occasionally get 21 even 22 MPG on pure freeway driving (4.6L stroker, with AW4 and just about every upgrade). You would need serious aerodynamic upgrades to make our favorite flying bricks get 24-25. Block the grill off, put an aero belly pan under it, and start thinking about shaving things like door handles and mirrors.

Two thoughts here, Renix fuel injection is said by many to be the most fuel efficient, This seems like the general perception anyway probably having to do with smaller throttle body and lower flowing heads (certainly leaner fuel maps as well).

However engine efficiency is one of those things you can't really use straight up common sense for... The poorer an engine breaths the less air it will take in and thus the less fuel it will take in, but also the less power it will make. The more it fights itself volumetrically the lower the power output and fuel efficiency: and the more you'll have to step on the throttle to push the jeep through the wind and up hills... Which means a more open throttle and less manifold vacuum. The lower the steady state manifold vacuum the easier the engine breaths and the more efficiently it runs..

Sounds like a bunch of contradictions doesn't it? Yeah me too... But it's the balance of these effects that dictate much of an engines fuel efficiency... It is for example the reason why 4 cylinder Jeeps barely get better mileage than I6 Jeeps... The lower displacement and wider throttle (less manifold vac) are canceled out by less torque output at cruise speeds... And its also why the new JK 3.8L V6 only gets 1 (ONE!) MPG better EPA rating than the last year of the I6... (please note that it doesn't even get ONE MPG on earlier I6 TJ's before the EPA changed the calculation!) despite being a MODERN overhead cam engine design. Its nearly gutless torque output cripples its ability to push the aero brick through the wind.

Incidentally its also why my stroked and completely built up XJ on 33 inch tires can average 19mpg... gobs of low RPM torque and a steady cruise speed/RPM that is almost exactly on the torque peak.

I'll tell you over the years after reading several books on the subject, two web sites about it, and articles from some of the best Aftermarket guys (David Vizard to name one), There's a WHOLE lot of engine building science to delve into when it comes to building for economy and performance... Performance is comparitively simple, with so much more aftermarket development having been done for it... Economy is more the domain of the OEM's and they don't post their research to forums like performance enthusiasts often do.

I will say this... A stock V6 Toyota Camry a few years back was rated at 26 mpg Highway (seriously I was shopping one at the time)... this is an aerodynamic and relatively light weight import car.... The XJ and MJ pulling 20-24 MPG (stock) is nothing to sneaze at, and improving that would take drastic measures, that would probably be more expensive than the fuel savings... At the very least they will make the Jeep less of a Jeep, and less of what we like them for. Aero improvements without making a Jeep unrecognizable would be a Herculean task to say the least.

[JeepCoMJ]

lol...1bolt, I read everything you had to say and am glad to say I actually understood it, and didn't get lost at all.

that said, I'll keep it short and simple...i'm here to listen and learn more than anything else.

camaro v6's are reserved for the other comanche...which is actually getting a grand prix 3800 S/C now instead since i spun a few bearings in the camaro one (the 3800 MJ is getting stripped to bare unibody then rebuilt)

to the current debacle...with 4.10 gears and 6.5" of lift I run 2700 RPM at 75mph which is MY cruise speed on the interstate (I usually drive 10 over at anything 60mph and above). that said, I think that the gears are deep enough for me...moving on to 4.56 gears would give me higher RPM still and for cruising speed, that's no good.

the goal is to get the engine the power that it needs to easily push the vehicle. by accomplishing this, the engine would have a higher torque curve around the same rpm (correct me if I'm wrong on that...not sure if the build will change the rpm/torque ratings or how much it will change it by), which would mean that it has to work less to push me at speeds...which means that rpms will be able to remain lower. by having the RPM lower than 2700, it should be able to get into the target RPM of 2200-ish (renix's "perfect" running rpm as I've found) and therefor meet my specs.

if I pull 20mpg out of it daily driving from speeds between 45 and 50mph I will be happy...that's better than it's currently getting (the motor currently in it hasn't been properly maintained, and this is it's first 2000 miles in 8 years...i refuse to do any work to the motor as I'm replacing it anyways) as I'm getting betwen 15.5 mpg and 18mpg depending on if it's city or highway.

do you have specs on the "most efficient" stroker combo?