Building 1st stroker, have some ??s

[waggy73]

Hello, I've read the majority of the threads here for the past 6 months, and have been a lurker on the yahoo strokers list for 5+ years. It's finally time to build my stroker, as the head gasket blew on my xj. Here's what I have and what I want to do, with a few questions to follow:

A bit of background first. The engine is out of a '93XJ. It was running with 178k on the clock, the engine was pulled due to gas mileage decreasing and a suspected head gasket leak. Upon removal and disassembly the engine appears to be in good shape. No ridge at the top of the cylinders, and the engine had good oil pressure despite the #2 and #4 main crank bearings that were pretty hashed. Very little sludge in the crankcase. The machine shop verified that a 0.030 overbore will clean up the block.

This Jeep sees mostly highway driving, with a bit of light towing duty with my 3500lb trailer. I live in VA, so we see 100 degrees in the summer and 20-30 degrees in the winter. I don't rockcrawl, so I intend to build the stroker with the lighter weight 4.2L crank. I already have my sports car that takes 93 octane, so I don't want to increase the CR much over stock as I want to continue to run 87 octane. I understand that I will be leaving some horsepower/torque on the table but I don't feel I'll need the extra 15-20HP with 93 octane costing me $0.30/gallon every time I fill up. So here is what I intend my buildup to contain:

'81 lightweight 4.2L crank
'93 4.0 block
'93 4.0 head
Melling High Volume oil pump
Flowcooler High Volume water pump
Already have a Borla header and full catback with a Random Technologies High flow Cat
Already have a K&N FIPK

My questions are:

I think I want to stick with the 4.0 rods, but that essentially means I need to purchase the forged pistons. I'm not a big fan of piston slap, is that something I will have to deal with until the engine warms?

I'm having a hard time figuring how to get the CR down to close to stock specs in order to run 87octane, can someone point me in the right direction with the calculator? Or with the upgraded cam, does that help the engine breathe better allowing a higher CR on 87octane?

How do you select a cam? Compcams has 8 different cams listed for this engine, and they are all relatively close in characterists.

Is there a preference for bearings, Clevite, Federal Mogul, etc? Same for rings, any preference?

Is it overkill to buy a new aluminum radiator, or will a 3 row keep the engine cool enough?

Is an adjustable MAP sensor necessary to get the Jeep running properly?

Same for a 62mm throttle body? I see a 65mm TB out there also, which one do you guys think I should go with?

Is a double roller timing chain a good idea? They are significantly more expensive than the single rollers.

Thanks for any help you can provide. I consider myself an above average mechanic but total rebuilds are pretty new to me. I'm not looking to cut corners or costs, but obviously I don't want to spend $500 on an aluminum radiator when a $200 3 row copper one will be fine.

[AlexTJ]

How do you select a cam? Compcams has 8 different cams listed for this engine, and they are all relatively close in characterists.

Everyone seems to be running the comp 68-231-4 for supreme low end torque (great for towing that trailer and is what our engines excel at).

If you really wanted an idea of what different cam profiles do check out a program like DesktopDyno or similar. You can put in the specs for your planned stroker (I even think theres rough head flow numbers around here somewhere) and then just change the cam options and watch what it does to your torque and horsepower curves. The numbers aren't super accurate but it provides a great visual for what each cam would do.

Is there a preference for bearings, Clevite, Federal Mogul, etc? Same for rings, any preference?

I used KING bearings, I've heard good things about them and they're not made in Mexico. (nothing against Mexico, I've just had a lot of bad parts come from there)

Is it overkill to buy a new aluminum radiator, or will a 3 row keep the engine cool enough?

I have a regular old copper three row and its always kept my stroker(s) at thermostat temp, even on 100+deg Kansas summer days. I pulled it from a junked 4cyl TJ, of all things, for 30 bucks lol.

Is an adjustable MAP sensor necessary to get the Jeep running properly?

As long as you size the injectors correctly it should run fine. Not optimal, but not bad either.

Same for a 62mm throttle body? I see a 65mm TB out there also, which one do you guys think I should go with?

I'm still using the stock TJ throttle body, I'm curious to see what a larger one will do for me. I went for a 99+ intake before I get a throttle body. My Titan stroker LOVED it

Is a double roller timing chain a good idea? They are significantly more expensive than the single rollers.

I got a cloyes adjustable double roller. I'm glad I did because my cam wayyyy too advanced from where it should have been so I was able to adjust it back down a bit.
Plus its good insurance. Won't it be great to know 80,000 miles down the line your stroker is closer to the timing it should be at as compared to a stretched stock chain?

[Cheromaniac]

You could consider the "poor man's" and the "low CR rockcrawler" stroker recipes from my site, as both will run on 87 octane. I'm living proof with the "poor man's" version. As for the other things:

1. Bearings: Either Clevite or F-M will do fine.
2. Rings: Sealed Power or Hastings.
3. Radiator: Stock 2-row will do fine. Run a 180* t'stat if you live in a hot climate. Flowkooler or Hesco high-flow water pump will keep the engine cooler under high load conditions e.g. scaling long uphill grade.
4. Injectors. You'll need 24lb'ers. MAP adjuster useful for fine-tuning the injector flow when engine computer is in open loop (warm-up, heavy acceleration, deceleration).
5. Throttle body: A 62mm is plenty enough for a mild stroker. My modified Mustang 65mm unit is overkill and makes the throttle response very sensitive. Great for the street but not when you're offroading.
6. Timing set: The stock single roller will suffice. I went for the '94-'98 factory timing set 'cause it has beefier sprockets than the '93 and earlier versions. It fits just fine. Double rollers are even better but I've heard that in some cases they can foul on the timing cover.
7. Intake manifold: If you can find a '99+ curved runner manifold cheaply, get it.

[waggy73]

Alex and Dino, thanks for the input, it is greatly appreciated. Regarding the rods, I can go with the 4.2 rods as I have a set that was on the 4.2 crank. I guess I am worried about dishing the pistons to get the CR down enough. Is this something that most machine shops can do without problems? Dino, I was looking at your stroker recipes, do the aftermarket cams allow for a higher static and dynamic CR while still running 87octane? I want the benefit of higher displacement, but I just don't want to end up having to feed this thing premium to keep it from pinging. I figure if I want more power later, I'll just turbo the engine and put premium in it then.

[rammit11]

If you need to have your pistons dished there is a guy on the site that goes by oletshot. I can say that his work is top notch and very reasonable as he did a set for me and a few others and they are exactly to the dish he said that he would do.

[AlexTJ]

Alex and Dino, thanks for the input, it is greatly appreciated. Regarding the rods, I can go with the 4.2 rods as I have a set that was on the 4.2 crank. I guess I am worried about dishing the pistons to get the CR down enough. Is this something that most machine shops can do without problems? Dino, I was looking at your stroker recipes, do the aftermarket cams allow for a higher static and dynamic CR while still running 87octane? I want the benefit of higher displacement, but I just don't want to end up having to feed this thing premium to keep it from pinging. I figure if I want more power later, I'll just turbo the engine and put premium in it then.

After market cams can give you a lower DCR which can let you get away with running higher SCR. Some people say that's a lazy way of running lower octane but I don't know enogugh about that argument to explain it.

I second the comment on oletshot, I had him dish my pistons. When I asked my machinist if he could he just gave me a look like I was an idiot and said he was a so-and-so piston dealer and he could get what ever dish I needed. He made a phone call and came back looking like the idiot lol

[Cheromaniac]

After market cams can give you a lower DCR which can let you get away with running higher SCR. Some people say that's a lazy way of running lower octane but I don't know enough about that argument to explain it.

A longer duration cam bleeds off cylinder pressure at low rpm so it can allow you to run a higher static CR without the engine pinging. Depending on other factors (elevation, ambient temp., coolant temp., A/F ratio, timing, quench height, aluminum head) you might still be able to run 87 octane fuel.