Jeep Strokers

I'm planning out a basic, comparably low budget 4.5L stroker for my 2003 WJ. My goal is to reuse as many stock parts as possible as can safely be done within reason, but also to invest in the best bang for the buck parts and procedures to make the whole process as worthwhile as possible. My other goal is to maintain a somewhat lower compression ratio as to enable use of 87 octane without pinging, and to avoid possible detonation with lower tolerance stock parts. My budget goal is based on staying well under the roughly $1000 cost of regearing my axles from 3.55 to 3.73 and instead pull an additional ~70 ft lbs of torque, which I expect to be far more beneficial in every capacity. Here are the parts I have figured out so far:

* 87-90 258 4 counterweight crankshaft. I'm choosing this for marginally better fuel efficiency as well as simplicity of already having the same 54 mm nose so it will drop right in without modification.

* '87-90 258 connecting rods, coming out of the same engine that I've sourced the crankshaft from. This is by far the most cost effective option.

* Stock 4.0 pistons. I understand these will press right onto the 258 rods without modification to either, and will also contribute to a lower compression ratio to allow for use of 87 octane gas.

* Stock 4.0 camshaft. I have no reason to upgrade when this cam is already built for low end torque and will work with the lower compression ratio I am shooting for.

* Stock 4.0 0331 cylinder head. This already has 102k miles on it and it is from my 2003 WJ, manufacture date 08/2002, and thus seems to be after DC addressed the cracking head issue. With a port and polish job, I think it should be ideal for the basic build I am going for.

* Stock 4.0 fuel injectors and fuel delivery. Without overboring the cylinders to 4.6L+ I can't see justification to swap in the ford 24 lbs/hr injectors and the stock 49 psi should be fine, unless the engine runs noticeably lean in the higher rpms. Should that happen, the ford fuel injectors will be added later.

* 63 mm bored out throttle body and 3" intake with amsoil dry cone filter. Self explanatory, and no need for anything larger to accommodate this build.

* Hi flow cat and muffler. While I will eventually upgrade to a 2.5" exhaust and an aftermarket header, I expect swapping to a magnaflow cat and flowmaster to be sufficient for the time being. Again, shooting for low end torque more than high end horsepower.

* New bearings, gaskets, etc. These types of details are what I don't know. What specifically needs to be replaced when tearing an engine down this far in terms of bearings, seals, etc? Should I upgrade to mopar performance valve springs/lifters, or should the stock ones be fine for the level of stroker I'm planning on? Am I best off keeping the stock 4.0 pistons or should I consider an upgrade to the Sealed Power 677CP pistons? Will this up my compression ratio so much that I will no longer be able to use 87 octane gas? What kind of grinding needs to be done to the crankshaft, and where do I have this done? Or, can I simply drop in the crankshaft entirely as it is if it appears to be ok? Is there any other rebuilding that needs to be done to my cylinder head? Should I go with the thinner .043" head gasket or thicker stock one?

I greatly appreciate any type of input from anyone. Nothing aside from the crankshaft and rods are set in stone at this point. I'm still entirely flexible on the parts of this build so long as I stay within my budget. I'm a little unclear how to crunch all the numbers, but based on everything I've read on other builds, I'm guessing I'll have about a 9.0 to 9.2 compression ratio, and I expect about 245 horsepower and 300 ft lbs of torque. What do you guys think?

A 4.5 stroker built with the stock pistons will have a 9.7:1 CR and it'll ping with the stock cam. The 677CP's will lower the CR to about 9.2:1 with the 0.043" head gasket. I have the 677P's in my stroker with the same head gasket and stock cam, and the engine runs fine on 89 octane.

Thanks for the reply. A few other questions, the 677CP pistons on summit racing ( http://store.summitracing.com/partdetai ... w=1&N=700+ ) specify up to a 1995 block. Is there a difference in the '96+ that will prevent me from using this exact part number (in which case I can't seem to find the correct one), or are these correct?

Also, as I am using standard size pistons, do I need to replace the piston rings, or are the stock ones fine/reusable? Is there any need to have the cylinders honed, or is that only necessary when overboring to begin with? Thanks again for your help... I've been learning a LOT reading through this site.

Edit: From what I've read, I understand I can dish the piston to bring the compression ratio down and thus be able to use 87 octane gas. Does doing so have a negative effect on power or torque? Also, is the quench height of 0.088" (as per dino's page) acceptable/safe, or would it be smart to invest time and money into dishing and milling to decrease the quench and keep a reasonable CR?

Even if you are not having the cylinders bored, i would still have a machinist measure the block and compare the wear in all 6 cylinders and the wear limit of each one. At the same time, if its in spec, i'd have them hone the block for you, and new rings is a MUST. The 677cp should work for all year 4.0 as the bore size and stroke was the same from 91-thru-last year of 4.0

I think that's when Chryco switch from SAE to metric sized piston rings?

IF you get rings that match whatever pistons you decide to get; you'll be AOK.
As stated above the Bore is the same 1987-2006.

<edit reason I fail an the internets>

Also I think theres a coating on the skirts of the later years around 96-97 and up. Its not a must, Im not running pistons with the coating in my 97 block. You can deck the block to get a better quench height which in my opinion helps the engine more more efficiently. A rule of thumb I found is that for every .010" that you deck the block, add 2 cc to the piston dish to keep CR around the same. So if you have .088" quench, decking the block .010" will take you to .078" quench. I think the 677 has a 17cc dish, machining it to 19cc will bring compression back down to the original CR you had for .088" quench. This was just a general relationship I found while messing with the old calculator.

yuppiexj wrote:I think that's when Chryco switch from SAE to metric sized piston rings?

IF you get rings that match whatever pistons you decide to get; you'll be AOK.
As stated above the Bore is the same 1987-2006.

Correct on all counts. You can buy the 677CP pistons (they have graphite-coated skirts but the 677Ps don't) and get the matching non-metric piston rings.

Thanks to everyone for the help. So it looks like my build will be mostly the Dino Poor Man's Stroker, with the exception of my cylinder head. So the basic parts list is:

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Sealed Power 677CP standard bore pistons and rings.
Stock 4.0 camshaft
Stock 4.0 0331 cylinder head
Mopar/Victor 0.043" head gasket
0.088" quench height
4.0 stock injectors with stock 49psi
Intake, TB, cat, muffler.

So I can deck the block and dish the pistons to lower quench and maintain CR, which sounds like a good idea. So all I need to figure out now are the detail parts like bearings and any other gaskets and bolts I need. I think I need new bolts to press the pistons onto the rods, maybe? If anyone can tell me a complete list of those details, that would phenomenal, as then I can figure out what the final bill for parts will be and start calling shops. This site really is amazing. Thanks for helping turn my idea into a solid plan.