New 4.2L mini-stroker recipes

[Cheromaniac]

Most of the stroker problems have been related to aftermarket cam/lifter failures, and those would have happened even if the bottom end was a stock 4.0. The stock cam doesn't have those issues and that's why I've popularized the "poor man's" stroker. If your original cam is still good, use it in your stroker with a new set of lifters. Crown Automotive lifters seem to be good quality so I'd recommend those.

[Eaglefreek]

So what would be the advantage for the mini-stroker vs. a 258 with a 4.0L head and cam? Is it just the increased compression? Does the 1/4" in difference in stroke make that much of a difference in performance?

[Cheromaniac]

So what would be the advantage for the mini-stroker vs. a 258 with a 4.0L head and cam?

If you had the same head, cam, and external performance bolt-ons on both short blocks, the higher compression and tighter quench of the mini-stroker would be its only significant advantages.
Nothing wrong with building up a 258 block with a 4.0L head, EFI, '99+ 4.0L intake manifold, and other performance goodies.

[matty401]

i am very interested in this 4.2 we have a 4.0 87-90 block and head my son's car has a 232 in it now 76 vintage do you have to change the pistons or can you run the stock 4.0 pistons and if you do what compression will we have thanks

[Cheromaniac]

If you run the 232 crank in the 4.0L block, you can run stock 4.0L rods but not the stock 4.0L pistons. You'll need to change the pistons to either Silvolite 2229 or Speed Pro 677CP. At a pinch you might be able to use the Speed Pro 825CP if you use a thicker head gasket.

[Knoxes]

The mini-stroker plan with the 3.5 crank calls for a 60 overbore. I hadn't considered that as specific, really, and just assumed that was ambiguous. With a stock engine, I wasn't planning on boring at all, unless it was needed - and if so, only going to 30. Is the 60 over necessary to get the right CR?

[Cheromaniac]

Doesn't matter. You can use the 232 crank and do a 30 thou overbore. Displacement will be 4121cc so the engine will end up being a 4.1L mini-stroker instead. CR will only be 1/10 lower.

[CJXJ]

Newbie doing a mini stroker. I am using a 90 Renix block as my 97 was cracked in #3 cyl. Will use 97 rods if they are not damaged and 232 crank with 2229 .060 pistons. 97 head ok and thinking about oem cam. Question is can I use stock cam and is the 90 cam the better choice?

[IH 392]

If your '97 cam is ok use it, if not personally I would get a new one.

[CJXJ]

Thanks I think I will use the 97 cam. The machine shop is telling me the engine will need balancing after the build for $350. I know it is recommended but is it necessary for daily driver / occasional wheeling?

[IH 392]

You don't "NEED" to balance it but it's money well spent, the crank, dampener and flywheel/pressure plate or flex plate can be balanced without the pistons and rods on a straight six, if you have access to a beam scale you can balance them yourself, the rods should be balanced for big end and over all weight but over all is better than nothing.

[SilverXJ]

Balancing the entire assembly will not only give you a smoother running engine but will prolong the engine's life. The pistons and rods are weight matched then the crank is spun and balanced (with out bob weights, a lot easier) then the flexplate/flywheel and balancer are balanced individually. Have the machine shop record the numbers for the rods and pistons in case you ever need to replace one. That way you can match them up.

You can certainly do the rods and pistons yourself. You need a good scale that measures in grams, a jig to put the rod on so you can measure the big end and small end and some way to remove material. A belt sander works well for the rods. The key to using the rod jig is to make sure that the rod is level. One end will rest on the scale and the other off of it. Then flip the rod around and do the other end.

This picture should give you a good idea of how it works:

[Knoxes]

The 4.2 mini stroker calls for Comp Cams 68-115-4. And then I've found this:

Notes: Not for fuel injected engines


A little lost at the moment (2003 WJ)....

EDIT: Ok, I called Comp. They said that it won't produce enough vacuum. And they don't have an alternative for a 2003...

EDIT #2: OK, after more research on Jeep Strokers, it looks like the 68-115-4 wouldn't work on my 2003 block anyway due to the thrust plate.

Looking for suggestions here, guys.

[IH 392]

That cam will work in your block, but you must retro the timing chain and possibly the cover too.
Did they say how much vacuum that cam generally produces??, according to two map sensors and my scan tool the OE OBDII cam only produces 12"

[Knoxes]

They didn't say how much vacuum, but I didn't ask either. I guess I'll start searching for the workaround, unless you can give me a hint. I'm also looking for other options if anyone has any ideas. I'd really like to keep this as simple as possible. So much so that I'd consider using the stock cam at this point - which means that I'll be de-tuning this back to almost stock.