Hey all! Lookin fer input on 4.5 ideas

[Ric]

As mentioned in the title... hey y'all!

I've skimmed thru the place here, and I have to say that y'all are much more oriented for my tastes than most 4x4 spots... I never knew of 4.0s taching over 8k till now! Not that I'm looking to do so, but I do have a 6000-rpm mill in mind for our XJ spoken of in my sig. Here's what I have gathered thus far:

- 4.0 out of 2006 Rubicon, 7k miles... the Jeep was getting repo'd so owner decided to drive it into a pond, thereby ingesting enough water to break two rods and bend the other four. Still have magnafluxing to do on block and head, though there's no rust cracks that'd tell the tale on either.

- Comp's valvetrain kit PN 68-239-4. Valvesprings, cam liters, retainers, locks, timing set

-Hi-volume oil pump

And here's what I need:

-Uhhhh, a crankshaft & rods

-A header, preferably stepped from 1 5/8" to 1 3/4"(picky ain't I?)into dual outlets... I might be dualing the exhaust out on the XJ, dunno yet.

Pretty much everything else I'll swap over from the stock engine where applicable.

Before I get too far to save, lemme just say that this mill WAS meant for my '85 CJ7, that already had GM HEI, Hedman dual-out hedder, Offenhauser dualport 4bbl intake w/Holley 450-cfm carb. However, I had to sell it to make bills, so oh well. I'd like to know y'all's opinions on what the best era crank would be to do this, knowing that pre-YJ cranks need a spacer to align the harmonic damper.

I've done some portwork on the head, matching to the gaskets, opening up underneath the valves, smoothing out the runners, hawging out the exhaust ports, etc. Would I benefit from smoothing the combustion chamber face to near mirror image so as to remove any hotspots in the cylinder?

Would I be better off with stock-length 4.0 rods and raised-pin pistons, or 258 rods with stock 4.0 pistons? Also I'm concerned about quench. Is there an off-the-shelf piston that'll give a 9ish:1 CR with around .055" quench? 87-octane's always cheaper than 93.

I've drilled/tapped for a 4-bolt water pump, so no worries there. However, are there any other caveats to using the newer block, like sensor placement, bracket bolt bosses, etc?

I bet y'all are thinking I'm an idiot by now. That's why I want your inputs. From what I've read in the advanced forum, a lot of you have knowhow that I truly respect, and I appreciate any tips or help you all can give me. Thanks?

[SilverXJ]

Make sure those Comp Cam springs are installed at the correct height.. iirc they don't install at the stock 1.64". Also, from what I recall they may be a bit too strong.

Before you do any work on teh block make sure that it will fit in our jeep. Check the block mounting bosses in particular.

The benefit of polishing the combustion chamber is to eliminate hot spots and prevent detonation. Do it if you have the time. As of now I am sick of polishing and grinding, having done my head, my intake manifold and my connecting rods.

I don't know of any piston choice that would give you a good quench and compression with our decking or dishing. You really have 3 choices on pistons, 1)Stock 4.0L pistons they are cast or hypertunetic (i can never spell that) and come in various dishes. Check the piston FAQ for that. Use with the 258 rods 2) the Keith Black 944 or 945 piston. One is designed for 9.x:1 compression the other for 10.x:1. These are forded pistons for use with the longer 4.0L rod. 3) custom.. do what you want here. It basically boils down to how much you want to spend. The stock 4.0L pistons are cheap, the KBs expensive (what sux is that they want +$200 for a .040 over a .030 bore piston), and custom is slightly more expensive but you do get to choose all the specs. I'm doing a build in the projects forum with the KB944s if you want to take a look at the numbers.

Header, there are several companies that offer the late model dual out let. Doug Throley, Rugged Ridge, and Borla I believe.

Oh yeah, and you won't get 300hp from a 4.5L

-Chris