My recipe. Opinions?

[Kidder]

2003 Block 0 deck
0331 Head
4.0L rods
kb 945 10.7:1 pistons
comp 68-232-4 Camshaft
Static 9.47:1
Dynamic 8.13:1
Quench 0.051

What is your opinion on this. I know I will have to run premium, but is there any info on what the stock 2003 ecm will do with this, and what problems could I have. I'm just in the research stage so any input would be helpful. Also is there anything that I will have to modify in the fuel system (besides injectors of course). Thanks

[SilverXJ]

Your math is incorrect. Using the KB945 pistons your SCR will be a good deal greater.

[amcinstaller]

what vehicle is this going into? the same one the block came from? to get teh full effect you may want to consider a chip of some sort, but other than that, just the injectors i believe.

[Kidder]

Sorry your right the SCR will be 10.53:1 and the DCR will be 9.01:1.
This engine will be going into a 2003 Rubicon. I already have a edge performance chip, intake and throttle body. Is that chip going to help me or hurt me?

[gradon]

You do not want a DCR higher than 8.5:1 unless you plan on using e85 or race fuel(octane higher than 93). If you plan on using 93, shoot for an 8.3-8.4:1 dcr that way if tolerances/measurements are a little off/wrong you will still be ok. I have compression knock(pinging) w/ 93 octane in closed loop b/t 2500-3000rpms due to my 8.57:1 dcr and the obd2 holding that 14.7:1 afr. Buy the 944s.

[Kidder]

If I go with the 944's should I stick with the same cam or go with a different one.

[gradon]

Comp's 231 and 232 seem to be the most popular choices for strokers, so as long as you have calculated the crs correctly, you should be good to use it.

[SilverXJ]

I don't think the edge chip does much do begin with so I doubt it will add or subtract anything.

[gradon]

It adds ignition which makes high comp strokers ping. Some of those programmers have different tunes for different octanes, so I could see how the lower tunes could help out. It'll come down to trial and error to see if it helps you out or not.

[Cheromaniac]

Your math is incorrect. Using the KB945 pistons your SCR will be a good deal greater.

Yeah, it'll be ~10.9:1. Unless you're going to be running the engine only on propane, I advise that you go for the IC944 pistons instead. These will lower the CR to a more acceptable ~9.8:1.

[rammit11]

hi , don't mean to hijack this thread but I would like to get an opinion on my recipie. I am building a 4.6 short rod engine and I am going to end up with around 9.1:1 scr and 7.83 dcr with a .056 quench. does this sound like a reasonable combination to run 87 octane, or should I try to get the quench closer to .051?

[Cheromaniac]

hi , don't mean to hijack this thread but I would like to get an opinion on my recipie. I am building a 4.6 short rod engine and I am going to end up with around 9.1:1 scr and 7.83 dcr with a .056 quench. does this sound like a reasonable combination to run 87 octane, or should I try to get the quench closer to .051?

Sounds good as it is. I can run mine on 87 octane with the hottest plugs (Champion RC12LYC) and a 0.088" quench. I think people get too hung up on the quench issue.