My 06 TJ 4.0 has only some breather mods, a custom 3 inch exhaust and custom headers, 3.5 inch intake with ported throttle body. My first poor man stroker failed on me and i have a new short block from a 05 TJ, im not going with another stroker just yet and im going to keep the short block stock. Im interested in milling the head to try up the compression to about 10:1 or 10.5:1. The car is ran on 93 octane all the time, also i would like to go with the comp 239 cam..
My last 4.6 was on stock head. This time im doing the opposite, my question is how much should the head be milled to up the compression that much, also would i have problems with valve to piston clearance or do you think i would be fine? Last question is would the 239 Comp cam be fine with a new OEM timing chain? And what are the part numbers for the Mopar valve springs and retainers i would need. While im in their i think ill give the head a quick manuel port and polish, nothing huge. And last but not least a nice tune
I don't have your answer for how much to mill your head for the compression number but one thing I know for sure is you won't get clearance issues by milling the head. you would only get that by milling the block.
When choosing your cam look up the difference between static CR and dynamic CR. Two totally different things.
I have my my static CR set up for about 10:1 but my Dynamic CR is 8.5:1
This allows me to use regular gas and has a dramatic improvement on the torque curve.
Its all in the cam. remember, compression only starts when the valves are closed not before.
Thanks for your reply, im thinking of going with the comp 239 Cam, have not found too much info on the cam itself, and been trying to figure out the change in compression ratio, but i believe that if i do mill the head to much i can also have clearance issues with piston hitting the valves if im not wrong.
Any Guru's here that can help with how much i can mill and there thoughts on the 239 comp cam? Also i found some part numbers for the mopar performance springs, is it only 1 type? Last but not least do i use the stock timing chain i have read about failures with the comp gears and change?
Your engine will have the retaining plate. It won't work with the comp cam, the same for your stock timing set. You will need an earlier timing set. Its not the comp cam timing sets that are prone to failure, but the single row chain style timing set.
You cam use the old style cam, the old style timing set and the bolt, spring, pin and washer setup. However I would delete the spring, get a longer pin and then set cam play manually. That way it is static and there is no spring to compress.
SilverXJ, thanks for your input i really appreciate it.. Just dont know much about these details and not sure if i can find all this at a jeep parts store.. I could find the bolt spring and pin from the older model for sure and that way fit the old cam.. But how would i go about a longer bolt? It would need to be custom right?
I wonder about the valve to piston clearance also. Maybe the way the timing is it wouldn't hit but it would become an interference engine? So if the chain ever went the pistons would then hit the valves? and on a stroker some pistons come up almost level with the block?
wizzo wrote: But how would i go about a longer bolt? It would need to be custom right?
You would have to fit the pin your self to achieve the desired end play. Use a dial indicator on the back of the cam and install the timing cover with gasket dry and check end play.
I think it will be easier to just stay with the stock parts.. Can anyone provide a diagram with the parts i would have to replace so that i can go to the local parts department? If its a big hasttle point me in the right direction
You won't have piston to valve interference issues.
I have a new head from 505 performance in my garage i measured it with the calipers and from one side of the intake valve to the flat face of the cylinder head is .276 inches. So with a lift of .490 or so wouldnt it hit the top of the piston if the chain ever broke or if the block was shaved?
have run with .120" off head ( kinda thin in places) currently have .110" off with 0 problems ,for 13 years on race truck. This is with 512 lift crane cam
