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Thread: What to do?

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    What to do?

    Last month i noticed i had been loosing coolant. After long diagnosis i found the leak in the head gasket so instead of just replacing it i felt ballsy and decided to build the top end of my motor. I took the head to a machine shop asked him to check for cracks and warpage and port and polish the exhaust. He recommended i also open the exhaust ports a little i agreed didnt seem to bad of an idea. Then came my bright idea to try and orded a cam off comp cams to give it a nice little rumble. After doing some research i found out that no company could guarantee fitment of there custom grinds because jeep changed the block from 05- 06 so i decided to use there specs and get my cam ground. The machinst called me back a few days later saying that the cam was ground but because of the difference in the cam i would need stronger springs. Looked and looked apparently no one makes them for my year block so to compensate for that he told me he measured up my push rods and with longer rods , my rocker arm ratio and different valves he could make it work. I agreed got the head back and the cam went onto tech connect got my service info buit her up... and now shes runs like shit throwing fuel trim codes. did some simple tests found out i only have 3 inHg of vacuum under 100psi of compression across all 6 cylinders. i verified timing both ignition and crank. i dont know what to do except go back to OEM
    which would cost allot more money that i dont have to spend

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    recheck the valve timing mite be out a tooth ..if all cyl are that even ...

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    Sounds like a whole ton of valve overlap.

    What numbers did you have the cam machined to? Duration etc?

    And check what ^ he said too....
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    i have the specs at home will post when i get home

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    Sounds hardcore. Lol

    What's the duration at .050" on this cam?
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    Quote Originally Posted by CTD NUT View Post
    Sounds hardcore. Lol
    Exactly and first post on this site to boot. WTF.

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    lol not my first post iv been a member under mennnis but for some reason it wouldnt let met reset my password so i made a new account

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    Yes, we remember you.

    definitely need to post duration at .050 when you get it. That will likely tell the story of what is up with the cam. And beyond that, lobe separation is critical on MPFI engines as duration goes up. Cams ground for a carb engine will not work well.

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    im gonna grab the specs tmrw morning in not at home currently but the second i do i will post them up

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    off base circle .275 cl 440vL 230 degrees @.050 Removal / off ex - .078 , Int - .085

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    Quote Originally Posted by mennis View Post
    off base circle .275 cl 440vL 230 degrees @.050 Removal / off ex - .078 , Int - .085
    I highlighted the problem. Lobe separation would be absolutely critical with that much duration in order to reduce what is called reversion. Reversion is the entry of exhaust gases into the intake at low RPM. While this isn't a ton of duration, it is more than enough to cause problems on a low rpm fuelie engine that is not set up to deal with it. Low cylinder pressure will also be the result at low rpm and idle with that duration at .050. Again, it's not a ridiculous amount, but it is certainly enough to have the potential to foul up the running quality of a low rpm fuelie engine not set up to deal with it. I can only guess that lobe separation is inadequate at this point. Poor running quality, drivability and poor low end power will likely be the result with this cam.

    Without complicating things further, the simplest solution would be to get rid of that cam.

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    What to do?

    Are you the guy who wheels trout farms in spawning season?


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    Thanks CTD NUT every one i have spoken to said take the cam out. Im going to try setting my timing again with a degree wheel and a dial indicator on sunday if i get some time and if that dosent help then well i guise out comes the cam. would u also recommend buying a new head since thats been modified to im not sure the specs on the valves i will call the shop today and see how much bigger he went
    thanks

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    Heads are a complicated topic. Without having a clue what has been done, it is difficult to give any meaningful comments. But what I will say is this:

    If you intend to put a stock cam back in and the assembled height of the valve assembly has been changed and/or the spring seat pressure has been increased beyond stock, get it all put back to stock or if it is easier or more affordable, just put a stock head back on.

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    i think im gonna buy a used 4.0 and drop it in

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    Quote Originally Posted by mennis View Post
    Thanks CTD NUT every one i have spoken to said take the cam out. Im going to try setting my timing again with a degree wheel and a dial indicator on sunday if i get some time and if that dosent help then well i guise out comes the cam. would u also recommend buying a new head since thats been modified to im not sure the specs on the valves i will call the shop today and see how much bigger he went
    thanks
    One other thing you can try is to advance the cam if you are in there degreeing it. If your timing chain gears have multiple keyways, advance the cam 8-10 degrees. This will minimize the effects of too much duration at .050 but will not help much if lobe separation is undesirable. Advancing the cam effectively lowers the operating rpm range of the cam.

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    Quote Originally Posted by mennis View Post
    i think im gonna buy a used 4.0 and drop it in
    LOL...probably easier at this point if you are stucking paying someone to fukc with all of this. Bullwinkle on here has great deal in the classifieds for a late model 4.0 in great shape.

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    Might seem a little silly at this point. Are you sure about you valve clearances Im not sure if the clearances can be changed or not If they are hydraulic then maybe too tight. has the same effect at low rpm

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    Quote Originally Posted by SHREK View Post
    Are you the guy who wheels trout farms in spawning season?


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    Next weekend im going to do a cylinder leak down figure out why i have such little compression and go from there. dont want to spend any more money until i know what exactly my problem is and maybe i can get away with just putting the OEM cam back in and leaving my head the way it is

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