I have a 4.7l and the heads were trashed so I bought a set of 4.7 jeep H.O. heads. Now I didnt replace the tensioners and there is a little noise for a moment at start up, there is a rattle around 3,500RPM's.... If I keep it under 3500 it runs and sounds great. Should I be running a shorter plug with these jeep heads? I used the stock head gaskets. I have a superchip tune and afe intake if that matters at all.

 

You can go to www.sparkplugs.com and type in vehicle information,
FF

 

You should replace the chain and the tensioners.

On a 4.7, loose chain adds wear to the tensioners and worn tensioners lead to wear and stretching on the chain.

IndyD

 

When I installed the heads I used the new gears,chains and rails, primary tensioner. I DID NOT replace the two hydralic tensioners and I am regretting trying to save that $110 bux now. Truck had me scared bad it was making a horrible knocking noise. Pulled plugs and saw electrodes with the tip bent over on it. After I re gapped them all and ran it down the freeway it sounds fine now..... Just trying to pinpoint my issues I had to swap a few things like the trigger wheel on the heads to get them to work right on my ECM. Just wanted to make sure the plugs are the same height since I ordered plugs for a 4.7 Dodge not 4.7 H.O. Jeep....

Edit: Found a site with some good H.O. info, plugs should be SPRC7PYCB4 not sure what I got in there whatever Autozone pulled up for it....