im thinkin bout rebuilding my 3.9 and im making a list of parts i need to get. i was wondering if a bigger cam would help out. if so can anyone reccomend one to me. should i replace the timing chain and gear and main bearings? thanks.

 

wait does that mean my 3.9 has a cam

 

If you're rebuilding a motor, you should replace ALL the bearings. You should get the block honed and get all new piston rings. If you want to go really crazy with it, get it bored .010, .020, or even .030 over and get new pistons too.

A new timing chain and gear would definately be a good idea, since yours is likely stretched a little bit with age. You should look at getting a double roller timing chain... they're stronger.

As far as a cam goes, you're really limited for the 3.9L, but I think hughesengines.com sells a selection of them. Keep in mind though that you HAVE to replace the valve springs with a new cam... so matter how mild the cam. The factory valve springs just aren't worth anything. As far as a cam choice goes, it really depends on what you want. If you get into the aggressive arena with cams, you'll need to look into a high stall converter for your transmission if its an automatic, and a new computer tune as well. But if you stay around 480 lift or below and below 220 duration at .050, you should be good with your factory transmission and computer and all you'd need are springs.

If you want to avoid replacing your cam and springs, you can get 1.7 ratio roller rockers instead. They don't make a kit that I know of specifically for the 3.9, but you can get them for a 5.2L v8 and hang on to the extras in case you'd ever need them.

 

All 4 stroke engines have cams... even your lawnmower.

 

wat kind of power would the rockers bring if i put them in? im not lookin to go real crazy right now on a count im in college and am a little short on cash.