1duke1

Hello all,

2010 JK Unlimited in the shop with broken #5 valve spring...valve dropped and currently won't move, suspect that it is bent, and probably had contact with piston. Waiting on scope results as to whether piston is damaged. With all the diagnostics, I'm probably already about $700 in....if piston comes back damaged, should I replace motor, or go with a rebuild? And, stupid question time, if I replace motor, can I replace with a newer Pentastar? I'd go with a hemi conversion, but I have 4 daughters....so no fundage

Thanks for help

-Duke

karls10jk

The Pentastar swap in the early years has been done but it's a little tedious to do/ have done. I'll be following because my '10 will be due for a motor sooner or later. I'm leaning towards a rebuilt. There's a company (I'd have to find the info) that offers a high year/ mileage "no fault" warranty that looks to be a good deal.

1duke1

Thanks...I'll let you know. Found out today they could see where valve had hit the piston, but could not tell if it had been damaged. They were going to remove the head to get a better look, but didn't get an update. I really don't want to have to replace the motor.

jedg

This might be worth your read.

https://www.jk-forum.com/forums/modi...r-swap-325039/

1duke1

Thanks jedg...was a good read. Fortunately, looks like I'm dodging a bullet with this one. Piston looks ok, rings look ok, so looking at new valves and springs.

Just hard to believe that a valve spring would break on a motor with only 41k mileage.....damn things are supposed to last forever!

ronjenx

I've seen it quite a few times over the decades. Saw a rocker arm break once on a 350 with only a few thousand miles on it.