I have a 2003 Dodge Ram 1500 HEMI. My truck has been having a **** idle. And today I put my compression gauge on the engine and found no compression in the number 4 cylinder. So I need a new engine.

My question…..what am I in for? I have replaced engines in the past. Just not on this truck.

Also where is a good place to find an engine?

And why did this thing blow?

 

A compression test will not tell you if you have a blown engine. It literally can only measure compression. There's a few ways you can lose compression. Burned valve, dropped valve seat, dropped valve (broken spring), broken ring, (badly) blown head gasket.

I'd first recommend you pull the valve cover and inspect your springs. It's very common for the springs on 03 hemis to break. It's a free diagnostic and doesn't require any other special tools.

Beyond that I'd run a leak down and find out where the compression is going.

 

Been known to happen, but it's not as all encompassing as everyone thinks it is. You only ever hear about the breakages, not the 1000's of trucks that are doing just fine lol (I have over 160k on my original 2003 springs).
Everything else is good advice. You may just need to fix/replace a head. Like he said, pull the valve cover and see what you got. If you don't have one I'd rent or buy a borescope or similar camera and look down one of 4's plug holes. If something catastrophic happened it will be PAINFULLY obvious.

 

I bore scoped the problem cylinder. The piston looks fine. So I’m going for a valve problem.

 

Pull the valve cover, see what ya got.

 

Agree with above ! Valves or head gasket. Just because you lost compression in a cylinder, doesn't mean you blew the engine ! A rod through the side of the block, then ya you got a blown engine. however you probably should do a top end on it !

 

If you can do it yourself, probably cost $200, If you have to pay someone, a lot more than that.

 

Replacing entire engines is in my skill set. If I can get away with just a top job then cool! Might want to pull and recondition the other head while I’m at it.

 

Doing both heads while you have it apart will likely have you doing the job only once, instead of twice.

 

My thought unfortunately also.