I just purchased a 98 model. I think the engine has been swapped out. How can I further ID the engine where are the numbers located? I think the engine could be from an 04 model as the thermostat is not correct for a 97 thru 03.

 

Take a picture of the top of the block on the front where it meets the heads, and under the throttle body.

 

'97 & '98 have two fuel lines going into the fuel rails on the driver's side. '99 and up have only one.

 

Whats the casting number on the heads? It will be on the front passenger side coner of the head, just behind your idler pulley.

 

The fuel lines and rails are correct for the 98 it has 2. But I am thinking the heads and block have been changed? I can tell someone has worked on the engine as the wiring to the injectors and coils was not put back correctly. Also it originally had the pcv lines running to both valve covers and now the right bank valve cover has no outlet for this hose. Hopefully here are some photos.

 

I see no number will look again.

 

241 is the only number I can see on the heads.

 

2000-2004 345&350HP head = 12564241

Locate the block # + 3 letter Suffix # and post if you can find them

98 head = 12558806 btw

 

This is another mystery. Can anyone tell me what this vacumn looking hose went to? It is coming up from the back of the engine around where the heater vacumn line connection is located but appears to hook into a hard plastic line and continue downward at the bellhousing? It also seems that it went forward on the right side of the engine btween the valve cover and the intake. Looks like it was held in position with a plastic clip but there is where I found it open. It doesn't have a vacumn draw on it when the engine runs?

 

Where do I find a block number? I do not see any numbers?

 

Yep, those are later model heads.

 

I must assume it is an 04 engine. Only explanation for the thermostat.

 

Your engine should have a PCV system that has hoses going the each valve cover. Mine had a bad gasket where the PCV valve is an intrigral part of the system on the pasenger side. Sounds like your engine may have been damaged and some different heads installed. Or he had the same proble with the original PVC system abd did not want to pay 150 buscks for some rubber hose/PVC unit. The newer engines have a different PCV system where the drivers side valve cover is plugged and a valley pan under the intake supports the ventalation back to the throttle body. Also, as stated you should have 2 fuel lines associated with your fuel injection system. The hose coming out the pasenger side on your photo should of gone to your valve cove on the driver side. Note; if this is not set up, you are loosing power and the electronic putr will compensate and mess up power output. I had a small leak (hose deteriation at the PCV unit.and once I closed up the leak, say a good increase in power.
Look into getting a LS6 valley pan and eliminate the current PCV system. This will rid you of the hoses and increase performance, better yet suggest you swap out your LS1 intake for a LS6 while your at it. Have fun and play!

 

TECH may be able to answer this