I'm planning to replace my worn out short block with LS3 FI short block in my 2003 Chevy truck. I will be using LQ9 stock top end with LQ9 intake. I have Isky Triple 12 to go in. I'm not after revving past 6200rpm and hence the smaller cam to keep near stock manners.

My question is the LS3 short block going to be direct swap using LQ9 covers heads/cam/intake?

I searched but could not get a definite answer. Do I need LS2 conversion kit? Are the covers from LQ9, timing cover, front and rear covers and valley cover going to fit?

Here is the short block, I'm thinking of. Mast tech tells me it will be direct fit but I'm in doubt.

Mast Motorsports High Performance Powertrain Solutions

Here is what I found out about the different blocks.

“GM does offer a Gen III and Gen IV 6.0L iron block. The Gen III block will be similar to an LS1/LS6 block and will use all necessary LS1 covers, gaskets, and components. However, the Gen III block will use the LS2/LS3 cylinder head bolts. The Gen IV block will be an LS2/LS3 style block that will use the LS2/LS3 lifter trays, timing cover with cam position sensor, valley cover, etc. If you are installing the engine into an LS1/LS6-equipped vehicle, you will need to choose the Gen III block. If you are installing the engine into a 2005 or newer vehicle, you will need a Gen IV block.”

 

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Is this a unique swap? hmmm

 

Yes the covers will work on the new LS3, everything will swap right on over, don't forget the oil restrictor (little bar bell looking thing) in the rear cover.

 

You mean the oil galley plug, yah. I've be through trouble with it before.



Ok, so all covers will fit. How to connect the cam sensor, since ls3 block does not have place for cam sensor at the back of block like LQ9/LS1 blocks?

I will be using LS1 cam but how to connect the cam sensor harness of LQ9 engine?

 

The only real differences you will need to plan for as far as I can think right now will be the cam position sensor and the knock sensors. You will need to rewire those or get a harness that will adapt to the new locations.

 

Rewiring will not be a big issue. My concern is cam sensor connection. LS3 block does not have rear tap for cam sensor to fit. LQ9 front cover does not have front cam sensor setup.

So, I guess I will need to change front cover with LS2 or LS3 cover. What else?

 

I am doing a GEN IV now that will be running on an older PCM. I have had to use the LS2 front cover, cam gear for the 3 bolt cam. The cam gear will have the portion on it for the sensor to pick up on the cover. You will need to tap the side of the block for the knock sensors and extend the harness to hook them up. I have not messed with the knock sensors yet, but it seems as though you need to sensitize them in the tune to have them pick up knock properly. If the engine you are getting does not come with covers, you will need the valley cover, or make provisions to block off the oil holes. On a GEN IV block there are 8 holes that run from the lifters to the top of the engine. The holes are blocked off by O rings that are mounted in the cover. If they are not blocked off you will leak oil internally, and lose oil pressure. Another option would be to tap them and use plugs. The GEN IV valley cover also has a tower in the back for the oil sensor. I have not held covers next to each other, but the easiest way would be to just get the cover and a gasket kit unless you wanted to mess with it. And last off the top of my head, you need to run the 24 tooth reluctor wheel. That's about all I can think of now.

 

Any pics & PN's?

 

This is what the O rings and gasket look like for the GEN IV.

 

My engine came with the valley cover. I ended up getting the LS2 cover with the sensor off of ebay along with the valley cover gasket (I couldn't find it at Summit). You could use your cam gear and reluctor wheel off of your LQ9.