I have a lq4 I would like to swap into my trans am. I also have a complete ls2 ( bad crank) to source parts from. My question is am I better off leaving the lq4 alone and just putting in a cam, swapping ls2 pistons and connecting rods, swapping the 243 heads, or a combination of the heads and pistons. I have read somewhere that the 243 heads would limit camshaft size, but I am not sure to what extent. I am just looking to make a little over 400 HP and have a usable power range for around town use as well as top end.

 

Forgot to mention I will be using ls6 intake and longtube headers

 

I would swap the 243 heads to the lq short block ,and install a cam to your liking .sell the ls2 short block and lq4 heads for parts money .

 

can the crank be turned down and repaired? i don't believe you can swap the ls2 piston/rods to an earlier lq4 crank without a balancing job. what year is lq4? for sure run the 243 heads.

 

That's what I've been leaning toward. I read somewhere that the 243s would have less PTV clearance thus limiting my can selection. I know the combustion chamber is smaller but I'm not sure about the depth of the valve faces in the chamber that would change the PTV so much. I guess I could check it out when I pull the 317s off. I believe the lq4 is an 03.

 

The stock 243's won't reduce PTV.

Is the LS2 block junk?

 

The block is good. #1 rod journal is worn down very badly from spun bearing. I am undecided if I will sell it or hold onto it for a future build.

 

Do u have a can recommendation? A fast intake isn't in the budget this season. Car will be m6.

 

Why not use the LS2 in your Trans Am? You could use the LQ4 crank, especially if it has a 24x reluctor wheel. Basically it boils down to whether or not you want an aluminum 6.0L or an iron 6.0L.

 

Wouldn't the crank and ls2 pistons and rods need to be balanced together as an assembly? I kinda don't want to just mix and match internal rotating assemblies and expect them to work out. The head swap seems very straightforward while not compromising the balance of the engine. Not sure on the weights of the different components as the rods and pistons are different designs but I'm sure it'd be enough to matter. Correct me if I'm wrong.

 

The LS2 has better rods in it than the 03 LQ4... and as a result you need to run the LS2 pistons.

I'd ether run the LS2 block with the LQ4 crank and LS2 rods/pistons (balanced), with the LS2 conversion parts. Or, if the LQ4 block can be salvaged and you can sell off the LS2 block (it will be worth more), then run the LQ4 crank and LS2 rods/pistons...

Comes down to whether you want to spend the extra cash on the LS2 valley, front cover, and harness extensions, or if you want the extra 100lbs of the LQ4 block on the front of the car. Also, if the LQ4 needs to be repaired, the LS2 might be cheaper to put together.

 

Yes the crank will need to be balanced for the LS2 rods and pistons, whether they go into the LQ4 block or into the LS2 block. It's not that complicated or difficult. I have LS3 rods and pistons and an LS1 crank in my engine. It all goes together just like any other engine.

 

Thanks for the insight. The lq4 was a good running engine. I think I will swap the 243s on there and pick out a can. Going to dyno it after install in the spring.