CitrusTheDragon

I have 7 seater Ascender with a leaking, misfiring, tired old 5.3L. I have weighed the option of pulling it rebuilding it and then reinstalling it after adding some power here and there but looking into it a 6.0 sounds like a better idea all around. So I know it has been covered before but all the posts I have read are rather hyjacked or leave to many questions up answered.

I want to build a LQ4/9 with L92 heads but am very unclear on what else I would need to make it run and swap easily.

I have heard the injectors are different and I might need pig tails. Is this true if so where do i get them?

What is the best intake manifold to run? I have heard the ls3 with a 90-92mm might work or something called a fast 90. can anyone tell me?

What is the best cam to run? I have heard some rvs came with 6.0L and bigger would one of those cams work?

Will LQ9 pistons fit in an LQ4? Is there something better to upgrade the internals?

And what misc parts would I need/what would be a good thing to upgrade while I'm at it? I would also like to find parts from other ls motors that would be "upgrades" compared to what came stock on an lq4/9.

I need an engine that will not break the bank but will also provide a long life and good power. Also wife says it has to idel smoothly. So any help is much appreicated.

Werewolf SS

iTrader: (3)

Well since I'm doing a lq4 to 408 setup I can answer some of your questions.

The l92/ls3 heads will mount directly though most feel that unless your bored out to .60 this will cause shrouding, the l92/ls3 has larger then average valves and require at least a 4' bore. That being said the .30 bore is very common and used to make a 408 so 4.03 on the bore with these heads is ok. In fact 4 would be ok to you just won't get "peak" flow due to potential shrouding. Unless you making an all out racecar/effort build then don't worry to much on this.

If your using an LS3 intake that came with the injectors than yes you'll need pigtails. Any EV6 injector will require pigtails to convert to be used on an EV1 harness. The pigtails are on Ebay and rather cheap. Most prefer the hard plastic shells over the wire extension ones as it's one less connection to worry bout (the hard plastic is direct metal to metal so one connection whilest the wire ones are two connections the ev1 to wire, wire. to ev6 ).

Mixed feelings on this from everyone. I'm told the L92 truck manifold is the best option over the LS3 manifold if you have the space to use it. Barring that the LS3 is your best bet it flows great as is and can be picked up for a fraction of what a Fast 90 or Fast 102 will cost and those will only gain you 15hp at most I'm told comparatively.

No clue, not a cam guy. Maybe someone else can speak up or hit up Martin Tick or Pat G they can custom spec a cam or recommend a shelf cam that will come close.

Only difference between Lq4 and Lq9 is the pistons and maybe the cam if I recall. The pistons for sure as the lq4 had dished pistons for low compression and the lq9 ran flat tops for higher compression. The pistons themselves are the same size so yes you can swap them and lots do for the compression bump. They can be picked up cheap used of course or you can get replacement pistons non forged aka hyperneutic if your not looking to "race" the motor or do anything heavy performance to it. ie spray or blown.

You need to decide first what this motor is going to be? Race motor, or just something sportier then what it is now? No sense spending a lot of money to make something that has lots of power if your not going to be using it. If your looking for something with more pep then stock lq4 with a cam swap and a head swap would be more then plenty. Remember the stock LQ4 was 300hp and 360lb of tq. Your 5.3 stock is 270hp and 315lb tq.

LS3/L92 heads flow up high but that means you lose down low in tq. Are you going to be turning the engine to over 6k rpm's a lot? If not then I'd recommend sticking to cathetrdal heads so you don't have to change intake manifolds. Instead look into a cam swap for you LQ motor to pep it up higher and still get a big increase over your worn motor as is.

Just for ref I'm in the middle of a LS3 top end swap and here's what things have cost so far. L92 heads :500 BTR Springs: 200 LS3 manifold with injectors: 325 So you can see I'm already over a 1000 on just the top end a cam will run me another 3 to 400 on top of that.

So you need to decide what your budget is and what your wanting first.
Hope this helps some.

CitrusTheDragon

How big is the L92 TB and man? I recently had someone tell me to use the TB and man off a Trailblazer SS I guess it runs a 6.0 with a 87mm TB and a truck manifold I don't know how easily found they are but if the LS3 or L92 are roughly the same price and just a tad bigger I might just seek one out.




This is a truck for towing not much else. SO I don't need a huge boost in HP/TQ just enough to move my large truck a little better.

Sorry I am a little put off here. I thought the L92 cam in a truck/suv the redlined at 7. If it's honestly not worth it then I won't do it but if it will then me some extra MPG or power then I think it's worth it.

My budget is roughly $10,000 but I hope it's less.

And now that I have done some reading I might set the motor up to a 408, that should mate to the l92 heads a little better right?