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383 240z

LM7 vrs LQ4 Need help deciding

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1972 Datsun 240z



Equipment already installed:


TH-7004r built to race spec

Dana 44m from '84 Corvette 1 ton half shafts

LS1 fuel tank

JTR kit with a Gen 1 SBC TPI injection

Megasquirt fuel control

LS1 fuel tank with Corvette FPR




450RWHP in a streetable package  

MAY add FI down the road if 450HP gets boring

Must run on pump gas. Prefer to have TQ in the low end, and give up some HP at the upper RPM limits



I've decided that the SBC in there just has to go. I've got 2 LS engines to choose from but I'm having a hard time deciding. What does the board think?


First up:


2004 Chevy van  2500, 5.3l LM7 4l60, AWD rollover.  Mileage unknown, oil looks good, radiator is full. It's drive by cable but missing PCM

No body panels are sell-able, no oil on the trans dipstick, rear axle looks good  Cant be started 

Whole van can be bought for $500 Craigslist deal  no returns


Second option:


2000 2500 Chevy truck  6.0l LQ4 with iron heads. 4l80  light front end hit, rad is fine, rusty truck. not sure why its in the yard

no dipstick, I grabbed one from a SBC and put it in the dipstick tube, no oil. I looked in the filler cap, no sludge.  They said I can pull the rocker covers and spin it over by hand.  no starter to spin it up for a compression test.  waterpump turns by hand, alternator has a little drag from corrosion, so it spins with a slight drag

I have to pull the wiring and PCM, they will pull the engine.  Only thing I see missing is the starter and dipstick.

I can get the engine, wiring and PCM for $450 From a junkyard, no warranty as they cant start the truck to test the engine




Thoughts on what would be better for my application and goals?  Thanks for the help guys this will be my first LS swap  Still putting together what works with what.  The +.400 crank on the LQ4 has me concerned.  From what I'm reading the 700 will bolt up if I slot the flexplate to fit my torque converter.  Not worried about the wiring, more concerned with the fitment using my JTR kit, the ability to keep the 700.  









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You won't get 450rwhp out of a streetable 5.3 NA, even if you go 11:1 compression ratio. Lq4 can get you there, but the if you're going NA, you'll need to bump up compression. if you decide to go NA, then decide to go forced induction, then you'll want to drop compression ratio a little bit. To save you money in the long run, if you think you're going to go forced induction, chances are you will eventually. Building a mean NA engine will eventually cost around the same price as a FI engine. I say get the lq4, build it for boost. Do it right the first time and save money

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I was thinking that my goal was a bit out of reach, I have a line on a set of 317 heads for if/when I decide to go FI.  


Am I correct in my thinking that a +.400 crank and a flat flexplate will work with a TH700r4?  Am I also correct that it will only work with pre-2001 4L60's?  

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Don't know anything about the auto trans. My truck's manual trans, cammed otherwise stock LQ4 with a LS1 car intake and long-tube headers made 389hp and 428#tq on the chassis dyno. In hindsight I would gladly give up some hp to not have so much un-burned gas coming from the tailpipe at idle. I daily drive it on 87 fuel. I don't know the specs on the cam. I think it is pretty easy to get 400-ish hp from a 6.0, but getting that extra 50 hp is gonna take some cost and effort. The new FAST intake is $1,000 and even with my mild can, parking lot speeds are a bit of a rodeo. An auto trans would likely calm the bucking that I have at low speeds. Good luck!

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