Hey everyone.

Im looking into swapping a LQ4 into a manual C5
I know the bolt pattern is the same on the torque tube, but I’m not sure about the engine mounts. Since it’s a truck engines are the mounts different? Will I be able to just drop in the engine? Wiring harness/ecu compatibility issues? I’m assuming it’s a pretty direct swap but I want to make sure I have my bases covered before trying to cram it in there and realize it’s a bigger job than I was expecting.

Thanks!

 

It might fit, but there’s no such thing as an easy swap

 

Beware which LQ4 you get. The older ones ('99 to '00) have the same length of crankshaft protrusion as the older small blocks. The older LQ4 are easy to spot with their iron heads. The '01 and later ones have a shorter crank, require a spacer between crank and flywheel to bolt on older transmissions. I don't know which "thickness" flywheel the C5 uses.

https://www.onallcylinders.com/2018/...ads-cam-specs/

Otherwise, I don't know of any real compatibility issues besides the obvious... intake, exhaust, oil pan/sump, etc.

 

Thanks! Thats good info. So if I got a later block (Which I plan on), I’d need a spacer. I’m planning on putting a different clutch with a lightweight flywheel when I put in the engine in, so I’d need to take that into account. Has anyone else done this swap or know someone who has?

 

It's quite possible the flywheel in C5 is already meant for the shorter crank flange. Only the LQ4/LQ9 are like that for those early years and I think it had everything to do with GM needing to stick with the 4L80E that came in 3/4 tons.

As far as I know, all other LS motors, 5.3, 4.8, etc have the shorter crank. Odds are the 5.7 does too.

 

One thing i remember the lq4 has a 58 tooth relucter on the crank, you'll need a converter box.

 

I swapped an '02 or '03 (forget which year) lq4 in my c5 6sp and didn't have any issues mating the clutch/flywheel to the motor. I did have to grind the lq4 block on the passenger side to get rid of a boss that was used for the ac when the motor was in the original truck. If you don't grind the boss and part of the web, your motor mount bracket on the passenger side won't fit.
I also had to run the driver ground cable to a different mounting hole as the lq4 block didn't have a hole in the same spot as the ls1.....no prob tho, the cable was long enough to bolt into one of the other unused holes on that side, just needed some slight re-route.
My lq4 was also 24 tooth.

 

I have an forged stroker LQ4 in my car. Since the crank is aftermarket it has the correct flange on it. Obviously 24x reluctor.

If you get the right LQ4 combo it will bolt into your car exactly the same way. Batwing pan and all.

Also I'm surprised no one mentioned it. You will notice that extra 95 pounds on the nose of the car. Some people care, some don't.

I ended up having to put C6Z shocks on the front of my car to control the extra weight.

If you have any other questions I can try to answer them as best as possible.

 

Moved to C5 Tech.

 

From the photos it certainly appears you’ve put the strength of the iron to good use. Do you regret the change?

 

Well unfortunately it was kind of a forced change. I do regret blowing up the original low miles LS1 in a fashion that has a lot of us including a bunch of professionals completely stumped. The collateral damage was extremely expensive even with the whole thing being done by my labor.

So where I am going with this is I regret making decisions based on finances and frustration of expense on the rebuild.

At the time finding a LS2 block was virtually impossible and the couple I did find they wanted way too much for.

The shop that built my short block could and would have built me a 416 out of an LS3 block but that was another 1400 to the bill.

At the end of the day it cost me 9600 dollars to put the car back together in a timely fashion all because I blew up the original motor.

Looking back at it now, yeah, I kinda wish I would have spent the extra money and been done with it. Between the block, the blower, and the intercooler system we're probably in the 185 pounds range for extra weight on the nose. That being said with the C6Z shocks and C5Z front sway bar additions and leaving the rear stock it really is pretty nicely balanced and most people would never be the wiser.

The other thing I'm at peace with is the motor is a very nicely documented build (built and rings gapped for 20psi) and any given point I could take that engine out and easily sell it for probably upwards of 10k dollars.

 

Hello, I'm thinking about doing this exact swap, but I currently have a forged ls1 with 243 heads in my 99 frc with an A&A supercharger on the way. I planned on just building a short block from my current lq4 I just got off of Facebook. My question is, should I just be able to take all accessories off of my ls1 and put on the 6.0? Does the batwing fit fine? Is there anything special I need to take into consideration? Thank you!

 

Everything is literally the same.

You just need to make sure your LQ4 isn't one of the early ones with a long crank. If it is a long crank version I don't know of any easy workarounds.

 

That is perfect. Thank you sir!

I don't think it'll matter for the year because its going to be a new aftermarket forged rotating assembly. So it should be updated with the new design I would think.

 

Ok cool. Same route I went. The aftermarket crank will be good to go.

You 6spd or Auto?

 

I don't know how I missed this the first pass through but this is not correct. They are 24x.

 

Yessir im excited for it!

6 speed.