Thread: *HOW TO* LS6 Intake Manifold Swap

Story:

I’ve been looking at doing this mod since about a month after I got the car, but for a lot of reasons couldn’t/shouldn’t do it until now. I definitely did my homework and mostly knew what I was getting into, so I took a half day on Friday and went to the auto parts store and the hardware store to get everything I needed. By Friday night I had the VLOM modified, the DOD connector modified, and the intake down to that last %$#@!*& bolt under the alternator bracket. I got the engine apart and cleaned up Saturday morning, then made the adapter plate, modified the LS6 intake, and then panicked when I saw how bad the fuel rail situation was going for me. The LS6 fuel rail just won’t fit, and requires totally different injectors. It is much much taller. The LS4 fuel rail doesn’t fit the LS6 intake, and it is off by almost 1/2”. So I got good at getting the injectors in and out and spent the rest of Saturday and most of Sunday massaging the LS4 fuel rail to get it to fit. I’ve heard that fuel rails are fragile, but mine might as well have been made of titanium. Sunday night I swallowed my pride and told my wife that I needed a ride to work, and then finished up by mounting the MAP sensor and doing a final mockup of the parts. Monday after work a friend came over and we cleaned everything up and bolted everything together. The fuel rail didn’t leak (thank you God) and she started up the first try. No trouble codes. I’m not mechanically inclined, but I do know how to use tools. All in all, I think that most people could do this mod, especially if you have done a head or cam swap on this engine. That looks even harder to do, minus the fabrication.

Parts List:

LS6 Intake and Fuel Rail, Crate Engine Take-off: $350 (skip the fuel rail and save the $$$)
VLOM: $200 New (Same part is on all cars and trucks with DOD, get one used and save $$$)
~3/16” Thick Plate of Aluminum (Intake to TB Adapter Plate, chosen cause I couldn’t bend it at all with my hands): $10
Miscellaneous:
Gasoline Safe Gasket Material
Auto-grade Wire (I used 18 Gauge)
Metal/Plastic Epoxy
Metal/Plastic Fuel Resistant Epoxy Putty
Heat Shrink
Split Loom (1/4”)
3/8” Vacuum Line Tee
3/8” Vacuum Line Inline Connector
1/4” to 3/8” Vacuum Line Adapter
3/8” to 1/2” Vacuum Line Adapter
3’ 3/8ths Fuel Line
2’ 1/4” Fuel Line
2 M6x1 70mm Bolts (65mm would work too)
1 M6x1 50mm Bolt
1 M6x1 45mm Bolt
1 M6x1 20mm Bolt
4 M6x1 Nuts
Assorted Washers, some will be cut up
Electrical Tape
Blue Lock Tite
Total Misc. Price: About $70, $100 if you don’t have anything.

Total: $630, although you could probably trim a lot more if you reuse your VLOM or buy a used one (which will make welding more difficult, but not impossible) and if you skip the fuel rail and buy a more heavily used intake. If you have a lot of the misc. stuff lying around, then you can save there too. I tried to make a complete list. A friend did the welding on the VLOM for me (thanks Alex!).

Pictures: (sorry about the quality, but I only have a cell camera)

1) A pic of that stupid bolt. It’s locktite’d, a 6mm (9/32 works) head, it took forever to get out.


2) LS4 fuel rail mocked up. The fuel injectors don’t even come close to being seated and the mounting points to the manifold are different.


3) The LS6 MAP sensor mounting point runs right into the power steering pump, and needed to be cut off and capped. Don’t mount the LS4 MAP to that point, cause it won’t fit either. (I tried it…)


4/5) Cutting up the LS6 to make room for the LS4 TB wiring harness. I needed to clear it up some more after this photo.


6) Modified DOD connector. I used a sawzall split the connector, then carefully peeled back the plastic to expose the conductors. I little soldering and heat shrink later, I thoroughly coated both ends in epoxy to provide additional strength. Notice the 1/2” vacuum fitting for the brake booster on the left: I had to step up the 1/4” LS6 vacuum fitting first to 3/8” then to 1/2”. I’m not completely satisfied with this, so I’m taking suggestions.


7) A pic of where the fuel rail clearance goes wrong.


8) Completed modified VLOM. THANKS TiredGXP for the idea!!!


9) The two VLOMs side by side. The official stock replacement part is thinner than what came on the car, and after I ordered it I checked and it is the same part number as the G8s and DOD trucks. Bolted in with no issues (107 in-lbs).


10) A pic of the Gen IV cast-in provisions for DOD.


11) The LS6 is a really tight fit, and if the power steering pump outlet was 1mm bigger this thing would not fit.


12) My adapter plate. I bolted the top hole to the stock LS6 location. I popped out the stock metal “nuts” from the LS6, and drilled it accommodate the LS4 bolt locations. They are not the same unfortunately. I then used the middle two holes to bolt the top of the LS4 TB to, and clearance the nuts by grinding the LS6. I still got 3 of the 4 holes in the wrong spots and had to hog those holes out. Should be a version 2.0 someday.


13) Grinding up a $300 intake… I was scared to go any further, but every little bit helped get the fuel rail on.


14) Plugged the LS6 hole and mounted the MAP sensor. Yes, it was a hack job, but I guarantee that sucker won’t be a vacuum leak. It just better never break. You can also see the mounting tabs that hold down the fuel rail. (87 in-lbs, lok-tite)


15) LS6 and LS4 side by side. The LS4 just looks weak. See the differences in the fuel rails though? No way that LS6 fuel rail will fit.


16) Better view of the Fuel rail mounting tabs. Yes, I shimmed them with washers, but that will get cleaned up later. I reused the EVAP Canister’s mounting bracket by drilling a new hole (front right).


17) Bolted Up! (87 in-lbs, lok-tite)


18) Notice how I routed the rear bank PCV hose to a T near the front PCV provision, and brought both in through a massaged stock fitting. Just personal preference. You can also see the that I had to make a new EVAP Canister vacuum line because I didn’t leave enough clearance for the stock quick disconnect. Oh well.


19) Another view, here you can see the OPSU hiding away as well.


20) Final view of vacuum lines and mounting tabs.


Easily the hardest part was getting the LS4 fuel rail to fit. I won’t promote or condone the violence I visited on mine, but a vise, a rubber mallet, and C-clamps were involved.

As for results, I really need to do a lot of tuning. It feels like I picked up a ton of low end torque and about 2MPG at light throttle. Other than that, sometimes it feels like a rocket and sometimes like a dog (as in no change, not slower), especially on the top end. This is such a drastic change that I feel like I should get tuned before I render a verdict. I’ll make it to the track as soon as I can after tuning.

PS – Yes it is the stock airbox, but I did take a sawzall to it.

Wow... Good job, not get her tuned and dyno'd

Nice work! I know the LS4s don't have much going for them but this definitely helps out a bunch.

Pic 8 was supposed to show how I modified the VLOM to make the OPSU clear the intake. I had some help on this part with the angle and the welding, from my friend and from TiredGXPs old post. I kept the OPSU in the same place by cutting the top off the mount just below the threads, then making a second cut at about a 30 degree angle so that when welded I would get the clearance I needed. I figured that I'd either have to plug the existing bung or have it welded shut, and couldn't find any M16x1.5 fittings (the size of the OPSU), so keeping it in the stock location like I did seemed easiest. A little grinding on the stock fitting would be necessary to clear the intake too. No reason you couldn't do it, it just seemed like 6 one way, 1/2 dozen the other, so I kept the sensor in the stock location cause somebody put it there for some reason. If you delete DOD, then there are a lot of other solutions.

Nice writeup for sure man!! Get a cold air and some exhaust work done to that thing...just wondering...why not run a LS6 throttle body too? Or can you not do that...just wondering since they are both DBW TB's

I really didn't look at the corvette TB... so maybe someone else can look at whether it is compatible or not with my E67 ECM. It would make the swap a lot easier. But, this decision was more about money because between this and the trans I've dumped a lot into the car, so the aluminum and bolts I used were a pretty cheap solution. I hope that I can sell the LS6 fuel rail and my old VLOM to cover some of the costs. I don't know why anyone would want my old LS4 intake manifold cause it is the worst ever put on an LSx, so I'm probably stuck with it.

I do want to get a CAI, mufflers and a Cat'd downpipe, but I think I should spread out my mods a bit so that I can enjoy them more. Also, I'm back and forth on which mufflers I want. I figure I'll at least do the mufflers by Christmas time.

wow man, that is sweet. nice work

Looks good Nate! Glad you were able to make it all work and it is running ok. Now onto the world of tuning and LS4

Thanks for the idea Panther, but no go so far. Maybe I'll clean up the LS4 intake up and hang it on my wall.

JDMC5 from over at LS1Tech helped me dial in my MAF last night, and the car really woke up. Never would thought that stretching out the tube that connects my TB to the airbox would make such a difference, but apparently it threw the MAF way off. I was running as rich as a pig.

There was snow on the ground this morning, so I will probably switch to my winter tires soon. I may not hit the track till next spring, but I will probably end up at a dyno with a few tunes in my pocket to see if I can't get dialed in and get some power numbers.

awesome work!!

way to be creative. i to would like to see what the diffrence is in power.

i know its old but did you have any cal issues after you swapped intakes?
and could you pm me the contact info for the guy that did your tuning.

Originally Posted by ford sucks

i know its old but did you have any cal issues after you swapped intakes?
and could you pm me the contact info for the guy that did your tuning.

JDMC is over on LS1tech.... he posts a good amount so just hit the LS4 Front Drive section and you will find him, he has the same name.

Yeah I had to retune. It helps to have someone show you the basics, which Jesse did for me. After you kinda get the hang of things, you can start searching and posting on the HP Tuners Forums for more advanced or specific stuff. Jesse is cool; I picked up a friend out of the deal too. He was just over this weekend helping me work on my cam swap. But, if you can't find someone close to you to help you get started, I highly recommend going to the library or the bookstore and picking up Greg Banish's Advanced EFI Tuning book. It will walk you through everything.

The swap changed my inlet routing, and thus threw off the MAF readings. The LS6 intake increased the Volumetric Efficiency by about 12% at the torque peak, but only about 5% near the redline because the cam was running out of steam. Good thing I just fixed that.... more to come.

i know this is old but i am doing this swap, and i noticed on ls1tech and gmls4 that nobody is having issues making the ls6 fuel rail work.
LS1/LS6 intake manifold swap why wouldnt it work for you?

Well, I did my swap first. I had a couple attempted/aborted swaps to look at, but no one else had taken this as far as I did. I also didn't know as much about all of the subtle differences in the various LS engines. I didn't realize that LS1/6, LS2, and LS3/4/7 used three different sized injectors until it was too late. David and others learned from this thread before trying several different things. You can use LS1/6 injectors, but they have different specs. David is only tuned with Diablo, which only has access to IFR and not all of the offsets and timings that account for non-linearities in injector performance. He has all of that error baked into his MAF transfer function, which I would argue is bad on several levels. It does still work though. If you have HP Tuners than using LS1/6 injectors is not as much of an issue. Regardless, I'm using drop in LS3 injectors now because of where my camshaft has placed my torque curve. I couldn't use LS1/6 injectors either, so I would have had to replace those injectors eventually anyway.

ok. thanks man.

care to share a little more detail on spliting the DOD connector up and how you went about it? im getting ready to do this and want to be fully prepared for everything.