LS3 install questions

E

Alex

Some questions about installing an LS3

- Where does the regulator go? before the fuel rails or after (i.e., loop the rails together, then have the regulator on the outlet side). Or does it matter if you're using OEM vs aftermarket fuel fails where it goes?

- How do you handle flipping the intake and the oil pressure sender? I see katech sells (or sold) an adapter specifically for manifold flips, would it require welding? What's the most common way to do this?

- If I'm going to do basics h/c/longtubes/fast 92, am I better buying a GM controller unit and using that, or going aftermarket with a self-learning one like the fast xfi or holley dominator? FWIW my tuner is most familiar with hp tuners, but I'd like to be able to drive the car w/o it being fully tuned first.
 
P-nut

Will Campbell

EFNFAST said:
Some questions about installing an LS3

- Where does the regulator go? before the fuel rails or after (i.e., loop the rails together, then have the regulator on the outlet side). Or does it matter if you're using OEM vs aftermarket fuel fails where it goes?

- How do you handle flipping the intake and the oil pressure sender? I see katech sells (or sold) an adapter specifically for manifold flips, would it require welding? What's the most common way to do this?

- If I'm going to do basics h/c/longtubes/fast 92, am I better buying a GM controller unit and using that, or going aftermarket with a self-learning one like the fast xfi or holley dominator? FWIW my tuner is most familiar with hp tuners, but I'd like to be able to drive the car w/o it being fully tuned first.
Click to expand...

Welcome to the land of the ordinary, Alex. :)

Re the intake, it's easy to flip, and I used the Katech valley cover and sender adapter. No welding, just a bolt-in. Remove intake, remove old valley cover, remove original sender, install new valley cover, install new sender adapter and your original sender, flip intake, tighten original bolts and verify fit to the gasket and heads.

I think the GM harness and computer is a great solution for "ordinary" engines. Unless you are going to do something very extreme, there is a lot of power in the GM OS. And everyone with an HP Tuner or similar has access to it. Did I mention it's under $1000, complete with harness, computer, MAF and related stuff?
 
E

Alex

P-nut said:
Welcome to the land of the ordinary, Alex. :)

Re the intake, it's easy to flip, and I used the Katech valley cover and sender adapter. No welding, just a bolt-in. Remove intake, remove old valley cover, remove original sender, install new valley cover, install new sender adapter and your original sender, flip intake, tighten original bolts and verify fit to the gasket and heads.

I think the GM harness and computer is a great solution for "ordinary" engines. Unless you are going to do something very extreme, there is a lot of power in the GM OS. And everyone with an HP Tuner or similar has access to it. Did I mention it's under $1000, complete with harness, computer, MAF and related stuff?
Click to expand...

My days of extreme are done sadly ...... now I long for simplicity :)

I guess the nice thing about the GM harness is there have to be dozens of tunes for head/cam/intake/exhaust engines so I should be good out of the box almost.

How about fuel rails ..... any ideas where to locate the regulator?


Also, what about the fact the digidash comes with different sensors than the GM harness?

For example, oil pressure - GM harness is a specific metric thread, digidash is 1/8'' NPT. Do I need to use 2 of each sensor s(one for the gm harness, one for the digidahs) or how would I go about doing this (using oil temp and pressure as an example, since they have different threads and different reading metrics)
 
P-nut

Will Campbell

EFNFAST said:
Also, what about the fact the digidash comes with different sensors than the GM harness?

For example, oil pressure - GM harness is a specific metric thread, digidash is 1/8'' NPT. Do I need to use 2 of each sensor s(one for the gm harness, one for the digidahs) or how would I go about doing this (using oil temp and pressure as an example, since they have different threads and different reading metrics)
Click to expand...

Alex...he's the new normal. :)

For the Digidash, each head has an unused plug for water temp, so you can use an adapter and plug in the DD sensor for that. For oil, I'm not sure. I have a dry sump, so there are plenty of places to tap into. Maybe Wayne has already done this?
 
E

Alex

I suppose you could just not hook up the oil pressure and temperature into the gm harness because that shouldn't care about those (just water temp)?

Or will it go 'OMFG! NO OIL PRESSURE! I NO RUN!'?
 
Big-Foot

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
So Alex, you came over to the dark side my son....

Going to carry your carburetor around in the passenger seat? :)

Sorry could not resist.. Fear not, you will never be confised for someone "normal"...

You will learn to love the LS3. Its a great mill....
 
E

Alex

Big-Foot said:
So Alex, you came over to the dark side my son....

Going to carry your carburetor around in the passenger seat? :)

Sorry could not resist.. Fear not, you will never be confised for someone "normal"...

You will learn to love the LS3. Its a great mill....
Click to expand...

If I could fit a carb I would. But you can't unless you use an ls1 intake manifold (which is really tiny runners) or you don't use a stock window.

FWIW I've got a fully ported LS7 intake manifold and a Braswell custom-built 4150hp carb sitting right here that was meant for the SLC initially. Frrrrrrrrrrrrrrrg.

Yes, I bought almost 3k worth of high end carb parts to use on this car before I even had the engine finished. :/
 
KENS80V

Ken Roberts

Supporter
Oil pressure and oil temperature sensors aren't used with the GMPP harness.

The easiest way to route the fuel system is to use the stock fuel rails and a returnless delivery. The C5 Corvette filter/regulator is ideal for this and cheap. It can support up to 600hp. The 6AN lines will support those horsepower levels.

Alex you can save money and modify your own valley cover. That is what I did. You simply cutoff the oil pressure sensor tower then give it to a machinist to mill down 1/8" below the top. Buy the sender elbow from Katech or CustomBuiltMotors then trace with a marker where it mounts and have that area milled down about 1/8". The modified valley cover from Katech costs $200. You can have yours modified for $50.

I've seen "Custom built motors" sell the elbows on EBAY with 1/8 npt threads too.
 
Last edited:
W

Wayne

Alex, regarding the oil pressure and temp sensors. There is a block off plate right behind the oil filter. If you are using just one sensor you can drill and tap that plate. If your running an engine oil cooler Lingenfelter makes a nice piece that has ports for both sensors. I didn't like running oil lines so close to the exhaust and didn't plan on running an engine cooler, so the Lingenfelter adapter is on the shelf. I made my own adapter. All three are in the pic. The small one is the stock block off plate and mine is the one with the sensors in. Whatever method you use make sure it's designed to circulate oil (loop).
 

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dlindemann

Dave Lindemann

Lifetime Supporter
P-nut said:
Welcome to the land of the ordinary, Alex. :)

Re the intake, it's easy to flip, and I used the Katech valley cover and sender adapter. No welding, just a bolt-in. Remove intake, remove old valley cover, remove original sender, install new valley cover, install new sender adapter and your original sender, flip intake, tighten original bolts and verify fit to the gasket and heads.
Click to expand...

Will - Thanks for that tip, I just ordered the valley cover and sender adapter for my LS3. One less thing to have to mess with once I get to that point.

Dave L
 
E

Alex

KENS80V said:
Oil pressure and oil temperature sensors aren't used with the GMPP harness.
Click to expand...

So is the only sensors the GM harness uses that the digidash uses then the water temperature? (I imagine it needs to know water temp to know when to do open/closed loop?)
 
W

Wayne

I have that aeromotive fitting on the fuel rail. No leaks.

regarding the tach signal to the DD, check out Dean's build log. He has two good pictures using the tach wire and 12V from the bulkhead connector on the GM harness and a 5k resistor. I have accurate reading on mine.
If you need a few male pins for the bulkhead connector let me know.
 
E

Alex

Can oem fuel rails be flipped around so the inlet is on the passenger side and not driver side?

Also, when you p[lug in the injector wiring harness, does the order change or do you plug it in as if the manifold were facing straight ahead and in a normal application?
 
P-nut

Will Campbell

EFNFAST said:
Can oem fuel rails be flipped around so the inlet is on the passenger side and not driver side?

Also, when you p[lug in the injector wiring harness, does the order change or do you plug it in as if the manifold were facing straight ahead and in a normal application?
Click to expand...

I was told recently that the rails were indeed flippable. Which, if true, is nice, as it allows more flexibility in fuel line routing.

The firing order doesn't change no matter how the manifold is flipped.. :) it should be obvious where the connectors go as they are pretty clearly labeled.
 
E

Alex

P-nut said:
I was told recently that the rails were indeed flippable. Which, if true, is nice, as it allows more flexibility in fuel line routing.
.
Click to expand...

True - all my fuel stuff is on the passenger side. I thought that the rail was on the passenger side because I figurd if you flip the manifold surely you have to flip the rail, haha.
 
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