About 20 months ago I installed an LS1 (from 2000 Z28) cam and E-fans in my otherwise stock 5.3L. I did this because I had a collapsed lifter, and believed the LS1 cam may improve fuel economy. I swapped in LS7 lifters, shorter pushrods (measured correctly), LS2 timing set, ported the oil pump, and replaced all of the gaskets in the process. I also swapped in LS1 fans with a Nelson harness and had them switch on the fans in the ECU (although I have NEVER seen the low-speed fans on, not once). And then I made a DIY 4" intake using the stock airbox, some 4" aluminum tubing, and 90 degree elbow into the TB.

Before this, my truck got around 17-18 MPG, 75% highway. Now it's getting around 13-14 MPG, 75% highway, consistently. I get about 300 miles on a tank before I refill, and before got 400+ miles to a tank. It runs completely fine otherwise and seems to have a bit more pep in the top-end after the cam install. I'm not towing or hauling anything, and I have a very light foot, IMO. I cruise on the highway around 70 mph. Air filter is clean. Tires are always at 40psi, with around 20% tread left.

I use SeaFoam in the tank every now and then. I changed the plugs about 20k miles (~4.5 years) ago and the fuel filter. I also SeaFoam'ed the engine before the plug install.

Any thoughts? I would like to send the ECU back to Nelson for an economy tune in the near future. I care very little about power, I accept that this is a truck, not a sports car. Fuel economy is my #1 concern, looks #2.

Thanks!

 

My guess is poor tuning. The LS1 cam isn't all that much bigger than the stock LM7 cam.

 

I'm going to have to tend to agree with Scott.

LM7 Cam 190/191 .466/.457

Depending on what year your LS1 cam is
98-2000
202/210 .496/.496

2001+
197/208 .467/.479

Info from http://www.smokemup.com/tech/ls1.php

I'm running a bigger cam (and other mods) and my mileage went up from ~16 to nearly 20.

 

you could have a vacuum leak from the intake or CAI that you built... did you leave the screen in the MAF?

 

LS1 Cams, which did you install? As you can see there are a few different stock LS1 cams, and this is not all of them! Why did you install shorter pushrods? All use the exact same part# pushrod, even the LS6 uses the same part # pushrod as the LM7.

12554710 199/207 .479/.479 117 97-98 Corvette
12560965 198/209 .500/.500 119.5 98-99 Camaro & Firebird
12561721 196/207 .479/.467 116 01-03 Corvette
12561721 196/207 .479/.467 01-02 Camaro & Firebird

 

I believe the cam is from a 2000 Z28. The LS7 lifters are 0.050" taller than the stock lifters, hence the shorter pushrods.

I could be wrong, but I think Nelson only "tuned" the ECU to turn on the fans, I don't think they changed anything else.

Not sure if there is a vacuum leak in my intake tubing, it's sealed pretty darn well! I guess I could take it apart and put it back together, or put the stock intake back on. The MAF is de-screened I believe and I cleaned it at the same time as the cam install.

Truck has close to 100k miles.

 

Stock LS7 cam is 210/230 .561/.558 120 LSA, with the LS7 pushrod length of 7.750....I think (just my way of thinking) the shorter pushrod may be costing you some power. I dont know, woke up at 3am this morning so who knows.

 

Right, but the LS1 cam has the same base circle has as the 5.3 cam (I hope). The LS7 lifters I used are 0.050" taller meaning I would need 0.050" shorter pushrods to achieve the same preload, assuming the head gasket thickness didn't change. I used an adjustable pushrod to measure and 7.350" pushrods came out perfect. I wish I remembered the preload I used

 

Get a tune for the cam, even though it isn't a big step up, it'll defiantly help.

Should have left the screen in it, big misconception is that it restricts flow, but it's actually there to straighten out the air coming in and increases the speed the incoming air. I don't think it's a major deal, but it can cost you a few HP and ft/lbs, and could make it kinda a pain to tune, don't know that for sure though, because I'm not a tuner.

The LS7 lifters are taller, and require shorter pr's on stock heads, they also have a lot of travel though too. I don't know enough about the LS7 on why they need that long of a PR.

 

Get another and do not touch the screen.... What most tuners do to compensate for a missing MAF is multiply the MAF curve by 10% in order for it to work... 10% increase will cause a loss of MPG because it will be rich...