• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Camshaft and Misc Mods

04AvGuy

New Member
Joined
Jun 24, 2016
Messages
8
Location
Phoenix
I have a 04 with am lm7 with 155k miles and a rebuilt 4l60e (rebuilt 1k miles ago).  I want more power for acceleration.  I am thinking about getting a cam and headers but I am fairly new to the performance world and I don't know what supporting mods I will need if I get a cam.  This is a daily driver but I wouldn't mind a big cam as long as it wont cause a lot of problems.  The 2 headers I am deciding between are Doug Thorley or OBX and I will probably run true dual straight pipes out the back.  The cams I am looking at are all Comp Cams they are XFI? Xtreme Truck, G3 XFI 260 HR15, XFI? RPM, XR265HR, or XFI? RPM, XR269HR.  Some of the cams say they need a programmer, do I need to buy a programmer to go with the cam or can I just have the truck tuned by a performance shop and if I need it tuned how much will that cost?  Also will I need new push rods, rocker arms, springs, or anything like that?  Any tips on what to get and do are greatly appreciated.
 
I've got a fair amount of experience with cams in these trucks.  I installed a Crane cam in my truck that was a bit bigger than the XR269HR that you are looking at.  I helped install the hi-lift version of the XR265HR in a truck that I later bought for my son and have since sold.  In our 2000 corvette's LS1 I'm running the hi-lift XR281HR.  I also installed a custom spec'ed Comp cam for when I was running a supercharger in my truck.

The XR265HR is a very nice cam for these trucks.  My Crane cam definitely had more power above 4000 rpm but it would have to downshift more to climb hills at cruising speed then the 265 cam.  When I custom spec'ed the blower cam I basically ordered the 265 but with a degree more lobe separation angle and 10 more degrees of exhaust duration.  Unfortunately at 289K miles I retired that engine due to a slight misfire in cylinder 7.  I'd been running aftermarket cams in it for nearly 200K miles.  I'm now running a crate 460hp 6.0 engine.

You need either a custom tune or a canned tune specifically for these cams.  If doing headers as well I'd spring for the custom tune, or do as I did and get the interface and software and tune it yourself.  You will basically need to add idle speed and airflow and likely want to tweak your shift points as well.  There's other things you can tweak as well but for these mods those will be the most important.

You should upgrade your pushrods and buy springs that are recommended or comparable to what is recommended by Comp if getting a Comp cam.  In the vette I'm running Crane dual springs that spec close to Comp's recommended springs.  I ran Crane dual springs in my truck for the above noted approximately 200k miles and in the process of figuring out if the springs were causing my misfire I took the two from cylinder 7 to a machine shop and they measured dang near right at their original spring pressure specs.  That's why I put Crane springs in the vette last August when rebuilding the LS1 although these new springs are stiffer than what I had in the truck.

Stock rocker arms are fine - I even asked a Comp rep on the Hot Rod Power Tour this summer about anything they had to upgrade and the only thing he mentioned doing in that regard was doing a trunion bearing upgrade on them.  I haven't yet done that on my vette and didn't do it on my truck - I don't think it's a big deal for the cams you've mentioned.  If you do want to do that upgrade to the rockers note that some folks on the corvette forum have disassembled some rockers with the Comp trunion bearing upgrade and found a good deal of wear.  The Comp upgrade still makes use of needle bearings - the corvette forum upgrade of choice these days seems to be replacing the needle bearings all together with the Straub upgrade kit which uses solid bushings with an oil feed hole for lubrication.  Those may be a vette engine winter project for me but then again I'm shifting the vette engine at 7000 rpm.

Some will say you need to install a looser torque converter as well.  I didn't do that until after I did my first cam install.  While I wouldn't say that you have to do that, the looser converter will add to the punch you get off the line as well as keep the rpms from dropping as much on WOT shifts.  When you do that however adding an aux tranny cooler becomes a good idea, especially if you use your truck for towing or do a good deal of mountain driving.  I've got a pretty loose converter, a 3000 stall Circle D, but I didn't add an aux cooler until just before we took the truck on a Blue Ridge Parkway trip.  But I haven't towed anything with this truck since it was stock.

One last thing, depending upon the cam you choose and from that how high you are going to rev the engine, you may want to go with titanium spring retainers.  I'm running them in the vette although they were originally in my truck but I was shifting it around 6500 rpm.

By the way, the trucks noted above were a 2002 and a 2003...
 
Back
Top