Hey guys- first post here, and I'm asking for quite a lot of info.

I have some experience hot-rodding old Mopars and Oldsmobiles, and had a mighty hot '95 Cheyenne, but have never messed with a Vortec engine. Everything I've done in the past has been "wrench & pray," not "plug n play."

My '99 Silverado just turned 300,000 miles, but that's just the body. It's perfect, save for the obligatory fenderwell rust (dime sized hole just opened up, many more to come) and metal-deep scrapes on the hood from ice sliding off over the winter. I've tweaked it out with Escalade heated power leather seats, rebuilt the transmission last year, and the previous owner says he replaced the old 4.8 with a low-mileage 5.3. Evidence supports his claim: new bolts on exhaust manifolds, manifold to cat coupling, clean valve covers & intake, no oil underneath, runs smooth and quiet... but that's about to change. The knock sensors have crapped out on me, so I figure while it's down to change that stupid little flash of GM engineering brilliance, it's time to upgrade.

I've purchased a cam kit for my 5.3 (which may actually be a 4.8- not certain) and am wondering about tuning for the new cam. It's a Comp XER blank: 224/224 duration (273 advertised) and .581 lift, on a 112 deg LSA. The guys at Comp said -and I anticipated- that it would "need a tuner," but I'm not sure exactly what that entails. Can I buy a Diablosport and plug it in, and expect the computer to "learn" what it needs to know? or do I need to buy a Diablosport, have someone who knows what they're doing reprogram it to accept the parameters of the new cam, and THEN plug it in and "flash" my pcm? OR is it necessary with a significant bump in cam profile to take the truck somewhere and HAVE it tuned, skipping the Diablosport altogether?

Also, on the topic of hot cams, the sales rep at comp urged me to buy either a new set of rocker arms or a trunion upgrade kit, and said that, while the rockers themselves are bulletproof in the LS1, the needle bearings have a habit of falling out and getting lost in the engine until they destroy something. I've never heard of anything like this, and while I suppose it's possible, it seems pretty unlikely, unless the tolerances inside the rocker are way out of whack anyway, or the rocker arm is already failing. Anyone had that experience, or was the guy just listening to my excitement over a hot truck, and trying to sell me stuff on account of my enthusiasm? What cam mods have any of you made, and what else did you have to change to make them work? I understand that the engine is a SYSTEM, it's comprised of interdependent parts and none of them can be changed without affecting all the others. No need to bless me with that bit of mechanical theory. I got it. But aside from the obvious cam, springs, retainers, seats, lifters, timing set, & gaskets, I'm curious as to what NEEDS to be changed on a vehicle that will never see a race track, will rarely see 6000 rpm, and will be driven primarily as a weekend cruiser and occasional grocery getter.

Anyone?

 

Skip the diablow tuners, they aren't what you'd want to buy. If you buy anything and want to learn how to tune these vehicles you will want EFI live or HP Tuners. This kind of tuning isn't something you can just jump right into either, it does take lots of readings and research to understand what is going on and how things work together.

The new camshaft and other upgrades change the amount of airflow through the engine, so all those things need to be adjusted in the calibration. New VE tables need to be created and new MAF tables, then you have to adjust idle situations and WOT fueling and so on. It's alot to get done for the vehicle to drive and act normal without stalling or sucking down fuel like crazy. A dyno tune by a performance shop is the other option. I dislike the email tuning options because you have to sit and wait and wait for them to get tunes and then do data logging and do more waiting and hope it's okay.


Other things you might want are some long tube headers and likely larger fuel injectors because the stock ones are too small.

 

I have replaced sorings and rockers on 2 or 3 newer vettes that the trunnion failed on, trunnion upgrade is a good idea as there isnt a whole lot holding the bearings in the trunnion on the stock rockers, i had a similar comp cam with not quite so much lift, sounds like you have the xr281 i think it is, i had the 222/224 .566/.568 112 xr275hr and it desparately needed a higher stall converter.... The 4.2 tb converter was a good temporary fix until i swapped my cam and trans and instalked a circle d 3000 stall... With unknown mileage on the engine a set of lifters is not a bad idea!!