rattlin' valves

I have a 99 Z71 Silverado with a 5.3L and 77K miles. When I bought this truck used about a year ago w/45K on it, i installed a hypoertech 3 tuner. I noticed running regular gas after installing this made the valves rattle sometimes, so I started using 93 octane and have ever since. (yeah, $1.71/gal hurts sometimes) Anyhow, I recently had to replace the head gaskets, the passenger side one had a small hair-line crack in it and it was leaking coolant intot he oil. Ever since I had this done, the valves rattle when going uphill or when the truck is under a minor load, if I stomp on it it goes away. I un-installed the hypertech for about a day and then re-installed it, but nothing changed. Has anyone had this problem before, and what can I do to fix it? Its starting to annoy me VERY badly. Thanks lots

I have a 1999 Z71 GMC 5.3 liter truck. When the hypertech 3 is installed in my truck and I give it gas without letting it downshift there is a bad rattle in my truck. It also is bad when going up hills. When it is not installed there is no problem. If anyone has a solution to the problem please let my know.
Thanks.
Tom

I've figured out what is causing them to rattle so badly. The fellow that installed my head gaskets said that he "may have" not set the timing back corrrectly. I'm not really fimiliar with these new vortec engines, but I havent seen a distributor on it. I know its got to have something like it, but I cant find it. I'd like to check the timing on it and see if it is off any. Do you check the timing on these engines like you do any other vehicle with a regular distributor, or is there some special way to do it?

There is no "adjustment" for timing on those engines...
If the distibutor was off, the SES light will illuminate and set a code.

To adjust the dist. you will need a Tech2 or other scan tool that is able to read camshaft offset...by turning the dist, the offset should be 0 degrees at 2000 rpm.

But is it possible for the rattling of the valves to be caused by the mechanic not having it set correctly, or is it possible that he could have even changed it?

$1.71 for 93 octane?!#$ i want some. 91 octane here in town is $1.89 :mad:

93 octane has been as high as $1.96, but now its on what I guess you'd call, a downfall. It hasnt been below 1.70 in quite some while though. I can get it in Columbus, Georgia for i think..$1.60? That city is 45 miles away, but worth the trip!