my engine is a DOG

jbeckett25 · September 26, 2012

Ok guys here's the rub... I had a lifter loose a bearing and chunks come out of the roller on my 2006 5.3 (T) 1500 sierra z71 crew cab. I was told it was do to a valve stem sticking in the guide on cylinder five not sure which valve it was... Anyways what I got back was (as I was told anyways) a 70k mile 5.3 from a Chevy van same year as mine. from the day I got the truck back I could tell right off it was lacking power and torque. I had the old engine tuned by Justin at Black bear so I could see all the numbers with the data cable and EFI live. As it was we were still working on tweaking things with the old engine so I still have the data cable I have ran several data logs and can see a big change I had been thinking that maybe I got a 4.8 instead but (would add up to the lack of get up and go) I pulled a plug and the piston feels dished... I can remember seeing a layer about 1/8" thick of tar in the intake ports before the shop put the manifold on. could this be the lose of spunk? could I have a 4.8 instead of a 5.3? did the 4.8's have dished pistons I thought they were flat top... any ideas would be greatly appreciated. With gas up so far I can't take the lose in MPG (down about 2mpg's ave.). I can send anyone who might want them the log files I have from old and new engines. I end on a "Please Help"

jaredlucky16 · September 27, 2012

The carbon build up will for sure rob power and MPG's

aflesch · September 27, 2012

+1 You can try Seafoam but if it is as bad as you say I would take it to your favorite mechanic and have them do a 3-part fuel system treatment. You might even go as far as to remove the intake and manually clean the runners. Just be careful about dropping stuff down into the cylinders. Make sure you only clean the runners while their respective valves are closed and then vacuum them out before you let the valve open.

jbeckett25 · September 28, 2012

thinking I'm going to pull the intake this weekend... as long as I loosen the rockers all the valves will be closed

aflesch · September 28, 2012

Or you could just rotate the crank to close them a couple at a time. Then you don't have to pull the valve covers.

tanked_darren · September 30, 2012

Those dished pistons are because you probably have the LM7 generation 3 5.3L which came with the chevy vans of that year.

If you have a 4wd you probably had a L33 (unless you had flex fuel then you'd have the L59) the L33 had flat pistons and a minor increase of like 15hp. But at the ages and mileages of these engines you'd never notice.

Why would you put such a used engine in your truck? Why would you let them put it together with this 1/8 tar you speak of? Something doesn't sound right here...

My 4.8 is rated about the same as 5.3's from your year

http://en.wikipedia.org/wiki/GM_Vortec_engine

KMGZ400 · October 1, 2012

i didnt think they even put the 5.3 in chev vans... i thought it was the 4.8 and 6.0

i know the d-max van engine is less powerful then the pickup d max so id assume the other engines have less hp

jbeckett25 · October 3, 2012

I didn't have a lot of options The warranty company was paying the bill and they told me they were only required to replace with equal to what I had. And I didn't have the cash to pay for a crate engine... as for the slug I didn't know about it at first I was basically forced into a shitty outcome!

Those dished pistons are because you probably have the LM7 generation 3 5.3L which came with the chevy vans of that year.

"If you have a 4wd you probably had a L33 (unless you had flex fuel then you'd have the L59) the L33 had flat pistons and a minor increase of like 15hp. But at the ages and mileages of these engines you'd never notice."

How would I be able to tell this? I know what I had was the T code here is my Vin: 2GTEK13T661169674

I did end up pull the intake and as I was turning the crank and watching the valves I could see lots of bubbling around the valve face so now I need to do a leak down test but most of the valves were doing it... lets see if I can post a video of one... http://s215.photobuc...30-16-45-38.mp4 if it works don't mind the rest of the vid just the valve lol

tanked_darren · October 5, 2012

Your old engine had the dished pistons you had a LM7. You probably just got a more "tired" and obviously dirty) engine. Never heard of this insurance you have. Don't get that in my area.

jbeckett25 · October 7, 2012

ok for all the GM techs out there after doing a leak down test at what percent would you tell the customer they needed heads redone or rings replaced how much leaking is to much?