Modified 8.1

Chris031486 · November 27, 2016

Hello fellas, first off i have been a long time creeper on this site and have gained allot of info from all the great posts. This is by far the best forum on the web, i cant believe the time others will take answering complete strangers questions and im hoping i might be able to give someone some insight from my lovely ten years with an 8.1l. I have a 2002 2500 avalanche with 183,000 miles and around 100,000 miles towing a 6500 pound box trailer on congested city streets. The only problems ive had were minor things that comes with any vehicle such as 3 wheel bearings and four front axles, btw i do offroad allot and pretty sure i caused the parts to break. But the reason i am posting is what i am currently doing with the truck and why. Around 15,000 miles ago i got a slight misfire on cylinder seven with a rough idle and really bad mileage, so i did the obvious plugs, wires, fuel injector, coil, fuel pressure regulator. I then figured it was a leaking intake gasket and one day i tore into her and replaced the gasket and bolts. And there wasno change to my disappointment, to say i was pissed is an understatement. So i did tons of research and figured it to be leaking or burnt valves which ive read happens with these engines. I took the heads off and number 7 valve was horrid with carbon buildup and you could see the exhaust valve wasnt seating properly. For this size engine the heads on this engine are terrible cathedral port design. So i took around 18-20 hours reworking the intake runners, combustion chambers, valve bowl, and exhaust ports. First off the casting flash on the heads are horrible and simply cleaning and smoothing everything out would do wonders for this engine. The intake gaskets allow you to open up the runners dramatically compared to stock and spent the most time simply smoothing out the runners as the cast was terrible. I also made a huge diff in the valve bowl and it actually smoothed out rather well. I basically enlarged the exhaust runners a little but made it as smooth flowing as possible. I didnt unshroud the valves which im sure would gain a little more hp but the risk just isnt worth the reward to me. I then had goffs machine shop do a valve job and replaced all the intake valves and the exhaust valves recut, i also replaced the valve stem seals. Now the fun part, i upgrAded to comps dual valve springs, retainers, and keepers. I also went with the 264 comp cam and timing set. i was also able to enlarge the intake and smooth the runners out. I also port matched the head and intake manifold and as i said earlier i was able to really open the intake manifold greatly. While i was at it I ported out the throttle body i cant remember the mm that i was able to open it up but will post later when i mic it again.

I bought nearly everything from rock auto and lucked out and got most of the parts on wholesaler closeout. Ill list the parts and prices as they are crazy cheap. All the parts are the exact brand name and part numbers, ill put the advance auto parts price to compare to. If you find the prices hard to believe just go check them out

Head gasket $7.75

Advance $30

Intake manifold gasket set $24

Advance $107

Head bolt set $12.35

Advance$54.00

Valve stem seal kit $ 2.85

Advance$36.99. Yeah like i said crazy cheap

Valve cover gasket$6.85

Advance$24

Water pump gasket set $2.86

Advance $11.85

I know i sound like an ad for rock auto but im just trying to pass the knowledge along in hopes of saving you guys money next time your wrenchin.

As of today i have the 90 pounds heads on and hopefully be up and running in the next couple days.

Only problem im having is finding valvecover bolts, i thought my kit came with new ones so i kind of lost a few. Let me know if you know where i can get some. Ill post pics of everything next post along with the sizes of intake manifold runners, head intake runners, and throttle body and how much i was able to enlarge them. Imhoping this info might help someone as im just trying to help as i have got allot of help from this forum. Btw does anyone know if that tierod guy is still on here??