bighdx

2007 Avalanche 5.3
I have a set of 862 heads to install. I'm mostly looking for torque. It already has the AFM deleted and a Truck Norris cam (216/220). Would I want to port these heads before installing or leave them stock?

Spamfritter

iTrader: (1)

I'm curious about this as well. My 2001 Camaro SS has a 5.7L LS1 and 862 heads. I believe the cam to be aftermarket as well but I don't know anything about it. I've never had it on a dyno.

G Atsma

I would just do a bowl blend (aka pocket port) to smooth the transition from the valve pocket to the port runner, plus clean up any zits and warts that might be there.
That and any milling needed to bring the compression to where you want besides a .040 head gasket to bring the quench up to where it should be.

bighdx

Thanks for the replies and pardon my stupidity, so I can't use GM .051 head gaskets? I already have a pair. (My knowledge is old and I haven't done a lot since the 80s-90s. GM part 28-12498544

G Atsma

Sure you can use the GM gaskets. It's just that ideal quench is achieved with a thinner gasket.

bighdx

Thank you. Got some .040s ordered from Summit Racing. 💪💪

slowride

iTrader: (3)

I mean if you want the most gain do port them, but stick with the stock intake valve size on a stock 5.3 bore. In a truck if you are doing truck things (towing etc) you might need to run premium fuel etc as you raise compression far beyond stock. I've actually found some small bore VR or Mahle composite gaskets in the 0.040" range also.

bighdx

Thanks. I think I have all the parts, now I'm waiting for a 4-day weekend to do it. My lower back can only take a few hours a day. The truck is a spare and I can leave apart for a week or two but I don't want it down that long.

bighdx

@GAtsma

Put all this back together and when I add antifreeze, it's pouring right out of the back of the engine. I'm assuming it's a head gasket issue. I double check everything. I was **** on all the torque specs. APR bolts.
I'm at a loss but giving up for today.
And I mean as I add it
​​​​​

G Atsma

Something got installed drastically wrong.
Pull it apart.

bighdx

Got to be head gasket related. Cosmetic only showed 1 part # for these. Was I supposed to look for a right and left?
Or can this be intake gasket related? I didn't get oem intake gaskets that had the lock tabs.

bighdx

I'm assuming since my original heads did not have rear steam ports that I have the 862 heads on without plugs in the rear steam ports.

G Atsma

That would do it.....

1FastBrick

iTrader: (16)

You have an early set of 862 with a notch in the decks. Standard MLS gaskets wont work.

wannafbody

iTrader: (2)

WS6store sells the correct MLS gasket