862 heads

[Tonyrodz]

Just curious, my 03 Hoe with a 4.8 has 862 heads, I'm swapping to an 05 6.0, it has 317 heads. My question : There's a guy on eBay who parts out nbs trucks, in an auction he was selling 862 heads, which are stock for 4.8 and 5.3 , he says will be a performance upgrade if put on a 6.0. He posted the flow numbers for for all the heads and the flow numbers are better with the 317 heads. Am I missing something? I'm not a mechanic, but going with common sense, doesn't make sense--to me.

 

[Z28TWITCH]

I know a few guys who have done it...mixed results. The 862 heads are smaller on all fronts and dont flow as well as the factory 6.0 heads. If it were me, spend the money on getting the factory head reworked. Just feel like its the 305 heads on a 350 thing again every time I hear about it. People swear it makes more power...until they dyno it. There's a guy local-ish to me who sent out a set and had them worked over real good and he picked up near 50 horses to the back, but he already had extra goodies in the motor...

 

[Tonyrodz]

That's kind of what I was guessing. Thx.

 

[Z28TWITCH]

Throw a cam and some long tubes at it...that'll wake it up pretty good

 

[iamdub]

They'll raise the compression from the smaller chamber volume which will increase TQ, but the smaller runner volumes will impede the flow and choke down the 6.0 at mid- and upper-RPM. I suggest keeping the 317s over the 862s and getting a cam to raise the DCR if you wanna boost low-end without sacrificing as much top-end. You could shave the 317s to boost the CR, but not much because the shape of the chamber can put the valves close to the piston. If you can find some cheap enough, 243s would give you about a 10:1 CR while flowing the same as the 317s and allow for a decent .030 +/- shave. Cam it accordingly if you're swapping that. I don't know what your budget is, but keep in mind one change can set off a domino effect of necessary following/supporting changes.

Regardless of camming it or not, long tubes and a custom tune are a must!

 

[Tonyrodz]

That's exactly what I'm doing, long tubes, can, pushrods, tq convertor, etc. I just read that info online, but wasn't too sure about it.