Treyvs

I need some opinions on what to do. I plan on EVENTUALLY running a procharger with a mild shot of nitrous. Until I have money for the procharger, the nitrous will be all that is ran. This is on a 5.3L LM7, so what should I go with, my stock 862's or the 853's I just bought? Which one is better for either application? I know the 853's will lower the compression considerably, so for N/A means it will may fall on its face. Let's hear it!

HCI2000SS

iTrader: (2)

The 853's are stock as well?

Treyvs

Yes sir, both are stock heads. The 853's have 40K on them while the 862's had around 117K.

HCI2000SS

iTrader: (2)

I'm certainly no expert here, but from my understanding (since we are comparing stock to stock) the 853's will be a little better

Treyvs

Won't the bigger combustion chamber make it fall on its face when it's just ran N/A without the help of the procharger?

HCI2000SS

iTrader: (2)

Well from what I know even though the 862's have a smaller combustion chamber they have smaller valves and a poorer flow rate in stock form, thus offsetting the compression bump

Treyvs

Point taken. Anyone want some 862's? Lol

HCI2000SS

iTrader: (2)

Well don't just take my word for it totally lol. Like I said i'm no expert, but I have heard this said before.

Treyvs

It makes sense, especially in the higher RPM's when the engine really needs all the air it can get.

LS5.3stang

iTrader: (4)

Casting Numbers 241, 806, 853
Head: 1997+ LS1 5.7 Liter Passenger Car
Material: Aluminimum
Part Number:
12559806 (1997-98) Chambers = 69cc
12559853 (1999-00)
12564241 (2000-03)
Combustion Chamber Volume: 66.67cc
Compression Ratio: 10.1:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 66.67 cc------0.100--0.200---0.300---0.400---0.500---0.550--0.600
Intake 200 cc------------67----122-----178-----215-----219-----223---227
Exhaust 70 cc------------52-----97-----133-----156-----170-----76----180



they flow almost the same. the 862s have a better design to get only outflowed by 1 cfm with smaller intake valve


Casting Number 706 and 862
Head: 1999+ 4.8L / 5.3 Liter Truck
Material: Aluminimum
Part Number:
12559862
12561706
Combustion Chamber Volume: 61.15cc
Compression Ratio: 9.5:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 61.15 cc----0.100--0.200--0.300-- 0.400--0.500---0.550---0.600
Intake 200 cc----------63 ---128----179-----210----218----221-----226
Exhaust 70 cc----------54 -- 93 ----121----145-----163----168----174


heres the website http://houstonperformancetrucks.com/...h-flow-numbers