862's vs 853's
 

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!

The 853's are stock as well?

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

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

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?

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

Point taken. Anyone want some 862's? Lol

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.

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

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