Rectangular Port GM Part No.:

Combustion Chamber Volume (cc):

Intake Runner Volume (cc):

Exhaust Runner Volume (cc):

Intake Valve Diameter (in):

Exhaust Valve Diameter (in):

http://www.offshoreonly.com/forums/g...ine-specs.html

They're GM 088 heads - you can find tons of info regarding post sizes and flow numbers on the web.
118-120cc chambers.
2.18/1.88 valves.
Carbed HP500's used Manley Extreme Duty exhausts.

GM doesn't make that casting number anymore. What casting number is on the newer moters that replaces it.

I thought there were 2 different versions of the 088 heads. The 454/502 Mags have 2.19/1.88 and the 500 hp, 500 efi, 575 Sci, etc used a 2.250/1.88 combo???
Eddie

If you are looking for some 088 heads, give me a shout. I have quite a few sets that we can freshen for you. Or, you can buy them as is.
Eddie

Maybe Mercury racing installed larger intake valves on the high perf engines?

I remember in a old service manual, the old 454/370HP,400hp had a standard bbc rect port head pretty much nothing fancy done to the head. But if you were a big spender, and got the 440HP, or 460HP cyclone engines, you got a multi angle valve job and some other stuff done to the heads, I cant remember.

Seahawk,

Rectangular Port GM Part No.: Casting # / Part#

6272990 / 6260482 or 14096188 Original LS-7/LS-7 Open Chamber Designed for the MK IV block

140970088 / 14096802 Service replacement head for the Gen V block

12562925 / 12562934 Service replacement head for Gen V / VI block with 7/16 accessory holes

12562926 / 12562934 Service replacement head for Gen V / VI block with 3/8 accessory holes

The last two are current working part numbers. All heads from GM have the 2.180”/2.190” intake valve
Verify block compatibility


Combustion Chamber Volume (cc):
118cc

Intake Runner Volume (cc):
325cc/318cc

Exhaust Runner Volume (cc):
125cc

Intake Valve Diameter (in):
2.180”/2.190” 3/8” Valve

Exhaust Valve Diameter (in):
1.880” 3/8” Valve

26º Intake valve
17º Exhaust valve
4 º Splay

All heads share the same basic port architecture and combustion chamber design. The is no significant performance differential between the heads.

Bob

Thank you Bob

WOW I see Bob is still giving good Head......
information

What would this place be with out him