Quote:
Originally Posted by Excaliber
18 degree heads? Can you enlighten us as to what those are?  |
The 18 degree Chevy head was approved by NASCAR in 1990 to replace the original 23 degree cylinder head. The 18 degree head was never on a production vehicle, nor was the SB2 that replaced the 18, nor the SB2.2 that replaced the SB2, nor the R07 that replaced the SB2.2
While cylinder head development for NASCAR abandoned the in-line valve configuration when it went to the canted-valve SB2, many other forms of racing continued to develope the 18 degree design. The 18 evolved into the 16, 15, 13, 13/11, 12.5, and now 9 degree head.
Most AFR heads (Ford and Chevy) are designed to be bolt-on replacements for original production car heads, maintaining factory port locations and such. Essentially, they are refined production car based heads with limited power potential compared to the more exotic race-only cylinder heads.