[455-4+1]

Hi all, new to 62 tech, so a quick question on compression ratios.

I see from the 62 manual, there are several different comp ratios for both premium and Std fuel (389 options)
But from what I can see there was only 1x cylinder head listing for this year ?
Am I missing some thing ??? is there an accessory code for different chamber volumes like the later 6X etc ??

From what I could see std engines used 538177 casting and the SD versions used 540306/544127
I couldn't find a different casting for the std engines with different comp ratios ?

Attached is the sheet listing the different ratios from 8.6 to 10.25
I realise these were just advertised ratios, but there is a big difference !!

EDIT----- I think I found it thanks to 61Man !!!!!

" 538177 is the casting number for 1961-62 heads, They have small valves compared to later heads, if they have an X & 0 stamped on the lugs above the center ports they are 10.75/1 with heavy duty valve springs"

[Jay S]

IRC…the low compression 389 had dished pistons

[Bill Hanlon]

Just to muddy the waters, a sheet from the 1966 Pontiac Parts Catalog, showing 1962 engines and what components made them up.

[455-4+1]

Ahhhhhhhhhh so not quite as simple then.......
Will definitively need to check engine codes ?