[Don66GTO]

I was wondering what the differences were between the YS and the YR or WG engines are other than the HP rating.

I understand that some of the engine codes are different due to the type of transmission the car came with I was just wondering what the factor was that made them have different HP ratings... I was it the heads and cam?

If anyone knows I would appreciate the help. Thanks!!

["QUICK-SILVER"]

65 an 66 models
WG 421, 338 hp, 4bbl, manual shift, 10.5 CR
YS 389, 335 hp, 4bbl, auto, 10.75 CR
YR 389, 360 HP 3X2bbl, auto, 10.75 CR

[Jerry H.]

On the 65-66 389 engines, all the blocks were the same. The HP difference came, as you noted, with the use of different heads and camshafts. All the blocks have the same casting #'s and are interchangeable. The only difference is the stamping of 'YS', 'YR', 'WS' or whatever.