Below are a list of the 400 Cid 1969 engines with HP heads and so on.

My question are as follows :

If you option for a -69 FB with a YS 400 cid automatic you would get a 330 HP engine with a 67 cam and std manifolds.

But then you want more power and think "Hey let's go for the HO option" but still want the automatic transmission and you will get a 400 cid YW RA III engine with the same camshaft and heads, sure you the manifolds and Ram air intake but only gain 5 HP...

The GTO with the YZ engine and RA III had 366 HP with an automatic trans and a 68 cam not available on the FB with auto trans, but Hey you you would get it with a manual transmission and a WQ engine but then "only" 335 HP..

So is this due to a HP limit on FB's ?? I have heard about secondary limiters on the carburetor and is that the only difference on the engines ?

And where the HP ratings only for the insurance companies ? has anyone ever taken a original engine to the bench to verify the HP ratings ?


HP CID Trans Code Comp Cam Heads Carb Year
265 400 A MM 8.6 254 45 4 69
345 400 M WH 10.75 41 722(RA IV) 4 69
335 400 M WQ 10.75 68 48(RAIII) 4 69
366 400 M WS 10.75 744 48(RAIII) 4 69
350 400 M WT 10.75 68 48 4 69
370 400 M WW 10.75 41 722(RAIV) 4 69
350 400 M WX 10.5 67 62 4 69
330 400 M WZ 10.75 67 16/62 4 69
350 400 A XH 10.5 66 62 4 69
265 400 A XM 8.6 254 45 4 69
345 400 A XN 10.75 41 722(RAIV) 4 69
370 400 A XP 10.75 41 722(RAIV) 4 69
340 400 A XZ 10.5 254 46 4 69
265 400 A YF 8.6 254 45 4 69
350 400 A YS 10.75 67 16/62 4 69
330 400 A YT 10.75 67 16/62 4 69
335 400 A YW 10.75 67 16/62(RAIII)4 69
366 400 A YZ 10.75 68 16(RAIII) 4 69