The 4.1 heads are absolutely horrible. I want to switch them for 4.9 heads because they flow better. Does anyone know if they fit? I know 4.9 heads will fit a 4.5, and the 4.5 heads and the 4.1 seem to be the same casting.

I'm using a 4.1L cadillac engine on a TH325-4L transmission longitudinal in my 87 fiero GT (reverse rotation).

I've got the exhaust side figured out except for the headers that I can't make until I know what heads I will be using. This engine will be exhaling through 2.5" stainless exhaust. High flow cats, H-pipe, 7" glass packs and ending in a pair of 4" stainless supertrapps.

nope, coolant passages are different. very different. i've got an old 4.9 that doesn't run, if you're interested for your fiero buildup!

Bah.. well, good to find out before I bought a set of heads. As far as your 4.9, it won't work. The 4.9 won't bolt to the TH325-4L tranny because it was a transverse only engine. The starter will be on the wrong side.

I asked the same question for my 4.5 -- bbob told me the same thing -- no way!