i have a stock 95 impalla motor in my 89. i'm about to put some lightly ported aluminum heads and a 224/230 cam in, and i was curious about how much difference i will notice. any one have any experience with this or any idea.

 

I'm assuming you have all the supporting mods....( headers, CAI, exhaust, etc)? Are you running 1.6rr's with that? You are not running stock springs...are you? You will need a tune!! Now with all that...you should notice a very decent gain. I hear the iron heads flow a little better but the weight you save on the aluminum equals that out. That cam is as big as you would want to go on stock heads...i run it and love it!! Don't know all the differences from the Impy motor to the f-body. I would assume injector, TB, and compression would be the same..??

 

yes i will be running shorties 1.6 rr and new springs.

 

ttt

 

big power increase

 

one way to find out

1) install cam with 1.6rr and shorties on iron head
Dyno tune it
Post the results on board


2) Flow your ported aluminum heads
swap iron heads to slightly ported aluminum
Dyno tune it
Post the results on board

I would be very interested to see the results

Back to your original question. Iron heads do flow better than aluminum ones, so probably a slight port job on aluminum heads will just make them flow the same as iron heads
And by swapping heads on your stock short block you will be running a risk of spinning a bearing since there is an opinion that changing heads without rebuilding the bottom end misaligns the bearings due to re-stressing the block. There were a couple posts about it in detail.
However, iron heads are heavier and they dissipate heat less. That's why there is 9c1 version of Caprice- to cool better