SalikDDD

on the 289 the largest valves u can ram in there are 1.94 and 1.60 correct? if not someone correct me on it, and what all i'd need to get to swap the valves over (i'm not doing it a shop is) i'd just rather get the parts myself.

mat11089

really depends on what else is done to the 289.

SalikDDD

i'm actually building to spec with what Mustangs Monthly did with their 289 - except i have a smaller cam apparently. ideally i'd like to raise compression on it by having the heads milled if it's better then going with larger valves - but i also don't know how much can be milled with the stock compression pistons.

andrewmp6

Depends on which heads you have and how good your machine shop is.If you want bigger ones buy aftermarket heads or do the cleveland swap.

109jb

The 289 and the 302 share the same bore diameter, so you should be able to use heads with the same valve sizes as a 302. 2.02 intake and 1.60 exhaust is a common valve size for the sall block. Although a shop could put in larger seats in your existing heads, the best thing would be to buy a set of aftermarket heads. The choice there depends on what you want. You mentioned a stock bottom end which would lead me to believe you would be better off with heads with smaller intake runner volume to keep flow velocity up at lower rpms.

my77stang

1.94 / 1.60 is the way to go for those heads, even 1.84 / 1.54 is a nice upgrade from the stock 1.78 / 1.46 crappers that are in there now.

if they are doing that kinda work, be sure to go ahead and get screw-in studs installed while you at it.

lastly, if your going to buy the parts yourself buy ferrea. they make the best valves you can buy and their lower lines are priced very reasonable.