how much of a difference is this going to make with swapping the heads out? does anyone have any clue? is it going to run like crap? they are the vortec heads that i have a matching edelbrock vortec manifold for. Thanks, Joe

You will have some cylinder shrouding issues going to a larger head like that. Also you will lose alot of compression which will affect how your engine runs. I would either get a set of Torquer SR heads or simply have yours ported and polished.

i'd skip the porting and have them milled down instead, those heads are already going to flow more air than a mild 305 is gonna know what to do with. which manifold do you have? what kind of cam are you using?

Can't disagree. I'd just make sure the shop doing the work is good and reputable and/or has done this before. They take too much off and he's stuck. hehe

you can always tell them to only take off minimal amounts, then you cc them and let them mill again, cc again and so on until you get it right
but i agree, sounds like a good idea to use the flow of the vortec 350 heads on our 305s.

i put the edelbrock 3702 cam in it, i also have the 2116 intake to go with the heads. i know it's a carb intake and was toying with the idea of putting a carb on since i have a 600 cfm edelbrock carb also. any thoughts on that?

you cant mill them down for them to get to the correct size.

the more you mill them the further down the intake holes go. your intake manifold will be too high and will not match up, unless you mill your intake too. i was thinking of doing the same thing, until i found out the problem. i decided to use heads that were the right size from the get go.

if you do mill the intake it will never be of any use except on those heads, and they will be trashed so you will not be able to sell them.

could decking the block the same amount fix that problem?

no you will have to take a lot off to get back to your prior compression ratio.
the problem will still be the same but now you will be further apart.
you have to cut a lot either way and way spend all that money and using heads that dont fit.
now think how much it will cost to get the correct size heads and no problems at all. you already have the manifold and everything else, so look for the correct heads, spend more money there so you dont have to spend more money to do things that you will need to make the wrong heads fit.
now how much does the manifold cost?
here is what you could do - find some nice 081 heads - they are tpi heads, and work them - and get a good tpi system from a 90 or 91 z28 - and have a ball.
there are a lot of things you can do using things already out there - you dont have to reinvent the wheel.
we have all been there.
if you want you can make the swirl ports you have run almost as good as those other heads that dont fit.
they are little torque monsters. they were made for a truck, so they will pull like crazy up to about 4500 rpm's, and that might be your fix.
before you start spending money you really need to decide what way to go and find out every possible problem that can happen. this board is good for that.
i went from working my swirl ports, to 601's, to vette heads, and finally decided on 081's.
everything has a problem, and when you use 20 year old parts they all need rebuilding. these new heads are not new, they are used. you will have to buy new stainless steal valves, maybe even get larger ones. new cam means new spings. will the cam exceed the heads modified capabilities? what new springs will the heads need to handle the cam? i dont know if the heads have screw in's or not. if now will they need to be pined or not? there are tons of questions and answers - when you know as many questions as possible then you look for answers.

good lcuk - tony

L30 305 vortec heads with casting #059 are a JEWEL on a 305.

fast you know heads better than most - all the different type. i have followed a lot of your suggestions. so would you go with 64 cc vortec heads on a 305?

you are right i looked and the 059 is 58 cc and they would be perfect.

The 059s are definately right at 58cc, I had some that I ported and installed 1.94/1.60 valves in, on a 10.5:1 .030" over 305 TPI with a Reed custom ground roller cam running SLP runners. 356 RWHP.