12558059 305 vortec heads

are these 12558059 305 heads any good? are they a true vortec head or a crappy swirl port head?
has anyone had any dealing with them?
i have a set of 601's & 416's, & if these are no better than them i'm not going to buy them.
all the info i can find is 1.84-1.5 valves with a 64 cc chamber. i've also read their a swirl port & not a true vortec head. i don't know, i've never seen a pair of 12558059's in person. help if you can. thanks


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These 305 vortec heads are simular to the 350 L-31 heads but not the same. They are not like the "swirl port heads" either.
They have a combustion chamber that is more like the L98 TPI heads 081 and 083 cast iron. The ports are simular to the 350 vortec heads. They use the same manifold bolt pattern and raised intake port position. The valve size is 1.84x 1.50.
The combustion chamber size is supposed to be 58cc but may well actualy be 64.
If you don't mind reworking these heads a bit and can get them real cheap they can be a good deal.
They will need larger 350 sized valves. they will need porting and maybe some chamber rework to take advantage of the large valves. they will need all the valvetrain machining that the 350 vortec heads need too run high performance cams.
They have potential thou.
The 416 305 heads have lots of potential too. With full porting and larger valves. 1.94x 1.60 is best.
I get over 240cfm on these heads, last head I did flowed 233cfm. Thats typical. Thats vortec head and Performer RPM head flow so can make a nice street head.
I'm not so crazy about the 601's but.....

it's for a 305.

Then you would want to retain the 1.5" exhaust valve. But the larger 1.94" inch intake valve works great with some porting work on any of these heads on a 305.
Why not just rework the 416's. They work very very well if you dont mind doing the required work. they make a decent affordable performance head in ported/modified form.

i took the intake valves out & the intake runner's of the 416 heads i have look like hell. there isn't anything that looks like they would be worth fooling with. the short side radius of the 601-416 isn't what i'm used to seeing. it looks like i would have to remove 1/8" of metal on the short side alone. whats the difference in the 416 heads & the 601's? they look identical. same crappy intake port.

i was hoping the vortec 305 heads where a better design so i wouldn't have to bother with any porting. it's just a stock 305 with a roller cam, but i think better heads would help with gas mileage & pep.

what does the stock 305 vortec heads flow?

http://cgi.ebay.com/ebaymotors/1997...080127400QQrdZ1

I don`t know what they flow. However, years ago I built a 305 roller engine with 305 vortec heads. The pistons were basic flat tops .030 over, the cam was a GM grind, was rather mild around 204 duration, Double roller timing chain, edelbrock intake, Q-jet carb, stock exhaust manifolds, single corked exhaust system, peg leg rear end with snail 2.56 gears. It had real good take off power, and had a decent mid range charge. It had a real responsive throttle and was a pleasure to drive. The customer was happy. If your monte has decent gears, it should be a nice runner. There`s alot of articles online about these heads, some say there better, some say they aren`t. If you could find some in a junk yard, you could look at the ports and compare. I wouldn`t recommend installing 1.94 valves in a older 305 casting head, it`ll just shroud the valve more unless you open up the chamber.

"i took the intake valves out & the intake runner's of the 416 heads i have look like hell. there isn't anything that looks like they would be worth fooling with."

But if you port them they look beautiful (and make power)

I guess you don;t get it. Just buy some 350 Vortecs and bolt them on. All of these heads need lots of work. It's what you end up with that counts. Not what you start with.
The potential is there. You have to do the work.
How do you expect a cylinder head to be different or show a improvement unless you change it. (port it)
Are you looking for something to be suddenly, magicly, something different without doing anything to it? (work)
here is a finished 416.

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i get it, trust me. i was just wanting to avoid all the work. i'm lazy ..

I know this thread is old but I just aquired a set of these heads and was looking for information about them and had a question.

I have a 93 K1500 with the 193's tbi heads and was curious about bolting these on the engine instead of the tbi heads. Would I notice any difference in the performance of the engine? I know I would have to change intakes but I was just curious about it

I was considering a set of the '520 305 Vortec heads for an engine I'm building for my '88 C1500. If you plan to keep your TBI and EGR, like I am, it starts getting real expensive. The Vortec TBI intake with EGR is close to $400 new and used ones don't go for much less than $250. It will require a driver side Vortec exhaust manifold or Vortec specific headers to run EGR also. Then you have to have a custom chip burned to get it to run right. If you were building a serious engine with L31 Vortecs it might be worth all that but to just swap heads? My vote is, no. Otherwise if you had a non-ECM vehicle and a 4 bbl. I'd say go for it, from what I've been able to find their stock flow is very close to and maybe slightly better than the old '441 heads even with the smaller intake valve. I do plan to use them on a carbed engine later on.