i was talking to a performance head remanufacturer today about vortec heads. when i mentioned my concern about going to a 64cc head, he told me there was a rare 58cc 305 vortec head that flowed as well as the 64cc vortecs. does anyone know whether this is correct or not?

have you checked with gm performance parts? they may offer you options on this. i think there is one vortec to stay away from. not sure which it is.

there is a 305 vortec head but it doesn't flow any where near as much as the 350 vortecs head do. I would just get the 350 vortec heads and use a thin head gasket. The vortecs make so much power you won't miss what little compression you might lose.

Yeah definately get the 350 heads. The 305 vortecs dont flow as much even if you mill the 350 head down to 58cc too. If you mill them down you can always run a thicker head gasket if you ever upgrade to a 350. Or run a thin gasket with the stock cc.

I milled mine, it only cost me 40 bucks then I put on a thin stainless steel head gasket.

how much did you mill yours? what did that bring your combustion chamber size to? what head gasket are you running? do you have the part number?

thanks

I milled them down .030. The head gasket was a bastard to find. People on here gave me simple part numbers to find what they used and none of the part stores had one in stock. I ended up getting mine at napa, dont have that part number. But I think the one I was told was a felpro 1094. Basically your looking for a .0015-.0017 if I remember right. Not sure on my exact cc after that.

One guy on here says he's running 10.25 compression with .030 mill and a 1094 gasket. But not sure without hooking up a gauge.

i dont think you want to go over 10.0/1 on compression on iron heads. maybe 9.5/1 is safer. you can measure this and calculate it. my engine builder did so. my pistons were -6cc if i recall and chamber 64cc. but i am not running a vortec. my compression i thought was 10.1/1 with aluminum heads.

You can get away with more compression on a vortec head because of the efficient combustion chamber. I run vortecs on my 355 with .100 domed pistons, which according to speedpro gives you about 10.65 to 1 compression on 92 octane fuel with octane booster and 34 degrees of total timing. It can be done, you just ave to know what you are doing to avoid detonation.:rockon: :rockon: :rockon:

Who told you that they were the same?

Obviously he doesn't have any experience with the heads. The 305 version isn't that rare, they're in junkyards all over here. Also they don't have a lot of the power making characterisitics that are worked into the L31 head, which is the main reason to go with Vortecs. If you're going to go with the 305 Vortec head, you might as well get a set of 081 87-92 heads 305 heads because they're just about the same.

.

Point taken.

Steve

One more thing, the 58cc Vortec heads are a big improvement over stock 305 heads. Many of the IMCA Modified Dirt Drivers here run these heads to bumb the compression up on a 355 race motor. These heads on a 305 moved the horsepower of a 305 up to the level of a pre-vortec 350. That is a pretty substantial jump. The 305, 58cc, Vortec heads may not be the greatest cylinder head in the world, but it may be the best lowbuck mod out there.

Another good point. ( . )

Steve

My old motor was a 305 rebuilt with around 10.3:1 compression. I ran QT 92 Octane gas and had no problem.
My new motor is a 360, 350 0.060 over. I am using Vortec heads, with a big cam, .292 in, 300 ex, .488 lift. Shop told me the motor will run around 10.8:1, 10.9:1 on the compression. I am hoping with the way the Vortec breaths I will still be able to run 92 octane gas. If not I will use 104 octane boost with each tank full.

Stats on 360. This is what's on my Bill.

GM 010 350 Block at 0.060 bore.
Forged 350 crank 10/10
Forged rods 5.7
Forged pistons TRW flat tops one set of eye brows.
Timing gear drive. Pete Jackson
High flow water pump
Cam .292/.300 intake/exhaust Duration, 106/114 intake/exhaust Centerline angle, 110 lobe centerline angle 76 valve Overlap. 488 lift.
Vortec heads ported and polish, 2.02 in. 1.6 ex.
Edelbrock performer RPM intake
Holley 670 cfm dbl pumper

Hp = 478 at 6500 rpm
Torque = 445 at 5000 rpm
Compression =10.87:1

I can't wait to put this in my camaro and see what it will do.

You think that this setup will run on pump grade gas?

Where are all you guys getting your information?
I've seen a flowchart somewhere that had the 305 Vortec head at 229/147cfm and the 350 Vortec at 239/147.

Everything I've ever read says that they have the exact same ports, the only difference is the 305 uses 1.84 intake and 58cc chamber and 350 uses 1.94 intake and 64cc chamber.

Either way, I've got a set of 305 Vortecs in my garage, casting number 520. Maybe I'll have them flowed if I can find a place near me that has a flowbench.

Fast355 made good power with stock 305 Vortec heads in this thread:
http://www.thirdgen.org/techboard/tb...tml?highlight= (300 HP Bolt-on L03 TBI)

EDIT: Plus, the 1.94 intake is more shrouded in a 305 then a 1.84 is. 1.84/1.5 in a 305's 3.76" bore is equivalent to running 2.02/1.6 in a 4" bore.

Guys:

I plan on running my 305 L03 with 906 vortecs and an 97 LT1 cam with 1.6 rockers.
Should I have these milled to 58cc? If I don't will I still have good power with these? And if I don't have them milled, what gasket do I need to use to keep the compression up?