406iroc

Any body ran vortecs on a 406 sbc????

Fast355

iTrader: (2)

305 vortecs. You need to drill the six steam holes in each head, use the self-aligning rockers and the vortec specific intake. You will also need a pair of center bolt valve covers.

The 305 vortec headed stock cammed 400 in a caprice is a very strong runner.

406iroc

thanks but what about 350 vortecs?

Fast355

iTrader: (2)

You will need to do the same thing for the 350 heads. The performance difference will be very little if any.

406iroc

Thanks

406iroc

What about compression will I be able to run pump gas?

Fast355

iTrader: (2)

Depends on the pistons and cam in your 406.

406iroc

230 duration cam 480'' lift 040'' over flattops

AJ_92RS

Certainly, you're not serious.

Fast355

iTrader: (2)

I am talking about the difference between the 305 and 350 Vortec heads. Not TBI heads but CPI Vortec heads such as from a 1998-2002 fullsize van. They are practically the same head. I have used both and there is next to no difference in power. The 305 heads use 58 cc chambers and the 350 heads 64 cc. The 305s use a 1.84" intake valve and the 350 uses a 1.94" valve. The ports are identical between the heads. The exhaust valves are 1.5" on both and the exhaust ports are identical. The slightly reduced flow on the 305 head is countered by the increased compression on some engines. In the case of a 400 with flattops I would use the 350 heads simply because the compression would be getting a little on the high side.

Another further proof that the 305 and 350 vortec heads differ very little is the fact that the dual cat 350 vortec makes 245 net HP in a G1500. The single cat 305 makes 230 net HP. They both have the same cam, same compression ratio, same exhaust manifolds, same intake, etc. The 305 is actually making more HP per cubic inch than the 350 is.

AJ_92RS

You actually believe this stuff?

GOY

If it's true, I don't see what's flawed in his logic. 45 ci and only 15 horse diference isn't too shaby.

Then again, that's balancing on whether it's true. I honestly don't know any serious data on vortec heads...... but just felt the need to post anyway... and I'll post about my bowl movements later in case your interested

Fast355

iTrader: (2)

http://www.media.gm.com/division/che...c3.htm#engine1

http://www.media.gm.com/division/che...gvan/index.htm

My bad the actual numbers are 220 vs 245(in a G-series I think the trucks are higher), still it is only 25 HP though. You have to remember that 305s in G-series have single cats and the 350s duals though.

Here is a quote

"Vortec 5000 (L30) and 5700 (L31) V8 SFI Engines

The small block V8 Vortec 5000 (L30) and 5700 (L31) truck engines give Chevy Van and Chevy Express owners more of what they want: hard-working horsepower and torque and longer intervals between recommended service than engines from just a few years ago. The Vortec 5000 is optional on Chevy Van/Chevy Express 1500 models only.

The Vortec 5700 also is optional on Chevy Van/Chevy Express 1500 models, and standard on all 2500 and 3500 models. Here are their credentials:

Vortec 5000 Features:

* 220 horsepower at 4600 rpm
* 280 lb.-ft. of torque at 2800 rpm.

Vortec 5700 Features:

* 245 horsepower at 4600 rpm
* 325 lb.-ft. of torque at 2800 rpm. "

They make the same torque per cube at about .92 ft/lbs a cube but the 305 leads the HP per cube at .72 horses a cube vs the 350s 0.7 hp a cube. Add the dual cats of the 350 onto the 305 and you see where you would be.

Fast355

iTrader: (2)

EDIT

Fast355

iTrader: (2)

Sometimes I wonder why I even bother with some of you. Gives me more 305 vortec heads at a cheap price if I just kept my mouth closed.

My dad has a G1500 that had a 350 in it. It broke a connecting rod. I picked up a vortec 305 with 25,000 miles on it for $550.00. I used the PCM out of a 305 van. It isn't programmed for the 2nd cat but it runs fine. Along with a LT1 cam this thing scoots better than the stock 350 vortec.

AJ_92RS

Well, since you don't know why you "bother" with some of us, I won't bother with you except to say, recently I aquired flow numbers from the 305 Vortec heads and the flow numbers are ~30 cfm lower across the board, except on the exhaust side. They flowed ~ 15 CFM more than the L31 heads.

I don't recall where I got those flow numbers though. But they are from someone who actually flowed them, not some editor in a "hi-po" magazine.

As far as "HP/Cubic Inch", there are many other explanations for that which aren't something I want to get into right now.

F-BIRD'88

I have 350 vortec heads on my 406 SB.

They are mildly/ moderately ported with larger 2.02 x 1.60 valves and upgraded valvetrain and machining.

The compresion ratio is 9.8:1 with 21cc d dish pistons and block decking and 64cc heads.

We did not drill the heads for 400 steam holes. Seems to be working fine.

runs on 92-94 gas. have not tried any thing lower in octane.

No timeslips yet but the heads seem to work nicely.

406iroc

Wow thanks 4 all the info keep it coming