Hello everyone, I have a question for you. I am in the planning stages of building a 406 for my street driven 72 Vette. Anyway, I am planning on something like 9.5 or 10.0 t0 1 comp, comp cams XE274,headers,th350 auto,etc. Just your basic street engine. What I was wondering is if you could use a set of Vortec heads on this engine and if so, what kind of power and TQ could you expect? I know the heads would have to be machined to accept that much lift.I also know these have small intake volumes. I have seen articles in the mags where they use these heads on 383's and get 400hp-500hp.
Anyone have any comments or ideas about this?

Thanks,

Mike

 

Anyone?????

 

They are darned good heads for the money, but they aren't perfectly suited for real power right out of the box. The valve springs are are weak and the valve guide bosses are fairly big (wide and tall) this limits valve lift to somewhere around .475-.480. Comp Cams makes a couple of tools that you can use in a 3/8" drill to widen the valve spring pockets and cut down the valve guide bosses.
There are some people running the heads unmodified by using LT4 springs (without the flat wire inner damper) and claiming to run cams with a lift of up to .510 without running into coil bind with the springs. I haven't seen it done so all I can do is report what I've heard from other people.
I've got a set of Vortecs that I have had for sale for a couple of months, I've had no bites, so I'll probably use them on my old shortblock when I rebuild it.
Another things about Vortecs, they are supposed to be 64cc, but really spec out about 61-62cc. So flat topped pistons with 6cc valve reliefs, are going to get you somewhere around 10.7-1 to 11-1, depending on your gasket thickness and how far down the hole your pistons are. This can be lowered by doing a little bowl work on the combustion chambers to unshroud the exhaust valves a little. You might be able to get down to 10.5-1 compression ratio with your 406.
With your automatic transmission the XE274 might leave you hanging a bit short on low end torque. I'd suggest getting a 2200-2400 rpm torque convertor as a minimum, for a little better lowend performance.
Desktop Dyno says that the engine with headers and open exhaust will produce 387 hp at 5000 rpm and 468 lbft of torque at 3000 rpm!
You might not need to worry about that torque convertor as this monster starts out producing 460 torque at 2500 rpm!

 

These guys sell vortec heads that have been modified for higher lift cams as a package deal. Heads intake and rockers http://www.sdpc2000.com/cart.asp?act...2174&pid=89535

 

There are a few potential roadblocks with the vortecs on your appilcation. On a 406, the 64cc chambers will give you much too high of a compression ratio for a cast iron head. You would have to increase the chamber volume or run dished pistons to keep the CR under 10:1. Also, the smaller intake port volumes and 1.9/1.5 valve sizes would probably choke a motor like a 406 at higher rpms. With that much displacement, you would probably want to look at a minimum of a 195 cc intake volume or larger depending on intake and cam. The vortecs would need a good deal of machine work ($$) to be optimum for your 406. A set of world or pro-topline cast iron heads with lareger ports and valves may be cheper in the long run.

 

In studying the build my 406 I have learned that anything less that 210-215 CC chokes the motor. Ol RJ did a dyno test with 195 CC on his 406 then 220 CC and found a 30 or so HP increase with no other changes. You can do a search of his name and look at his website!