Hey,

I was looking around and found that some Bowtie Vortecs are available. The casting numbers are 25534351C and 25534371C.
Seems GM has done all the stuff the average hotrodder would do to them. Better springs, valves, bigger runner. The interesting thing is that they're drilled for ragular intakes as well as vortec style intakes. I thought the intake runners wouldn't match up. Oh well, thought I'd give the heads up to anyone looking. They're a little on the expensive side it apears though!

From http://www.gmgoodwrench.com/gmgoodwr...373&section=ep

25534421 Vortec Bow-Tie Small Port Cylinder Head, Complete
GM Performance Parts' latest and most powerful iron cylinder head for Street or Racing. This Vortec design Special Performance cast iron cylinder head features revised intake and exhaust ports and includes 2.00" hollow stem intake valve P/N 12555331 and 1.55" sodium filled exhaust valves P/N 12551313. The deck surface is .450" and features 65 cc combustion chambers, 175 cc intake and 65 cc exhaust ports. All Vortec intake ports are taller and narrower than early model Chevrolet heads. The valve cover mounting holes are for both early model flange and late model center. This head also includes intake manifold mounting holes for both early model 6 bolt main and late model 4 bolt Vortec design. The head has screw in rocker studs P/N 12552126, large valve spring pocket machining, and will accept up to .530" lift camshafts without modifications. Heads are identified with the Bow-Tie logo on the exterior of the head below exhaust flange and Vortec logo on top of intake port area. They also feature GM logo cast into bottom of intake ports. Includes valve spring P/N 12551483, valve seal P/N 10212810, and spring cap P/N 10212808.
Technical Note: You must use a raised runner design intake mainifold P/N 10051103 (6 bolt mounting), or Vortec design 12366573, 12496820, 12496821, 12496822, and 12499371 (4 bolt mounting) with this head. You can use production Vortec intake gaskets P/N 12529094 (torque spec. 11 ft-lb/ 15Nm) for mounting Vortec design heads or use P/N 12497760 (torque spec. 30 ft-lb) with conventional material when using on early model raised runner or Vortec design intake manifolds, this gasket has both 6 bolt and 4 bolt Vortec attaching holes. Head casting P/N 25534351C.


25534431 Vortec Bow-Tie Large Port Cylinder Head, Complete
GM Performance Parts' latest and most powerful iron cylinder head with "Large Port" for Street or Racing. This Vortec design Special Performance cast iron cylinder head features revised intake and exhaust ports and includes 2.00" hollow stem intake valve P/N 12555331 and 1.55" sodium filled exhaust valves P/N 12551313. The deck surface is .450" with 65 cc combustion chambers, 206 cc intake and 77 cc exhaust ports. All Vortec intake ports are taller and narrower than early model Chevrolet heads. The valve cover mounting holes are for both early model flange and late model center. This head also includes intake manifold mounting holes for both early model 6 bolt main and late model 4 bolt Vortec design. The head has screw in rocker studs P/N 12552126, large valve spring pocket machining, and will accept up to .530" lift camshafts without modifications. Heads are identified with the Bow-Tie logo on the exterior of the head below exhaust flange and Vortec logo on top of intake port area. They also feature GM logo cast into bottom of intake ports. Includes valve spring P/N 12551483, valve seal P/N 10212810, and spring cap P/N 10212808.
Technical Note: You must use a raised runner design intake mainifold P/N 10051103 (6 bolt mounting), or Vortec design 12366573, 12496820, 12496821, 12496822, and 12499371 (4 bolt mounting) with this head. You can use production Vortec intake gaskets P/N 12529094 (torque spec. 11 ft-lb/ 15Nm) for mounting Vortec design heads or use P/N 12497760 (torque spec. 30 ft-lb) with conventional material when using on early model raised runner or Vortec design intake manifolds, this gasket has both 6 bolt and 4 bolt Vortec attaching holes. Head casting P/N 25534371C.

 

Very interesting new stuff from GM performance.

 

love to see flow #s at different lifts

 

CHP just had a short article on them. No flow number however. Ports are 205/77 IIRC.

 

K thx, wish i still had my subscription to chp

 

Super Chevy just did an article on them, Dec 2005 issue small port head flowed 251 at .500, large port head flowed 258 at .500, no exhaust flow listed, very good article... makes me want to go get them right now

 

Isnt this it.

http://chevyhiperformance.com/techar...er/index1.html

 

Yes, but they were upgraded with larger 2.02/1.60 valves and an application-specific valve job. Not sure if the flow numbers posted are for a stock casting or after they did the mods. I don't know if it would make a big difference, but probably some.

 

the one in Super Chevy tests both the large and small port designs, also stock vortec, vortec truck heads, and aluminum vortecs i believe

 

Stock small port Bowtie Vortec

.100 062 049
.200 128 106
.300 183 134
.400 225 152
.500 235 161
.600 236 163

Quick clean up 3cc Removed

.100 064 050
.200 135 110
.300 188 140
.400 232 165
.500 251 179
.600 252 183

 

confused....I'm under the impression that the "Bowtie Vortec" is different than the standard, humdrum vortec head? That you can go and purchase "regular" vortecs, or "bowtie" vortecs?

Magazine articles sometimes have a way of making things complicated Maybe I'll go reread the article.

somebody clear the fog,
Brandon

 

well theres the stock vortec heads and then theres the GM Performance Parts Vortec heads which have upgrades over the stock vortec heads...
anyone else may be elaborate more

 

that's what i thought, wasn't sure...thanks

 

Yeah I just dug up this post because one of the magazines just did a dyno article on them. My friend is building a "sneaky-snake" street sleeper small block for his disco nova. Its my old 415 which with .060 over will be 421 CID. Im telling him to run these 206cc ones and use stock black centerbolt valve covers.

 

I got a set of GMPP vortec heads and they were no different than a stock vortec heads.

 

I think he is talking maybe about the differences between available stock vortecs, then the stock ones they have with just the spring and seal mod, and then the two models of newer iron "bowtie" vortecs. That would make 4 different complete vortec assemblies that are available from dealers now.

 

I wish I had gotten the modified set now. Ive been reading on the Bowtie set and they look great except for the lift, 530 max. I really liked the fact that they are drilled for old stlye intakes.

 

why would you want a redrilled set? the only intake that would come close to fitting any redrilled set of vortecs is a port matched LT4 intake, or high port intakes which are generally "wider" than the vortec port which creates a side to side fitment problem unless you widen the transition on the head.

a regular intake wont even cover the top ports, they are open to atmosphere.

See for yourself:

 

Well they drilled them for a reason, there must be some tall port old style intakes out there.

 

Even if you could port match a standard intake for a vortec port the floor approach angle in the manifold is all wrong.

You'll have more work and epoxy in it trying to make a vortec intake than its worth. There are many vortec intake on the market now. Even used stuff.
Holley just came out with a new blower manifold and a "EPS"
, "CYclone Plus+" style mid rise intake.

 

yes, there is a reason. the reason is that some people will still compromise. Just like a person running a stock intake with a 1205 gasket on heads made for a 1206 gasket. People do it, its about people who are still willing to compromise the gain of running a vortec head with the loss of port mismatch. Maybe with the intention that they will get the right intake when they can afford it. Maybe they have a blower or EFI, and its not available in vortec yet, there are a few reasons which allow the compromise.

like mentioned above the "tall port" intakes will work, and with less compromise but they still have a port floor mismatch.

People have been doing this thing of thing for years. Have you ever seen how most stock heads arent even close to the ports on a aftermarket manifold? people still put them on.