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Chevy Heads


labrat

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Depends on who you ask. Most of the time folks make names or terms up as they remember em or as they fit. "won't turn over" to me (and most of the folks I ran with in SO Cal) means dead battery and it won't even rotate the engine. Here most folks use that term to describe an engine that cranks but won't fire (left over I presume from hand cranking tractors and having it not turn over on its own past the spark point).

 

A Bow Tie head is a head as cast from (or for) the GM factory - hence it wears the registered trade mark BowTie. The vortex can be a bow tie in this context.

 

Usually though - in the same context as "the camel hump being the head of choice" (even though there are several flavors of hump and only one is the "real deal" performance wise right from the factory) the reference is to an early model head. In this context the Bowtie can be found on all 85 and older vehicles, most 86 (and into 87 on trucks originally equipped with Carburator). The 87 is a blend year for GM which blended the early head with the one piece rear seal block.

 

In 88 Generation II heads brought center bolt valve cover - as opposed to the older perimeter bolt, and changed the intake manifold bolt angle. This head is sometimes to refferred to as a Bowtie by folks who call generation I early model and Gen II Bowties. Most intakes for these are adaptations of the earlier models - using plugs to choose which angle the bolts go at.

 

In 96 'Gen III brought the Vortec to the V8 line (Vortec technology originally appeared in the 90 deg v6 4.3 in 85 and was junk for the most part IMO). Looks much like the Gen II heads - but obviously missing the center two bolt holes for the intake. These heads require a specific manifold as not only did two bolts disappear - the angle on the intake machined surface (relative to block deck) is slightly different. They can be milled to fit and accept the Gen I and II intake - but why bother - just use a late intake its probably already tuned closer than the early one right out of the casting process!!!! The L31 (96-03 5.7 truck) is a good performer on either block with little mods. But be warned - it IS a Vortec and will be ruled as such during tech inspections!

 

To sum it up for the first step of id: Gen I - perimeter valve cover bolts, Generation II center valve cover bolts 6 bolt holes on intake side, Gen III (Vortec TM) center valve cover bolt 4 intake bolts.

 

Whenever in doubt - use casting number! Your machinist/builder can relate to that far better than trying to keep up on all the street slang! Then its pretty much a given as to what cam to select for what desired RPM range and power curve you want.

 

Even some engine builders are obviously confused. On the 86 when I bought it had 409 camel hump on one side and 884 Gen I on the other. If you know numbers this was a 67-69 327 1.94 head on one side and an 81-86 350 1.94 on the other. Two completely different runner shape and volume! And these were on a .060 over 305 block!

 

edited to add - Vortec is apparent in the intake runner - where you will see that it is designed to "spin" the incoming charge before introduction to the cylinder. - Some folks actually port this feature out - but again why? - the vortex it creates keeps your fuel suspended better and is the whole basis behind choosing this head!

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Sorry to ask such a stupid question, but are the Chevy Vortex heads also known as Bow Tie heads or are they totally two different type of heads?

 

Thanks for any and all replies!

 

There are actually three different animals that go by the name "Vortec" and "Bow Tie" when it comes to chevy heads. The 350 chevy Vortec heads bear casting numbers 062 or 906 (last 3.)

 

The Bow Tie heads are a racing head not offered on any production vehicle. They have come in I believe 3 "phases" over the years, with the latest being the Phase 3 Bow Tie heads. The casting number on the Bow Tie heads (last 3) is 034. You will have to look closer at some of the other casing marks/ridges to tell if a head is a phase 1, 2, or 3.

 

Lastly, GM has fairly recently come up with the "Bow Tie Vortec" heads, a race-only head. I'm not sure of the casting number of these heads, but a quick Google search would take care of that.

 

From my limited experience and research, they rank like this in terms of performance from best to worst:

 

Bow Tie Vortec

Vortec

Bow Tie

 

Like Mr. Bishop mentioned, sometimes the terms "Vortec" and "Bow Tie" are used for other parts, but I believe these are the heads you were asking about.

 

Good luck

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the first three are bare, all in order that I would pick. There are other castings as well - but i just like the 363 - easier to shape the bottom of the port and inside radius to the seat a little. The 352 extrude it and run it out of the box.

 

10134352 Bowtie, Lo port, alm. 18º, angle plug, 45cc, 223cc intake port

10134363 Bowtie, Hi port, alm, 18º, angle plug, 45cc, 210cc intake port

10134363 Bowtie, Hi port, alm., 18º, angle plug, 60cc, 215cc intake port,

10134363 Bowtie, Hi port, alm., 18º, angle plug, 50cc, 250cc intake port, CNC machined, 2.15-1.625 valves

10134363 Bowtie, Hi port, alm., 18º, angle plug, 65cc, 250cc intake port, CNC machined, 2.15-1.625 valves

10134363 Bowtie, Hi port, alm., 15º, angle plug, 36cc, 223cc intake port

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iron choices (there are other - but rarer and harder to find choices)

 

14011034 Bowtie, Phase 2, iron, angle plug, 64cc, 2.02-1.6, 184cc .080 taller intake port

10239906 350, Vortec 5700, L-31, 64cc heart shape chmber, 1.94-1.5, 170cc intake port

3991492 Over counter, strt or angle plug, 64cc, 157/62cc ports

 

According to the guy whose shop I used to manage - we should only be referring to the heads sold thru GM Performance as "Bowties", thats what the desigination was for - to distinguish between aftermarket performance heads and GM performance heads - a brand awareness response to the competition (the 492 listed above is before the designation of the parts line - and is a continuation of the 70 LT1 350 straight plug hump).

 

Therefore Bowties come in all three generational configurations. So basically when track rules say NO BOWTIES they mean no heads sold as a specific 'racing" head from GM Performance and are limiting you to run production heads (so the scrap yards can compete in the supply chain and keep costs under control).

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