Chevy performance 12691728 vs small port bowtie vortec

[Justa1time]

Good Afternoon,

I have been looking at the GM cast iron head offerings and have found some fairly interesting claims from distributors who offer this 1728 casting.

GM 12691728

Many of the adds for these cylinder heads state: "The Vortec head out flows the Bow tie head out of the box and is a 20 to 40 horsepower bolt on increase over earlier cast iron small block heads." Which is difficult to understand because no other casting numbers are used. Which bowtie heads do these outflow?
https://paceperformance.com/i-6255341-1 ... plete.html

Which is a better cylinder head for a 350 ci street/weekend warrior engine. The 1728 or the small port vortec bowtie?


Thank you,

Bryan

[mag2555]

From what I found on line about these heads they do not out flow a 906 vortex casting .

[PRH]

If you want to know how two heads compare, it’s best get flow data obtained from both heads tested on the same bench.
Not the same type/model of bench....... but the same actual bench.

Why?
Here’s an example.
These two sets of numbers are from the same head, same ports, tested on the same brand/model of flow bench........ but two different ones.
The head has not been altered in any way between the two tests, and they are the same valves in the head for both tests:

Intake flow(same port, same head):
Lift———A———B
.200— 163—— 138
.300— 220—— 199
.400— 270—— 249
.500— 319—— 290
.600— 347—— 333
.650— 336—— 346
.700— 334—— 329

Exhaust:
Lift———A———B
.200— 124—— 101
.300— 169—— 139
.400— 210—— 177
.500— 242—— 211
.600— 265—— 237
.650— 273—— 244
.700— 275—— 253

[F-BIRD'88]

These are not Bowtie Vortecs. (not small port nor large port ) They apear to be a new part number for the new revised oem L-31 production vortec heads.
The old 96-2000 era 906 and 062 vortecs flow 228 cfm out of the box.
These may be the castibgs made now in Mexico which have been reported to flow some 10 cfm LESS than the old oeigional L-31 heads.
They can be ported of course to increase flow.

The GMPP "Bowtie Vortecs" Are better castings and do flow more as cast and even better ported.
Yes the old Bowtie cast heads with the old sbc ports and bolt pattern flow less in as cast form.
These old Bowtie heads are intended to be pro ported by the end user and flow a lot when fully ported, as intended.

Again these vortecs offered apear to be the replacement heads that come on the crate motirs now, cast in Mexico.

[Tom68]

If you want to know how two heads compare, it’s best get flow data obtained from both heads tested on the same bench.
Not the same type/model of bench....... but the same actual bench.

Why?
Here’s an example.
These two sets of numbers are from the same head, same ports, tested on the same brand/model of flow bench........ but two different ones.
The head has not been altered in any way between the two tests, and they are the same valves in the head for both tests:

Intake flow(same port, same head):
Lift———A———B
.200— 163—— 138
.300— 220—— 199
.400— 270—— 249
.500— 319—— 290
.600— 347—— 333
.650— 336—— 346
.700— 334—— 329

Exhaust:
Lift———A———B
.200— 124—— 101
.300— 169—— 139
.400— 210—— 177
.500— 242—— 211
.600— 265—— 237
.650— 273—— 244
.700— 275—— 253

Clearly somethings wrong with a bench here, what do you think it is ?

[PRH]

Clearly somethings wrong with a bench here, what do you think it is ?

It could be as simple as the range value calibrations.

But that’s the point.
There is a pretty big differential there........ which one is correct...... or are either correct?

It’s a real world example of why I never assume numbers from different benches are comparable as truly “apples to apples”.

[rebelyell]

agree entirely w/ F-bird

much ado 'bout nuthin'

the pictured GM 12691728 ... IS simply a replacement L31 Vortec head ... look closely and you can see casting number x062. Not Bowtie

GM 12691728 is simply part number for a complete assembled L31 Vortec head of Either OR two casting numbers x062 OR x906, Not Bowtie

as has been known and well-documented for some 25 years ... it's a great head w/ fastburn type chambers ...but not Bowtie

[Justa1time]

Thank you guys for the reply.
I was looking at the 1728 because of the better than bowtie comment in the description. I find it very odd they don't have any casting numbers or flow data to prove the claim. I am trying to find the best iron heads for my application.

So the small port vortec bowtie is about the best iron sbc head available for a small displacement Sbc?


Thanks,

Bryan from Oregon

[Tom68]

Thank you guys for the reply.
I was looking at the 1728 because of the better than bowtie comment in the description. I find it very odd they don't have any casting numbers or flow data to prove the claim. I am trying to find the best iron heads for my application.

So the small port vortec bowtie is about the best iron sbc head available for a small displacement Sbc?


Thanks,

Bryan from Oregon

Better than the Darts ?

At least with the Bowtie Vortec you have all manifold choices covered with the double drilling.

[rebelyell]

Nope, AFAIK, GM hasn't published flow specs for 062 / 906 vortecs ... and, AFAIK, GM hasn't published flow specs for their other sbc heads either.
However, those flow numbers are all over the web ... simply google.

If you have a vortec pattern intake hangin' around ... 062/906 are likely best unmodified bang for the buck; again, old news

Suggest it'll pay off in spades for ya to download a free Chevy Performance catalog from the Chev Perf site ... lotsa specs & part numbers & cast numbers.

also, some good info & some hype at castheads.com

[1980RS]

Good Afternoon,

I have been looking at the GM cast iron head offerings and have found some fairly interesting claims from distributors who offer this 1728 casting.

GM 12691728

Many of the adds for these cylinder heads state: "The Vortec head out flows the Bow tie head out of the box and is a 20 to 40 horsepower bolt on increase over earlier cast iron small block heads." Which is difficult to understand because no other casting numbers are used. Which bowtie heads do these outflow?
https://paceperformance.com/i-6255341-1 ... plete.html

Which is a better cylinder head for a 350 ci street/weekend warrior engine. The 1728 or the small port vortec bowtie?


Thank you,

Bryan

If that 728 casting is the same as the old 906/062 Vortec head then it will be a good street head. In my testing a set of mild worked over 062's with stock valve sizes, hyd cam, stock rockers and single plane intake ran high 10's@120mph. So which do you think is better now?

[Justa1time]

1980rs: I Have a set of Engine Quest ch350C's but are damaged - brand new even! I am having troubles finding someone to fix them in my area. I am looking at either the small port vortec bowties or the 728 castings. I am totally open to other iron suggestions as well!

I hear you on the 10s with your combo. Must be on a 400?

Thanks,

Bryan from Oregon

[F-BIRD'88]

You guys are jumping to conclusions posting that the head casting number for these heads is now 728.

Only the part number has changed . xxx060 to now xxx728. I bet the casting number is still 062.

[mag2555]

Those flow numbers posted up show a 21% difference, and there can’t be that much between the same model benches unless one big thing is way way off, or a bunch of smaller things combined are screwed up!

Not even the use of a much different size bore adapter or setting a head up different on the adapter could make for that drastic a difference!

Years ago a sold my SF110 bench to a fellow and I set it up in his Basement for him.
A year later or so I went back to buy some car parts from him and he had set it up in his new garage, but I found a problem.

He had sat it on a bench that was way off level and never readjusted the inclined manometer to compensate for it.
All of his test where way high!

[rebelyell]

JMO, if you have a new, but damaged, pair of EQ 350C heads, then (so long as they're Not cracked) have them repaired ... end your search ... install & run them. Milling heads' decks can reduce chamber volume.
EQ350C are essentially replacements for GM x062 / x906; they are functionally copies but w/ slightly larger chambers. I've seen (google) where EQ350C flow bigger numbers than GM x062 / x906. But keep in mind, flow numbers are but one aspect of a performance profile ... while Velocity is as important.

It's clear (to me, at least) those quotes touting (sic) flow of x062 / x906 castings are superior to GM Bowties ... are referring to those older generation Bowtie heads made BEFORE advent of Vortec Bowtie ... such as Phase 1 and Phase 2 iron castings. Keep in mind how those older Bowties do Not have the fastburn type chamber found in Vortec Bowties.

x2 on bench install ... and management & maintenance