041X Chevy cylinder head info - Chevy Nova Forum
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Old 26th-September-2008, 09:10 PM   #1
1974_SS

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041X Chevy cylinder head info

Hello guys, I have a question for ya. I picked up a set of chevy heads with the casting # 394041. I know there the 69-70 HP heads. But my question is these are both stamped on the bottom side with the letter "X". Can anyone tell me for sure what the X stands for?
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Old 26th-September-2008, 09:14 PM   #2
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Quote:
Originally Posted by 1974_SS View Post
Hello guys, I have a question for ya. I picked up a set of chevy heads with the casting # 394041. I know there the 69-70 HP heads. But my question is these are both stamped on the bottom side with the letter "X". Can anyone tell me for sure what the X stands for?
Is the "X" cast in the water jacket or a stamp?
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Old 26th-September-2008, 09:25 PM   #3
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Its on the bottom side of exhaust ports if this makes sense? There are also stamped on the bottom 041
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Old 26th-September-2008, 09:38 PM   #4
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My fault they are 3947041 is the casting #'s
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Old 26th-September-2008, 09:49 PM   #5
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those are known as : "041X" castings.. and are sought after... ebay them suckers...

the X casting were factory performance upgrades to the standard head...

The X castings generally have larger intake runners than the same number counter part... whether they are the 441x, 041x, 461x, etc.. Generally speaking the "X" castings are a better breathing casting with the X than with out the X
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Last edited by veno; 26th-September-2008 at 09:52 PM.
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Old 26th-September-2008, 09:56 PM   #6
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I little info on the 041X

copied from:

Sometimes class rules make you do things that are out of the ordinary. Such
is the case with NHRA Super Stock engines. Read more about some testing
done by Larry Meaux on 162-165 cc intake runner SBC heads.

Could it be in the case of the bike heads the original ports were too large?

Originally Posted by maxracesoftware

here's some Threads from a couple of Posts that might explain
CHOKE to you

here's a very good quote from STEVES
that explains the general idea and reason why Choke
or too fast FPS hurts HP+TQ
just read rest of Posts with that in mind .

As I understand it, ports don't actually go into sonic choke at .55 Mach - but
at this point (approx.) we reach the trade off where the energy required to
move the air through the port becomes higher than the power increase
(cylinder filling) that comes from higher velocity.
---SteveS

Posts=>


From a previous Thread

too fast Velocity FPS can be a total disaster

Note=>all 3 of these Heads were tried on
the same Short Block with all the same pieces
and Dyno Tuned for best possible HP/TQ Curve
with those pieces.


#041x SBC Heads = 165.0 CCs
1.940/1.500 valves
these are the very Hi-Velocity Heads
with too much velocity everywhere inside
the Intake Port, same FlowBench numbers

and the "BEST" Dyno test with them
600 RPM/SEC , i don't have the Sheets
that we started at 3000 RPMs and all the
rest of the Sheets , but only kept the
Copies that stood out, and these are every
200 Hundred RPM increments as its too much Info to type
every 100 RPMs, but it should give you enough Info ?

note=> at 600 RPM/SEC you get a little Needle/Seat
action showing up especially with small gas bowl
chamber in Q-Jet, so look at Fuel Lbs/Hour trend
as well as rate (Same Q-Jet Carb all Dyno Tests)

RPM---TQ----HP----Fuel Lbs
4500-419.3-359.3--178.4
4700-438.1-392.1--171.5
4900-449.1-419.0--177.2
5100-451.0-437.9--169.8
5300-445.8-449.9--174.1
5500-443.2-464.1--188.3
5700-441.0-478.6--209.8
5900-429.6-482.6--222.1
6100-424.3-492.8--227.4
6300-413.9-496.5--214.9
6500-412.7-510.8--200.8
6700-407.6-520.0--210.3
6900-388.8-510.8--221.9
7100-363.7-491.7--236.1
7300-345.3-479.9--239.8
7500-325.1-464.3--233.4
7600-312.6-452.4--226.1

Avg=>406.5-464.9--206.0

--------------------------------------------------------------------------------

with #041x Heads back-to-back on same Short Block
same basic Flow CFM Numbers, same valves, same CC's
but with Port Velocity slower and more acceptable
throughout the entire Intake Port

RPM---TQ----HP----Fuel Lbs
4500-449.5-385.1--166.1
4700-444.2-397.5--164.5
4900-455.2-424.7--177.0
5100-456.2-443.0--158.3
5300-464.1-468.3--169.6
5500-471.1-493.3--192.9
5700-470.2-510.3--199.2
5900-468.2-526.0--199.3
6100-465.0-540.1--204.5
6300-459.8-551.5--209.7
6500-456.6-565.1--216.3
6700-442.6-564.6--223.1
6900-432.8-568.6--217.2
7100-426.6-576.7--215.3
7300-418.3-581.4--224.5
7500-401.8-573.8--238.2
7600-394.1-570.3--231.0

Avg=>445.7-514.1--200.4

================================================== =

with #462 castings 1.940/1.500 162.0 CC Ports
differences just 3 CCs can make when ground out in the
correct places, again FlowBench CFM between the
#462 and the other 2 #041x Heads were very close
and CFM numbers don't indicate the HP/TQ differences observed
and Ports had different Velocity Profiles.
Same ShortBlock and all pieces the same.

RPM---TQ----HP----Fuel Lbs
4500-443.0-379.6--168.3
4700-441.8-395.4--159.8
4900-450.6-420.4--164.4
5100-456.9-443.7--169.8
5300-459.2-463.4--183.9
5500-465.9-487.9--190.6
5700-464.1-503.7--192.0
5900-463.0-520.1--195.2
6100-460.6-535.0--196.6
6300-454.9-545.7--206.5
6500-446.8-553.0--216.1
6700-438.0-558.8--225.1
6900-428.4-562.8--220.8
7100-422.0-570.5--223.9
7300-410.1-570.0--219.5
7500-395.3-564.5--226.4
7600-388.8-562.6--231.1

Avg=>440.6-508.1--199.4


Quote:
Very well put - I have thought for some time that "Choke" is actually a
misleading term here. David Vizard has called it "Power Limiting Port Area",
a more accurate description, but unlikely to catch on.


i just use the word "Choke"
because sometimes the Engine will be Choked by an Area
and sometimes by the same cross-sectional, but now has one of the walls
with too much local velocity FPS and/or diverging too quickly on 1 wall

in the above Dyno Test examples the
one extreme hi-velocity #041x SBC Heads
is using more Fuel, but if you try to lean it out, you loose even more Torque
and HP...notice it makes Peak TQ and Peak HP lower and runs out quickly
with rapid rising BSFC numbers as rising RPMs show Choke problem even more.

the 2nd pair of #041x heads
make more Peak TQ & HP and at higher points,
and don't lay over top end.

the #462 castings with 3 less CC's
make Peak TQ at same point, but past Peak HP point start to layover
more than the #041x

Fuel consumption is about identical

Same FlowBench CFM Numbers
but different Intake Port Pitot Probe profiles/velocities



note thats a 117.9 HP "LOSS" for the extreme hi-velocity Heads at 7600

yet..on a steady-state FlowBench test,
"BOTH" Heads flowed almost as exact CFM as you could possibly
make them be equal on both Intake + Exhaust sides.

even used and swapped the same exact Valves out of both Heads
for those tests

same #041x castings , both same Chamber+Port volumes


what i call the extreme velocity FPS #041x Heads were;

every possible portion of that Intake port that could have
Epoxy added to it, and that Flow CFM was not reduced at all,
was epoxied up.

and the rest of that Port was enlarged just enough
to hold the same Port Volume CC's

the Short Turn Apex speed was to the moon
and so was the pushrod area...and just about every where else in the
Port....the Floor had some "Ski-Jump" shape to it also...as it kept
the CFM Numbers up and the velocity sky-high

i guess you could call it an experiment to see how far
you could "shrink" certain CSA areas of a Port
and not reduce the FlowBench CFM numbers .

pretty evident from Fuel Consumed Numbers -vs- Dyno HP/TQ Numbers
that Intake Port could not handle that much speed FPS
without Choke or Separation

you can also see why just about everyone i know
will Run the #041x heads over the other Legal #462 castings,
those 3 more CC's can be used to "SLOW DOWN" the already
too fast FPS

one other thing that stood out in some of the Tests, was the very hi-velocity
too fast FPS Heads that had a choke problem,often liked "more" low to mid
lift flow.The engine's being fed sooner and more, so the cylinder depression is
lesser until Choke occurs...and you still have good low-lift to take advantage
of high velocity at end of stroke

also the velocity FPS is slower in the smallest CSA areas, in the low to mid lift
portions of the Flow/Cam Lift Curve...pumping losses working thru rod angle
leverage in early and latter parts of stroke are going to be lesser than at Peak
Piston CFM demand point where leverage is great and Choke makes more losses.

a Closed Intake Valve has "ZERO Port Velocity FPS"

at Max-Lift , typically the Cyl Head has its best FlowBench CFM Number
or about in that vicinity...so Port Velocity FPS is highest at Peak Lift or
so. as the valve starts to move towards max lift, Port FPS is increasing...
also the minimum csa area FPS is starting to really increase or any too
fast FPS area is also increasing in FPS (add to that max Piston CFM
demand in vicinity of 70-80 deg ATDC and volume CCs increasing till
BDC, + Flow Lag Times, pumping losses working thru Rod Angle
leverage/velocity, etc.)


FPS = (CFM * 2.4 ) / CSA

if Head Flows 127 CFM at .200" Lift = 156.6 fps @ 1.948 csa

if head flows 260 CFM at .700" Lift = 320.3 fps @ 1.948" CSA

but in reality there will be CSA spots in Heads that will be
smaller than 1.948 sqinches, so the FPS will be higher than 320.3
other CSA will be larger than 1.948
and other localized spots can have too high FPS
even though your Average CSA of 1.948 says its only 320.3 fps


the Port Volume is the same in both cases,
the FPS changes up or down inside the Port
in relation to the Lift/Flow Curve -vs- Piston CFM demand

picking up the Low to Mid lift flow in the too-fast-velocity heads
helped...but it still didn't run as fast down the DragStrip.
the best way i've found so far is to slow the FPS to as close
to reasonable speed as possible, as long as its not too slow,
take the choke CSA out of the picture as much as possible.


As I understand it, ports don't actually go into sonic choke at .55 Mach -
but at this point (approx.) we reach the trade off where the energy required
to move the air through the port becomes higher than the power increase
(cylinder filling) that comes from higher velocity.
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Last edited by veno; 26th-September-2008 at 10:02 PM.
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Old 26th-September-2008, 09:59 PM   #7
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I Just Bought These From A Guy On Ebay For $150. Hey, These Are Also Marked In The Inside Of Head (under Valve Cover) "conv 4"
Any Idea On What Conv 4 Means?
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Old 27th-September-2008, 12:26 AM   #8
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Veno,
the link has some interesting head flow discussion. I'll have to read it more closely later.

As far as the 041x heads go, they are more of a collector item than something that has use on the street.
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Old 27th-September-2008, 01:45 AM   #9
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i also have a pair of these 041X heads... anyone have any dyno specs or dyno runs showing some HP and TQ figures in stock un-ported configurations with the stock 1.94-1.50 valves in place? thanks
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Old 27th-September-2008, 08:38 AM   #10
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I bet that Jeff Cuppy (stock z/28) will have some great input on this. Hopefully he will chim in
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Old 27th-September-2008, 02:27 PM   #11
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If your thinking of selling them, try ClassRacer.com, that's where the Stock/Super stock guys are.
Don
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Old 28th-September-2008, 11:27 AM   #12
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Any of the old heads are obsolete.

The ones you have are a wanted in Muscle car restoration.

And maybe a Pure Stock racer. Not because they are great head, the rules limit and this is best available within the rules.

They will work great for a small CI engine 283 exc. where more CFM is not a great benefit.

In there day, they were the best available until the 292 angle plug head came available.

It most cases the heads are not cost effective, they will need major machine work, seats & guides are common.

The most basic aftermarket head or even the 300.00 Vortec head will out perform those heads by a great margin.

In todays world they are just one notch above a smog head.

You can sell them for more than a budget aluminum or Vortec head will cost new. And have a greater performance.

The 041X is the rarest to find. (IMO)

041X considered the "FUELIE HEAD"
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Old 28th-September-2008, 01:44 PM   #13
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hi
i figured out a cheap way to rebuild my 041X heads for cheap. Dynagear sells 1 pc. stainless steel valves for cheap like about $80.00 a set. and they come in .003" oversize on the stem or even larger if you want. ( i have done this before) except the keeper area is standard. so i have the worn guides honed or reamed out to fit the .003 over size valve and magic your done for cheaper! oh and valve job is should be included last time i checked. and just make sure you use 1.25 diameter valve spring to keep cost down. K-motion has .500" lift springs that are 1.25 for 45 bucks.... and no need for screw in studs, i bought a used stud gridle for cheap incase i need it..... i love budget building!!!!
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Old 29th-September-2008, 01:42 PM   #14
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I am doing a set of the 041 Casting heads (but not the X version) on a 66 283 Nova Block for my car. My stuff is at the machine shop right now. My engine guy says he has done some of this combination before and that it worked really well. If I am not mistaken didn't the 041X come with NO accessory bolt holes versus standard 041's having the bolt holes? I know mine standard 041's have the bolt holes.
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Old 29th-September-2008, 03:37 PM   #15
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hi, nope my X heads have the accessory holes in them

Quote:
Originally Posted by HR&CNovaRod View Post
I am doing a set of the 041 Casting heads (but not the X version) on a 66 283 Nova Block for my car. My stuff is at the machine shop right now. My engine guy says he has done some of this combination before and that it worked really well. If I am not mistaken didn't the 041X come with NO accessory bolt holes versus standard 041's having the bolt holes? I know mine standard 041's have the bolt holes.
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