67' Barracuda 273 (Camshaft Results at the Track)

-
blownhemi said:
Been hanging out all week for an update.

Nice work. Mid-12s is nothing to sneeze at, but I get the feeling there's going to be a lot more in this as the cams get bigger.

I'm amazed at how well it goes with stock heads and intake.

So the hp figures are all rear wheel?
Click to expand...

I thought I remember reading the heads were all worked over .:confused:
I must have missed something.
 
You are correct ..... sorry ..

I'm Very impressed with the little 273..
somedy I'll have to put a dial indicator on my cam and see what is it.
my cam must be more than stock to stay with 340-360 abodies .

Thanks for all the info 69 cuda .
john
 
Thanks for the info,69 Cuda. Getting to the point,heads /valvetrain would need some tweaking.
 
The Cylinder Head Specifications;

Casting # 2658920

* The heads were milled, to achieve a 57.3 CC 'combusuon chamber volume'.

* Martin-Wells (Well-Tite) 'hardened seats' were installed.

* Bronze Valve Guides

* The intake and exhaust ports were 'gasket/port' matched, and the high-spots 'casting flashes' were removed.

* No porting, other than 'only' going a 1/4" depth into the port for 'smooth-transition' blending.

* Minor 'rounding/blending' at the 'valve guide boss' inside the 'bowl area'.

* Intake Ports were equally matched to a 131 CC 'volume'. (4 CC's over 'stock' measurement)

* Exhaust Ports were equally matched to a 64 CC 'volume'. (4 CC's over 'stock' measurement).

* Intake 'Valve Seats' were cut '5-Angles' == 70* - 60* - 45* - 37* - 20*

* Exhaust 'Valve Seats' were cut '5-Angles' = 70* - 60* - 45* - 30* - 15*

*Seat Width = .040" Intake ~ .060" Exhaust

* All 'sharp edges' were radiused, and smooth-sanded with 400 Grit Wet-Dry Sandpaper,
while using a light film of Marvel Mystery Oil as a lubricant.

* Valves are Ferrea #5000 Series 'stainless steel'. 'High Performance Street/Strip Series' with 'swirl polish finish'.

* Intakes = 1.78" with 3/8" Stem
* Exhaust = 1.50" with 3/8" Stem

* Valve Angles = 45* with a 30* back-cut (.025" wide) on the Intake Valve
----------------------------------------------------------------------------------------------------------

Note; We didn't want to perform a 'full blown' Port & Polish Job on the Cylinder Heads, as we wanted to see what
we could get performance-wise out these heads.

Note; A 'gasket/port' match was neccessary, and 'rounding/blending' of the valve guide boss was required, to
promote a smooth flow and to increase the port velocity on these relatively stock port cylinder heads.
 
69Cuda

Been following this thread, and the Racer Brown ST-12 looks very impressive. I have a Racer Brown STX21 taken out of a 273 that was used in a circle track car. I put that motor in my challenger with a six-pack set up and it was a screamer, pulled to 7500 no problem. I am pretty sure it was faster than my 340.

I looked the profile up on 4seconds flat, a little more cam than the St-12. Probably will never put the cam back into anything, its still looks perfect. I would donate this to you if you are interested in testing.
STX-21M306272.560.597
 
R Bob,

Thanks, much appreciated.

But we can only go up to a .530 Lift (Piston-to-Valve Clearance), without
'notching' the 1969 Profile 'JE Pistons'.

Racer Brown #STX-21
Lift............ .560"
Duration...... 306*
Overlap........ 96*

OH BABY !!!!

That Racer Brown STX-21 has a {+70 Horsepower Gain} over a 'stock' 340 Camshaft.

For everybody who has added to this thread with compliments.

Thanks To All,,,,,

For all you 1966 'Back-In-The-Day-Racers',

We 'broke' the 1966 NHRA C/FX National Record of ...{ 12.56 }
 
1970 La said:
Any chance of a valve spring change before the next cam swap?
Click to expand...

Yes,,,,we have to,,,,,, otherwise there will ba 'party' between the Valves and Piston Top.

We are going with Compu-Cam #926 Valve Springs.

#130 lbs. with 'valve closed'
#316 lbs. with 'valve open'

These are Single-Coil with dampers.

We are debating whether to pull the Cylinder Heads, or do the 'unthinkable'.

Yes, attempting to change 'valve springs' with the Cylinder Heads mounted on the engine.

Next Camshaft Upgrade #8,........Crane 'Zip 488'.. .488 Lft /300* Duration
 
69 Cuda 440 said:
The Cylinder Head Specifications;

Casting # 2658920

* The heads were milled, to achieve a 57.3 CC 'combusuon chamber volume'.

* Martin-Wells (Well-Tite) 'hardened seats' were installed.

* Bronze Valve Guides

* The intake and exhaust ports were 'gasket/port' matched, and the high-spots 'casting flashes' were removed.

* No porting, other than 'only' going a 1/4" depth into the port for 'smooth-transition' blending.

* Minor 'rounding/blending' at the 'valve guide boss' inside the 'bowl area'.

* Intake Ports were equally matched to a 131 CC 'volume'. (4 CC's over 'stock' measurement)

* Exhaust Ports were equally matched to a 64 CC 'volume'. (4 CC's over 'stock' measurement).

* Intake 'Valve Seats' were cut '5-Angles' == 70* - 60* - 45* - 37* - 20*

* Exhaust 'Valve Seats' were cut '5-Angles' = 70* - 60* - 45* - 30* - 15*

*Seat Width = .040" Intake ~ .060" Exhaust

* All 'sharp edges' were radiused, and smooth-sanded with 400 Grit Wet-Dry Sandpaper,
while using a light film of Marvel Mystery Oil as a lubricant.

* Valves are Ferrea #5000 Series 'stainless steel'. 'High Performance Street/Strip Series' with 'swirl polish finish'.

* Intakes = 1.78" with 3/8" Stem
* Exhaust = 1.50" with 3/8" Stem

* Valve Angles = 45* with a 30* back-cut (.025" wide) on the Intake Valve
----------------------------------------------------------------------------------------------------------

Note; We didn't want to perform a 'full blown' Port & Polish Job on the Cylinder Heads, as we wanted to see what
we could get performance-wise out these heads.

Note; A 'gasket/port' match was neccessary, and 'rounding/blending' of the valve guide boss was required, to
promote a smooth flow and to increase the port velocity on these relatively stock port cylinder heads.
Click to expand...

Okay, that's a bit more work than I thought. I'm surprised you didn't go to 360 valves when you bought new stuff, but can understand you wanting to see what can be done with the stock sizes.
 
69 cuda

can you briefly explain why my 65 273 dartcharger will rev right up to 7500 without any issues (valve float etc etc ).. doesn't sound like a big cam when idleing. but just revs to the moon. it has just single valve springs .. no dampeners ..
could a stock cam rev that high without breaking something ?
Thanks !
 
Stroker,

Some 273 Engines are 'Freaks',,,,,,

No Rhyme or Reason.

We ran several 273 Cars (Barracuda's) back from 1967 thru 1972.

We built 'two' with identical components, and one ran 13.70's @ 103 MPH and the
other ran 14.20's @ 98 MPH.

The 'stock' 273 Commando had 'peak horsepower' at 5200 RPM's, and a
'Red Line' at 5800 RPM's - but many have pulled higher RPM's with little trouble.

This I can attest to, when we ran one of our 'stock' 273 Commando's in our 1967
Barracuda 4-Speed with 4.89 Gears {1968}, classed in J/Stock.

When going thru the 'traps' the valves floated out at around 6000 RPM's and we
bent every valve.

From my information sheet, the 273 Commando was equipped with 'stock' valve springs
that had a load rate of #103 lbs. (valve closed) and #184 lbs. (valve open).

But some, when tested ('Rimac' Valve Spring Tester) had a load-rate between 205 -215 lbs.

Also, we 'split' several of the 'hourglass shaped lifters' when hitting high RPM's.

Like I said, some 273 Commando's were.............'FREAKS'

Below Camshaft and Valve Specification Details

$(KGrHqJ,!iwFD)3PFL4fBQ-YPyPmEQ~~60_57.JPG
 
Ed,

We're pulling the Cylinder Heads, so we can change the Valve Springs to a higher
Load-Rate.

The current Valves Springs (Crower) were rated for a Top RPM of 6500.

Crower #6805X1
* Single Coil w/Damper
* #95 lbs. @ 1.65"
* #250 lbs. @ 1.20"
* #268 lbs. @ 1.15"
** Coil Bind @ 1.050"
-----------------------------------------------------------------------------

The new units (Comp-Cam #926) are listed for a Top RPM of 7000

Comp-Cam #926
* Single-Coil w/Damper
* #109 lbs. @ 1.80"
* #130 lbs. @ 1.70"
* #317 lbs. @ 1.15"
** Coil Bind @ 1.10"
 
so... the valve springs are what puts the limit on the rpm limt.. and breakage so to speak.

so If my 273 revs 7500 rpm with ease , someone has changed my valve springs ?
stock 273 is not suppose to rev 7500 rpm all day long. correct ?

Thanks !
john
 
Stroker,

Not saying it can't be done,,,,

The 'stock' 273 Commando has a Single-Coil Valve Spring with 'no damper'.

And the original 'Lifters' are 'Hourglass-Shaped' and would usually 'split' at
High RPM's.

Not saying I'm the so-called expert, but we ran enough 273 Mopar's from
1967 thru 1972 to know what they could and could not do.
 
I have a factory paper service manual for a 1967 , dart, coronet, charger. I will try to list the stock cam for the 273 engine. 2 cams one std 2 bbl engine 9.0 compression ratio. one 4 bbl engine 10.5 compression ratio
2 bbl engine
1. intake valve duration 240 degres
2. exthaust valve duration 240 degrees
3. intake valve lift .395 in
4. exthaust valve lift .405 in
4 bbl engine :::::::::::::::::::::::::
1. intake valve duration 248 degrees
2. exthaust valve duration 248 degrees
3. intake valve lift .415 in
4. exthaust valve lift .425 in
 
451 Cuda,

I'll be the first to admit,,,,,,,

Some of the 273 Commando's were 'slow dogs', yet others ran 'wild'.

Tighter clearances, better compression, 'mystery' camshaft, could have been in
part, the result of the 'FREAKS'.

Some old Mopar Racers swore that 'some' of the 273 Commando's were equipped with
a special 'long duration' Camshaft.

Back in the late-60's when we contacted Chrysler Performance for information on
the 273 (Dick Maxwell and Dave Koffel), we were given little or no information on any
secrets for the 273.
 
Rico,

The Valve Springs have been changed to the higher load-rate Comp-Cam units, and the Crane Zip-488 Camshaft is in.....

We should have it on the Chassis-Dyno tomorrow night.

It is a more aggressive Camshaft than the Racer Brown #ST-12.....

The Crane Camshaft has a slightly rougher 'bumpier' idle,
* Crane Zip-488 ............ .488" Lift / 300* Duration
* Racer Brown #ST-12 ... .480" Lift / 294* Duration
 
You must log in or register to reply here.
-

Back
Top