Any hope for 273 Commando heads?
#648710
03/23/10 03:22 AM
03/23/10 03:22 AM
|
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
69HemiGTX
OP
master
|
OP
master
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
|
I have a pair of 273 Commando heads I scored off an engine with a broken block and crank I found abandoned in a junk yard. A four-speed at that! Anyways, how far can they be ported? What do y'all think the max cubes they can support is? I have the intake, too, but like an idiot, I sold the rockers a long time ago.  I have no idea what casting number the heads are. These are deffinitely Commando parts - closed chambers, adjustable rockers, and an iron single plane intake.
OIF V and OEF X veteran and proud of it!
|
|
|
Re: Any hope for 273 Commando heads?
[Re: 69HemiGTX]
#648712
03/23/10 11:38 AM
03/23/10 11:38 AM
|
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
|
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
|
The 273 used the same heads for the commandos and non commandos untill the commando went away in 68 then they used the 318 open chamber head. Absolutly nothing special about a head from a commando VS a head from a 2bl motor.
As for how many cubes they can support, well that depends on how many RPM you want to turn. The 273 D-dart engines would go 7000 so in a 360 that would equal about 5300 rpm. The 360 will unshroud the valves a little more so might go 5500, max ported with big valves they can mabey make 400hp on a 360.
For casting numbers they are probably a 315 or 920 depending on year. 920 was the 67 only head.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
|
|
|
Re: Any hope for 273 Commando heads?
[Re: HotRodDave]
#648714
03/23/10 12:52 PM
03/23/10 12:52 PM
|
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
|
Quote:
The 273 used the same heads for the commandos and non commandos untill the commando went away in 68 then they used the 318 open chamber head. Absolutly nothing special about a head from a commando VS a head from a 2bl motor.
As for how many cubes they can support, well that depends on how many RPM you want to turn. The 273 D-dart engines would go 7000 so in a 360 that would equal about 5300 rpm. The 360 will unshroud the valves a little more so might go 5500, max ported with big valves they can mabey make 400hp on a 360.
For casting numbers they are probably a 315 or 920 depending on year. 920 was the 67 only head.
and if they're 315 heads, they're probably the funky oddball intake bolt angle used in 64-65 or 64-66 IIRC.
port volume wise, for a performance app, I wouldn't go above a 318 for displacement. for a torque app, they'd be nice on a stock long block 360 with a small, fast rate cam (voodoo 60401 maybe)
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
|
|
|
Re: Any hope for 273 Commando heads?
[Re: patrick]
#648716
03/23/10 02:50 PM
03/23/10 02:50 PM
|
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
69HemiGTX
OP
master
|
OP
master
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
|
The general consensus here is what I was thinking. The ports just look too small for anything north of 320" in a performance application. As far as RPM, peak would be around 6800-7000, with the bottom being near 3000. Sorry, I don't have any pics, and I can't take any right now (8500 miles from home  ). After doing more research, RHS X heads would be the minimum I would use, albiet with some porting. Of course, W2s would be the optimum choice, but I'm not a fan of the pushrod angles involved. The engine rules below just got my mind working. These are for dirt modifieds: Devil's Bowl Speedway USA Modifieds Quote:
POWER TRAIN:
A) Can use any American-made engine with iron heads and block.
1. Rear of engine (bell housing flange) must be mounted at least 72” forward of the centerline of the rear axle. Engine offset must be within 2” of the centerline of the front frame crossmember. The minimum engine height is 11” from the ground to the front center of the crankshaft.
2. Cooling systems can be modified as long as radiator and/or coolers do not extend above the interior. Overflow tubes must be directed toward the ground inside the frame rails.
3. No total dry sump oiling systems allowed. The wet systems must be operable.
4. Fuel can be gasoline or alcohol. No performance-enhancing fuel additives of any kind. Use of any such additive will subject the driver to a $1,500 fine, four weeks suspension from races for the driver and car, and loss of all points for the year.
5. A single two-barrel or four-barrel naturally-aspirated carburetor is allowed. Fuel injection, electrical fuel pumps, and/or magnetos are not allowed.
6. Engines used in competition must be capable of use in a conventional passenger car without alterations. Motor mounts, castings, and/or fittings cannot be altered. Machine work on the outside of the engine, front of camshaft, or rear of camshaft is not allowed.
7. The heads must be in stock configuration. Valve degree cannot deviate more than 1 degree from stock. No raised runners.
Enid Speedway Modifieds
Quote:
23. ENGINE SPECIFICATIONS: Any American make engine allowed. Iron heads and blocks. Steel oil pan only.
All engines must be able to be used in conventional passenger cars without alterations. Engine mounts cannot be
removed or altered. Castings and fittings must not be changed. No machine work on outside of engine. Wet oiling
systems only.
Obviously, roller cams and unlimited cubes are the norm, but traction is limited by small, somewhat hard spec tires.
OIF V and OEF X veteran and proud of it!
|
|
|
Re: Any hope for 273 Commando heads?
[Re: 69HemiGTX]
#648717
03/23/10 03:02 PM
03/23/10 03:02 PM
|
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
|
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
|
Well I too hate the PR angle of the W2 but they would be the best choice, you have to make up for the lost lift with a bigger cam or higher ratio rockers. Guys out there turn 8000 with W style rocker set ups all the time. By the way a higher ratio rocker helps the PR geometry in a SB. Run the biggest bore you can to deshroud the valves, what stroke you run will just be determined by the gear you want to run (shorter stroke=more RPM=lower gear ratio and vise aversa). I would get the heads angle milled to 17*
If you want to run the RHS heads you will make less power, my theory is always build as much HP as you can and then figure out how to use it.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
|
|
|
Re: Any hope for 273 Commando heads?
[Re: 69HemiGTX]
#648719
03/23/10 03:40 PM
03/23/10 03:40 PM
|
Joined: Nov 2006
Posts: 637
Kokomo,IN
StripeHOG
mopar
|
mopar
Joined: Nov 2006
Posts: 637
Kokomo,IN
|
is a big block out of the question?????
Andrew Brough D372
1969 Dodge Dart GTS
1.43 60'best
6.82 1/8 98mph
"the light came on and I ran out of talent"
|
|
|
Re: Any hope for 273 Commando heads?
[Re: StripeHOG]
#648720
03/23/10 11:39 PM
03/23/10 11:39 PM
|
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
|
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
|
A BB will add a lot of weight over the front where it is not needed.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
|
|
|
Re: Any hope for 273 Commando heads?
[Re: HotRodDave]
#648721
03/24/10 08:04 AM
03/24/10 08:04 AM
|
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
|
is a 48 degree block legal, since it deviated from a stock production application?
for that powerband, I'd think about maybe a stock stroke 400 with some iron indy SR's....
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
|
|
|
Re: Any hope for 273 Commando heads?
[Re: StripeHOG]
#648722
03/24/10 08:32 AM
03/24/10 08:32 AM
|
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
69HemiGTX
OP
master
|
OP
master
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
|
Quote:
is a big block out of the question?????
A big block would affect the CG, roll centers, roll axis, F/R percentages, and crossweights too much. A 400 weighs about 80 pounds more than a 360. If it didn't, a 400 would be perfect.
Quote:
is a 48 degree block legal, since it deviated from a stock production application?
The rules don't specify that the block has to have been a production part. They just say they have to be iron. There are plenty of Bowtie, World, and SVO blocks out there. I've seen a few R3s, but sadly, they were the only few Mopars in a sea of Chevy garbage with some Fords sprinkled in. I have no idea if they were 48 degree blocks, but if I was spending the coin, I wouldn't choose anything else.
|
|
|
Re: Any hope for 273 Commando heads?
[Re: 69HemiGTX]
#648723
03/24/10 12:07 PM
03/24/10 12:07 PM
|
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
|
so are all the chevy guys limited to 23 degree heads (what a stock Gen1 SBC is)?
what kind of HP are the top guys in the class making?
is there a CID limit?
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
|
|
|
Re: Any hope for 273 Commando heads?
[Re: patrick]
#648724
03/24/10 01:55 PM
03/24/10 01:55 PM
|
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
69HemiGTX
OP
master
|
OP
master
Joined: May 2003
Posts: 3,265
Pyeongtaek, South Korea
|
Yes, they have to run 23 degree heads. I'm not sure about most guys, but here's an example of what's out there: 620HP/590TQ 415 Chevy Hard to beat for $10K. No CI limit, but like I said, the tires are not the best to work with. That's why the car above has such an agressive attitude. You really need to manipulate the suspension geometry to plant the car to the track. If you want to see what I mean, watch this video. Can you say pinion angle? 
|
|
|
|
|
I was thinking along the lines of a P4876673AD siamese 48-degree R3 block, W2 heads, a solid roller and offset lifters, and a custom billet steel crank on alcohol. A 4.100 bore and a 3.750 crank yeilds 397" 
