273, could it be a commando and CAM question?

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trebor75

trebor75

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I have a couple of questions but first a little info. My 70 Duster was originally a /6 car but I have swapped out the slant for a 273. The motor runs great and seems really healthy so I have not really done anything to it besides plugs, oil changes, filters and tuning. Instead I have made upgrades to the cooling, drive line, exhaust and brakes. I now have an 8 ¾ axle with a 3.55 sure grip and a 727 with a shift kit and a 10” 3000 stall converter with a tranny cooler etc. I figured I’d get a 360 to build in the future so now it’s ready for that.

The thing is the 273 has grown on me because it’s a little beast with the new ratio and converter that takes it right into its power band. I’ve tried to find out from previous owners if it might have the Commando pistons, but I don’t know. Is there a way to tell without removing the heads?
Previous owner said he installed a 340 cam and that the brand might have been Sealed Power, I’ve done searches on Google but could not find it. Anyone knows the specs for that or if they even made one?

This is what I do know about the engine and combo

1965-273
727 / Shift Kit
10" 3000 stall converter
According to previous owner a 340 cam from Sealed Power
Edelbrock D4B intake
Edelbrock 600 Performer Carb
Pertronix ignition
Headers
2.5" Dual Exhaust / free flowing mufflers
8 3/4 - 3.55 – SureGrip

I have 245/60-14 tires and it smokes the tires from a rolling start :burnout:
So after this long rant, how can I tell if it’s the hi comp pistons without taking it apart and anyone knows about specs for a supposedly 340 Sealed power cam? It runs great like I said, but is there a better cam for this setup? What HP would you estimate it’s putting out (ehh, hard to answer I guess)?

I might ad I’m a beginner and this is my first project, had to learn everything from the start on everything I’ve done so far, had tons of help reading this forum!!!

Here it is idling
[ame="http://youtu.be/ymqHjeFaotc"]302 Found[/ame]
 
have you done a compression test yet, that might give you an idea. I had a 273 that was a commando and whoever rebuilt it put in stock pistons, only had about 110psi on all cylinders - and mine had a bigger cam in it also. Needless to say - it now has a 360 in it and the 273 is probably going to the scrap yard. Would think with the 10.5 pistons you should get over 140 anyway.
 
Thanks for the input berlins. Will do a compression test asap.
Kennygene, Two years ago I took it to the strip with the stock converter and 2.76 ratio and no sure grip, takeoff was poor needles to say. Have not had a chance to try it on the strip with the new converter and 3.55 sure grip yet.

Anyone have any input on the cam questions above?
 
the fact you can smoke the tires from a rolling start tells me you probable have the commando motor - the one I had sure wouldn't do that but I didn't have a 3000 stall either. How in the world did you get that hooked up to a 727 - did you drill out the pilot hole on the crank? Mine had a 904 with the small spline shaft and was a 67 273. Also, I went with a 904 on the 360 because they are supposed to use 20hp less than a 727.
 
The 727 came with the engine so someone of the previous owners probably swapped crank or drilled it to the larger register. I also been told to go with a 904 and that I dont need a 727, but this is what I got and it shifts great and is in good condition so I'll stick with it. Living in Sweden parts are hard to find and very expensive :(
 
You might be able to look into the spark plug hole and see if it has the commando pistons still in it. They are raised in the middle compared to the flat tops the 2bbl engines had.
 
just wondering due to 727 on a 273 -- you ever crawed under the motor and looked at
the engine number stamping above and left of starter under exhaust manifold. Should be some numbers and then a 273, 318, 340, 0r 360. Curious if someone put a bigger motor in there for you - they look pretty much the same from the outside. Would be sweet if you really had a 340!!!
 
berlins said:
just wondering due to 727 on a 273 -- you ever crawed under the motor and looked at
the engine number stamping above and left of starter under exhaust manifold. Should be some numbers and then a 273, 318, 340, 0r 360. Curious if someone put a bigger motor in there for you - they look pretty much the same from the outside. Would be sweet if you really had a 340!!!
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That would have been extremely sweet O:) It's a 273 though, casting is: 2465330 273 LA 1964-66.

Thanks for the tip Cudamark, I also thought about carefully try to feel the top of the piston with a screwdriver through the plug hole. is that a no no?
 
Probably has a Crankshaft from a Late 67 - 69 273 or a 68 - 72 340 in it (although anything 273/318/340 would fit in it) Bonus if it's a Forged Crankshaft (some early LA 318's have the same forged crank as a 340)

68+ (late 67) have the larger register on the crankshaft. I've got a '69 273 in my '84 Dodge D50 pickup, with a hybrid transmission. A 1972 TF904 Small Block Case with the guts from a 1984 MA904 and the Torque Converter from a 1971 TF904 (slant 6, higher stall)

Didn't have to worry about the register size, due to it being a later 273 engine.
 
I couldn't look through the plug hole on mine but didn't try that hard. Didn't know till I
pulled the head and saw the flat piston. Think if you go out to the Egge website that still sells 273 HP pistons you can see a picture of the regular and high compression pistons. Got a feeling that whoever rebuilt your motor did it right and put the good pistons in it for you. By the way - what's regular gas going for over there a gallon?
Ours is in the $3.8xs now.
 
berlins said:
I couldn't look through the plug hole on mine but didn't try that hard. Didn't know till I
pulled the head and saw the flat piston. Think if you go out to the Egge website that still sells 273 HP pistons you can see a picture of the regular and high compression pistons. Got a feeling that whoever rebuilt your motor did it right and put the good pistons in it for you. By the way - what's regular gas going for over there a gallon?
Ours is in the $3.8xs now.
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I'll try the Egge website!

One liter of 98 octane gas is 16.33 sek (in Stockholm) and 2.45 usd if google calculated right for me. It's very expensive now.
 
Instead of a screwdriver, maybe try using a pipe cleaner or a long straw??? Something rigid, but not going to scratch the piston
 
You could borrow one of those tiny cameras to look inside the cylinder.
 
These are 273 hipo pistons. It's kind of hard to see how they sit out of the cylinder.
 

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think my stock ones had 4 valve reliefs and was flat across top
 
Yeah the dome tops have only 2 valve releifs and can be installed only one way.
The standard pistons have 4 valve reliefs and a notch to indicate which way the should be turned. This is because thr wrist pin is just slightly off centered. I was told one could install those flat top pistons backward and get just a tiny bit more compression from them but I haven't seen it or tried it.
 
I have a similar combo, built a 273 HIPO from a standard 2 bbl 65 273.
The tranny is a 904 by 76, i.e. with big pilot button. The crank is forged so it has to come from a 340 or a 273 after 67.
Finished the motor will have the following spec:

D4B Edelbrock intake, 4 bbl dual plain
Edelbrock 1406, 600 cfm carb
Comp Cam cam part # 20-246-4 Duration @ .015 270/270, duration @ .050 224/224, .313 lobe lift, valve lift .468/.468, 110 lobe separation
Electronic ignition
Domed pistons, comp. ratio of 10.5:1
Spitfire headers

I have also switched to front K-H disc brakes.
Plans for the future is an 8 3/4 rear axle


The motor start will be done within a week.
 
Thanks for all the replies and information, greatly appreciated! I'll try the compression test, have a peak inside the plug hole and feel with a straw to see if I have those Commando pistons :)

I'm still curios about the cam though, previous owner staded 340 cam from Sealed Power, so It's a reproduction If he's right. I found this on the forum "268/272 and .444" on both intake and exhaust is the Reproduction spec" for a 340 cam.

A friend have one of those sb whiplash cams from hughes on the shelf, he also have a Comp cam Xtreme Hi-lift XE275HL.
Links:
http://www.hughesengines.com/Index/...V2hpcGxhc2ggTXVzY2xlIENhciBDYW1z&partid=25114

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=631&sb=1

Are these way to big for my combo? Just curios since we share garage and they are availible!
 
The first thing I would do is try 87 octane gas. IF it pings like hell it could be a commando :)

Should be solid lift cam also, but that could have been swapped out.
 
Djakken said:
I have a similar combo, built a 273 HIPO from a standard 2 bbl 65 273.
The tranny is a 904 by 76, i.e. with big pilot button. The crank is forged so it has to come from a 340 or a 273 after 67.
Finished the motor will have the following spec:

D4B Edelbrock intake, 4 bbl dual plain
Edelbrock 1406, 600 cfm carb
Comp Cam cam part # 20-246-4 Duration @ .015 270/270, duration @ .050 224/224, .313 lobe lift, valve lift .468/.468, 110 lobe separation
Electronic ignition
Domed pistons, comp. ratio of 10.5:1
Spitfire headers

I have also switched to front K-H disc brakes.
Plans for the future is an 8 3/4 rear axle


The motor start will be done within a week.
Click to expand...

Be sure to get it on camera, I'd be really interested to see! Nice to see another Swede here at the forum also! I was joking around with friends that I must be the only one in Sweden with this much in to the drive line and such small engine :)

Trapster, lowest octane we have is 95, but I think we use a different scale or reading.
 
trebor75 said:
Be sure to get it on camera, I'd be really interested to see! Nice to see another Swede here at the forum also! I was joking around with friends that I must be the only one in Sweden with this much in to the drive line and such small engine :)

Trapster, lowest octane we have is 95, but I think we use a different scale or reading.
Click to expand...

I thought I was the only crazy guy in Sweden who is sticking to a 273 and pays to trim it. But I do not want a 318, it is too common. Would love to put in a 340, but they are unavailable in Sweden. 360 is a truck engine. So therefore I have chosen to invest in my 273 from 65, I decided to 100% when I got hold of a D4B intake.
I think you and I are unique in Sweden.
I’ll post some pics.
The motor pic is from last winter, the headers are in place now.
As you can see in pic #3, the engine compartment has been painted this winter aswell.
 

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Alright. So today I stopped by the garage and did a compression test. The picture reads 140 psi but the needle dropped before I got my camera up it was actually closer to 150 psi. The tool was one of those where you press a rubber nosle into the plughole and I really dont know how accurate it is. Also I was in a hurry!

Anyway, do we have reason to believe that it actually is a commando now?

Please feel free to chime in on my cam questions above aswell. I found out today that it is a hydralic cam, lifters and rockers, so the cam is aftermarket and probably is a 340 cam. Should I just be happy with it?

Djakken that is awsome, do you have a build thread here? I have some pictures and a little info here, it is not up to date though.
http://www.forabodiesonly.com/mopar/showthread.php?t=116478

I agree with your comments on 340, I would love one, but the money when they do show up.... Just cant afford it right now. Had a hard time finding the 8 3/4 axle. But now I finally have a 3.55 sure grip and I'm very happy. Had 2.76 before and stock converter. The change now is dramatic :)
 

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360 is a truck engine.
Click to expand...

Maybe in Sweden, but here in the USA, a truck can be equipped with a /6 to a 440. The 360 was built and designed not as a performance mill, but as a people mover mill that powered all sorts of common vehicles of the day.

It's first performance appearance was in the '74 model year, in the Challenger, Cuda and Duster.

If you guys want to stick to the 273, great, otherwise, screw the "Truck" monkier and just use the 360.
 
rumblefish360 said:
Maybe in Sweden, but here in the USA, a truck can be equipped with a /6 to a 440. The 360 was built and designed not as a performance mill, but as a people mover mill that powered all sorts of common vehicles of the day.

It's first performance appearance was in the '74 model year, in the Challenger, Cuda and Duster.

If you guys want to stick to the 273, great, otherwise, screw the "Truck" monkier and just use the 360.
Click to expand...

I actually plan to find and build on in the future like I wrote in my first post :) but 360's are also hard to find over here. For now Im having a blast with the 273! Any help with compression and CAM posts above very appreciated!
 
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