Commando 273 cam specs

[Miranthis]

I have been researching the posts on the Commando 273 cam specs as I rebuild my 66 Commando 273. My engine guy is asking for the "full specs" for the Commando 4 bbl cam including "duration at 0.050". From the stuff below, can I glean all that I need?

From 66fs 's post on another thread:

The Commando cam works very well. We measured an original 67 Commando cam with 50,000 miles on it at Racer Brown's Cam Doctor's Analysis.

Intake:
110.4* center ATDC
202.8* duration at .050 Crank degrees
.405" net valve lift

Exhaust:
110.4* center BTDC
202* duration at .050 Crank degrees
.414" net valve lift

From other net-sources, what the usual "published specs" show is:​

 

[Dana67Dart]

Did you like in the FSM?

 

[Miranthis]

Did you like in the FSM?

I did and page 9-75 says what the "published specs" above do. My guy is asking for duration @ 0.050 as he says that this tells us the real shape of the lobe. The duration at 0.050 is not on the specs there.

 

[RustyRatRod]

This information is posted on here "somewhere", but good luck finding it. I think our search feature is worse then ebay and that takes some doing.

 

[perfacar]

ok, here , at .050 is 202 int and 208 exh. advertised is 248 /248, lift it .414 int and 425 exh. just food for thought.

 

[Kendog 170]

Maybe this will help? I copied it from here somewhere.

 

[AJ/FormS]

Just so you know,
For a True 10.5 hi-compression 273, that's a pretty small cam. Using modern gasolines, you may have cylinder-pressure issues; which is likely what your engine guy is wanting to avoid.. (see note-1)
Since it's a solid, the hot-lash (013/021) is gonna give away some of that advertised duration, and some of that lift. I was remembering that aftermarket Solid-lifter cams are usually spec'ed at 020 tappet rise;
but since, in this case, the tappet-lift for the advertised is not specified, the numbers are still somewhat vague, and
so again, adding more vagaries.

Note-1
A small cam is usually a good thing, because the early-closing intake valve, brings up the cranking cylinder pressure, which makes for good low-rpm torque..
But if the pressure gets to be too high for the shape of the chamber/etcetera, and the octane of the fuel, then the engine may become undriveable, because of detonation.
If that happens to you, then;
yur putting anti-knock in every tank, or
yur installing water-injection, or
yur swapping out the cam, or
yur stuck taking the engine down for less SCR.

More food for thought.

 

[krazykuda]

Did you like in the FSM?

I have been researching the posts on the Commando 273 cam specs as I rebuild my 66 Commando 273. My engine guy is asking for the "full specs" for the Commando 4 bbl cam including "duration at 0.050". From the stuff below, can I glean all that I need?

From 66fs 's post on another thread:

The Commando cam works very well. We measured an original 67 Commando cam with 50,000 miles on it at Racer Brown's Cam Doctor's Analysis.

Intake:
110.4* center ATDC
202.8* duration at .050 Crank degrees
.405" net valve lift

Exhaust:
110.4* center BTDC
202* duration at .050 Crank degrees
.414" net valve lift

From other net-sources, what the usual "published specs" show is:​

View attachment 1716368777

I made the spead sheet with the factory service manual data... They don't give any dur @ .050" in the manuals...

I have been ridiculed for trying to estimate it by interpolating from cam data from the MP catalog...

 

[toolmanmike]

I did and page 9-75 says what the "published specs" above do. My guy is asking for duration @ 0.050 as he says that this tells us the real shape of the lobe. The duration at 0.050 is not on the specs there.

View attachment 1716368813

Duration at .050 wasn't used back when those cams were made. That all started in the 70's I believe to put all the aftermarket cams on a level playing field. Before @.050, the manufacturers would measure their cams at different lifts and it was near impossible to compare 2 different grinder's cams.

 

[oldkimmer]

The Mopar Performance manual says to times the advertised duration at .850 to get the duration at .050. Idt it works all that realistically. Kim

 

[krazykuda]

ok, here , at .050 is 202 int and 208 exh. advertised is 248 /248, lift it .414 int and 425 exh. just food for thought.

Where is that data from???

 

[toolmanmike]

I have been researching the posts on the Commando 273 cam specs as I rebuild my 66 Commando 273. My engine guy is asking for the "full specs" for the Commando 4 bbl cam including "duration at 0.050". From the stuff below, can I glean all that I need?

From 66fs 's post on another thread:

The Commando cam works very well. We measured an original 67 Commando cam with 50,000 miles on it at Racer Brown's Cam Doctor's Analysis.

Intake:
110.4* center ATDC
202.8* duration at .050 Crank degrees
.405" net valve lift

Exhaust:
110.4* center BTDC
202* duration at .050 Crank degrees
.414" net valve lift

From other net-sources, what the usual "published specs" show is:​

View attachment 1716368777

Are you going to have a cam ground or is your builder just wanting all the specs to get as close as he can to original? o one makes a replacement cam for those engines but you could always have one made. Oregon can grind you one if they have a core or regrind one you have if the core is in good enough shape. Krazycuda had the 340 cam duplicated by Delta cams in Washington State. That information to follow.

 

[krazykuda]

The Mopar Performance manual says to times the advertised duration at .850 to get the duration at .050. It it works all that realistically. Kim

Thanks Kim...

I did that with my interpolating, but got criticized by the keyboard jockeys here...

Most of the MP cams @ .050" are 85% of the advertised duration... But what do I know???

 

[RustyRatRod]

ok, here , at .050 is 202 int and 208 exh. advertised is 248 /248, lift it .414 int and 425 exh. just food for thought.

I'm curious to know where you found that too, but it appears probably spot on.

 

[krazykuda]

Toolmanmike is the 273 expert here, I would take his advice...

 

[toolmanmike]

Here's the specs I have found and use.

1965 180 hp 2 barrel .395 /.405 lift 240°/ 240° duration
1965 235 hp 4 barrel .415 /.425 lift 248°/ 248° duration
1966 235 hp 4 barrel .420 /.430 lift 248°/ 248° duration
Isky E4 .425/.425 lift 260°/260° duration 216° @ .050

 

[RustyRatRod]

Also too, using .850 to calculate .050" duration was for the MP cams only, but it wouldn't surprise me if it doesn't work for all of the Chrysler cams, since they were made by Chrysler. I'm curious as to who makes the current "Purple" cams that Mancini carries. A friend and I were discussing this recently at our car club meet. He said that someone at Mancini told him that they were ground by Howards. But he said they didn't sound 100% sure of themselves, either. But that would be acceptable to me if Howards was grinding them.

 

[oldkimmer]

Thanks Kim...

I did that with my interpolating, but got criticized by the keyboard jockeys here...

Moist of the MP cams @ .050" are 85% of the advertised duration... But what do I know???

It’s pretty easy to criticize when you’re hiding behind a keyboard. Most ppl are blurting **** out b4 they have all the facts. Ofcource u can’t believe everything u read. I’ve talked to Larry Shepherd a time or three. Kim

 

[krazykuda]

View attachment 1716368894


Here's the specs I have found and use.

1965 180 hp 2 barrel .395 /.405 lift 240°/ 240° duration
1965 235 hp 4 barrel .415 /.425 lift 248°/ 248° duration
1966 235 hp 4 barrel .420 /.430 lift 248°/ 248° duration
Isky E4 .425/.425 lift 260°/260° duration 216° @ .050

The 340 cams that we used for the repros were custom ground by Delta Cams, they can grind them from the specs, Oregon doesn't do that, they just map a already made cam and copy it...

Delta Camshaft – We manufacture horsepower!

 

[krazykuda]

Also too, using .850 to calculate .050" duration was for the MP cams only, but it wouldn't surprise me if it doesn't work for all of the Chrysler cams, since they were made by Chrysler. I'm curious as to who makes the current "Purple" cams that Mancini carries. A friend and I were discussing this recently at our car club meet. He said that someone at Mancini told him that they were ground by Howards. But he said they didn't sound 100% sure of themselves, either. But that would be acceptable to me if Howards was grinding them.

I was told by the Mancini guys back in the 2011 time period that the MP cams were being ground by Comp Cams...

Ans Comp was having "problems" back then and both MP and Comp cams were getting lots of bad criticism for their quality....

 

[toolmanmike]

The 340 cams that we used for the repros were custom ground by Delta Cams, they can grind them from the specs, Oregon doesn't do that, they just map a already made cam and copy it...

View attachment 1716368895

Delta Camshaft – We manufacture horsepower!

View attachment 1716368896

Good to know. I thought Oregon ground your 340 cams but I guess not. Let me change my post above. No reason for me to post misinformation.

 

[toolmanmike]

I was told by the Mancini guys back in the 2011 time period that the MP cams were being ground by Comp Cams...

Ans Comp was having "problems" back then and both MP and Comp cams were getting lots of bad criticism for their quality....

I wouldn't doubt that.

 

[oldkimmer]

I was told by the Mancini guys back in the 2011 time period that the MP cams were being ground by Comp Cams...

Ans Comp was having "problems" back then and both MP and Comp cams were getting lots of bad criticism for their quality....

I heard that also Karl. Last time I bought a comp cam was in 2001. A 270H for a small block. In fact I still have it. Kim

 

[LO23M8B]

Compression is the one thing that the 273 Hi-po had going for it. I think I'd leave the comp. alone and just add 2 gallons of race fuel per tank, carry a bottle of additive just in case. What I usually do at the start of the season is start off about 50/50 and if I have to fill up on the road it not a big deal.

 

[toolmanmike]

Compression is the one thing that the 273 Hi-po had going for it. I think I'd leave the comp. alone and just add 2 gallons of race fuel per tank, carry a bottle of additive just in case. What I usually do at the start of the season is start off about 50/50 and if I have to fill up on the road it not a big deal.

Measure everything carefully. I ended up with 9. 6 something with the HP Egge pistons. That was the .100 down method.