273/ 2 barrel camshaft options

[Jim Kueneman]

the Racing Manual says multiply the advertised duration by .777

to get 0.050"?

 

[66fs]

Just so you know;
a 318 is just the equivalent of a big-bore 318.
So, anything off a 318 , except the piston assemblies, will swap over.
Except the 65 and older heads, sorta need the matching bolt-angle intake. So then;
if you intend to put a 4bbl on it, at some time in the future, IMO, I would start with 67>69 closed chamber heads. If you go with the open chambers and a bigger cam, then the cylinder pressure will fall way too low to be fun.

as for cams;
> on a low compression engine, with an automatic, if you install a lopey cam, you will be sorry, see Post 13, above.
> if you change the cam, I highly recommend to tighten up the LSA(Lobe Separation Angle) in an effort to keep the cylinder pressure up.
> IIRC, the factory gasket was 020 thick, with an appropriately-sized borehole. Those are no longer available, off-the-shelf.. the closest available is 028, and the bore-hole is huge. the new gasket is thus 6.3 compared to about 3.5cc/atock.
This one single change will drop a true 8/1Scr 273 to 7.76 and the pressure is expected to drop to 130, from 136psi. It may not sound like much, but that is the same as installing a cam of 8* more intake duration, which is more than two cam sizes bigger. Bad trade-off.
Closing up the LSA from the factory 112* to 108, with no other changes, on the 7.76SCR engine, is predicted to jump the pressure back up, to 133 Good Deal. and the bonus is better fuel-economy. Now, if you advance this cam to in at 102, this will reduce your Powerstroke back to what you now have, but increase your pressure to 134, over the factory, 129(with the 028 gasket). This is another good deal.
The point I am trying to make is this;
the factory 2bbl cylinder pressure is already extremely low. and it's only gonna get lower after the gasket swap. That's bad. Adding a bigger cam with a later-closing intake event, is gonna drop the pressure even lower.
If your engine needs pistons anyway, and you need a cam
now is the time to pump the compression ratio up, and neatly get around the problems.

As an example, building to a true 9.5 Scr, will allow you to slide a cam in there of about 10 degree later Ica(intake Closing Angle) and the pressure might jump to 161psi. Excellent deal.
Ten degrees is about equal to 4 sizes, going from a 112Lsa to a 108. That's a lot.
and, on a 108LSA, the compression /power degrees end up about the same as you have now, But the overlap jumps to 46 from 28. If you put headers on that, those extra 18* will make a nice little power bulge starting in the midrange. and the pressure increase will make the bottom-end feel about 22% stronger.
Again, the point is this, careful selection of parts at this stage, can make or break the combo.

Putting that same bigger cam into a 7.75 Scr engine is predicted to lower the pressure to 117psi, and the engine will feel about 15% LESS powerful, on the bottom, as it does when stock.
That's a bad trade! This will require a much higher stall convertor, and likely, a deeper rear gear, just to get moving as it once did.
and/but
46* of overlap is about what the 340s had, so, not much of a lope to it, but maybe enough to satisfy your hunger, lol.
--------------------------------

Oh and to answer your question about the cam lobes falling into the pan,
"My first thoughts wouldn’t this just continue to break down quickly and send shrapnel through the system into the block and bearings and so on?"
yes, that is a possibility. In my case, I was willing to take that chance.
The post you are referencing, was about what I did.
As stated, "your results may vary".
-----------------------------------------
Several decades later, I did lose a cam that way.
However, I run very little preload on my hydraulic lifters, and the ticking began almost right after an oilchange. This was back in about 2004 when the oil companies took the zinc out of the oil, and failed to send me a memo.
Anyway , I figured it out pretty quick, slammed a new cam into it, changed the oil and filter again, added a bunch of supplement, and hoped for the best.
The following winter, I took the engine down, cleaned it out, made some compression/spring changes, and slammed it all back together.
Back then, my car was a DD, so every fall, I took the 360 out for freshening, and swapped in a 318 for the winter; sometimes with an automatic, and sometimes with a manual, sometimes with an overdrive, whatever I was planning to run the following summer. and I changed the rear end ratios around pretty regularly as well. By 2005 or 2006, my kids had all grown up and moved away, so I bought another DD, and the 360 has been under the hood ever since........ with no more cam-trouble.

You should not give advice for 273 engines. There is so much wrong information in your post. The 273 was the original LA engine. They were never a smog motor. The 2 barrel pistons were almost at zero deck and were almost 9:1 compression ratio. Closed chamber heads were used from 64 to 67 with solid lifter cams and valvetrain. The 64-65 heads have a different intake bolt size and angle than all the rest of 66 up LA engines. Solid cam and lifters easily last 300,000 miles if you use good quality oil and filters and change them regularly. A 318 has a larger bore than a 273, but to keep compression low they dropped the piston in the bore and used open chamber heads in the 273 and 318 for 1968. To keep the compression ratio in the 273 the same, they raised the piston in the bore and that brings the 273 to zero deck in 1968 and 1969. As for the cams, I'm not talking theoretical numbers. I have run them, and helped others who were happy with their 273s.

 

[66fs]

to get 0.050"?

yes

 

[cudamark]

You should not give advice for 273 engines. There is so much wrong information in your post. The 273 was the original LA engine. They were never a smog motor. The 2 barrel pistons were almost at zero deck and were almost 9:1 compression ratio. Closed chamber heads were used from 64 to 67 with solid lifter cams and valvetrain. The 64-65 heads have a different intake bolt size and angle than all the rest of 66 up LA engines. Solid cam and lifters easily last 300,000 miles if you use good quality oil and filters and change them regularly. A 318 has a larger bore than a 273, but to keep compression low they dropped the piston in the bore and used open chamber heads in the 273 and 318 for 1968. To keep the compression ratio in the 273 the same, they raised the piston in the bore and that brings the 273 to zero deck in 1968 and 1969. As for the cams, I'm not talking theoretical numbers. I have run them, and helped others who were happy with their 273s.

I guess that depends on your definition of "smog motor". They had both with and without C.A.P. which is an early stab at smog control. Granted, the engines are built the same, but, are tuned slightly different. The carbs are jetted and adjusted slightly different too.

 

[AJ/FormS]

The 2 barrel pistons were almost at zero deck and were almost 9:1 compression

Yes in the early years they were advertised 9.0; but as I recall with small bore 020 metal-shim head gaskets, and since the total chamber volume to get to 9.0 is 70.2cc, you can see where this is headed, after a rebuild.
First, you're not gonna find those gaskets, and Second the bore size is increasing, and third, after 55 years, you can bet the valves are no longer in their original locations. So
By the time you bore, clean up, and assemble that engine; you can bet it ain't gonna be at 9/1 anymore without other machining. Simple math puts it at 8.8@zero-deck, before decking or milling, with the already existing 040 overbore; and in post #1, OP states that he wants to do as little machining as possible.
So yes, I used the wrong Scr numbers (7.76), but I used those wrong numbers correctly; and the results while not exactly correct, still speak to the same problems and results.
And yes, I assumed the OP was at least thinking of up-camming cuz why else would the title say what it does.
I'm gonna stand with my post for now; but admitting and apologizing for the rather large Scr error.

 

[66fs]

to get 0.050"?

After checking numbers, I'm sure the .777 factor is wrong to get duration @.050. We had a Commando cam with 50,000 original miles on the "Cam Doctor" and the .777 factor does not prove out. Please disregard that post. I also do not believe it works for a 340 factory cam either. I feel it is just wrong information. I knew I should have proven it to myself before posting.

 

[66fs]

Yes in the early years they were advertised 9.0; but as I recall with small bore 020 metal-shim head gaskets, and since the total chamber volume to get to 9.0 is 70.2cc, you can see where this is headed, after a rebuild.
First, you're not gonna find those gaskets, and Second the bore size is increasing, and third, after 55 years, you can bet the valves are no longer in their original locations. So
By the time you bore, clean up, and assemble that engine; you can bet it ain't gonna be at 9/1 anymore without other machining. Simple math puts it at 8.8@zero-deck, before decking or milling, with the already existing 040 overbore; and in post #1, OP states that he wants to do as little machining as possible.
So yes, I used the wrong Scr numbers (7.76), but I used those wrong numbers correctly; and the results while not exactly correct, still speak to the same problems and results.
And yes, I assumed the OP was at least thinking of up-camming cuz why else would the title say what it does.
I'm gonna stand with my post for now; but admitting and apologizing for the rather large Scr error.

Unmilled early heads run about 65 cc and .020 thick head gaskets are long gone. Although I always hated them, they always seemed to work, but seeped oil. I believe 8.8:1 was the advertised ratio and that is with the thicker gaskets. As for sinking valves, If someone knows what they are doing, they won't sink much at all. Yes, you do gain compression with a larger bore, but not much. The custom Racer Brown solid cam is very close to an original Commando/Charger cam per the "Cam Doctor" analysis. It also is small enough to be used with a 2 barrel intake and carb.

 

[PRH]

We had a Commando cam with 50,000 original miles on the "Cam Doctor"

Care to post those numbers?

 

[66fs]

Care to post those numbers?

I can and will, probably tomorrow.

 

[toolmanmike]

Care to post those numbers?

I put the parameters for a 235/273 into Desktop dyno and got 234 horse (or somewhere close) The programmers probably start with stock specs and add percentages for improved parts.

 

[Bewy]

The 'magic' 0.777 multiplier in the MP book is only for MP cams, not production cams.

If the lifters in post #44 are the ones used with the cam pictured earlier, then they need re-facing. Lifters can be re-faced 2-3 times. I see Oregon cams gets mentioned a lot on this forum for lifter re-facing, with positive comments.

 

[Dan the man]

The 'magic' 0.777 multiplier in the MP book is only for MP cams, not production cams.

If the lifters in post #44 are the ones used with the cam pictured earlier, then they need re-facing. Lifters can be re-faced 2-3 times. I see Oregon cams gets mentioned a lot on this forum for lifter re-facing, with positive comments.

According to the Mopar Engines speed secrets catalog the 0.777 multiplier is for production cams and 0.850 is for the MP cams. This information is on page 143 of the above catalog. The part # for this catalog is P4452790.

 

[Dan the man]

The 'magic' 0.777 multiplier in the MP book is only for MP cams, not production cams.

If the lifters in post #44 are the ones used with the cam pictured earlier, then they need re-facing. Lifters can be re-faced 2-3 times. I see Oregon cams gets mentioned a lot on this forum for lifter re-facing, with positive comments.

 

[Dan the man]

This time I have evidence on how duration is calculated for the mopar production and the purple shaft camshafts. I can't be accused of lying or saying that im repeating something that I heard or read in some magazine some place. This information came right from the engine speed secrets catalog. If this information is in correct I can't help that.

 

[66fs]

I guess that depends on your definition of "smog motor". They had both with and without C.A.P. which is an early stab at smog control. Granted, the engines are built the same, but, are tuned slightly different. The carbs are jetted and adjusted slightly different too.

I don't call a hose to the air cleaner and a slightly leaner carb a smog engine, everything else being the same. Look at the mid 70s engines and and up for the changes made. Those poor gutless engines.

 

[66fs]

Care to post those numbers?

1967 Commando 273 cam with approximately 50,000 miles as measured using the Cam Doctor Analysis

Intake and Exhaust @ .050
Lobe center separation = 110.4 cam degrees
Valve Overlap = -17.2 crank degrees

Intake @ .050
Valve opening = -9.6 *BTDC
Lobe center = 110.4 *ATDC
Valve Closure = 32.4 *ABDC
Duration = 202.8 Crank Degrees
Max cam lift = .2702 in
Net valve lift = .4053 in
Lobe area = 20.44 in*deg

Exhaust @ .050
Valve opening = 34.5 *BBDC
Lobe center = 110.4 *BTDC
Valve closure = -7.5 *ATDC
Duration = 207 Crank Degrees
Max cam lift = .27598 in
Net valve lift = .41398 in
Lobe area = 21.33 in*deg

Intake and Exhaust @ .018
Lobe center separation = 110.4 cam degrees
Valve Overlap = 32.3 crank degrees

Intake @ .018
Valve opening = 6.3 *BTDC
Lobe center = 110.4 *ATDC
Valve Closure = 59 *ABDC
Duration = 245.3 Crank Degrees
Max cam lift = .2702 in
Net valve lift = .4053 in
Lobe area = 20.44 in*deg

Exhaust @ .018
Valve opening = 56.3 *BBDC
Lobe center = 110.4 *BTDC
Valve closure = 26 *ATDC
Duration = 262.3 Crank Degrees
Max cam lift = .27598 in
Net valve lift = .41398 in
Lobe area = 21.33 in*deg

 

[toolmanmike]

1967 Commando 273 cam with approximately 50,000 miles as measured using the Cam Doctor Analysis

Intake and Exhaust @ .050
Lobe center separation = 110.4 cam degrees
Valve Overlap = -17.2 crank degrees

Intake @ .050
Valve opening = -9.6 *BTDC
Lobe center = 110.4 *ATDC
Valve Closure = 32.4 *ABDC
Duration = 202.8 Crank Degrees
Max cam lift = .2702 in
Net valve lift = .4053 in
Lobe area = 20.44 in*deg

Exhaust @ .050
Valve opening = 34.5 *BBDC
Lobe center = 110.4 *BTDC
Valve closure = -7.5 *ATDC
Duration = 207 Crank Degrees
Max cam lift = .27598 in
Net valve lift = .41398 in
Lobe area = 21.33 in*deg

Intake and Exhaust @ .018
Lobe center separation = 110.4 cam degrees
Valve Overlap = 32.3 crank degrees

Intake @ .018
Valve opening = 6.3 *BTDC
Lobe center = 110.4 *ATDC
Valve Closure = 59 *ABDC
Duration = 245.3 Crank Degrees
Max cam lift = .2702 in
Net valve lift = .4053 in
Lobe area = 20.44 in*deg

Exhaust @ .018
Valve opening = 56.3 *BBDC
Lobe center = 110.4 *BTDC
Valve closure = 26 *ATDC
Duration = 262.3 Crank Degrees
Max cam lift = .27598 in
Net valve lift = .41398 in
Lobe area = 21.33 in*deg

Thanks. THat get's it right down to the nitty gritty!

 

[66fs]

Thanks. THat get's it right down to the nitty gritty!

Nice to have real numbers, even if there is some slight wear on the lift.

 

[Bewy]

Below is from a Crane cams catalog, where the actual adv duration was compared to measured duration.
One of the lobes is the Chrys 440 Magnum exh lobe. Bit hard to see, but 284* adv duration [ as advertised by Chrys ] has 225* @ 050. That ratio computes to 0.792, not 0.777.

 

[Dale Davies]

Hello forabodies community and thank you for welcoming me and my family!

(Warning: I am NEW to ANY Internet forums/ community and I tend to babel. I don’t know when to shut up so please feel free to correct me with keeping it short and sweet or over sharing)

I do have a detailed heartfelt story explaining the backstory to my individual background and the importance of the Barracuda that I am working on if anyone is interested in reading, not sure if this is the correct outlet for any storytelling, but the offer is on the table. (This car has been a part of my fathers life since he was 7 years old, the car “disappeared” for many years and after 10+ years of VERY difficult searching and legal matters, I was able to find and rescue the car in 2018. This is a family project with my two daughters in getting it safe and road worthy to surprise my dad when the time is right)

Currently, the 273 block and heads are at a local machine shop for a very light clean up and inspection for cracks or any potential build concerns.

(A quick blueprint: The engine is original, was rebuilt in 1985 with .040 bore, .020 on rods, .020 on mains (can still see clean, clear crosshatch on the cylinders and rod caps) I have the original build badge that was on the block for this information if that’s helpful. The car was driven for a few years after the rebuild. The trans reverse went out and the car was parked for 20+ years, until I found it)

As of right now I would like to keep it as factory/ basic as financially possibly because this is THE engine that my dad learned and worked on in is developing years. We are trying to avoid any unnecessary machine work, a refresh if you will, clean up and reassemble)

I disassembled the engine (I did take measurements first. I was able to get it to run briefly beforehand. It had oil pressure and compression was roughly 120 across the board, but sounded ugly in the lower end)

I was recently told by the machine shop that the cam “got hot” and is “trash” and here is my cry for help in joining forabodiesonly. The cam does show “pitting” please see pictures.

What are my options in either “repairing” the existing camshaft or replacing it without having to take out a loan. I have not been able to find another original 273 cam. Is there a direct swap out for just a cam or will it have to include replacing everything, pushrods, lifters, rockers and so on? What’s the risk of just reusing the cam and lifters as is?

I understand and respect that quality isn’t cheap. But this isn’t going to Pomona for drags and I won’t be looking for Milner to race for pinks, I’ll leave that up to Harrison Ford. It will be driven to take the family to get ice cream on the weekends and the occasional cruise for my dad.

Any information and or experience is greatly appreciated with help regarding the original camshaft or any other challenges this may present. What can be done or should be done? I have had very little luck on eBay or Craigslist in finding another original cam for solid lifters. If I need to share more pictures please let me know. I am willing and capable of receiving constructive criticism.

(If it helps, I’m in my late 30s, I’m a mechanic in the gas/oil fields in the Midwest, my mechanical experience came from working on chainsaws in a logging shop as a child into automotive machanic work on cars and trucks from the 50s, 60s and 70s and modern as a well… if I’m being honest to help put myself in your crosshairs I’m gonna say that I enjoy watching The Waltons, Vice Grip Garage and Uncle Tony’s Garage if that helps in introducing myself.

Again I apologize for the babbling and the long story. My daughters and I are excited to be a part of this community and we look forward to your participation. (I am a working man with a schedule so if I don’t respond or communicate clearly while I figure this out in chatting, forgive me while I learn the ropes. Thanks again and Bad Fish for Life!

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The cam is due for retirement. The pits on the lobe are spalling, caused by running new oils after they took the ZDDP out. Of course that was done for catalytic converters and they did not tell us, let the cams fail, sell us a new car (POS), and crush the old one. All corporate crap.
The electric fan in my 1940 Ford Fordor failed and I got stuck at an A&W drive-thru after driving on the highway for 250 miles. It got pretty hot and lost ring tension, giving blowby. The engine is a 1966 289 2V. When I took it apart, the cam looks very similar, spalling on the lobes and a few pits in the lifters. Mine are hydraulic lifters and I happen to have a cam I took out of a 351W that I had for a short time. The guy that bought the car for parts to build his grandfather's 1948 Mercury pickup had to rebuild the engine. Ran great and did not burn oil. It could have benefited with a Performer intake and 4V carb. Anyway, I got that Engle cam and lifters. I had drilled 2 pieces of 2 × 4 to hold the lifters in the positions they came out of the engine.
With what you describe as the intent, a short duration cam is needed considering the small displacement. The Isky cam mentioned looks pretty good to me, but I would order from Isky directly, and seriously consider specing it with a 106° LCA.
Also consider getting the machine shop to cut the exhaust seats to 40°. This aids early blowdown, enabling a single pattern cam for more torque. Uh Oh, now I stepped in it, the HP guys are coming to kick my butt. Look up and watch David Vizard's Powertec 10 videos on cam selection. I can hear newbomb starting to snort already.
With a FT cam you need to use an oil with ZDDP in it like Rotella T4 10W30 or a Lucas oil.
You and the girls have fun with it and ignore the racers that tell you it is better to just build a 360 with big cam and heads. Just put it together fairly stock so you and your girls can take grandpa to Cars and Coffee or ice cream. Your father will likely love that.
By the way, I am a mechanic also. Automotive, Heavy Duty, and Instrumentation. I also volunteered as a Corner Marshal at Can Am, Trans Am, Formula Atlantic, and Indycar races in Edmonton.
FYI; my SBF Ford cam is from Engle.
210° @ 0.050" tappet lift
256° advertised duration
109° LCA
105° Installed
0.472" lift with stock 1.6 rockers

I am having Chev LS valves, 1.9"/1.55" installed in the heads and using 1.72 ratio roller rockers. Roller tips to reduce pull on the valve stems to prevent guide wear. According to David Vizard's cam formula, those intake valves in 289 heads indicate a 106° LCA to be about optimal on a 289. Run higher compression and quick opening of the valves and you compensate by spreading the LCA a couple of degrees. In my case the 109° should be close.

 

[Dale Davies]

“Just so you know” and “I already have…” never did I think my eyes would light up with hope reading those words haha. Thanks so much for taking the time to read my post and comment! I like that positive motivation!

Curious though, you mention having ran a cam with worse lobes than mine… are you confirming and or denying that it could be maybe should should not do don’t haha to run my cam as is? This was suggested to me from another source once before saying to get it cleaned up, no grind just remove the surface rust and run it with the same lifters and add a zinc additive in the oil. My first thoughts wouldn’t this just continue to break down quickly and send shrapnel through the system into the block and bearings and so on?

The isky racing cam seems to be tried and true from what I am reading. Again, I am inexperienced in certain portions, what else would need to be changed or altered to be able to run that cam? Springs, pushrods, lifters?

Thank you for the information and the clever grammar truly appreciate the attention to detail.

Ed Isky is still kicking at 103 years. Lots of experience designing and grinding cams.

 

[Dale Davies]

Hey there, after some further digging, I see that you crossed this bridge back in 2016 so I hope I haven’t worn you and the community out with a rinse and repeat of the topic.

Would you be willing to educate me further on the process of installing the isky cam?

Have the machine shop install the cam bearings and the isky E-4 cam.

(No machine work of any kind is being done at this time, just thorough cleaning and reassembling)

Reface and use my existing lifters.

Any other parts that need to be replaced and or adjusted in doing this install?

This setup won’t hurt and or “over cam” the remaining components in the engine?
As of right now, EVERYTHING is going right back in where it was after cleaning. The only parts being replaced will be bearings and gaskets as far as block related items, as of now.

Again this will be a basic daily driver on weekends and the occasional cruise.

I appreciate your patience! Thank you!

Is the machine shop equipped to put the proper convex surface on the lifters? With the problems people have had with lifters and cam failure the last 20 years you want good component match. IMHO the best bet if ordering the Isky E4 is to get the matching lifters from them. You do not want to take a chance of wiping the cam and having to take the engine apart again.
Another little tip from Brian Salter Racing Engines and David Vizard, is to round off the bottom edges of the cylinder bores a bit. It is kind of like the rounded or flared horns or velocity stacks on the intake. Consider this, as the piston travels up the bore at 2,000RPM, the air and oil mist follows the piston up. A square edge creates a flow restriction which reduces HP and fuel economy, efficiency. It is not much, but everything helps. This needs to be done before the short block is assembled, as you know and should you decide to do it.

 

[toolmanmike]

Is the machine shop equipped to put the proper convex surface on the lifters? With the problems people have had with lifters and cam failure the last 20 years you want good component match. IMHO the best bet if ordering the Isky E4 is to get the matching lifters from them. You do not want to take a chance of wiping the cam and having to take the engine apart again.
Another little tip from Brian Salter Racing Engines and David Vizard, is to round off the bottom edges of the cylinder bores a bit. It is kind of like the rounded or flared horns or velocity stacks on the intake. Consider this, as the piston travels up the bore at 2,000RPM, the air and oil mist follows the piston up. A square edge creates a flow restriction which reduces HP and fuel economy, efficiency. It is not much, but everything helps. This needs to be done before the short block is assembled, as you know and should you decide to do it.

"the bottom edges of the cylinder bores"? Do you mean the top edge?

 

[Dale Davies]

"the bottom edges of the cylinder bores"? Do you mean the top edge?

After boring the top edge has a slight bevel machined in so the rings do not catch. I am talking the bottom of the bores. It aids airflow following the bottom of the piston up and down the cylinders. David Vizard and Brian Salter both describe this minimum cost. Basically falls under "block deburring".

 

[toolmanmike]

After boring the top edge has a slight bevel machined in so the rings do not catch. I am talking the bottom of the bores. It aids airflow following the bottom of the piston up and down the cylinders. David Vizard and Brian Salter both describe this minimum cost. Basically falls under "block deburring".

The bottom of the bore into the crankcase. Strange.