stroker402
1968 dart GTS convertible
wondering how much of an improvement will a stock 273 commando take before it won't climb anymore in hp/ torque ? would it be wise to go a few sizes larger with a cam? or did MA mopar have the specs right on ?
commando cam .. how much will it take with stock specs ?
- Thread starter stroker402
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I haven't ran the stock Charger/ Commando cam on the D Dyno. If it's anything like the Isky E4, The Hp peaks at 5,000 and starts falling off to below stock specs at 6500. Torque is at about 250 @ 1500 and tops at 330 @ 3500. It gets back to 250 @ 5500. Pretty broad torque curve. The Stock cam will be similar but less.
pishta
I know I'm right....
well, you could build it to "Super Commando" (D-Dart) specs and wring out ~275HP out of it but youll need to wind it out with headers. Youll lose low end. Is it a stick or auto? Mopar would not cam it past what the factory exhaust would handle
Ya but let's not go there.
The other thing being is how far are you willing to take it. You could put in a tunnel ram and twin Holley’s or AFB 600’s, 1-7/8 headers, etc...
You’ll have zero low end & mid range torque but scream HP
up top.
You’ll have zero low end & mid range torque but scream HP
up top.
All I can tell you is not much in it’s size could touch it. Even with 100K on it with a slipping clutch and burning a quart every 500 miles. My brothers 289K motor would have probably beat it but we never raced.
stroker402
1968 dart GTS convertible
how about piston to valve clearance > ..... how much cam lift before things are getting too close? commando pistons and stock heads. would adding a larger cam help this stock engine or break it ?
You have to measure lobe lift against your rocker ratio. (1.5 vs 1.6)
Fyi, we put a Comp 270S cam in our 273 with 2bl pistons. 0.468 valve lift 0.313 lobe lift. Sounded great, ran "great" but was a dog. Put Ld4b on it, I did a diy redneck port cleanup. Didn't make much of a difference.
I've started to build another Small block to transplant.
IMO Commando pistons account for a lot of the 273 potential. Limited mfg for the pistons out there. When I knew I wanted more hp, I knew the 273 was going to cost me more $$ per hp gain than other sb choices. Look at the engineering it took to get the D-Dart to 275 HP. A lot.
Just an fyi, good luck whatever route you choose.
Fyi, we put a Comp 270S cam in our 273 with 2bl pistons. 0.468 valve lift 0.313 lobe lift. Sounded great, ran "great" but was a dog. Put Ld4b on it, I did a diy redneck port cleanup. Didn't make much of a difference.
I've started to build another Small block to transplant.
IMO Commando pistons account for a lot of the 273 potential. Limited mfg for the pistons out there. When I knew I wanted more hp, I knew the 273 was going to cost me more $$ per hp gain than other sb choices. Look at the engineering it took to get the D-Dart to 275 HP. A lot.
Just an fyi, good luck whatever route you choose.
stroker402
1968 dart GTS convertible
Soooooooooooo, just to change things a bit ....... How would my big erson cam react with the factory 10.5:1 dome pistons and my closed chamber 920 heads with .028 thin gaskets , headers , ld340 intake and 650dp carb ? sweet or what ? those dome pistons should like that cam . I may have a commando engine coming .
OK, let’s get a grip here. Commando pistons don’t matter very much. I’ve had 273’s for 45 years. My brothers 67 Barracuda had a 2 barrel 273 with a 904. I had a 64 four speed 273 that was stock 2 barrel for about a month before it was pulled to add a TRW 284 duration solid lifter cam, Offenhauser intake and Holley 600, TRW forged 10.5 pistons, Mallory double life mechanical advance quick curve distributor, and a 65 Commando straight thru exhaust. Both were basically test mules. The 64 was fast, but would get even faster over the years. The 67 was rebuilt around 100K with 2 barrel pistons, Commando intake, AFB, distributor, and Commando cam and valve springs. While I tried almost every combination imaginable, my brother racked up another 300K on the 67. The 67 was always a joy to drive had good power, good mpg, and was stone axe reliable. A friend just put a 273 together with 2 barrel pistons, Commando AFB, intake, distributor and an Isky E-4 cam. 266 HP, pulling to almost 6K. The reality is power is in the combination and tuning. The most power my 273 made was with a used 72 340 cam. Of course that does not tell you much since there is too much to tell about the rest of the combination. There is no silver bullet that will make your car fast. Not a cam, not a carb, not pistons, but if you get the right combination and tune it well it is well worth the time. Anyway, you have all the parts except the cam, to have a sweet 273. If you want to buy another set of pistons, take the 318 that was offered, get pistons for that, get a good pair of heads, then drop your Erson cam in that. Take your time, enjoying the 273, and build that killer 318. If you want to run the Erson in the 273, then I’d be talking to AJ and toolmanmike. They have software and the math to get a good combination without all the trial and error.
Krooser
Building Chinese Free Engines since 1959...
You must really love that cam...
moper
Well-Known Member
Every cam is an exercise in compromise. A compromise between parts that support it, and needed results from it. The factory cams all make sacrifices to get good economy, service life, idle quality, ease of production, ease of assembly, etc. We replace cams to compromise some of that stuff to lean more towards a certain performance goal. Personally there's not any engine I would build where I would not upgrade from the factory cam . There is no reason not to.
Well said. The things the Commando/Charger engines had going for them that made them rev, solid lifter cam,dual point, single plane intake and 4 barrel. The standard 2 barrel parts and hydraulic cam will run out of steam at a lower rpm. I think that's what the op was getting at. How far does it rev b/4 it runs out of steam. 5000 rpm. I'll run some numbers in a bit.
stroker402
1968 dart GTS convertible
Yeah,,,,,, that is one mean sounding cam , you wouldn't believe how many people that came up to me and asked if I had a big block in the cuda . Don't get me wrong with all the previously posts but the cuda had no problem turning over the tires at a roll so it was making some power and torque with the combo I had in it. I was just referring to in this post that if I were to install the 10.5:1 pistons in my combo it would add a few ponies to it and the big erson might strive from it . IMO
I do realize the "MA MOPAR" has hit there goal when they built this commando engine in 1965.
That cam is not for your engine combo and a couple points of compression won't make it work.
QUOTE[ well, you could build it to "Super Commando" (D-Dart) specs and wring out ~275HP out of it but youll need to wind it out with headers. Youll lose low end. Is it a stick or auto? Mopar would not cam it past what the factory exhaust would handle] QUOTE
Sorry, no "Super Commando 273". D Dart only. (Commando is a Plymouth term and Plymouth didn't have a D Dart equivalent.)
Sorry, no "Super Commando 273". D Dart only. (Commando is a Plymouth term and Plymouth didn't have a D Dart equivalent.)
Here's as close as I could come to a stock HP 273 with the cam specs I have. As you can see the HP tops out at 4500 and the torque peaks at 3000. You will also notice the Dyno program is pretty accurate. Stock HP was rated at 235 and the dyno rated it at 225.
Just to confuse you even more, Here's a 318 with a Whiplash cam. It idles like a top fuler but over about 1800 rpm it smooths out and runs like a kitten. I have seen and heard the car after he built a 360 for it (so he could go fast). He liked the idle of the 318/Whiplash but it didn't perform like it idled. You could probably talk to a cam grinder and they could build you a solid lifter version if that's what you want.
Krooser
Building Chinese Free Engines since 1959...
I love those 273's but you need the correct cam to keep them happy
65Val
Average Length Member
ValiantRacing
Well-Known Member
My 273 has stock lift, but the duration is not stock, and i run it over 7000, you need to find the right balance that works best for your build, and what your going to use it for.
I don't have a good video of our cuda with the Comp 270S. If you give it a couple weeks for it to come outta storage I can take and post a video.
65Val
Average Length Member
I know I've asked this before, never getting an answer, but, has anyone tried a Whiplash cam in their 273, Commando specs or 2 bbl specs??
I haven't heard of anyone that has. I would have to plug some specs into the dyno and see what happens.
Torque is basically cid and VE. Most decent engines will make about 1.15-1.25 lbs-ft per cid. And the higher you move that torque up the rpm ladder the more hp you'll build.
The main limits for power is the head and cr.
The stock head is good for at least 300 hp maybe 325 hp with the right combo. The stock cr might make it hard to make above 300 hp.
The main limits for power is the head and cr.
The stock head is good for at least 300 hp maybe 325 hp with the right combo. The stock cr might make it hard to make above 300 hp.
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