273 commando HELP!!!

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bamacuda

bamacuda

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:cheers:
It's a toss-up...
What I want is a good running, mildly above stock 273 commando for my 65 barracuda project.
I have a 273 commando in the machine shop and I have questions. The block is .030 over with .030 domed pistons (previous owner) and is ready to go. ( all is or will be balanced) I will be running a 904 with a mild shift kit (runs like stock until you "call on it" and it is supposed to crispen up a bit)
  1. Q1) stay solid or go hydraulic? roller?
  2. Q2) domed or flat top?
  3. Q3) what cam?
  4. Q4) intake?
  5. Q4) what other factors? Heads?
I want the engine to look as stock as possible, may even just dump all ideas of pepping it up and go stock, but I still feel the need to improve a bit. I have pertonix, original carb (rebuilt) and am planning an 8 3/4 3.55 suregrip but that is debatable. I will be running the Formula S stock exhaust with resonator tip.
All advice appreciated!

Again, I want a stock appearance that is dependable and will squeak the tires if I have a notion to. Most driving will be cruising, not racing.

Thanks a-bodies family!!!:-D
 
Well, if you want it to look stock it should sound stock to. Put in an Isky E4 Solid cam. The 10.5 to one pistons, of course. Stock 4V intake. No headers as they sure don't look stock..... A fresh HP273 runs really nice so use it. The Isky cam is a bit more power than stock but VERY close. Balance it so you can use that tight windin' lil motor. Have fun!
 
Gasket port the Heads, Intake (If you have the stock carb this Intake hollowed out a little will be sufficient for your needs) and Exhaust manifolds. Be a man and buy some carbide that you feel comfortable wielding, a respirator, face shield, new gaskets, and get crackin! I have seen people cut out the center cross section of the manifold to adapt different carbs for more CFM from up top.. Get a good valve job. Keep the lighter Adjustable Valve train. If you want find a Cam with about .480 lift and near stock duration (cannot remember off top) Keep the dome tops and you shouldn't have to have the heads milled... and don't be shy with the Octane on fill up. She'll love it. You oughta smoke em plenty for kicks with a 904 and 3.55 even with some 245s at the end of a Sure Grip. It will be fun to drive. Get a descent Tachometer as it will be impressive to watch it whip around. That is fun too.
 
If you want to keep that 273-4 with a solid lifter cam, Schneider cams has a
264/480 solid lifter bumpstick. It might be borderline too big for a stock converter but it's been a long time since I've messed with cam/convertor
combinations. Check out Flatlander Racing's website. toolmanmike
 
Stock 4bbl cam is mech 248/248 duration and .415/.425 lift.

The Isky E4 Part no. 390144 is 260 (216@50) duration 425/425 lift.

Low end goes away pretty fast with a very big increase in duration with the 273. The D-Dart used a 284 with 500 lift and it idled like a purpose built race car. Even though the Isky E4 is advertised at 260 the .050 numbers (216) are fairly mild and a 273 idles well, retains good driveability and raps up nicely. FInd a cam with near that duration and you'll like it.
Stock 2bbl cam is mech 240/240 and .395/.405 for comparison purposes.Sorry I can't tell you what the factory cams were at .050......
 
Good info there grimreaper. When I rebuild my 273 I may get stupid and
try both cams. I have a 4-speed so a little rough idle isn't a problem. Allthough a bit of work, I could allways switch to the E-4 if needed. Do you have any video's of the E-4. I'd love to hear the sound.
toolman
 
This is just the kind of info I am wanting! You guys keep it up, I am nearing the time to give more info to the builder.
 
I rebuilt my 273 2 bbl in auto shop in 1975 or 1976. We weren't allowed to do anything that wasn't "stock." I put in the domed 4 bbl pistons & used a factory 1965 4 bbl manifold & carb and dual point distributor. I added Isky valve springs & a solid lifter .474/284 (IIRC) cam. The teachers suspected what I was doing, so I was told that since there weren't any emission specs for 1964 my engine had to meet 1973 tailpipe specs. One teacher also used to tell us that 273's never idled smooth. My engine idled so smooth you couldn't tell it was running & it passed the 1973 sniffer test. (I might have leaned out the idle mixture to get it to pass....:snakeman: ) After it left shop class it got an Offy manifold, Mallory dual point, Holley 3310 carb, headers, 3.91 gears,......:toothy10:
 
As far as the 273 goes you'll want to go with a good intake if possible D4B and a good Carter around 625 cfm. Go with the Hipo exhaust but skip the muffler and run just the resonator. Accurate Limited has an enhanced single exhaust kit. You should have the good closed chamber heads so don't go too crazy on the cam. Try and find a cam that compliments the flow of the heads. You may even consider going with a larger valve. PM me and I can give you more specifics.
 
I just went through a 273 for my kid's 74 Duster and I picked the Comp Cams 270S Magnum, P/N 20-264-4. The specs on this one is 270 advertised ( 224 @ .050 ) and .468 lift. It's a single pattern profile. We just got the car fired and I'm still working all the bugs out of this Slant Six swap, but the idle had a nice mild lope, not lumpy like I expected and vacuum was around 11". I still need to fine tune it and get 'er on the road, but I'm not ready yet (bracket problems) I'll let ya know how this guy runs. I had a hard time finding mild solid cams, but this one was recommended on a 273 site I checked out.
 
Videos would be great. I'd love to hear the sound. toolmanmike
 
I didn't have a lot of this kind of information available when I rebuilt my Commando back in the 80s. I wound up with a Crower hydraulic cam, very similar in spec to the stock mechanical cam. If I did it again I'd go back to solid for the sound, if nothing else.

Nobody has mentioned heads, for the reason that there isn't much to do about them besides gasket match, as mentioned. 318 heads wouldn't be an improvement, and big valve heads would just kill the responsiveness that makes this engine so cool.

What I have been thinking about recently is that the 273 has the lightest rods and pistons of the LAs (presumably), but has those hunkin' massive wristpins. I was pondering if you drilled them out to a more reasonable wall thickness, they would still be plenty strong for a 250hp motor, and you could shave a little off the crank, for even less rotating mass (balancing the whole assembly, of course). Then it should really respond. Crazy idea?
 
I'm sure Ma Mopar had to add weight somewhere. The pistons are pretty light beacuse of the small bore size and they didn't want to keep drilling the crank.
The crank would look like swiss cheese if you'd use aluminum rods. LOL Of course there's knife edging now days. That takes weight off the throws without weakining the crank. I'm thinking about having a solid lifter cam made.
Specs would be closer to stock than the E-4. That cam has been around for years and allthough a good stock replacement the new cam lobe technology
they use now days would be a plus. I talked to BJR Racing in the chat room the other night and he got into modern cam design cam design. I was messing around with my dyno program and his suggestions found more horsepower without sacrificing torque. For a stock 273 with a little head work and a different cam it figured out to 294 hp@5500 rpm and 273 ft./lb. of
torque at 2000 rpm with a max of 321@ 4000rpm. That's through stock manifolds and exhaust. Headers really helps, bumping it up to 340 hp and 354 ft.lb.I keep messing and finding a couple of horses here & there. toolman http://www.forabodiesonly.com/mopar/showthread.php?t=55641
 
You are the Man toolmanmike! I love your in depth chase for a ripping street 273! I admire your attitude about it all. I just had my engine balanced after rod machining and I gasket matched the heads and blended out the transition in the Combustion chamber squelch area... Stock cam. Head milled (Do not have numbers) two + times... Bored .030 and a 600CFM Holley.. Oh stock manifolds & Dual exhaust. I am guessing about 280 HP or so.
 
toolmanmike said:
I'm sure Ma Mopar had to add weight somewhere. The pistons are pretty light beacuse of the small bore size and they didn't want to keep drilling the crank.
The crank would look like swiss cheese if you'd use aluminum rods. LOL Of course there's knife edging now days. That takes weight off the throws without weakining the crank. I'm thinking about having a solid lifter cam made.
Specs would be closer to stock than the E-4. That cam has been around for years and allthough a good stock replacement the new cam lobe technology
they use now days would be a plus. I talked to BJR Racing in the chat room the other night and he got into modern cam design cam design. I was messing around with my dyno program and his suggestions found more horsepower without sacrificing torque. For a stock 273 with a little head work and a different cam it figured out to 294 hp@5500 rpm and 273 ft./lb. of
torque at 2000 rpm with a max of 321@ 4000rpm. That's through stock manifolds and exhaust. Headers really helps, bumping it up to 340 hp and 354 ft.lb.I keep messing and finding a couple of horses here & there. toolman http://www.forabodiesonly.com/mopar/showthread.php?t=55641
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We built a 273 based 258 inch motor that has very light weight pistons and pins. Also built a 318 using light weight components. In each case when they were balanced the counter weights were turned down with a lathe, more than .125". Both engines have seen 7500 rpm and they do it easy.:love7:If I do another 273, I will use 318 wrist pins! The small engine has .224 @ .050 with 434 net liftsolid cam. It is a little weak below 3000, then hang on. Pulled a 4100 lb truck to a 15.16 at 92 mph in the 1/4. With stock heads and intake some of the low end torque would return because port velocity would be better.
 
'64 Cuda said:
I rebuilt my 273 2 bbl in auto shop in 1975 or 1976. We weren't allowed to do anything that wasn't "stock." I put in the domed 4 bbl pistons & used a factory 1965 4 bbl manifold & carb and dual point distributor. I added Isky valve springs & a solid lifter .474/284 (IIRC) cam. The teachers suspected what I was doing, so I was told that since there weren't any emission specs for 1964 my engine had to meet 1973 tailpipe specs. One teacher also used to tell us that 273's never idled smooth. My engine idled so smooth you couldn't tell it was running & it passed the 1973 sniffer test. (I might have leaned out the idle mixture to get it to pass....:snakeman: ) After it left shop class it got an Offy manifold, Mallory dual point, Holley 3310 carb, headers, 3.91 gears,......:toothy10:
Click to expand...
AH YEAH!!,the 3310!!Me likey this carb. on my 340(372)stroked 4 speed with XE284h comp cam!452 hp!Lump with idle.
 
Running a comp. cams solid unit (20-246-4 http://store.summitracing.com/partdetail.asp?part=CCA-20-246-4&autoview=sku) in my 65 Valiant with 273 commando. Close to stock modern grind. Also have slightly ported the heads & port matched the stock intake & exhaust manifolds. Only other mod is enlarging bores on stock intake for modern eddy 600cfm carb. My bottom end is stock. With this combo and hi-po single exhuast this little sleeper will definately chirp second.

Oldschoolcuda
 
pettybludart said:
AH YEAH!!,the 3310!!Me likey this carb. on my 340(372)stroked 4 speed with XE284h comp cam!452 hp!Lump with idle.
Click to expand...

I had an 1850 on my engine. My brother had the 3310 laying around. One day I swapped on the 3310 & took a friend who was familiar with my car for a ride. He said there was so much change it felt like I'd put steeper gears in the rear. It really was an amazing difference. Maybe the 1850 wasn't set up quite right, but since then I've never trusted those formulas for figuring out the size carb you should run. Everything I've ever read says a 3310 is WAY too much carb for a 273.
 
'64 Cuda said:
I had an 1850 on my engine. My brother had the 3310 laying around. One day I swapped on the 3310 & took a friend who was familiar with my car for a ride. He said there was so much change it felt like I'd put steeper gears in the rear. It really was an amazing difference. Maybe the 1850 wasn't set up quite right, but since then I've never trusted those formulas for figuring out the size carb you should run. Everything I've ever read says a 3310 is WAY too much carb for a 273.
Click to expand...
Ran a 1050 dominator on the 258.....not recomended for street use.
 
Very nice Valiant oldschoolcuda! I can't wait to get mine assembled and post some pictures! You guys are really a lot of help!
 
Been following the Isky E4 posts and Toolman, youre Dart sounds great. I went one step up with Isky’s T3 for my 273 Charger, Automatic, 3:23s. Mechanical 455,455,260,260,108LC,44 overlap. Still in box. Can not wait to hear it. Anybody running this? Will post spec sheet next. KG
 
ChargerKG said:
Been following the Isky E4 posts and Toolman, youre Dart sounds great. I went one step up with Isky’s T3 for my 273 Charger, Automatic, 3:23s. Mechanical 455,455,260,260,108LC,44 overlap. Still in box. Can not wait to hear it. Anybody running this? Will post spec sheet next. KG
Click to expand...
I can't wait either. Keep us posted.
 
Please see my answers in red within the quote.

bamacuda said:
:cheers:
It's a toss-up...
What I want is a good running, mildly above stock 273 commando for my 65 barracuda project.
I have a 273 commando in the machine shop and I have questions. The block is .030 over with .030 domed pistons (previous owner) and is ready to go. ( all is or will be balanced) I will be running a 904 with a mild shift kit (runs like stock until you "call on it" and it is supposed to crispen up a bit)

  1. Q1) stay solid or go hydraulic? roller? Stay solid flat tappet.
  2. Q2) domed or flat top? Why would you change this when you said you already had the domed pistons? Stay with them.
  3. Q3) what cam? The E4 is a decent grind. Been used for decades as the 273 "go to" camshaft. It's ok, IMO, but there are better grinds.
  4. Q4) intake? If your heads have the odd early intake bolt angle, intake manifolds will be very limited, unless you modify the intake bolt holes, which is easy to do.
  5. Q4) what other factors? Heads? If I had a 273 engine, I believe I would use either the 302 318 castings, or 5.2 Magnum heads.
I want the engine to look as stock as possible, may even just dump all ideas of pepping it up and go stock, but I still feel the need to improve a bit.

If I had the car, and it was a real 273 Commando engine, I would build it stone stock, but blueprint it. In other words, make all of the specs, compression ratio and whatnot exactly what the book states. Also, I would degree the stock cam. IF you decide to run something like the E4 or another small solid, make sure to degree it as well ans also use the correct valve springs.

I have pertonix, original carb (rebuilt) and am planning an 8 3/4 3.55 suregrip but that is debatable. I will be running the Formula S stock exhaust with resonator tip. Even more reason to stay very mild or even stock. The stock exhaust system will not handle too much over stock and would be a bottleneck for something much over stock, IMO.
All advice appreciated!

Again, I want a stock appearance that is dependable and will squeak the tires if I have a notion to. Most driving will be cruising, not racing. Built as I outlined above and with a good HOT ignition curve, it will paint black marks on the street. @Halifaxhops (Ray) can set you up with a NICE distributor with a custom curve. He's a good dude, does reasonable work and he's a great forum member. You'll get a very good product at a reasonable price while helping a fellow member. What's not to like?

Thanks a-bodies family!!!:-D
Click to expand...
 
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