Need A Recipe For A 273 Rebuild

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Hell_Fish said:
My 273 is a factory Commando. I reused the orginal pistons and sleeved some cylinders. You can get a new set of oversized 10.5 to 1 pistons through Egge.com, but they are expensive. Finding a old set of pistons and sleeving the block will save a lot and give you a stronger engine, since sleeves are steel vs. iron you will get much less wear down the road. I polished and balanced the rods. The steel crank was polished and new bearings installed. Bearing are the same for the 318, so lots of choices. New I use a set of 85 318 heads (302 casting, swirlports). I bought mine already ported and polished. Followed up with a hyd 340 replacement MP cam. Sorry, I can't recall the specs at the moment. I had planned to use a edelbrock performer intake and a 500 cfm carter. The intake had a issue with my factory A/C stuff. If it wasn't for A/C it would have been fine. last is a set of spitfire headers. Dakota magnum manifolds will do the trick too and look more stock.

Just to defend the 273 a little. The only expensive part is the pistons. All other parts will have the same cost as a 318/340/360, but none will get the fuel savings as a 273 and face it, no one gets excited over a 318 or a mild 360, but have a 273 or 340 and watch the reactions and stories you will hear from back in the day.
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Right on, Very true.
Would like to hear about more 273's. anyone else?
 
I never considered the cost of re-sleeving versus new pistons for the 273. Probably not cost effective for other blocks (maybe 340s) but an option for a 273 if that is what you have your heart set on. I also did not consider the adavantage of steel vs iron. Good points.
 
Wow! Go away for a few days and this post comes alive with activity!! Again, this is a street cruiser, not a racer. Something I can be proud to light up now and then, but let's keep in mine she's a ragtop cruiser and I have no intention to twist the frame in half. Thanks for all of the input. There have been a lot of great comments and I appreciate all of them. I'm going to put all of it into a list and work out my total price. I have a great local machine shop that is going to do the prep work and is pretty excited to get their hands on this old piece of iron. I'll keep you posted on the progress.
 
if i can remember back 3 pages,you said it was a /6 a body .... that 71/4 is not ging to take the power that most are rec. if you want to make it a crusier, my be,if you dont light the tires and then theres the brakes ,those 9 incher arent going to stop that flying machine the d darts had 10s and 8 3/8...............man ive done5 or6 of these early a trans plants..its alot better and cheaper to go with the 360,..if you add more power to the 273 ,you are going to have to change to a better rear end and brakes any way ,so why not save some money and go 360 ....you will end up doing it in the long run...good luck............
 
I found this old post with a lot of 273 info. Eat it up guys! Mike
 
Wow, lot's of good info and advice here. This answers alot of questions I had requested in my post. For Mooser, I think freshening up the 273 would be the most cost effective and prudent thing to do for now. Hey, at least he'll have a V8 instead of a Slant Six. Before I get bombarded by all you Slant Six guys out there, let me tell you that my dad drove a '68 4 door Dart with a Slant Six,rubber puke mat, lighter delete plug, AM radio, heater, 13" skinnies on 9" drums and drove that thing for 500,000 miles and sold it in the mid 80's to a high school girl for $500. They run! But boys want noise...right?
 
Hhmmm. I've never built a 273 of any kind. So this may not be the "best" thing.. but I'd go something like this:
I'd use custom pistons... mainly because in order to get decent squeeze you need them up at zero deck, and at 0 deck, you have very little room for valves. I'd also use magnum heads vs 302s. The chambers are better design and smaller. I'd also run Cometic head gaskets to set a decent quench and get the gasket bore back to a 318's 3.910. that leaves room for bore notches to help unshroud the 1.92 intake valve. You'll only ever buy them once anyway. For a cam, I'd be looking at something like the XE256H. The rockers and pushrods (for the solid cam crowd) can be sold to make soem money back. You can save $$ by buying done stock Magnum heads as they will be more than fine for the smaller cam so a set for under $800 is pretty easy to come buy. They will need to be milled to seal with Cometics, but use this to bring the chamber size down to 56cc. With a Performer intake and 500cfm AFB I think it would be a ripper. I'd bet you could have it all done, balanced, and ready to go for less than $4K with the custom pistons(I'd use Diamonds...) and Cometics. The smaller cube engines do require a little more care, but I think with more modern high velocity type heads and cylinder pressure building cam, with modern machining and design the 273 could hit 300hp under 4K rpm and have decent torque from 2500 up to hp peak. It works out to about 9.7: static, 8.2 dynamic, very pump gas friendly.
 
BobsDart said:
I've done the 273-360 swap in my 64 Dart. No comparison!!! You can rev the 273 higher but low end grunt is not there. I did the cam swap in the 273, stay with a 268-270 max duration cam. The repo 340 cam works great in that and a 318... Dual plane intake a must also...

Bob
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Bob,
Did you use the later trans or keep the pushbutton setup with the 360? Any major install problems?
 
My Dad was and still is a huge fan of the 273. Years ago when he still had his 66 barracuda S I bought a 70 340 duster. He was convinced the smaller barracuda with the 273 commando would run with my duster. He didn't talk to me for the whole day after we lined them up. The 273 was outdated when it came off the line. Cool looking motor but the small block Chev 327 was blowing it out of the water in the nova SS. Thus the development of the 340. I'm a monster 340 fan but still know that a built 360 will out do a 340. Even though the 360 is now a proven performer I'll stick to my 340 for the nostalgia. I understand the attachment to the 273 despite the fact a 360 has way more potential. Build it the way you want it and you will be happy.
 
djwhog said:
Yep there are several pistons, but keep in mind the quality and weight. I think the Ross units are better and weigh less. Like I said I would lean toqwards forged if you are gonna spend that kind of money and you will need to spink 65500 + to make any real power to speak of and gear it accordingly.

I can post you some details on cam etc that works in several applications.

PS I even tested back inthe day the mopar cams from a 340 and the 260, 272, and I think the 280 grinds. These were back when they did the purple series cams. All were slugs on the bottom end and torque curve was flat but very unimpressive too.
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Dave -- Mr Cam Man.
Did you ever hear of a cam with a 436 grind? Or something like that. Al Adam built the 273 engine that's in my D/Dart and when I was talking to him at the Hemi Reunion, he mentioned what the cam was ground to, and I didn't have anything to write it down. Maybe you can help. He said the engine had mushroom lifters in it due to the profile of the cam. Al worked in the hemi program in the 60's and 70's so it could be off of one of them.
Any help would be appreciated.
Alan
 
HI I just have to put my 2 cents in.In the late 60s i raced amatuer class with a 65 formula s 273 4 spd 391 single exaust. 14.70s all day long. I easily beat stock zs 327 chevys and 289 270 horse mustangs.I came out of the hole like a jack rabbit at 4000.I had one helluv a lot of fun and pissed off a lot of people.Im' just glad i didn't kill some body because most of it was on the street.(how many of you heard of amatuer class).
 
I would imagine the 438 grind is a lobe profile number.To use that agressive
of a lobe you would need mushroom lifters. They were used before roller cams became popular. toolman
 
What are mushroom lifters? Have you guys swapped out the Valve Springs or anything Special to Rev up those 273's to over 6,000RPM?
I am looking at needing new rods and a cam for my Motor.
-Eagle I beams 6.123
-COMP Cams Adv. 268 In. 274 Ex. .488 .501
CL20-233-4
-5901 Hooker Competition Headers
 
ddartdude said:
Dave -- Mr Cam Man.
Did you ever hear of a cam with a 436 grind? Or something like that. Al Adam built the 273 engine that's in my D/Dart and when I was talking to him at the Hemi Reunion, he mentioned what the cam was ground to, and I didn't have anything to write it down. Maybe you can help. He said the engine had mushroom lifters in it due to the profile of the cam. Al worked in the hemi program in the 60's and 70's so it could be off of one of them.
Any help would be appreciated.
Alan
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ddartdude,

Well I need to look in the old National Service data book. These books have the specs for about eveything, there are like 3 times as thick as the old motors and later mitchel books.

I recall it was like around .515 lift, about a 268-280 ish duration, they also had some incredible still springs and the seat pressues value closed were over 200+ lbs as I recall stood out. it had very little overlap and was a very step flanked cam. it was made by racer brown in 65-66 to compete with the 271 hp cal special 289 mustangs. There were rated at 275 hp 273, dual ex, dual point dist, 10.5: compression, same ex manifolds, same heads etc.

Now that said there were some dealer installed factory type break apart headers.

I built mine with a Isky cam that was custom made, the Mopar purple series and 340 cams killed the bottom end. I played with the 260, 270, and the origional 340 grinds. They all kinda sucked for torque.

Comp cams has some grinds that are close.

Camshaft, Mechanical Flat Tappet, Advertised Duration 274/ 280, Lift .502/ .511, Mopar, Small Block, CCA-20-230-4


Camshaft, Mechanical Flat Tappet, Advertised Duration 268/ 274, Lift .488/ .501, Mopar, Small Block, CCA-20-233-4


But if you had the money you could machine and do a better roller today I am sure with less were etc and make better power than I did.

If you look at many of the cams and grinds descriptions etc, keep in mind they are really for the larger 430-360s. DO NOT over cam, you can almost say that if it is list as extreme it is next noth up and going act like race in the little 273.

Like if you go this big:
Camshaft, Mechanical Flat Tappet, Advertised Duration 252/ 262, Lift .542/ .555, you are going to kill the power all to hell, they list it as a 3500-7000 stick, but on a 273 it is more like a 4000-7500 stick.

I think if you can go a decent set of heads with at least 360 intakes, exh, notch the block, decent heads TTI etc and a smaller solid with 10:5's pistons and tricked ignition, the 273 needs a lot of intial spark about 34 max and have it all in by 2500-3k depends on setup etc, air gap with a 600-650 max carb, or maybe a little less inteake depends what you want ou will be good. But you are going to need 3.91 or better to make her launch too.

I used to spin mine very high, had a forged 318-3 truck crank, and custom rods, windage tray and oiling mods done. 8k was not an issue, but I had rocker shafts that were bushed too.

HP to 300 HP in a 273 that can run on the street is do-able.

I will look for the specs in the book for you on the D dart 273 -275 HP cam.
 
madmaximum said:
What are mushroom lifters? Have you guys swapped out the Valve Springs or anything Special to Rev up those 273's to over 6,000RPM?
I am looking at needing new rods and a cam for my Motor.
-Eagle I beams 6.123
-COMP Cams Adv. 268 In. 274 Ex. .488 .501
CL20-233-4
-5901 Hooker Competition Headers
Click to expand...


I could use that cam in my .030 over 360.
 
The D-Dart cam was ground by Camcraft and it was a 284 duration
.495/.505 lift. I would call the cam companies with your combination
and see what they say. 273's don't like much duration and most early cams
had too much compared to todays standards. There is power gains in the shape of the lobe. (how fast the valve is opened and how slow it is closed)
Mike
 
mullinax95 said:
I could use that cam in my .030 over 360.
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Yeah. So um that don't tell me much about what it would do in a 273. Please ad some information to your advice...:read2:

So my motor Spun 3 and destroyed a 4th ROD BEARING!!!](*,) it was numbers 3-6 (the center 4) I can not tell exactly why this happened. I believe some gasket sealer was foolishly used on the oil pump last re-build (Me and my buddies where fresh outa high school and couldn't work on this thing fast enough so who knows who is to blame for this perversion:sign10:) Could have plugged the Center main oiling galleries.. Plugging oiling until the Assembly got Hot enough to melt it out. Bye that point my Bearings where toasted and Spinning up. Now my 4 Rods are Effing PURPLE.

My step-dad, Richard MacHale, of Sunnyvale used to drag race all the time and was one of the only Compitent Wrenches in his crew... Therefore has had his hands on Everything. We cased the scene and found no definitive clues as to why my rod's saw that much heat!!! 400+degrees to DARK blue!!! Also Elongated two of them.. So WTF?! :confused: We are both gear heads and Machinists and have no idea how to prevent this from happening.

The common theme is that the 2.125 Rod journals and a Basically stock 273 that never saw more than 6500Rpm.

-it was 1 Quart low when this happened. I drove the car about 25 miles easy after I first thought it was making a new noise... It became obvious it was a serious internal PROBLEM!!!:stop:

Any Experiences that ring ya'lls bells?1
 
I t sounds like you may have spun a main bearing and it stacked it onto the other half and starved the rods of oil. I have seen a few. (allthough not mopars) toolman
 
Ok I understand.

The engine had all new bearings. Was rebuilt only 8k miles ago 8000 . . .
I may have just over spun it seeing as how my Original Tach is no longer reliable let alone accurate. Tons of guys said they have wound out their 273 all the time...
*Wonders*
Heavy wristpins too much weight Elongated the bearings and then spun?!...

Never on a Mopar type scenario near as I've heard. Not even common. Wow, I am Lucky huh?!
 
Too bad it happened. Was the oil pressure allways good? toolman
 
mopar340dave said:
You can think that but I have to disagree!
Can you show me a pump gas 360 that makes 600 HP?
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Was there ever a pump gas 340 that made 600HP?

madmaximum said:
Yeah. So um that don't tell me much about what it would do in a 273. Please ad some information to your advice...:read2:
Click to expand...


I wasn't advising anything ... I was just stating that cam would work in my 360.
 
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