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  #1  
Old 11-07-2006, 01:55 AM
65 Signet 65 Signet is offline
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Default 273 build

I'm building a 273 for a 65 Signet. I wondering if I can have the O.G. heads bored and ported or if there are an aftermarket set That I may buy, or I f anyone knows the where abouts of a set of four barrel heads I could pick up.
I'm planning on a 272-.454 cam. I'm planning on a 275 about horse power plant. Any advise or pointers would be greatly appreciated. I'm want this set up to keep all matching numbers.

Thanks for your time,

Signet
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  #2  
Old 11-07-2006, 04:08 AM
DartGT66 DartGT66 is offline
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273 two and four barrell engines used the same cylinder head castings and valve sizes. The original heads of the '64 and '65 are a little tough, because they have different manifold attaching system than the newer '66&up LA engines. So, there is no intake manifolds available for the '64-'65 heads, except the originals. Or, you have to modify newer intakes to fit (or redrill the heads for correct bolt size & angle). The 273 has got another problem too; because of its odd, small bore, there isn't decently priced high CR pistons available.
Here is what I would do, I would build a short block with flat top pistons coming to zero deck. Then, I would find late 80's LA engine heads, "302" castings, have 1.88" intake valves installed and port them. Retaining the stock 1.50 exhaust vavle you would still have hardened exhaust seats, and 1.50" exhaust valve should be enough for the small 273. The heads hould be milled the needed amount to achieve the compression ratio you want. I think mi,,ing about .060" would bring it to around 9.5:1 with the closed chamber heads. But it's also possible, that you need dome pistons to get there. If going with new pistons, I might consider something like ROSS custom pistons. They are pretty pricey, but such is life. I would use a performer intake manifold with a 500-600 cfm vacuum carb. And I propably would use a smaller cam than what you have planned. Maybe a mopar performance 260/268 degree or something similar. Small primary headers and a good ignition with a high performance advance curve, and you should have around 275 TRUE horsepower in a pretty driveable 273.
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  #3  
Old 11-07-2006, 04:59 PM
earlymopar earlymopar is offline
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I saw your post and noted the area your're in and thought I should reply.

I am in Newberg Oregon, about an hour from you. I have some very nice 273 parts that you can PM me on if you're interested in them for your build.

I have an almost new, assembled 273 short block (with about 1/2 hour of run time on it). This was an engine that was built for a "spec" boat racing class that high lighted the 273 2-barrel engine. The throttle cable broke on it's first race which was the last race of the season. Hence the 1/2 hour of run-time. You could part-out these pieces and for far-more than what I would ask.

This is an assembled, very clean short block (with turned crank, oversize pistons, re-sized stock rods, new camshaft, new oil pump, new timing gears and chain, new hydraulic lifters).

I also have 66-67 273-318 heads (with newly rebuilt adjustable rockers, new rocker shafts, new valves, seals, springs, and new 3/8" diameter push rods.

Good luck and have fun which ever direction you take.

- EM
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  #4  
Old 11-07-2006, 08:25 PM
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pishta pishta is offline
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The old heads were closed chambered already, right? My 273/4v just had taller pistons. For sure, get the 302 heads and everything already posted.You can get a used 318 short block for about 20 bucks in the local recycler newspaper, then you can get all the piston you need for cheap. 273 was a cool motor, but a 318 is bigger and more common and no one would tell the difference unless he was looking at the VIN letter on the block or the casting code on the side. Hell, a 360 is carbon close for that matter.
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Old 11-07-2006, 09:18 PM
65 Signet 65 Signet is offline
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Folks thank you so much for the feed back and I appreciate all of your advice and input!! I will be doing more research and notifing ya'll of my findings. Again Thanks
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  #6  
Old 11-08-2006, 02:46 AM
DartGT66 DartGT66 is offline
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One thing I forgot; if you convert from the stock solid cam to hydraulic, you also need new shorter pushrods. They are readily available from comp cams, crane and summit and the price is reasonable. I agree with the answer above, if you really don't insist on having a 273, I would use 318 as a starting point too. Bigger bore for better breathing, better piston availability, almost 50 cu in more to begin with, still internally balanced and like said above, almost no one can tell the difference from outside. The bigger, the better, at least in this case.
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  #7  
Old 11-08-2006, 05:01 AM
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cageman cageman is offline
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I have a 273 in my Valiant, I used magnum heads on it and I have a 480 ish cam in it with the 1.6 rockers the magnums have, real strong motor and I have been getting 17 mpg with it, and I drive fast, If I was to drive a little slower, I might get better. But that is no fun, I like to light em up a few times every day, I have 4,000 miles on it already, and I need a new set of rear tires, as they are bald.
I like my 273, I once took the 273 out, and put a 318 in it, and I have a 273 back in there, if that tells you anything.
I had to notch the bores for the magnum heads, and luckily I was able to just re ring the motor, as the wear was excellent. Pistons were kinda spendy for it. Thankfully I didnt need to bore.
Go with the 273 build, the best part about it is the fact that most people have never heard of a 273, and they look at you funny when you tell them what it is.
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  #8  
Old 11-08-2006, 06:15 AM
DartGT66 DartGT66 is offline
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I understand the point with the 273, it's "different". If you have to bore and get new high cr pistons for a 273, it will most likely cost less to buy a 318 short block and build from there. Everything, except the bore size and piston availability are otherwise the same, and with a 318 you don't have to notch anything to fit the big valve heads.
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  #9  
Old 11-14-2006, 10:25 AM
aoehero aoehero is offline
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Default bore

Hey all, lots of good info here. thanks. I have a 273 that is just broke in at 50,000 miles and am considering changes. What is the max you can bore 1 to? I understand the LA had thin walls. I know a 318 is a better build but this is a numbers match car. Also is this a steel crank? It is a late model 65.
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  #10  
Old 11-15-2006, 12:04 AM
Billydelrio Billydelrio is offline
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273 replacement cast pistons and rings can be found up to 3.685" bore diameter. This would be .060" over the stock bore. Going larger than that would require extensive research on piston/ring/rod combos, or custom pistons and rings. In most blocks I have checked, a 3.700" bore leaves .100" to .125" minimum wall thickness in the major thrust areas.
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  #11  
Old 11-15-2006, 12:09 AM
Billydelrio Billydelrio is offline
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The crankshaft that came in the 1965 273 was a steel crank, but over the last 40+ years, it could have been replaced with a newer cast crank. The balancer would be the same in either case.
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  #12  
Old 11-15-2006, 02:37 AM
DartGT66 DartGT66 is offline
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And to be honest, it shouldn't matter much, wether the crank is steel or cast. With the commonly available cast 273 pistons, you will end up with a pretty low CR. You should get them to zero deck, and have the heads milled to about 55 cc. to get the CR in to about 9.7:1, still good for pump gas in a quench style combustion chamber engine. I have no idea about the compression heights of the 273 pistons available, but if extensive milling is needed, it might be a less expensive, and a better option to order custom dome pistons for the engine.
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  #13  
Old 11-15-2006, 10:59 AM
aoehero aoehero is offline
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Default steel crank

It is a steel crank. It is a low mileage engine. 54,000. Does anyone have a educated guess on the longivity of a 60 over block? Im not that familiar with Plymouth. (Sorry to cause everyone to miss a heart beat.) But always love fast!
But your right dart I dont think this motor would put out enough HP to require a steel crank. What are we talking 230 and under on pump gas?
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  #14  
Old 11-15-2006, 11:26 AM
BJSracing BJSracing is offline
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I built a .060 360 out of an 85 block. I ran it very very hard for about 2 years then sold the car. I know the guy that bought it from me put a different carb on it and then used the motor as a race motor in a foot brake car for about a year that I know of. So as long as the block sonic checks to go that far you shouldn't have any issues. I don't know how long after that motor ran because I haven't talked to him in a couple of years. But the last time I talked to him it was still gitten it done.
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  #15  
Old 11-15-2006, 10:53 PM
benno318 benno318 is offline
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the 273's have real thick bores so i dont forsee any problems whatsoever with .060".
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  #16  
Old 11-16-2006, 04:02 PM
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perfmachst perfmachst is offline
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hello, I did some research on 273 . the 180 hp, has an 8.8 cr listed. according to the NHRA specs, which are provided by mopar are; deck hgt. - .011, a .028 gasket, 57.3 cc head will provide a cr of 9.5. the 4 bbl motor, has deck hgt of +.129, .028 gasket, 57.3 cc head, cr. is 11.5. this little motor is a very good runner. in NHRA stk, there is 273/180 motors being run. a 1965 valient with 180/273 runs 13.30,s, in a 1965 plymouth, ran 13.43 @98 mph.
I realize not everyone is into stock racing, but the fact is, these motors can be very quick. many many years ago, I ran a 235/273 dart as a stocker, plus drove it. it ran 13.31 @ 102.30 mph. some people like smaller motors, others like big motors. to each his own. .060 over is about the limit on overbore in these motors. just food for thought.
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  #17  
Old 11-17-2006, 09:54 PM
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rumblefish360 rumblefish360 is offline
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Great info going on here, though I would shy away from a 1.88 valve in the 273 head due to port velocity down low. Back cut the stock valves and do some bowl work to the stock head.
I see a Magnum head swap in the postings. This larger valve works with the better flowing Magnum head.
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  #18  
Old 11-18-2006, 01:44 AM
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13's in the 1/4, shit, my 273 must be able to do that then, my Valiant cant weigh any more than that car, and I think it makes 200 hp at least, it runs good. Im going to have to go drag race this car next year for sure. I just need a driveshaft hoop and an overflow bottle and I think it will pass tech then.
13's here I come.
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  #19  
Old 11-18-2006, 03:29 AM
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hello, to run 13's you'll need some gear in rearend, and make it dead hook with out spinning a tire. i can assure you these cars have a ton of gear in rearend!!! my old 273 dart had 5.13 with 29.5 slicks. when dodge built the 275/273 darts in 1966, they installed 4.86 gears in rearends. they ran low 14 seconds through the muffler. just food for thought.
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  #20  
Old 11-18-2006, 06:26 PM
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5.13 in the 1/4 huh, thats a lot of gear.
I have 3.91 gears with a 5 speed.
I just might have to take a weekend off from circle trackin' to see what it does.
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  #21  
Old 11-26-2006, 03:24 PM
65 Signet 65 Signet is offline
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wow head swapping?

Will 318 heads work on this 65' solid lifter 273? Or is there an option. Will boring the original heads out and finding a 4 barrel manifold (that might fit?) work?

My books haven't mentioned this avenue. They tell me that 340 heads on a 318 are the way to go( police cars ect.....) so why wouldn't the same approach affect the 273, aslong as the gaskets aren't hitting the valves. What would the repercusions of this action be??
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  #22  
Old 11-27-2006, 01:56 AM
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hello, to install 340 heads, the bores have to be notched for valve clearence, so they will not hit. plus, you will have a lot of shrouding around the valve.
this causes a flow loss. the best head for your motor would be the 66 to 67 273 head. if you want larger valves, turn down a 1.88 to 1.80, turn the 1.60 down to 1.56. use the mopar sst valves. useing this size will not affect shrouding. the 318 heads will fit just fine. the later 318 head have a larger chamber over the 273/ early 318 heads. a 273 head will flow @25" test pressure 160 cfm, this will support about 345 hp. I'm working on a 273 now, with this combination.just food for thought
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  #23  
Old 11-28-2006, 12:38 AM
Billydelrio Billydelrio is offline
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Default Another 273 build

In my opinion, for a good economy engine, the 273 is the better engine between it and the 318. The smaller bore and closed chamber head can be configured to give a 9:1 engine that will require less ignition advance, thus better fuel economy than a larger bore engine with the same stroke. The early 273/318 head has a chamber that is not too unlike the newer '302 casting, although the bowls and ports are different. Small bore and long stroke engines are popular today with the computer controlled fuel and ignition systems. The use of the engine still dictates the type of build, of course.

Building an inexpensive high horsepower 273 is quite a story. I have one built and ready to go for next race season. two years ago, I switched from a factory headed 273 to a W2 headed 318. The 273 was 11.04:1 and had a CompCam292 hydrolic with solid lifters. It ran a best of 12.36 @109 in the 1/4. The 318 has 9.8:1 and a MP .541" lift circle track cam and just ran a 11.26 @119 a few weeks ago. The 318 has quite a bit more horsepower still to be found, but that will have to be looked for later as the 273 is being put back in very soon.
This 273 is a true 11.0:1 assembly with factory 273 heads modified with my porting work and cut down 1.92/1.60 Chevy +.150" long valves installed. The cam is a MP circle track grind with .528" lift. The pistons are an old set of Jahn's cast that stick out of the hole .230" at the dome. Regular iron rings are all I could find, much less afford. The engine has the regular trustworthy 8553 Felpro head gasket. The intake manifold is a Chrysler marine item that is very similar to the original 273 4bbl unit. It did require some coolant flow modifications in order to work on the 273 with a regular automotive water pump. With the same AFB Double Pumper carb that I used on the previous 273 build, I expect to see time slips in the 11.80 range in my 3281 pound Dart.
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File Type: jpg 273 out of block .230.jpg (28.6 KB, 11 views)
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  #24  
Old 12-01-2006, 02:28 PM
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cageman cageman is offline
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My Valiant doesnt even weigh that much with me in it, they must be lighter.
What gears you run in the dart?
I need to race my car, it feels quick, But is it?
Thats awesome 12.36 with a 273, that kicks ass.
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  #25  
Old 12-01-2006, 06:36 PM
Billydelrio Billydelrio is offline
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Cageman, my 64 dart is a little heavier than most due to the 727, dana 60, subframe, and the roll bar. The 3281 lbs included me in the seat. The 12.36 was run with a 5.57:1 gear and 29.5x10.50 slicks and a 5000+ PTC converter.
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Old 12-02-2006, 11:38 AM
Rug_Trucker Rug_Trucker is offline
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Offenhauser may have an intake for the stock heads. They built all kinds of oddball stuff. And it would have a cool retro look! I wouldn't put a regular Performer on anything as it is a loss of HP from a stock Mopar iron intake.
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  #27  
Old 12-02-2006, 06:47 PM
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Quote:
Originally Posted by Rug_Trucker View Post
Offenhauser may have an intake for the stock heads. They built all kinds of oddball stuff. And it would have a cool retro look! I wouldn't put a regular Performer on anything as it is a loss of HP from a stock Mopar iron intake.
any loss of HP will be made up in torque with an Edelbrock Performer, even the Edelbrock LD-4B. Edelbrock Performer is almost an AL version of an OEM dual plane (somethimes has a Mopar part number on it). The original 273 4bbl intake was a single plane due to the fact that the hood clearance would not allow a dual plane. I would go Performer before I would use the OEM single plane 4bbl intake for the 273. Offy will make you one but MAKE is the key word. You'll have to place an order and they will cast it when they can, not alot of NOS on the shelf for the oddball intake hole angle of the early 64-65 273 heads. The performer will work, just hog out the holes to match the more current hole angle. did it to my first 273. Remember to check for any intake dowels in the block!
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Old 12-02-2006, 08:08 PM
Rug_Trucker Rug_Trucker is offline
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LD4B might have had the Chrysler part number, many LD340's did. The performer won't. Its a basic 4bbl intake. Sits lower than a stock iron one, smaller ports. Bet those 273's love to rev!
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Old 12-02-2006, 08:26 PM
Rug_Trucker Rug_Trucker is offline
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I guess Offenahauser has a 2X4 intake for this engine. Jegs lists one. Just was informed of this fact on a thread on Moparts.com. Someone wanting a 2 4 setup for the SB Mopar.
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Old 12-03-2006, 12:41 AM
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I thought the bolt holes were smaller, not at a different angle. I think my commando heads are 66, but the motor in my Valiant is a 65, but I didnt use the heads, I still have them though, I just dont think the angle is diff, just a smaller bolt size is all.
My 273 with a dual quad intake would be sweet, but I think this setup would be the sweet deal for that.
http://retrotekspeed.com/
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