1965 273 Heads

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PolarBear

PolarBear

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Anybody have a pair of heads from a '65 273 4-bbl? And maybe the cam, as well?

My 273 was a factory 2-bbl setup. I was lucky enough to find a vintage 4-bbl Edelbrock DB4 aluminum intake - which fits nicely and looks pretty cool - and I put a new 500cfm Edelbrock carb on it.

Performance was instantly better, but I'd really like to boost the compression enough to get a little more juice out of the old block. From what I've been able to learn, the difference in the stock heads that came with the 2-bbl setup, versus the ones that came with the 4-bbl Commando (?) setup was like night and day.

Because of the bolt angle situation with the pre-67 273's, I can't just slap on younger heads, and I would kinda like to "maintain" some semblance of "original".....
 
I believe the bump in compression between the 2bbl and 4bbl engines comes from the pistons and not the cylinder heads. toolmanmike
 
65Val said:
toolmanmike is right. The heads on early 273's are all the same ,whether 2 or 4 barrel.
Click to expand...


dual exhaust is needed if you haven't done that yet.

If you want to "cheat" build a 318, and use the old heads/
valve covers, timing chain cover, and water pump.

100_0471Medium.JPG
 
I had some new duals bent, and attached to the existing exhaust manifolds (which I'd also like to replace with some TTI's)......... that's another story, though.

Tell me what I'm missing - the spec manual says that the 273 Commando (235 HP) had something like 12:1 compression... and that the 273 2bbl only had something like 9:1. That difference doesn't come from the heads? ...... or do I just need to change the valves? .... or what? How would the pistons make that difference?

The spec manual also says that the Commando had a different cam. This, I'm sure, would give the old block a little kick.
 
PolarBear....Yes the compression (and power) comes from the high-comp (higher squeeze) pistons. The 273 "Commando"(Plymouth) and "Charger"(Dodge) engines have 10.5:1 compression and the 2 barrel engines have 8.5:1. The 4 barrel cam is also a hotter grind. That grind is not available today,but you can probably get an aftermarket cam very close in specs. The heads,block and exhaust manifolds are all the same,be it a 2 barrel or 4 barrel motor. A stock 2 barrel motor definitely performs better with a 4 barrel installed,but still not as good as having a true Commando engine. Good luck with your project

Hope this helps...
 
PolarBear said:
I had some new duals bent, and attached to the existing exhaust manifolds (which I'd also like to replace with some TTI's)......... that's another story, though.

Tell me what I'm missing - the spec manual says that the 273 Commando (235 HP) had something like 12:1 compression... and that the 273 2bbl only had something like 9:1. That difference doesn't come from the heads? ...... or do I just need to change the valves? .... or what? How would the pistons make that difference?

The spec manual also says that the Commando had a different cam. This, I'm sure, would give the old block a little kick.
Click to expand...

The addition of a slightly bigger cam would help,
but if you really want more power go with a larger engine. ;)

The 273 High compression pistons {10:5} are hard to find,
and not cheap.

Another problem, with the High compression 273 is fuel quality/octane
of the fuels you can buy at the pump.

Are you planning on street driving the car? What rear gear is in the car?
If its the stock 2:93 you don't want too large of a cam,
in a small CID engine.{I have learned that the hard way.}

273;
8:8- 9:1 to 1 2bbl compression,
10:3- 10:5 to 1 4bbl compression, bigger cam, Same exact heads.

1966 D Dart race only 273 was even higher compression,
but was a Race only setup, with about 50 cars built.

factory 4 bbl,273, with the 10:5 compression made 235 hp.

in 1967 the "New" 2 bbl 318 made 230 hp, and More torque.

"No replacement for more displacement"

Your 273 heads are limited in valve size, because the 273 bore is so small.

If you want to use larger valves, which are not needed, even with a 4bbl,
the block needs to be notched, which is not cheap,
or the larger valves will hit, and ruin the valves, and the heads.

For all these reasons, I built a 318 when my 273 was very tired.

Think I have no clue, what I am talking about, read Larry Shepards books
on small block Mopars, and buy some of the older Hustle Stuff books, etc.

A 1965 Service manual has a lot of good info too. :)
 
Okay.... I'm convinced - heads are heads (at least in this instance).

Laysons has 273 Commando pistons - as factory replacements, and also in 30 over and 40 over - but Layson's is VERY overpriced (with all their parts, typically).

And I had wondered about the octane business, too. With such high compression in the Commando engine, you'd probably be faced with adding octane boosters each time you filled up.

Anyway, I'm really not looking to build a racer............. but someday, an upgrade to a 340 would be cool.
 
hi, the 275 hp/273 was sold for the street use. only difference was, larger cam, headers, racer brown springs, holley carb, 4.86 gears. rest of motor was same as 235 hp/273. C.P. pistons makes 235 /273 pistons. egge also.
isky makes a very good grind for the 273, E 4 grind, works very well in 273 motor. the 1966-67 heads are closed chamber style, used on 273 /318 in those years.1967 for 318 though.
 
perfacar said:
hi, the 275 hp/273 was sold for the street use. only difference was, larger cam, headers, racer brown springs, holley carb, 4.86 gears. rest of motor was same as 235 hp/273. C.P. pistons makes 235 /273 pistons. egge also.
isky makes a very good grind for the 273, E 4 grind, works very well in 273 motor. the 1966-67 heads are closed chamber style, used on 273 /318 in those years.1967 for 318 though.
Click to expand...
http://www.autohobbydigest.com/ddart.html

The 1966 D/Dart
The 1966 D/Dart
The 1966 Dodge D/Dart was a Factory Dart package built solely for drag racing. The 273 v8 was rated at 275hp and weighing in at just over 2900 lbs. The car qualified for NHRA's D/Stock category.

Dodge's normally aspired high performance 273 was rated at 235hp. The extra 40hp the D/Dart produced was basic hotrodding. Off the speedshop shelf bolt on's included Racer Brown valve springs, a Camcraft 284-degree .500" lift cam, Doug's Headers, and a Holley 4160 bolted to the stock intake. All were equipped with the A-833 4 Speed and a Hurst shifter, Weber clutch components, and an 8 3/4 Suregrip with 4.86 gears. Unavailable for this car were air conditioning and a warranty. There were no external badging or markings to note the D/Dart package over a regular Dart GT.

The picture in the 1966 Car Craft article was of a white Dart GT with Cragar S/S mag wheels. They tested the car at 14.33 @ 92.21 mph.

This kind of package makes the identification of an original D/Dart nearly impossible without a paper trail, or some photographs. The cars were Dart GTs (I can't find any information to suggest that the D/Dart package was available in a sedan except for the fact that the lighter sedan might have put it in a different NHRA category). 1966 cars can be certified by obtaining a copy of the IBM "punch card" for the vehicle that indicates sales codes.

These cars should have a VIN that begins LO23 or LP23. The order should include the following sales codes: 699 - Special Order (Super Stock Dart); 409 - Special Order Axle; 364 - Super Stock; 624 - heavy-duty suspension; 32 - engine code; 554 - delete rear seat belts; 393 - four speed transmission; 21 - 6.95 X 14 BSW rayon 2-ply tires; 408 -Sure Grip; P4H - trim code (red); WW1 - paint code (white).
Click to expand...
 
Well said! the only place I've found Hp273 pistons listed is on Egge's
website. I would imagine thats where Laysons gets theirs. The HP273 is a
fun little motor but if you want to go fast build a bigger engine. Unless you need to keep your car 100% original you can build any small block you want
and put it in your car up to over 400 cubes. The HP is limited only to your pocketbook. I'm building a stock bore 318 with mildly ported Magnum heads
(9.0-1) Air gap intake etc. to replace the very tired HP 273 in my 66 Dart.
I may like the way it runs so well I'll just leave it in there and store the original. toolmanmike
 
Polarbear;

If your going to rebuild the engine, look for a ratio of not more than 9.5-1. That would be a 93 octane useage.
If the engine is in good shape, a milling of the heads can make up the difference. Just go to 9.0-1 and you'll be good. In general, a point of compresion is worth about 3% on the dyno. So it is not really worth pushing the ratio if you don't have to.

On a camshaft, the rest of the cars specs should be known before making a selection. Things like wieght of the car and rear gear ratio as well as your intended useage of the car.

Everyday driveabilty, some spirted driving, alot of spirted driving, street strip, etc.....
 
PolarBear said:
Okay.... I'm convinced - heads are heads (at least in this instance).

Laysons has 273 Commando pistons - as factory replacements, and also in 30 over and 40 over - but Layson's is VERY overpriced (with all their parts, typically).

And I had wondered about the octane business, too. With such high compression in the Commando engine, you'd probably be faced with adding octane boosters each time you filled up.

Anyway, I'm really not looking to build a racer............. but someday, an upgrade to a 340 would be cool.
Click to expand...

The question is do you really need to rebuild the motor. With the CR at about 8.8 to 1 about .011 in the hole. All it would take is to shave the heads about .020, a head gasket change to .028 orange gasket and you'll be in around 9.2 CR. There are a lot of cam grinds out there specificly for a small displacement motor in a light car. As far as intake and carb the Edelbrock D4B with a Carter 625 would fit the bill. Exhaust could be handled by the TTI's or Spitfires.
 
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