318 head???

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68dart-sb

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I have a 318 engine runs, I have a set of rebuilt 273 heads. (new unleaded value seats, new 340 springs). I will be adding a purple shaft cam.

I have been told that the 318 heads donot create great compression because of their shape.

Would changing from the 318 heads to the 273 rebuilds heads help or hurt the engine?

Additional information 4 barrel carb, duel exhaust.

What does everyone think???

Thanks,

Sam
 
68dart-sb said:
I have a 318 engine runs, I have a set of rebuilt 273 heads. (new unleaded value seats, new 340 springs). I will be adding a purple shaft cam.

I have been told that the 318 heads donot create great compression because of their shape.

Would changing from the 318 heads to the 273 rebuilds heads help or hurt the engine?

Additional information 4 barrel carb, duel exhaust.

What does everyone think???

Thanks,

Sam
Click to expand...
If your talking about the 920 closed chamber 273 head, yes it will increase the CR.
 
I think you will need a 273 intake as well. The bolt hole angles are different. Also the 273 heads will have non hardened seats so check the seats.

Magnums would do the same and deliver more power imho.
 
needsaresto said:
I think you will need a 273 intake as well. The bolt hole angles are different. Also the 273 heads will have non hardened seats so check the seats.

Magnums would do the same and deliver more power imho.
Click to expand...

64 AND 65 were the only ones with a different angle on the intake bolts. The later models will interchange with most SB intakes.
 
SGBARRACUDA said:
64 AND 65 were the only ones with a different angle on the intake bolts. The later models will interchange with most SB intakes.
Click to expand...

This is correct. You can tell what heads you have by the intake bolt size. "64"-"65" use a 5/16 inch bolt and take a half inch socket. Normal LA heads, "66" and up use a 3/8 inch bolt and take a 9/16 socket. What are the last 3 casting numbers? Sounds like you should have a good combination.
 
Everyone has great information - I would like to ask a couple of more questions.

The casting number is 2658920-5.

The heads come with a valve train - solid lifters and adjustable push rods. (I know I should replace the tappers, when I change the cam)

I also have the hydraulic set that is currently in the 318.

The cam is Mopar part number P4286630 - 280 duration, 60 overlap, .474 design lift @value, 106 Rec. Install Center line and Zero Valve Lash Intake Exhaust.

I know I will be using the 318 and the cam.

What heads to use??? and why?? What valve train to use, and why?? with the 318 and this cam??

I am very interested in hearing what everyone thinks, please give me the why, so I can understand, what you are thinking.

Thanks,

Sam
 
I would use the 920 heads after a good valve job and the exhaust seats replaced to stand up to the beating they take from unleaded gas. With the closed combustion chambers you will raise the compression ratio as the 318 pistons are pretty low in the cylinders at TDC. That cam will be ok with this combo. Use the adjustable 273 rockers and push rods.
 
Ported 318 heads milled for compresion of at least 9.5-1 (Unless you allready have a high compresion slug within) and stainless steel Ferra racing valves, 1.88/1.60 (360 valves) port matched to the intake. This will give a max velocity intake charge. Or the same for the 273 heads. There smaller chamber is a plus in the compresion deptment.

On the cheap, MP HD Hyd. rockers are OE rockers, but new. There ratio isn't all that, so, if need be a must to have the lift, Ya might as well go with something like a Hugesengines or Comp cams roller rocker set up and custom length Pushrods on a chrome hardened shaft with bitchin billet hold downs. But thats money.
 
68dart-sb said:
Everyone has great information - I would like to ask a couple of more questions.

The casting number is 2658920-5.

The heads come with a valve train - solid lifters and adjustable push rods. (I know I should replace the tappers, when I change the cam)

I also have the hydraulic set that is currently in the 318.

The cam is Mopar part number P4286630 - 280 duration, 60 overlap, .474 design lift @value, 106 Rec. Install Center line and Zero Valve Lash Intake Exhaust.

I know I will be using the 318 and the cam.

What heads to use??? and why?? What valve train to use, and why?? with the 318 and this cam??

I am very interested in hearing what everyone thinks, please give me the why, so I can understand, what you are thinking.

Thanks,

Sam
Click to expand...
If the "67" 273 heads are done, they sound like you are good to go.? Nice cam. The 318 valvetrain is simpler while the 273 valvetrain is adjustable and will require 340 6 pack pushrods. I like solid cams myself but I would not change what you have since it is already installed. Right now you are only looking at a head swap? You can run the 318 valvetrain now and try the 273 in the future.
 
66fs said:
If the "67" 273 heads are done, they sound like you are good to go.? Nice cam. The 318 valvetrain is simpler while the 273 valvetrain is adjustable and will require 340 6 pack pushrods. I like solid cams myself but I would not change what you have since it is already installed. Right now you are only looking at a head swap? You can run the 318 valvetrain now and try the 273 in the future.
Click to expand...

340 Six Pack pushrods? No you can use the 273 pushrods. Also the 1.5 non adjustables are any where from 1.20-1.50 actual ratio!
 
Any thoughts on using the above cam in a 318, with 273 heads and the mechanical rockers???

I am new at this I am looking for some direction.

Thanks, Sam
 
comp has 2 entry level/adj stock replacement pushrods, 1 for the direct replacement of 273 solid cam Pr's, and 1 that says 'with 3 2brls carbs' which are shorter than the 273' pr's

However when we tried the '6 pak' part # PR's, they were still too long on the 360 we were working on that used a mp.455 lift hyd w/273 adj/pushrods.
I can't remember what length we ended up with, it was 2 yrs ago.

fwiw.
 
The 273 heads will raise compression on your 318, which is a good thing. However, the ports and valves are still the same size, so you won't make a heck of a lot more power, especially at higher RPM. But on a street engine, they will be just fine. And, it's a no-brainer if you have a set ready to go.

As for the cam, it would depend a lot on the rest of your setup, especially gears and converter. Personally, I would go a step milder. The Comp XE268, milder Voodoo, or even Hughes 1523 would be fine. Isky still makes a mild mechanical (E4) which I'm seriously considering for my 318 build.
 
66fs said:
I do not think you can use mechanical pushrods with the hydraulic cam and the 273 mechanical rockers.
Click to expand...

Absolutely they work. Being 55 I've done that years ago when I was to broke to pay attention. The rockers do not oil thru the push rods. They oil thru a hole in the head to the rocker shaft. The 318 and 273 PR on the lifter end are both ball ends. The difference is on the rocker end the 273 being a cup and the 318 is a ball.
 
273 mechanical push rods are too short to use on a hydraulic cam.... even with the adjustables. mine were
 
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