273 heads on 318

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RobW75

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Hey all, think this is my first new post! Just a quick question that I couldn't track down an answer to in old posts. I've seen some of the 318 build ups with people putting 273 heads on a 318 and was wondering what that gains you, besides the adjustable rockers? Thanks, Rob
 
with my little knowledge is SB i think the 273 has a closed chamber for higher compression.

but the 273 heads have smaller valves and ports which would be fine for a very low RPM engine but not good for anything other than towing...
 
and the adj rockers will fit any other the stock heads other than the T/A heads
 
I'm totally ashamed to admit this, but when I "dumped" my '70 RR it had a 360 short block with 273 commando heads and intake. The damn thing was a torque monster all the way up to about 4500 RPM (memory is foggy, this was late 70's early 80?) and then you might just as well shift or get out, because it was NOT gonna run better above that

You could mash on the thing at 55 and the torque was just incredible.

The heads and intake came off an engine that had froze and broke, and no, I was not responsible for that little detail.

The idiot kid that ended up with my old car must have gotten into a DUI/ hit/ run situation, because the car simply disappeared, and his brothers would never admit where it went, other than "we think it's over a cliff in the hills."

He also did something I never could do---got one wheel in the mud one night, and completely destroyed the clutches in the Dana
 
Make sure you get the 66-67 273 heads, the 64-65s have a different bolt angle for the intake manifold.
 
273/318 heads are basically the same, same valve and port size but some are open and closed chambers 64/65/66 273 heads are closed chambers 64/65 have a different intake bolt size and angle but there is solutions to bolt on a later intake. The 67-85ish 273/318 heads are open chamber and 85-91 318 (302) heads are closed chamber also and Magnum 5.2/5.9 are the only other closed chamber heads. Closed chambers will help raise your CR which all 318 could use.
 
Putting closed chamber 273 (66 & 67) down on a 318 works as a compression boost, do a .030 cut and you'll fall into about a 9.2 to 9.4 comp ratio, so long as you use a thin gasket. Add 1.88, 1.6 valves, cam and intake and you'll have a snappy "teen"; some may think it's a 340/360 cuz they'll never believe a "Teen" could beat them.
 
Thanks for all the info! The 273 came out of my '67 Fastback and I was just curious whether there was the possibility of using some parts off of it. The original Commando 4 BBL was long gone when I got the car, this is a 2BBl version so I wasn't too concerned with keeping it. Thanks again!
Rob
 
Not the original 273, but if the right year could give you three nice things for a 318 build, adjustable rockers, steel crank, and closed chamber heads plus lighter rods.
 
The casting number on the 1966-1967 273 head is 2658920. They have either 1.78 intake and 1.50 exhaust valves --- or --- 1.87 intake and 1.50 exhaust valves.
 
So if these heads turned out to be decent, what's the solution for an intake? If the 273/318 heads are basically the same then will any 4BBL intake for a 318 work, aftermarket or otherwise? Sorry these are pretty rookie questions, I'm a bodyman not an engine builder! (Yet?!)
 
You have several choices: Eddy Performer, Eddy LD4B, Holley Street dominator.

The Holley and the LD4B are out of production, so you'll only find them used.

Many will say that the LD4B is the only one to buy; don't know never used one.

A decade ago I did a 318 with 66 273 heads in my Barracuda, used a Performer intake, I thought it worked well, went 13.92 in the 1/4 with an unsorted combination.

I am a firm believer in using what you've got and what you can afford; some differences are almost too close to measure.
 
This is what I am running in my dart. I took the 273 heads, ported, and gasket matched them. Had 1.88 and 1.60 valves put in them with a great valve job. Added the Edelbrock RPM springs. Had them milled just a little. Used the thin MrGasket head gaskets. Put them on a freshened up 1971 318 short block. With a deep pan, windage tray, and a Comp Cams 223 grind cam.

I did the math and my compression should be 9.5 to 9.7 to 1.

As for the intake I am running a old Eddelbrock LD4B that has been gasket matched, and had the center divider notched. Toped with a tricked out Holley Street Avenger 670.

Runs great. Starts to fall off about 5,500 but I still have not had the $$$ for headers yet.


Now all that said. If I were building a totally new from the ground up 318, I would use dome pistons and run a set of 340 or 360 heads (my next engine). But on a budget this combo works really well!
 
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