what heads to run on a 273

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Youngthrill

69 GT
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so i had my block boiled and board out .30 over..stock crank and using
egge dome pistons....

what can i do with the heads? i need bigger ports..does anyone know of a good flowing head out there for this little beast?..

i would prefer to use my the heads and cut cost but whats the biggest valve i can run? what to port them out to?do 318 heads fit on these 273??

thanks fabo!!:D
 
A set of 302 casting heads would do wonders for that motor.
 
a little more info im a bit new to this mopar stuff..were can i buy some or what im a looking for when i ask?..mopar is very addictive!! im glad im still able to drive my 69 gt while this block sits on the stand want to finish sooner than later..any out there with some aggresive 273 combos..help and input are welcomed !!302 im interested
 
302 casting heads are found on late 80s 318s. They feature a swirl port design and just the right size valves for your engine. I'd also recommend an Edelbrock preformer intake (not the rpm version) for your car. If you do a quick search using the search feature on the site, you'll find tons of info on the 302 heads.
Also the 273 and to an extent the 318 are more costly to build, it's cheaper to throw a 360 or stroke it to a 408 less and make more power doing it.
Not that I'm trying to sway you against the 273 but other will throw that info out there.
 
Yep, 70 Duster is correct. 302 casting heads are a good choice for the small bore 273. They have a bit larger ports that flow good and have a heart shaped combustion chamber that is relatively the same size as the stock 273 heads so you won't loose compression. They also have hardened seats so they're unleaded gas friendly. Mopar used them in the mid to late 80's 318's found in Diplomats and Le Barons (M Bodies) (from Mopar Muscle article)

Chrysler's small-block cylinder head design changed very little until 1987 when the 302 casting (last three digits of the casting number), commonly known as the swirl port, was introduced. While the 302 casting, as well as the later 308 casting, were most commonly found on low-performance 318s, they shouldn't be overlooked for a performance build. Even with small 1.75-inch intake and 1.50-inch exhaust valves, the design of this head's heart-shaped quench-style combustion chamber makes it a good choice for mild to moderate performance. An engine with these heads in stock form will outperform an engine with stock X or J castings simply due to the improved combustion chamber design. Additionally, these heads have hardened valve seats, which make them compatible with unleaded fuel. The swirl port heads were utilized through 1991 (302 casting) and 1992 (308 casting) and respond well to port and bowl work, offering better power potential than all of the earlier small-block heads. Another nice feature of these heads is they utilize valvetrain and intake manifolds common to early small-blocks, so parts are readily available. Simply bolt these heads to your small-block and enjoy the extra power they provide.

Magnum Heads



Read more: http://www.moparmusclemagazine.com/...opar_cylinder_head/viewall.html#ixzz1l8b5PH2l
 

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If you want to work with your 273 heads, they respond to a bit of clean up and porting. I had my original heads done and they turned out good. You can see them by clicking on the link below. I will say the 302 castings are a better head without modifications than the stockers. Make sure you use a thinner head gasket so you don't loose compression. I don't have that info handy but I think I mentioned it in my thread. Cometic multi layer steel gaskets are the best and If I were to do it over I would have some made. Keep us posted on your progress. toolmanmike


Here's my stock heads after a little clean up.
 

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I've always thought stock Magnum heads would work well on a 273, but not sure if they'll clear domed pistons.
 
so i found a set of 4323302 heads full stock rebuild for 500 bucks...im picking up this weekend..just want to double check that this is the ones i want...so question now when i look for a manifold ill be looking for a 88-91 318 manifold??want to make sure befor i spend $500 bucks....thanks again fabo!!

also will those stock springs work with a comp cam 20-231-4..or im i going to have to get beefyer springs
 
...............If ur domed piston is above the deck, 302s wont work unless u get a pretty thick head gasket.........i'd be doing some more checking 1st....any 67 up LA intake will work.....kim.............
 
Youngthrill said:
so i found a set of 4323302 heads full stock rebuild for 500 bucks...im picking up this weekend..just want to double check that this is the ones i want...so question now when i look for a manifold ill be looking for a 88-91 318 manifold??want to make sure befor i spend $500 bucks....thanks again fabo!!

also will those stock springs work with a comp cam 20-231-4..or im i going to have to get beefyer springs
Click to expand...

What dome size? The "302" head chambers are small or also known as closed. A dome very well might have interference with them. Double check with Egge. The piston maker right? Or who ever made the slug.

As far as intakes go, there are 2 different intakes for the early engines. The 273 often takes a odd angled intake attaching bolt as well as a smaller size @ 5/16 instead of the normal 3/8.

(Unless the year of the head is different, like a newer 302 head is used of course.)

Then, any other 66 and up 318, 340/360 intake can be used.
 
If what I've read is correct... All 273 heads had the same ( heart shaped buldge ) closed chamber design wheather dome top Commando pistons or not. A different dome top piston could hit something but I dont think The Commado pistons will.
I've also read that the adjustable rodker assemnlies from the 273 heads will tranfer to those 302 castings as well.
My memory sux though so stay tuned.
 
RedFish said:
If what I've read is correct... All 273 heads had the same ( heart shaped buldge ) closed chamber design wheather dome top Commando pistons or not. A different dome top piston could hit something but I dont think The Commado pistons will.
I've also read that the adjustable rodker assemnlies from the 273 heads will tranfer to those 302 castings as well.
My memory sux though so stay tuned.
Click to expand...
You are correct. Lots of good info here. I would add that you shouldn't get carried away with bigger valves. With that small bore, you can easily shroud a bigger valve resulting in worse performance that if you kept the stock valves. Also, on the 302 head, you'll need to fill the smog port holes on the side or they will leak exhaust using the earlier manifolds.
 
pishta said:
not with domed pistons...but my choice too with flat tops...
Click to expand...
Really? the stock 273 heads were the same shape and size of combustion chamber.

(Good thing I didn't use the word "exactly" in the sentence above or I would be in trouble) LOL
 
rumblefish360 said:
What dome size? The "302" head chambers are small or also known as closed. A dome very well might have interference with them. Double check with Egge. The piston maker right? Or who ever made the slug.

As far as intakes go, there are 2 different intakes for the early engines. The 273 often takes a odd angled intake attaching bolt as well as a smaller size @ 5/16 instead of the normal 3/8.

(Unless the year of the head is different, like a newer 302 head is used of course.)

Then, any other 66 and up 318, 340/360 intake can be used.
Click to expand...

The Egge HP pistons won't give you much more than 9:1 without milling the heads and using a thin head gasket.
 
im really shocked to read what ive just read from some of you...

ALL 273/318 HEADS HAVE THE SAME PORTS
SOME ARE CLOSED CHAMBER LIKE THE EARLY 273 AND LATE 302, AND THE REST ARE OPEN CHAMBER LIKE THE 68-85 318 HEADS.

IF YOU GO FROM CLOSED CHAMBER 273 HEADS TO 302 HEADS, CONGRATULATIONS... YOU'VE JUST WASTED YOU'RE TIME AND MONEY.

A better head than all of those is the '234 casting 1967 318 truck/motor home heads, they do not have the heat cross over port in the exhaust which can hurt flow on one port in each head....though still the same intake port as the rest.

If any of you think im wrong, prove it...im calling you out.

If you want more power but dont want to use 360 heads....have a look at the 318 head porting sticky and just have the heads 'you already own' done up like those.
 
i have them all, looked at them, flowed them and cc'd them as well.
its another rumor that always gets passed around...and people believe and parrot it.
the heads all have 'swirl' so to speak.lol
after a while it wears me out to read the same rumor passed as fact.
just trying to help somebody.
 
btw, im not trying to dog anyone, just wanna know wether they are reading and repeating or wether they've had a look and actually flowed them to say.

if you put them side by side, you'll see it right off the bat.

btw, no 318 '302' ,.or any other stock 318 head , is gonna flow more air than a stock 360 head....and no way is a closed chamber alone gonna trump the 35 cfm that the 360 head has over the 318 head.

318 wether 302 or 675 flows around 175 cfm
360 small valve head, any of them..flow around 210-215 cfm

i just want people to know whats what.

Maybe IQ52 can weigh in on this?
 
btw the op can do whatever, use whichever.

if the closed chamber fits the build, i say do it...

just stating what i have found to be fact.

i really think a marketing gimmic is all it is, they were that way from the get go.

btw...do 426 hemi's 'the bad azz of all mopar' use ''swirl port technology''?

nope.lol
 
toolmanmike said:
Really? the stock 273 heads were the same shape and size of combustion chamber.
Click to expand...
Not exactly but pretty close. The only real advantage of the 302's are the hard seats, and in my experience, a little better gas mileage. If you have the 302's already, sure, use them, but you'll have to decide if it's worth the expense to buy some for those minor advantages.
 
cudamark said:
Not exactly but pretty close. The only real advantage of the 302's are the hard seats, and in my experience, a little better gas mileage. If you have the 302's already, sure, use them, but you'll have to decide if it's worth the expense to buy some for those minor advantages.
Click to expand...

Exactly. The 302 heads aren't going to make a 273 a lot stronger or faster.
If and when you tear down a 273 for rebuild, you find valves recessed into the heads or other issues, The 302 casting is the most practical way to renew the engine to at least its original specs.
 
My point exactly. The 302's are a good replacement for the old original heads. I don't think they would do wonders though. The 273 is so small that compression is more important than port flow. Granted, a bit of port work will improve performance but the little 273 can only handle so much.
 
the '64 273 head was a heart shape chamber, after that they were kinda closed but actually had a lil concave/wedge 'so to speak' to that side of the chamber.

and unless you are lower than the factory 273's 9.1 or 8.8...flow will trump the minor half a point 'if even that' that u might gain.


flame hardend seats arent as good nor do they last like a real pressed in seat.-fact
and who's to say you can find them cheap and still runable.

spending 500 bucks or more for 5 hp 'if even that' is joke.

put this in perspective.


if he's stuck with the old bolt pattern and cant find a performance intake and the heads are shot to hell.....then i can see some advantage , but only in wider parts expansion to select from.

ever hear a closed chamber actually shrouds the valve more and effects flow as well?
 
1wild&crazyguy said:
...
if you put them side by side, you'll see it right off the bat.

btw, no 318 '302' ,.or any other stock 318 head , is gonna flow more air than a stock 360 head....and no way is a closed chamber alone gonna trump the 35 cfm that the 360 head has over the 318 head.

318 wether 302 or 675 flows around 175 cfm
360 small valve head, any of them..flow around 210-215 cfm

i just want people to know whats what.

Maybe IQ52 can weigh in on this?
Click to expand...

AMEN!!

The largest intake valve I would run in a 273 is the 1.88, and then I would mock up the heads on your block and check it. I used offset dowels to locate a set of 72 340 heads on my favorite 273. I'll also add that the chamber cc's are not that far off from 340/360 to 273/318. At .040 off the block side of a 340/360 head you are down to 65 cc's.
 
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