X heads on a 273??

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4spdragtop

4spdragtop

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I was just wondering if X heads would fit/work on a 67 date code 273?? No pistions or anything yet, its a bare block...I have 2 sets of X heads and my mind was wandering.....
 
Sure you can bolt them up but you'll have to notch the block
 
The 340 x heads will work on a 273 but only with modification. The Cylinder walls will need to be fly cut from the top of block towards side to accommodate larger valves. Not sure of exact machining but 2.02 + 1.60 valves = 3.62 while the standard bore of a 273 is 3.63.(No room for error) Would think that only benefit would be in upper RPM range if you went this route & port volume would kill bottom end but sure others will chime in. Late model 318(302) heads are the cats meow for 273's IMHO.

Oldschoolcuda
 
i have stock pistons and rings came outa my 71 360and brand new arp bolts to fasten them there 4.000 or if you wait i have some used 4.040s comming they are on my sir rods when i have them changed i would have rods and pistons for your 340 now you only need a cast crank we aint makin no 500 hp engine here and those x heads have a place to be and go 1 up i have a set of 273 heads off a running motor 340 torker intake and 650 or 750 dp holly"s we need to talk my man find a little duster, dart , scamp, i got a tranny with converter pick up some cheapass headers
i got an old eletric dizzy no box call me lets deal hell i got an old cam and lifters extra set of rockers on shafts pm me hell i got an early a radiator old starter i got parts u got parts we need a solid body phuk paint
we"ll finger paint it im me i"ll shoot you my # call me lets make some smoke
 

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hope this helps a bit. Cheers
 

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1970Duster said:
The 273 bore is small, to say the least and with the x head valves (2.02/1.60) you'll hit the block with the valve do to there size.
Click to expand...

Thanks 70D, I was just thinking out loud as I have "spares"

Oldschoolcuda said:
The 340 x heads will work on a 273 but only with modification. The Cylinder walls will need to be fly cut from the top of block towards side to accommodate larger valves. Not sure of exact machining but 2.02 + 1.60 valves = 3.62 while the standard bore of a 273 is 3.63.(No room for error) Would think that only benefit would be in upper RPM range if you went this route & port volume would kill bottom end but sure others will chime in. Late model 318(302) heads are the cats meow for 273's IMHO.

Thanks OSC, there is an option...

Oldschoolcuda
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Wheels said:
hope this helps a bit. Cheers
Click to expand...

Thanks Wheels, I dont want to do anything "irreversible" to Dads 273 block....where did ya get the bulletin from??

Thanks all!
 
I love putting those heads on the 318 block but the 273 bore is so small.

Notching isn't unreversible but really would not hurt much, just lower the compression by like .1
 
Yes the would need to be notched but the big problem is the X heads big open chamber would drop your compression way too low you would need to have to custom reverse dome pistons made I was thinking of something similar for my 273 with 1.88-1.60 J heads.
 
4spdragtop said:
Thanks 70D, I was just thinking out loud as I have "spares"





Thanks Wheels, I dont want to do anything "irreversible" to Dads 273 block....where did ya get the bulletin from??

Thanks all!
Click to expand...

Glad I could help, I would look at the 302 heads first.
 
Waste of time on a street motor, 273s are WAY short on torque anyway, and those heads would kill it even worse. Now, if you wanna turn 9000+ rpm, it might work..
 
There is really no point in doing it

Why, to get more HP, well then drop in a 318 or 360 and use those X heads.

A 318 short block with 11 to 1 pistons would likely be around 10.25 with the X heads and a .050 head gasket, Fel Pro has a head gasket that was like .052 when I check mine. Forgot the part number but summit had them just a few years back.
 
4spdragtop said:
Thanks 70D, I was just thinking out loud as I have "spares"





Thanks Wheels, I dont want to do anything "irreversible" to Dads 273 block....where did ya get the bulletin from??

Thanks all!
Click to expand...

Your welcome , I have had this book since 1980 or somewhere around
then , a friend of mine gave it to me , he had just finished building an old
signet and I was building a 68 notchback at the time. I still remember
when he put it in my hands he said "read this whole book Wheels and you will be smart". Now if I could only remember what I read yesterday.LOL.
Cheers , pic of the book did not load . It is an old Direct Connection Racing Manual
printed 1976.
 
About 20 years ago "Mopar Action" did a write up of a 67(?) 273 Dart call "Darn Dart": it went 10.80's . "X" heads, TRW pop ups, MP .509 cam, I don't remember carb or intake. Yes, they twisted the liven daylights out of it, that was the point!

It was some place in the Virginia/West Virginia area.

So it's been done, boaderline practicle; just a matter of what are you trying to accomplish?
 
I've run 72 340 1.88 intake J heads on a 273 on the street. No problem with torque. Used offset dowels to center the chambers on the bores, 10.5 TRW .040 over, .040 off the heads, no bore notch. Stock 71 340 intake, cam, and carb. It did have a 4 speed and an 11 inch scalloped clutch to hold it. Easy and quick 7k redline. Breathtaking acceleration. Maybe i'll have time to put it back together someday. 2.02 would probably need the notches and I'd mock it up and double check everything.
 
replicaracer43 said:
Waste of time on a street motor, 273s are WAY short on torque anyway, and those heads would kill it even worse. Now, if you wanna turn 9000+ rpm, it might work..
Click to expand...

I have on my 273 commando ported 318 heads with 2.02/1.60 valves. I had to notch the cylinders, but it was no problem. 340S cam-shaft, dual-plane high rise intake. Edelbroock 600, HP exhaust with 2,5" x-pipe
 

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