what heads to run on a 273

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1wild&crazyguy can i ask you something while we are on this subject and i think you are the person to ask seeing you have played around and dissected these heads, i have a 273 commando 4 v and i wanted to know if it would be any benefit in increasing exhaust valve size from 150-160 as they say it would increase intake flow because of the larger ex valve would this be correct as some say there is some benefits HP gains?Ive read some have to bore them right out as the valves might clip the edge of the cylinders and some say you need to fly cut the edges to provide sufficient clearance.Im undecided as to leave the factory cam or step up to the comp cams 270s which is the largest to go without changing my TQ converter. Cam part number 20-246-4 which is a solid.I have the LD4B manifold and was looking at purchasing a set of flow tech ceramic coated headers, updating the carby to a edelbrock 600 vac sec if i go with the cam or a 500cfm if i leave the factory cam. Should i just leave the heads alone and just go with the cam and carb or go with some slight massaging on the ports as the car will be used as a cruiser but will cope a banging from time to time.Cheers
 
What's the rest of his combo? He will need some pretty good heads to make that cam work. And the stock springs won't work with that cam either. Time to back up and regroup. Not saying that a radical 273 is impossible to build but you can't just throw parts together to make it happen. tmm
 
1wild&crazyguy said:
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.


I have a question since you have done a bunch of research on different small block heads. A couple of years ago I had a 273 HiPo short block and I set a pair of the magnum heads on it to see if the pistons would clear. They cleared(I dont know how much because I didnt clay check them) but at the time I was thinking that with a stock magnums flow numbers and the smaller valves that they have maybe I could bolt a set on a 273 and make some power with them. Have you ever seen anybody try this? Would the stock magnum valves clear the small bores of the 273? (I know when we used to put 340 heads on we would notch the bores) I was always curious if this combe would yield significant power gain oor if they would be too much. I sold my short block so I never got to try this combo although I have spent time wondering.
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I havent messed with the lil 273, though it's a small bore 318/340..it's too small for my interest/$$$$

Just mic across the valves if you have the heads...and there will be ur answer.

the magnum stuff cc'd around 153.
stock la 360 1.88 valve heads cc'd around 160, with the 2.02 at 155cc.....the bigger 2.02 factory tulip valve eats up a lot of bowl volume...'so much for the too much intake port bs'...lol...and thats the only explanation i have for the funny diff between them, both were bone stock 915 castings, stock valves. fwiw

If you 'read' aound mopars press releases...u get impression there are 2 iff mag heads, though some say they are ''1 size fits all''....

Something to read, and it coincides with my findings on them

http://www.moparchat.com/forums/showthread.php?s=&threadid=60387

thats mopar and herb mcandless info

now if you check my ''360 head trip'' thread...

http://www.forabodiesonly.com/mopar/showthread.php?t=145748

you can see the actual flow numbers of the 1.88 974' casting head....and then even some ported numbers. They are about as good magnum stuff, performance valve job on them both would make them nearly identical....and i think the diff is mainly from the 'skinny valve stem'....and remember....the PORT controls velocity, not the valve.
 
67 gt said:
1wild&crazyguy can i ask you something while we are on this subject and i think you are the person to ask seeing you have played around and dissected these heads, i have a 273 commando 4 v and i wanted to know if it would be any benefit in increasing exhaust valve size from 150-160 as they say it would increase intake flow because of the larger ex valve would this be correct as some say there is some benefits HP gains?Ive read some have to bore them right out as the valves might clip the edge of the cylinders and some say you need to fly cut the edges to provide sufficient clearance.Im undecided as to leave the factory cam or step up to the comp cams 270s which is the largest to go without changing my TQ converter. Cam part number 20-246-4 which is a solid.I have the LD4B manifold and was looking at purchasing a set of flow tech ceramic coated headers, updating the carby to a edelbrock 600 vac sec if i go with the cam or a 500cfm if i leave the factory cam. Should i just leave the heads alone and just go with the cam and carb or go with some slight massaging on the ports as the car will be used as a cruiser but will cope a banging from time to time.Cheers
Click to expand...


the valves dont really need to be bigger, when i port them , they go into the 177 cfm range w/1.50 exh valve.
if you mean to say scavenge....i dont think you need anymore...or in theory, u may be pulling raw fuel right out the exh port depending on cam choice.

Honestly....i wish that chrysler would have cast the same exhaust floor shape into the 340/360 heads....for if they did, there would be none left...for everyone would be using them instead of the aftermarket stuff that in reality flows only a hair better than 2.02 stock and needs attention to get any really good numbers. Even the eddelbrock & RHS stuff, it still ootb only go's in the 240's range and needs either port work or new bigger valves and accompanying multi angle valve job to be in what i consider 'good numbers'...number worth the 1400+ plus they go for.

jmo
 
Personal experience-
'85 302 2-bbl vs '65 273 2-bbl heads, on a 273:
273 heads have larger ports by a substantial margin
302 heads have slightly smaller chambers by about 2cc
273's made better high end power, sluggish below 2k rpm
302's made better low end torque and more responsive, less top end rush

302's need a lot of porting to get the potential people talk about.
 
toolmanmike said:
What's the rest of his combo? He will need some pretty good heads to make that cam work. And the stock springs won't work with that cam either. Time to back up and regroup. Not saying that a radical 273 is impossible to build but you can't just throw parts together to make it happen. tmm
Click to expand...


toolmanmike with the comp cam i was going to fit the comp cams dual valve spring retainers 1.437 #740-16 and comp cams 1.494 single w/damper valve springs 901-16 , COMP CHRYSLER 2 & 4-GROOVE 10° MACHINED SUPER VALVE LOCKS... and for the cam i dont think the 270 MAGNUM SOLID CAM is too aggressive as the operating range is from 1800-5800 DURATION - ADV IN 270 EX 270 @.050 IN 224 EX 224 VALVE LIFT @ 1.5.1 IN .468 EX .468 AND LOBE SEP ANGLE 110.
'


http://www.ebay.com.au/itm/140677774767?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


http://www.ebay.com.au/itm/200638428992?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


http://www.ebay.com.au/itm/140691688614?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 
I went back and looked at the specs on your cam. I must have been looking at the the wrong cam number on the Comp website when I responded earlier. That should work good and sound good with a bit of lope at idle. It's 10 deg bigger duration than my Isky E-4 and .043 more lift. I wonder if anyone here has used this cam in a 273. It would be fun to hear what it sounds like. Mike
 
toolmanmike as i was looking at your engine rebuild i noticed the windage tray is the same as i was thinking of getting,Is that the Milodon? but what i wanted to ask was the windage tray install kit, was it kit 81151 for the 340- 360 or the 81182 318?.Reason asking is im finding it difficult to track down the 81182 318 install kit thats if i need it and can use the other.Cheers
 
65TerrorCuda said:
Personal experience-
'85 302 2-bbl vs '65 273 2-bbl heads, on a 273:
273 heads have larger ports by a substantial margin
302 heads have slightly smaller chambers by about 2cc
273's made better high end power, sluggish below 2k rpm
302's made better low end torque and more responsive, less top end rush

302's need a lot of porting to get the potential people talk about.
Click to expand...

You havent measured the port volume...its no diff. ill measure and post pics, that way everyone will have factual info and this can be put to rest.......cause 273 2 or 4 brl have the same port as any 318 non police head..
 
67 gt said:
toolmanmike as i was looking at your engine rebuild i noticed the windage tray is the same as i was thinking of getting,Is that the Milodon? but what i wanted to ask was the windage tray install kit, was it kit 81151 for the 340- 360 or the 81182 318?.Reason asking is im finding it difficult to track down the 81182 318 install kit thats if i need it and can use the other.Cheers
Click to expand...
Keep in mind that a factory 318/340 windage tray won't fit on a 360 or a stroker without some modification. Some of the aftermarket ones I've seen that were universal, didn't fit very tight against the crank. Probably better than none at all but one made for the engine/stroke will work better.
 
I was referring to the port cross section only. And in that capacity, the exhaust port is where I saw the biggest difference. The pushrod passage on the 302 intrudes more on the intake side and there is a pronounced hump in the exhaust port floor compared to the 273 heads.
Then again, I haven't looked at a stock set of 273 ports in probably a decade
 

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I made a big mistake one time back in the early days and put "x' heads on a 1965 273 .If you do not want any compression in a hurry , don,t do it .The block had to be notched and i did not read enough , and was very young at the time .
 
Youngthrill said:
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
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I have been running 78 360 swirl port ‍♀️ cop car heads on my 273 problly hard to find
 
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