273 Build

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toolmanmike said:
Woah! Nice hot rod!
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Work has FINALLY started back up again. The guy, Bob, who has done most all the work on this car, well in the past 7 years, his wife had breast cancer, she also had to have her one knee replaced, Bob had open heart surgery, then major kidney problems, then he had/has depression, lost alot of strength, then he fell in his garage, and really messed up his right shoulder, and has finally admitted to himself that he needs help in finishing this project. The good news is, is that work has started, and it's a good possibility that it will be finished for this Summer events. It's nice to hear of progress. It's just too bad, that this is a couple of years too late for Olga to see and ride in this car. It was being built to show her, just what it takes to make one of these streetrods.
 
BTW.... on the subject of 273 blocks.... I just noticed yesterday that our '68 273 block has the chamfers on the tops of the lifter bores like are on the 340's. Never noticed this before as I was not expecting it.

TMM, do your 273 blocks have the lifter bore chamfers? Just curious to see how extensive this is.
 
Measured one chamber on the 302's and the 920 heads that have a valve job, hard seats, stock valves and of course the typical .003-.005 milled off.
65.5
Safe to say they were around 66 or so cc's from the factory.
The 302's are still 64cc.
 
nm9stheham said:
BTW.... on the subject of 273 blocks.... I just noticed yesterday that our '68 273 block has the chamfers on the tops of the lifter bores like are on the 340's. Never noticed this before as I was not expecting it.

TMM, do your 273 blocks have the lifter bore chamfers? Just curious to see how extensive this is.
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Don't see them on my 66 block. these are the closest photos I have.

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MOPAROFFICIAL said:
Measured one chamber on the 302's and the 920 heads that have a valve job, hard seats, stock valves and of course the typical .003-.005 milled off.
65.5
Safe to say they were around 66 or so cc's from the factory.
The 302's are still 64cc.
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It looks like it's best to use the larger chamber numbers of those posted. I don't know where they came up with those 57cc chambers!
 
Their numbers are minimum to which you can take a chamber for legal competition in certain classes. The leeway allowed is to be bigger than this minimum for any given head. Each head casting and year has a minimum spec.

Check the link and pick a make/year and look it will list all engines for each make/year with specs... It will all make sense.
 
MOPAROFFICIAL said:
675 ,315,178 and 920 all flow pretty much the same, talking 2 cfm diff. Chamber shrouds more on the closed versions..as expected. I can flow the 302's i have again...but nothing makes me believe they flow any different.
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The funny thing about the early 273 heads is they jump + 9 cfm (178 cfm) at .400 lift compared to 675 (169 cfm) using your numbers and others. Then they drop back down to about equal (174 cfm) with 675 (171 cfm) heads at .500 lift.
 
The only explanation i can offer you is the 920 has had a valve job, seats/faces ground while the 675 had only a bead blasted factory valve job...and thats the diff.
With the exception of .400 lift, the numbers are very close everywhere else. If i were to find that same cfm difference from .100-.300..then id have to say there is an advantage using this casting...but its like the 270cfm @.500 lift head vs the 300 cfm @.700 'with only 240@.500' and the cam used is .520
I like the 920, id use it, and its 2+ cc smaller chamber 66cc than a 675 is @68cc. Do i have a preference? Well... For what i would do with them, not really.
 
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66fs said:
The funny thing about the early 273 heads is they jump + 9 cfm (178 cfm) at .400 lift compared to 675 (169 cfm) using your numbers and others. Then they drop back down to about equal (174 cfm) with 675 (171 cfm) heads at .500 lift.
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Almost like they planned it that way.

Basic 273 cam specs:

1965 180 hp 2 barrel .395 /.405 lift 240°/ 240° duration
1965 235 hp 4 barrel .415 /.425 lift 248°/ 248° duration
1966 235 hp 4 barrel .420 /.430 lift 248°/ 248° duration
 
So many small but significant factors when comparing.
Different valve jobs
Clean and sloppy casting-core shift & flash
Different flowbench

The last should be close if the testing procedure is correct, accurate and repeatable.

Fwiw i've found that all of Chrysler's wedge heads bump around .400-.450 lift.
 
MOPAROFFICIAL said:
So many small but significant factors when comparing.
Different valve jobs
Clean and sloppy casting-core shift & flash
Different flowbench

The last should be close if the testing procedure is correct, accurate and repeatable.

Fwiw i've found that all of Chrysler's wedge heads bump around .400-.450 lift.
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Talk about core shift, look at the lifter bores in my 273 above (post 254)
 
Dug out my 302 heads...
Damn, thin decks, insane amount of intake valve shrouding, like more than ive ever seen on any 273/318 head. What kind of valve, incolnal or sodium? Lol honestly...
Look at the big peak between the valves... that helps huh? They go on the bench soon and we will see what head is king of the 318 heads. Btw more like butt shaped chamber.lol and by the time you relieve it, shape it... its a while lot bigger than the factory 64cc it is now.

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MOPAROFFICIAL said:
Dug out my 302 heads...
Damn, thin decks, insane amount of intake valve shrouding, like more than ive ever seen on any 273/318 head. What kind of valve, incolnal or sodium? Lol honestly...
Look at the big peak between the valves... that helps huh? They go on the bench soon and we will see what head is king of the 318 heads. Btw more like butt shaped chamber.lol and by the time you relieve it, shape it... its a while lot bigger than the factory 64cc it is now.

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Very observant.
 
We need to remember, I started this thread describing my 273 build. Small cube, small bore, small cam, small port v8. It doesn't need too much to make it happy.
 
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