273 warm up!

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66fs said:
You guys miss the intent of the OP. You are rebuilding the whole engine, when he has a rebuilt engine to begin with. He just wants a little more power. A cam, springs and a 4 barrel carb would make it sweet. For some reason he is AWOL... I think I should write a corollary to RRR guide to Hot Rodding Bliss.
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nm9stheham said:
Yet the OP asks about swapping in high compression 4 BBL 273 pistons. So he appeared ready to tear it down to a pretty extensive degree.

And he asked for better performance.... so is that at the low end, with more torque (higher CR) or at the high end for more HP (bigger cam).....?? Inquring minds want to know....
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nm9stheham said:
Yet the OP asks about swapping in high compression 4 BBL 273 pistons. So he appeared ready to tear it down to a pretty extensive degree.

And he asked for better performance.... so is that at the low end, with more torque (higher CR) or at the high end for more HP (bigger cam).....?? Inquring minds want to know....
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I originaly posted to get some thoughts and ideas from guys with experience with these motors. And I sure have a lot more options than I thought,So thanks for everyones input! My intent is to drive this car as often as possible in the summer (I am in Wisconsin) I may take a couple passes at the local drag strip, but it is not my sole intent at all. the motor lacks horsepower for todays traffic. Getting any kind of wheel spin would be nice along with a little bit of cam and exhaust rumble. A compression check tells us the motor is good there. from the info I've gathered since the begining of my post there appears to be several things i can do without going through the bottom end and upping the compression with new pistons. I hope I can be satisfied with getting some horse power with some bolt ons and some tuning because after that I guess its "pull the motor time" and I really only want to do this once. After that is done it will be time for some body work and paint!
 
dennis degeneffe said:
That's right. I did buy the correct intake for this motor. But, when I had the heads done( burned valve ) that is when I should have gotten a nice set of 318 heads and then just about any sbm intake would have bolted up to that. It would have opened up my options. I suppose I still could go that route. At the time I was thinking of just getting it running good then in a few years go to a 383 I have waiting for a build. However plans change and I think I want to have some fun with the 273!
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Good thing you didn't get those 318 heads. Unless they are are mid to late 80's # 302 castings, all 318 heads have a open combustion chamber which lowers your compression even more.
 
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Wheel spin is more associated with torque and low end grunt... that is compression ratio related. And your intended use typically is better met (by most folks) with a wider torque band and lower end RPM performance....compression ratio again. So you were on track to begin with.

What compression readings did you actually get?

One other thing to help low RPM torque is to advance the cam timing.

BTW, toolmanmike (or memike? ONE of those Mike guys!) has a lot of good documentation on the pistons. The EGGE 4 BBL L2222 replacements give the best CR versus the Kanters IIRC from Mike's work. (Correct me please if I am wrong...)

A local machine shop here also has worked over some old Ford 256 8 cylinder pistons for use in the 273; bore is identical and the 1.857 compression height means you can get a zero deck or above deck installation. Eyebrows are machined and the smaller pin diameter is used by bushing the Mopar rods' small ends. You end with a true 9.3 SCR with 57 cc chambers and the proper head gaskets IF the pistons heads are left flat; you can get even higher if you mill the piston tops with a dome left in the middle. SO a LOT of work, but you can push the Static CR on up a bit higher than the (actual) original CR with the Commando pop-up pistons. (And I don't know the end piston/pin weight to tell you what happens with the balance.)

The 3.625" bore diameter and pin height and compression height make the choices in other pistons very limited.
 
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nm9stheham said:
Wheel spin is more associated with torque and low end grunt... that is compression ratio related. And your intended use typically is better met (by most folks) with a wider torque band and lower end RPM performance....compression ratio again. So you were on track to begin with.

What compression readings did you actually get?

One other thing to help low RPM torque is to advance the cam timing.

BTW, toolmanmike (or memike? ONE of those Mike guys!) has a lot of good documentation on the pistons. The EGGE 4 BBL L2222 replacements give the best CR versus the Kanters IIRC from Mike's work. (Correct me please if I am wrong...)

A local machine shop here also has worked over some old Ford 256 8 cylinder pistons for use in the 273; bore is identical and the 1.857 compression height means you can get a zero deck or above deck installation. Eyebrows are machined and the smaller pin diameter is used by bushing the Mopar rods' small ends. You end with a true 9.3 SCR with 57 cc chambers and the proper head gaskets IF the pistons heads are left flat; you can get even higher if you mill the piston tops with a dome left in the middle. SO a LOT of work,but you can push the Static CR on up a bit higher than the (actual) original CR. (And I don't know the end piston/pin weight to tell you what happens with the balance.)

The 3.625" bore diameter and pin height and compression height make the choices in other pistons very limited.
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I don't recall the compression figures...they were within factory specs before the heads were redone, except for number 3 cylinder, which had a burned valve and a bent push rod. I will have to recheck the compression when I get the car out of storeage in a week or two, and recheck it with the reconditioned heads. You and Mike and Several other guys here gave Me a lot of info and plenty of options to consider. It just dawned on me that I never mentioned this car is an automatic with I believe 2:72 gears in the rear end.
This is a great website, thanks guys!
 
toolmanmike said:
Too much cam for a 2 barrel based 273.
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Toolman, I would like your opinion. I am looking to wake my Commando up a bit. Headers, performer intake and a 625 Carter are in the mix. My questions is the cam. Your comments got me thinking. I want a modern hydraulic vs the stock solid (less adjustments and modern tech). The heads are gasket ported to the largenport gasket and cleaned up in the bowl. What would you reccomend for a cam to get me 1 hp per cube and some better drivability?
 
drewmac said:
Toolman, I would like your opinion. I am looking to wake my Commando up a bit. Headers, performer intake and a 625 Carter are in the mix. My questions is the cam. Your comments got me thinking. I want a modern hydraulic vs the stock solid (less adjustments and modern tech). The heads are gasket ported to the largenport gasket and cleaned up in the bowl. What would you reccomend for a cam to get me 1 hp per cube and some better drivability?
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Wake up a bit and 1 hp/cubic inch really don't belong in the same sentence. You need more compression to start with. Probably a bigger carb too. I would keep a solid lifter cam too. You could start with the recipe that the 66 D Darts used. They were rated at 275 horse. They had 10.5/1 compression., (Probably more if the truth be known) , headers, 700 cfm Holley, open plenum intake, a .495/.505 284 degree solid lifter cam with 300# open pressure Springs. They used a 4 speed and 486 rear gear. The build was not a streeter by any means. With your low compression 2 barrel, it is so easy to over cam it. It would be best to just stick with some tried and true bolt ons.
 
toolmanmike said:
Wake up a bit and 1 hp/cubic inch really don't belong in the same sentence. You need more compression to start with. Probably a bigger carb too. I would keep a solid lifter cam too. You could start with the recipe that the 66 D Darts used. They were rated at 275 horse. They had 10.5/1 compression., (Probably more if the truth be known) , headers, 700 cfm Holley, open plenum intake, a .495/.505 284 degree solid lifter cam with 300# open pressure Springs. They used a 4 speed and 486 rear gear. The build was not a streeter by any means. With your low compression 2 barrel, it is so easy to over cam it. It would be best to just stick with some tried and true bolt ons.
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I am starting with a real '67 Commando so I have the solid already and the better compression pistons. I will look at the carb and bigger solid. Thanks!
 
drewmac said:
I am starting with a real '67 Commando so I have the solid already and the better compression pistons. I will look at the carb and bigger solid. Thanks!
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Do you have a automatic or a stick? It's easy to over cam the 273's and then you need a higher stall converter and rear gears to make it work.
 
toolmanmike said:
Good thing you didn't get those 318 heads. Unless they are are mid to late 80's # 302 castings, all 318 heads have a open combustion chamber which lowers your compression even more.
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Hi again toolman mike. so if i find a set of 302 heads, will that be an improvement...will it up my compression? Then I'll have to get a new intake,( and carb) which I am ok with.
 
The 302's are closed chamber jusy like the 273 heads so it won't raise your compression. They do flow better than the 273 heads and they do have hardened valve seats for unleaded gas.
 
Problem is a 273 needs to rev to make any real power. And to make use of that power a lot of gears and stall is needed. And with the small bore your stuck with stock valve size.
Heads are the main limit to power potential so porting or notching the the bores for magnum heads would open up the engines capability. And low CR is gonna limit cam choice.

So your choices are just go 4bbl and a mild cam and duels and maybe some gears. And live with a little power boost . Or invest in total redesign of your powertrain at which point your better off going with a different engine.
 
For the Op's goal, I think I would just recommend to stick with a looser TC and more gear, and see how that goes. These are tried and true performance upgrades that are gonna be needed later anyway if he decides to cam it. And who knows; with 40% or maybe 50% more "hit", OP might be happy. This is cheap and easy. This will be the biggest improvement.
Later, headers and a hi-flo exhaust will pave the way for a 4bbl.
Then a cam.
And finally a boost in compression, and another matching cam.
With each additional stage bringing in a bit more torque, then power and finally the entire power band gets shifted.
And each stage costing progressively more money.

If you start with a cam, and 4bbl, and nothing else;OP will be in for a nasty surprise.And now he may have spent his wad.

And I know nobody wants to say it but a stock 318 2bbl was rated 230hp(crank) in 60s/70s, and a 5.2Magnum was rated 230hp (in chassis),back in the 90s. These are drop-ins, almost no mods required. The Magnum is an excellent builder platform,with about 95hp and tons more torque than the 2bbl-273, and is by far, the best bang for the budget-buck.
[FOR SALE] - 318 complete
 
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It sounds like the gains of the things mentioned above will not break the bank but i may not be very satisfied, so in the end they are not cost effective. I think I'll be putting more effort in finding a 340 or 360.
 
66fs said:
Try to find an original AFB, otherwise have the intake bores opened up for a 500 cfm Edelbrock.
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I put a 500 Eddy on a factory '66 manifold without any intake bore problem. Am I missing something here?
 
dennis degeneffe said:
It sounds like the gains of the things mentioned above will not break the bank but i may not be very satisfied, so in the end they are not cost effective. I think I'll be putting more effort in finding a 340 or 360.
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I'd just get a running magnum regrind the cam add airgap and headers.
 
Here's how I did mine. It runs wicked good.

273 Commando - 1965
Heads: Gasket matched and ported
Cam: Solid lifter Comp Cams Magnum 282S - 282/282 Lift 495/495
Beehive Springs
Edelbrock D4B intake / Street Demon 625 carb
PerTronix Ignitor II Billet distributer & Flame Thrower coil
Hooker Headers
2.5" Dual Exhaust / Super 44 Flowmaster
727 auto / Shift Kit
10" Turbo Action Street "S-800" converter
8 3/4 - 3.55 - SureGrip

Video proof :)
 
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