Another 273 commando build .. This one will be a "BEAST"

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stroker402 said:
update on the remaining 6 stuck pistons . Knocked them out this morning with no issues. Check the fitted wooden block I made . It worked Great !
I cleaned them up and are now bathing in deep creep solvent. I'll soak them with solvent a couple times a day for 3 days and them start removing the rings..

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Good that you got them out. It will be interesting to see the next steps.
 
Just for curiosity, how many miles on this engine?
 
BTW, if the rings grooves are worn or have been damaged, there are 'ring spacers' that can be used to realize a repair on worn grooves. I have used them before on worn pistons to get back to 'new' spec ring side clearances.
 
update on the pistons ...........
worked on removing the rings from the ring lands . .. What a job !! got approx 10 hours in removing on the rings and cleaning the ring lands . anyway everything looks great !
Block is going to the speed shop this week to get cleaned /baked, new freeze plugs and cam bearings.

IMG_6606.JPG
 
valiantwagonguy said:
From the photos it looks like the motor could be stuck from bad gas being run thru it before it was shut down.I had this happen on my 48 Plymouth after a long storage.I was young and didn't know any better and fired it up after letting it sit for 3 years.Went back a week later and the motor was rock solid. I pulled the plugs and filled the cylinders with Marvel Mystery Oil and let it sit for a month.When I went back I put a battery to it with the plugs removed and spun it Then she ran fine. Those pistons may not be rusted in place is what I'm getting at so heat and oil may free it
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The cylinder walls look Great with no pitting . just a hone and Ball job will do it.
 
JBurch said:
The other thing you asked about is how to deal with stuck rings, I've had reasonably good luck with this method. I soaked the pistons in dip parts cleaner ( you have your Gunk, good start ) to soften/remove carbon build up, rinsed that off and then working one ring at a time, took a small ball peen hammer and lightly tapped the the ring into its groove, start at the gap and work your way around. The good sign you'll be looking for is when the portion of the ring opposite where you tapped it in will spring out.

As I said, I've had reasonable luck with this method, one ring would not give up, 2/3 of it was free around the piston, the last 1/3 just didn't want to give up; so I broke the ring and dug it out with out buggering up the groove. I reused these pistons in the first version of my "Mean Teen", went 13.92 at just a lick over 98 mph.
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The rings put up a fight for sure. they just kept breaking off in 1/2" pieces. With all the solvents I used , nothing got into the ring lands to free them up. they were dry as a bone under the rings .
 
I came across some good info about the 273 from a guy on another site ................. "DATED 2006 " ....................Quote :
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hello, I did some research on 273 . the 180 hp, has an 8.8 cr listed. according to the NHRA specs, which are provided by mopar are; deck hgt. - .011, a .028 gasket, 57.3 cc head will provide a cr of 9.5. the 4 bbl motor, has deck hgt of +.129, .028 gasket, 57.3 cc head, cr. is 11.5. this little motor is a very good runner. in NHRA stk, there is 273/180 motors being run. a 1965 valient with 180/273 runs 13.30,s, in a 1965 plymouth, ran 13.43 @98 mph.
I realize not everyone is into stock racing, but the fact is, these motors can be very quick. many many years ago, I ran a 235/273 dart as a stocker, plus drove it. it ran 13.31 @ 102.30 mph. some people like smaller motors, others like big motors. to each his own. .060 over is about the limit on overbore in these motors. just food for thought.

Here's another story >>>>>>>>>>>>>>>>>>>>>>>>>
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Another 273 build
In my opinion, for a good economy engine, the 273 is the better engine between it and the 318. The smaller bore and closed chamber head can be configured to give a 9:1 engine that will require less ignition advance, thus better fuel economy than a larger bore engine with the same stroke. The early 273/318 head has a chamber that is not too unlike the newer '302 casting, although the bowls and ports are different. Small bore and long stroke engines are popular today with the computer controlled fuel and ignition systems. The use of the engine still dictates the type of build, of course.

Building an inexpensive high horsepower 273 is quite a story. I have one built and ready to go for next race season. two years ago, I switched from a factory headed 273 to a W2 headed 318. The 273 was 11.04:1 and had a CompCam292 hydrolic with solid lifters. It ran a best of 12.36 @109 in the 1/4. The 318 has 9.8:1 and a MP .541" lift circle track cam and just ran a 11.26 @119 a few weeks ago. The 318 has quite a bit more horsepower still to be found, but that will have to be looked for later as the 273 is being put back in very soon.
This 273 is a true 11.0:1 assembly with factory 273 heads modified with my porting work and cut down 1.92/1.60 Chevy +.150" long valves installed. The cam is a MP circle track grind with .528" lift. The pistons are an old set of Jahn's cast that stick out of the hole .230" at the dome. Regular iron rings are all I could find, much less afford. The engine has the regular trustworthy 8553 Felpro head gasket. The intake manifold is a Chrysler marine item that is very similar to the original 273 4bbl unit. It did require some coolant flow modifications in order to work on the 273 with a regular automotive water pump. With the same AFB Double Pumper carb that I used on the previous 273 build, I expect to see time slips in the 11.80 range in my 3281 pound Dart.
 
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stroker402 said:
I came across some good info about the 273 from a guy on another site Quote :
View attachment 1715321902
hello, I did some research on 273 . the 180 hp, has an 8.8 cr listed. according to the NHRA specs, which are provided by mopar are; deck hgt. - .011, a .028 gasket, 57.3 cc head will provide a cr of 9.5. the 4 bbl motor, has deck hgt of +.129, .028 gasket, 57.3 cc head, cr. is 11.5. this little motor is a very good runner. in NHRA stk, there is 273/180 motors being run. a 1965 valient with 180/273 runs 13.30,s, in a 1965 plymouth, ran 13.43 @98 mph.
I realize not everyone is into stock racing, but the fact is, these motors can be very quick. many many years ago, I ran a 235/273 dart as a stocker, plus drove it. it ran 13.31 @ 102.30 mph. some people like smaller motors, others like big motors. to each his own. .060 over is about the limit on overbore in these motors. just food for thought.
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"Very quick" is quite subjective. There are a BUNCH of daily driven mopars on this site that are WAY faster than that.
 
still sitting on the build for my 273 .. lot of options out there ............how would a 273 commando engine stock bore with 10.5 compression pistons with a solid 300 dur 600 lift cam respond to trick flow 190 heads 2.02 heads ?
or maybe a procharger ?
 
stroker402 said:
still sitting on the build for my 273 .. lot of options out there ............how would a 273 commando engine stock bore with 10.5 compression pistons with a solid 300 dur 600 lift cam respond to trick flow 190 heads 2.02 heads ?
or maybe a procharger ?
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Too much. Big heads don't like 273's the chambers are too big compared to the bore and the large valves will hit the bores. You need to notch the bores so there isn't a collision there. The small 273 bore doesn't need huge flowing ports to work unless you are spinning it to 10,000 r's. It's all up to you, big heads, big cam, big rpm, big bucks.
 
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toolmanmike said:
Too much. Big heads don't like 273's the chambers are too big compared to the bore and the large valves will hit the bores. You need to notch the bores so there isn't a collision there. The small 273 bore doesn't need huge flowing ports to work unless you are spinning it to 10,000 r's. It's all up to you, big heads, big cam, big rpm, big bucks.
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turbo or procharger maybe way to go ..
 
stroker402 said:
turbo or procharger maybe way to go ..
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Do you really want to turbo charge an already high compression engine? Seems like you would want a low compression engine, that way you can get more unit charge in the cylinder and therefore more bang.

And why would you want to torture a 273 like that ? stroke a 360 and then turbo charge it if you don't care about originality.
 
trapster said:
Do you really want to turbo charge an already high compression engine? Seems like you would want a low compression engine, that way you can get more unit charge in the cylinder and therefore more bang.

And why would you want to torture a 273 like that ? stroke a 360 and then turbo charge it if you don't care about originality.
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Agreed.
 
Just found this thread and I'm following along. I was wondering of Evaporust would have been an option for rust removal to help getting the pistons out?
 
stroker402 said:
still sitting on the build for my 273 .. lot of options out there ............how would a 273 commando engine stock bore with 10.5 compression pistons with a solid 300 dur 600 lift cam respond to trick flow 190 heads 2.02 heads ?
or maybe a procharger ?
Click to expand...


To make crazy NA power you need lost of rpm and very deep gears.
Trick flow heads and 273 would need to spin 9000-10,000+ rpm to get the full use of them.
To make 400 hp you'd need to be revving around 7000 rpm for peak power.
Peak power at 6000 rpm would be about 350 hp.
Peak power at 5000 rpm would be about 300 hp.

I'd go more with something like speed master heads with a solid cam around .500-.525 ish lift 110 lsa and a 225-235 ish duration and at least 4.56 gears.
 
Boost on a 10.5 compression engine will be a great way to destroy the pistons, head gaskets, and possibly the whole engine.
 
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