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Please help me build my 273

Posted By: gmoritz625

Please help me build my 273 - 04/24/11 08:16 PM

Hi guys. I have a 67 barracuda. Finished building a 340 for it but it has a funny vibration that shakes the car between about 2300-2800 rpm. I should have had the rotating assembly balanced. Anyway, I'm going rebuild a 273 right and save the 340 for a future product. I don't want to screw up designing this motor and am hoping for some help. I want to maximize performance. Car has 727 with 3.23 sure grip and 68 hi po exhaust manifolds. I have some 302 castings I was planning on using. Wanting to generate about 275 hp. Any comments appreciated.

Greg

Attached picture 6600775-cuda.jpg
Posted By: gmoritz625

Re: Please help me build my 273 - 04/24/11 10:19 PM

Anyone?
Posted By: RapidRobert

Re: Please help me build my 273 - 04/24/11 10:29 PM

The OE 273 pins were very heavy (smaller ID) so that the smaller dia (therefore lighter) 273 pistons could be balanced the same to a 318 crank as heavier 318 pistons were. a person could use 318 pins since you are rebuilding/balancing from scratch but I think 273 pistons are not avail & even if they were the CR would b too low. Hughes may have something for you but depending on what head there may b a bore shrouding prob. Not much help to offer but wanted to kick things off for you
Posted By: Coronet-R/T-Rag

Re: Please help me build my 273 - 04/25/11 01:50 AM

Any chance your 340 is externally balanced and you've got a non-weighted converter? Or vice-versa? As for the 273, why not just get a 360 core and make a ton more power for less money? Just thinking out loud.
Posted By: gmoritz625

Re: Please help me build my 273 - 04/25/11 02:00 AM

No, 340 is forged crank from 69 swinger. I've analyzed that angle to death. used eagle rods and custom pistons and did not get it balanced. Pretty dumb really. I spent afternoon tearing down the 318 that was in there contemplating just throwing my top end from my 340 on there and running the piss out of it. I went with the 340 originally because it is just cool to have a 340. 360's are pretty common as are 318's. A really well built 273 would be cool too. Hard to do though. I'm thinking a 408 crate motor might be better than struggling with a 273. Thanks
Posted By: HYPER8oSoNic

Re: Please help me build my 273 - 04/25/11 02:06 AM

The 4bbl pistons can be found at EGGE Machine Company (try egge.com) Look under Dodge 273 V8.
This may help you, since the compression boost was
in the pistons (domed type) and NOT the head. FWIW, it is a good build!! The
275 hp level you seek lies in the cam selection as well as compression.

Posted By: gmoritz625

Re: Please help me build my 273 - 04/25/11 04:51 AM

Quote:

The 4bbl pistons can be found at EGGE Machine Company (try egge.com) Look under Dodge 273 V8.
This may help you, since the compression boost was
in the pistons (domed type) and NOT the head. FWIW, it is a good build!! The
275 hp level you seek lies in the cam selection as well as compression.





what cam do you think? i think the 10.5 pistons with the 64cc heads would yield under 10:1 which would be perfect.
Posted By: patrick

Re: Please help me build my 273 - 04/25/11 02:20 PM

tuck the 273 in a corner of your garage, and pick up a running, lower mileage 318 magnum. get an eddie RPM air gap for magnum motors. get some hughes #1110 springs and their retainers, and their camshaft snout extender to run a fuel pump with an LA timing cover. send the cam to Tim at bullet cams, get it reground with their HR259/316 lobe for both the intake and exhaust. if you tear down the motor to rering/regasket/rebearing, do the head porting mods Dulcich details in the may '05 issue of mopar muscle (biggies, opening up the pushrod pinch, and getting a good 5 angle valve job, and opening the VJ up to a 1.9" seat intake, 1.605" exhaust). run headers, and a 600 carb

will be a solid 300-320 HP an returned 18.6mpg with the last tank of gas in my 5th ave....
Posted By: Baxter61

Re: Please help me build my 273 - 04/25/11 03:36 PM

I like that your going with the 273 and 340 to do something cool and be a little different than every other 360 and 318 out there. Use your 302 heads, do some minor porting, build your 273 shortblock and shove a solid roller in it. that would be cool and hit your hp goals.
Posted By: patrick

Re: Please help me build my 273 - 04/25/11 09:06 PM

Quote:

I like that your going with the 273 and 340 to do something cool and be a little different than every other 360 and 318 out there. Use your 302 heads, do some minor porting, build your 273 shortblock and shove a solid roller in it. that would be cool and hit your hp goals.



yeah, a 273 is different, but unless you look at the castings #/engine stamping #, you'll never tell a 273 from a 318.

and you're giving up 45 cubic inches, which is a significant torque differential--rule of thumb, for a decently thought out street combo, 1.0-1.2 lb-ft per cubic inch is doable for peak torque.

stock 302 heads suck for flow potential, and without significant port work, will max out at about 250-270HP...

the 3.625" bore of a 273 will severely limit valve diameter and flow capability. the pistons will be much more expensive, to the point where you could buy new pistons and a 318 or 360 core motor....

there's a reason 318 and 360 builds are popular...because they make economic sense.

I love oddball stuff as much as the next person, I'd love to build up a hot slant 6, but I could never justify dropping serious coin on a seriously modded turbo slanty that would make as much power as a warm 318/360....
Posted By: cdp

Re: Please help me build my 273 - 04/25/11 09:24 PM

Seriously, for the $$ spent, why not find a good running 360 from a truck/van, add an aluminum intake, 340 manifolds, and mild cam, re-use the 360 converter and your 302 heads.

Around here, I've found several late 70's trucks/vans with good 318/360's for under 1000, most being in the $500 range. Sell whats left over for scrap.
Posted By: Mopar_Country

Re: Please help me build my 273 - 04/25/11 09:37 PM

Here is a link with some info concerning the 273 conversion that Chrysler did in 66 on the Darts. Contained in the link is a conversion parts list.

http://www.seriousviewers.com/D-Dart/spec.htm
Posted By: dan9

Re: Please help me build my 273 - 04/26/11 02:43 PM

Years ago i had two hp 273's I'm sure i remember reading an article about moving pistons from one side to the other to gain compression. I don't remember if it was just for the hp version or not. I never tried it nor did i ever have to tear them apart.
Posted By: scratchnfotraction

Re: Please help me build my 273 - 04/26/11 03:20 PM

want a fast 273??

talk with the Rev member "class of 65"

think his 273 still holds a record time slip,he has not posted in a while.

that is one fast almost stock 273

Posted By: scratchnfotraction

Re: Please help me build my 273 - 04/26/11 03:26 PM



bumped an old 273 post back up for you to read

might have some good info in there also,IIRC

post "64 273 ?"
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