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Re: 273 building and info needed PLEASE!
[Re: dart4forte]
#1661688
08/20/14 08:39 PM
08/20/14 08:39 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
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I Live Here
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No, I don't think they will fit. I believe the roller lifter blocks have taller lifter bores.
But I'm going to be the first to say, build a roller cam 318 instead. Go to the yard and find a Fifth Avenue and take the whole engine. It's almost guaranteed to be great condition inside, and it's like the 273 in every way except the intake manifold has some bolt holes that are at a different angle.
I am currently running an '86 318 with a little over 100K miles, nearly no ridge, valve job was still sealing, valve guides were good. I put in new rings, a slightly larger cam and roller timing chain, and used a mid '70s Thermoquad intake off a 360. Oh, yeah, I home ported the heads and used the Mr. Gasket thin head gasket.
It runs so good, and my mileage in my half-ton pickup is 20 - 22mpg on the highway.
You will pay more for pistons for your 273 than you'll pay for an entire 318.
If you are stuck on that 3 5/8" bore, at least use the 302 casting heads from the roller 318.
R.
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Re: 273 building and info needed PLEASE!
[Re: dogdays]
#1661690
08/20/14 10:01 PM
08/20/14 10:01 PM
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Joined: Jan 2003
Posts: 1,255
Columbus, GA
Michael Ecks
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,255
Columbus, GA
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Quote:
No, I don't think they will fit. I believe the roller lifter blocks have taller lifter bores.
But I'm going to be the first to say, build a roller cam 318 instead. Go to the yard and find a Fifth Avenue and take the whole engine.
"Low buck" and "mild 273 build" don't belong in the same sentence.
Factory roller lifters will not fit. The late LA rollers and magnums have taller lifter bores that are also machined for the dog bones to sit in, and the valley has added cast in and tapped bosses for the bolts needed to secure the spider plate.
If you insist on the 273, and will be happy with a rebuild, the common 318 non adjustable rocker gear with a hydraulic cam will work. But if the heads are '64 variety I believe they have a different intake manifold bolt angle. Not sure if it is the same as magnum engines or not. But an original early 273 four barrel manifold will be hard to locate and probably expensive.
As mentioned, roller cam 318s are common in junkyards and cheap. All accessories from the 273 should bolt up. I'm all for working with what you have, but you'll be spending twice and much for a fraction of the performance.
"The happiness of your life depends upon the quality of
your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: 273 building and info needed PLEASE!
[Re: ronhug]
#1661692
08/21/14 09:09 AM
08/21/14 09:09 AM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Ron how far are you from Lincoln? I have a 273 adj rocker arm assy(s) for you
live every 24 hour block of time like it's your last day on earth
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Re: 273 building and info needed PLEASE!
[Re: ronhug]
#1661693
08/21/14 02:59 PM
08/21/14 02:59 PM
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Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
dart4forte
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
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What are you going to do with the car? I disagree on the 273 costing more to build. First 273/318 are in the same LA family. gasket sets are pretty much the same as well as some of the wear items such as valve train. Lots of parts interchange. The stock 273 flat top piston was rated from the factory at 8.8 to 1 CR. For a street car you don't really need much more than that. You can contact Comp Cams and they can suggest a grind that will compensate for the lack of CR.
Other mods
LD4B Edelbrock
Carter 9636
Electronic ignition
Depending on what you are looking for in a street motor the 273, given it's low on low end torque and across the power band can use low gears. A good compromise is 3.55's with the next step being 3.91s.
If you want to go the 318 route a good combo is a 318 with a J head, a good intake and some old school camshaft such as a stock 340 grind.
Stay low maintenance as much as possible and enjoy.
I forgot to mention that you will want to use the #920 casting 273 head. It was the head used on the 273 4 barrel motors, closed chamber and has the standard 3/8" bolt angles.
The 302 swirl port head is another good option.
Last edited by dart4forte; 08/21/14 03:27 PM.
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Re: 273 building and info needed PLEASE!
[Re: dart4forte]
#1661694
08/21/14 03:50 PM
08/21/14 03:50 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
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Neither Federal-Mogul (Sealed Power) or UEM (Silvolite) currently make pistons for the 273.
Egge cast pistons are $428 a set.
The chances of the late model 318 being ready to run with new rings and bearings is very high, as I said and others have noted before, after over 100K miles there was basically no ridge and the honing marks still in the cylinders.
You can buy a late 318, do the rings, bearings, gaskets and seals, and have money left over compared to the 273 pistons by themselves.
As for compression, the late 318 with thin head gaskets calculates out at very close to 9:1, I cannot remember whether over or under. But mine runs on the lowest grade fuel.
IF the OP is just replacing rings, bearings and gaskets, then the 273 will be inexpensive as well. In that case I'd suggest the 302 heads and the thin head gaskets. But for cruising I'd rather have the extra 44 cubic inches, which means probably 60 extra lb-ft of torque, and a lower numerical rear gear. It's hard to relax when the motor is buzzing 3000 rpm at 60.
As for the "360 head on a 318" suggestion, time would be better spent putting a Magnum head on a 318.
R.
Now for crazy: You need custom pistons anyway, why not go stroker? I don't know if the connecting rod shank would run into the lower edge of the cylinder wall with a 4" stroke, maybe the 3.58" would be better.
3.655 x 3.58 = 300 cubic inches
3.655 x 4.00 = 336
Bet it'd outpull a 340 to the torque peak!
Last edited by dogdays; 08/21/14 03:55 PM.
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Re: 273 building and info needed PLEASE!
[Re: dogdays]
#1661695
08/21/14 07:23 PM
08/21/14 07:23 PM
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Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
dart4forte
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
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Quote:
Neither Federal-Mogul (Sealed Power) or UEM (Silvolite) currently make pistons for the 273.
Egge cast pistons are $428 a set.
The chances of the late model 318 being ready to run with new rings and bearings is very high, as I said and others have noted before, after over 100K miles there was basically no ridge and the honing marks still in the cylinders.
You can buy a late 318, do the rings, bearings, gaskets and seals, and have money left over compared to the 273 pistons by themselves.
As for compression, the late 318 with thin head gaskets calculates out at very close to 9:1, I cannot remember whether over or under. But mine runs on the lowest grade fuel.
IF the OP is just replacing rings, bearings and gaskets, then the 273 will be inexpensive as well. In that case I'd suggest the 302 heads and the thin head gaskets. But for cruising I'd rather have the extra 44 cubic inches, which means probably 60 extra lb-ft of torque, and a lower numerical rear gear. It's hard to relax when the motor is buzzing 3000 rpm at 60.
As for the "360 head on a 318" suggestion, time would be better spent putting a Magnum head on a 318.
R.
Now for crazy: You need custom pistons anyway, why not go stroker? I don't know if the connecting rod shank would run into the lower edge of the cylinder wall with a 4" stroke, maybe the 3.58" would be better.
3.655 x 3.58 = 300 cubic inches
3.655 x 4.00 = 336
Bet it'd outpull a 340 to the torque peak!
The overall question is what is he going to do with the car. Until that's answered no exact suggestions can be given. Also, what's wrong with the pistons he has in his 273 assuming he already has a motor.
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Re: 273 building and info needed PLEASE!
[Re: dart4forte]
#1661696
08/21/14 08:10 PM
08/21/14 08:10 PM
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Joined: Jan 2005
Posts: 12,424
Kalispell Mt.
HotRodDave
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I Live Here
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Kalispell Mt.
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The stock 920 or 315 casting 273 heads will kill a 302 casting on the flow and have a smaller chamber, keep the 273 heads. Even a 360 valve needs a very small notch at std bore. If your interested in an all out 273 I have a CNC ported 302 casting head by modern cylinder head that flows over 220 CFM and very small chambers that would make good TQ and spin a 273 to the moon while looking stock to most guys and they are cheap.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 273 building and info needed PLEASE!
[Re: HotRodDave]
#1661698
08/21/14 11:51 PM
08/21/14 11:51 PM
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Joined: Dec 2003
Posts: 22,808
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,808
Bitopia
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I question the widely held belief that the 273 vs a 318 or 340 is a higher revving motor, which I think you maybe implied, I think the contrary would be more accurate.  http://rehermorrison.com/tech-talk-53-big-bore-or-long-stroke-which-is-better/
Last edited by jcc; 08/22/14 01:11 PM.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: 273 building and info needed PLEASE!
[Re: jcc]
#1661700
08/22/14 12:10 PM
08/22/14 12:10 PM
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Joined: Jan 2003
Posts: 1,255
Columbus, GA
Michael Ecks
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,255
Columbus, GA
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Quote:
I question the widely held belief that the 273 vs a 318 or 340 is a higher revving motor, which I think you maybe implied, I think the contrary would be more accurate.
I can see it side to side against stock 4 bbl versions of each. I don't know about exact piston weights, but assuming similar casting material the smaller 273 bore should be a lighter piston, also IIRC the 273 had a lighter rod that is still sought after, early ones also had solid cams so no hydraulic lifter rpm limit. Lighter rotating assembly, higher rpm potential and faster acceleration of the engine internals.
Again this assuming comparison against a stock 4 bbl version of each LA engine.
That said, I stand by my previous statement about a late 318 being a better/cheaper choices for the OP, considering his 273 is not complete and not a 4bbl package for a starting place.
I picked up a complete roller 360 in a yard do $250. A running 318 could probably be found for less. Used eddy performer or weiand stealth intake to match the 302 ports, 100 bucks maybe? Regrind the factory roller cam to a performance grind $200? haven't priced regrinding. Gaskets, bearings, rings, 4bbl carb for either about the same price and should be replaced in either motor anyway.
If OP was doing a resto then sure build the 273. It doesn't seem like originality is a goal, so the upgrade is a no brainer to me.
"The happiness of your life depends upon the quality of
your thoughts" ~ Roman Emperor Marcus Aurelius
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Re: 273 building and info needed PLEASE!
[Re: dogdays]
#1661702
08/22/14 02:11 PM
08/22/14 02:11 PM
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Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
dart4forte
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 16,169
Mesa, Arizona
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Quote:
The 273 and 318A used EXACTLY the same crankshaft and rods. It is right that the 273 piston weighs less than a 318. To keep using the 318 crankshaft without modification, Mopar engineers spec'd a heavy wristpin. The bobweight of a 273 and 318 is exactly the same.
An early A/LA connecting rod weighs 723 grams. The 645 rod (also 496) weighs 758. A decent modern rod would weigh 600 grams. The piston/pin combo is also 100 or more grams overweight.
Take off the weight and port the heads and it'll act completely different, rev much faster, accelerate the car faster, etc. For this I'm talking custom forgings.
One other thing - if you're married to the 3 5/8" bore, keep in mind that the smaller diameter means you can run more compression on the same fuel.
Whatever you do, get some squish into the chamber.
R.
7784 Paul Wong, Las Vegas, Nev. ('65 Belvedere/273) .106 13.769 87.71 U/S 14.90
-1.131
That's running a 273 2 barrel
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Re: 273 building and info needed PLEASE!
[Re: ronhug]
#1661704
08/23/14 01:23 AM
08/23/14 01:23 AM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I'll post a pic soon of the light rods. Not sure what year they originated
live every 24 hour block of time like it's your last day on earth
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