273 warm up!

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dennis degeneffe

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I have a 1965 273 2bbl standard bore and compression with original heads/rebuilt.
I recently acquired a factory 4bbl intake, casting number 2465726. My goal is to get better performance without swapping motors. I was planning on adding a cam and headers and probably better ignition. I know there was a commando 273 with 275 hp. what are the differences between that motor and mine? Besides my planned changes, would the only thing I need to do, is to change pistons for a compression boost? I was told this is THE place to go for small block MOPAR advice. Any suggestions on specific carbs and cams and ignition systems etc. would be appreciated. If you can't tell, I am trying to keep this a low budget hop-up.
 
dennis degeneffe said:
I have a 1965 273 2bbl standard bore and compression with original heads/rebuilt.
I recently acquired a factory 4bbl intake, casting number 2465726. My goal is to get better performance without swapping motors. I was planning on adding a cam and headers and probably better ignition. I know there was a commando 273 with 275 hp. what are the differences between that motor and mine? Besides my planned changes, would the only thing I need to do, is to change pistons for a compression boost? I was told this is THE place to go for small block MOPAR advice. Any suggestions on specific carbs and cams and ignition systems etc. would be appreciated. If you can't tell, I am trying to keep this a low budget hop-up.
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Suggest you get a factory service manual for your car. It should tell you the difference in motor specifications, then just build the original motor to commando specifications and you're golden.
 
dennis degeneffe said:
I have a 1965 273 2bbl standard bore and compression with original heads/rebuilt.
I recently acquired a factory 4bbl intake, casting number 2465726. My goal is to get better performance without swapping motors. I was planning on adding a cam and headers and probably better ignition. I know there was a commando 273 with 275 hp. what are the differences between that motor and mine? Besides my planned changes, would the only thing I need to do, is to change pistons for a compression boost? I was told this is THE place to go for small block MOPAR advice. Any suggestions on specific carbs and cams and ignition systems etc. would be appreciated. If you can't tell, I am trying to keep this a low budget hop-up.
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The Commando motor came with a Carter AFB 500 cfm carb, 10.5 CR pistons, solid lifters/cam, and adjustable rocker arms. Can't remember lift/duration of cam off the top of my head! Hope this helps! 65'
 
Try to find an original AFB, otherwise have the intake bores opened up for a 500 cfm Edelbrock. Assuming you have the original solid cam setup. I'd run an Isky E-4 or call Racer Brown for an ST-1 or what ever Jim suggests. Add 340 springs and a double roller timing chain. Is it an automatic transmission? Exhaust manifolds are the same as the Commando / Charger engine. The difference was the Charger exhaust was single 2.50 pipe with 2 straight through mufflers in series. You don't need different pistons. A good quick curve electronic distributor would be good also.
 
dennis degeneffe said:
I have a 1965 273 2bbl standard bore and compression with original heads/rebuilt.
I recently acquired a factory 4bbl intake, casting number 2465726. My goal is to get better performance without swapping motors. I was planning on adding a cam and headers and probably better ignition. I know there was a commando 273 with 275 hp. what are the differences between that motor and mine? Besides my planned changes, would the only thing I need to do, is to change pistons for a compression boost? I was told this is THE place to go for small block MOPAR advice. Any suggestions on specific carbs and cams and ignition systems etc. would be appreciated. If you can't tell, I am trying to keep this a low budget hop-up.
Click to expand...
All good information. Might as well forget about the 275 horse 273. It was a specially built engine that was used in
D stock classes at NHRA tracks. Only a handful of the D Darts were made but you could order those parts at your Mopar parts counter back in the day. Intake,carb, properly curved distributor,small cam, and the HP single or 2 1'4" dual exhaust will liven up your 2 barrel 273. Let's talk cams a second, Keep it small. I used the Isky E-4 with good results.
 
Build to Commando specs except the cam. Use a Comp Xtreem Energy or Lunati Voodoo 262/268 Hydraulic and appropriate springs. I have a Commando and I do not really like the cam very much.
 
drewmac said:
Build to Commando specs except the cam. Use a Comp Xtreem Energy or Lunati Voodoo 262/268 Hydraulic and appropriate springs. I have a Commando and I do not really like the cam very much.
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Too much cam for a 2 barrel based 273.
 
Yes, the street 273 Commando was rated 235HP, not 275. You will not get the same performance just with bolt-on parts, because you won't have the CR. You can still get a worthwhile improvement.

That factory intake is a single plane and might not be the most effective for your build. They make a small port dual plane intake for 318s, I forget the name. Here's some info on Mopar cam upgrades.

67_back_cover.jpg



273Factory Cam.jpg
 
You could mill the heads down to get the compression ratio up a bit more.

Plus, I would not be surprised if the original thin shim head gaskets were replaced at the rebuild with thicker aftermarket ones; that is a significant compression reducer. Some thinner head gaskets are in order if that is the case. Of, course, you'll have to pull the heads to see ......Edit to add: Maybe not.... you can probably measure the head gasket thickness when you pull the intake.

Good move to add headers. That will help all through the RPM range. Putting in longer collectors will help the bottom end torque a bit.
 
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The 65 heads use smaller bolts ant a different angle than all other LA engines. Edelbrock made a D4B for the 64-5 273's.
 
nm9stheham said:
You could mill the heads down to get the compression ratio up a bit more.

Plus, I would not be surprised if the original thin shim head gaskets were replaced at the rebuild with thicker aftermarket ones; that is a significant compression reducer. Some thinner head gaskets are in order if that is the case. Of, course, you'll have to pull the heads to see ......

Good move to add headers. That will help all through the RPM range. Putting in longer collectors will help the bottom end torque a bit.
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Steel shim head gaskets are not available any more, wish they were. Cometic is the closest. thin steels. .040 compressed thickness is about the thinnest you can get.
 
Yeah, I know. My point is that the OP may well have lost compression in the rebuild and it would be desireable to rectify that as much as possible.

Cometic offers a .027" MLS thickness. Has anyone asked about them in the smaller bore for the 273?
 
nm9stheham said:
Yeah, I know. My point is that the OP may well have lost compression in the rebuild and it would be desireable to rectify that as much as possible.

Cometic offers a .027" MLS thickness. Has anyone asked about them in the smaller bore for the 273?
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There has been talk about that a year or so ago but I don't know whether anyone ever had any made. I believe Cometic will make about any thing you want. Steel shims are still available for big blocks. I wish the small block ones hadn't disappeared.
 
For what he wants, everything is good. He does not need to replace head gaskets or get a different intake. Toolmanmike is right, stick with the E-4 cam or something close. That intake and a 500 cfm Carter or Edelbrock will be fine if he opens up the throttle bores in the intake. If he can't find an good original.
 
toolmanmike said:
Too much cam for a 2 barrel based 273.
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I agree if he uses the 2bbl pistons but if he gets some of the 4bbl variety I think it could work. You may have to advance the cam a few degrees. My Commando's solid is pretty lumpy but does not seem to pull like it should to higher rpm's. The rebuild was a pretty stock rebuild with no extra machining done. I'd like to go with one of those cams, a performer, headers, a bit of porting and a full header, 2.5 in exhaust. This is just my thoughts.
 
drewmac said:
I agree if he uses the 2bbl pistons but if he gets some of the 4bbl variety I think it could work. You may have to advance the cam a few degrees. My Commando's solid is pretty lumpy but does not seem to pull like it should to higher rpm's. The rebuild was a pretty stock rebuild with no extra machining done. I'd like to go with one of those cams, a performer, headers, a bit of porting and a full header, 2.5 in exhaust. This is just my thoughts.
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You answered your own question so to speak. "My Commando's solid is pretty lumpy but does not seem to pull like it should to higher rpm's." Too much cam regardless of the compression/pistons.
 
My 273 build is begging for me to let it loose. With 400 miles on the build, I am waiting to get 1000 miles on it, put full synthetic in it and cut her loose. I built it for 5500 rpm so we'll see. Details on my build thread.
 
toolmanmike said:
There has been talk about that a year or so ago but I don't know whether anyone ever had any made. I believe Cometic will make about any thing you want. Steel shims are still available for big blocks. I wish the small block ones hadn't disappeared.
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When we built my 273 about 4.5 yrs ago we got Cometics to make up head gaskets. They were pricy though. Just call them.
 
DesertRat said:
My 273 build is begging for me to let it loose. With 400 miles on the build, I am waiting to get 1000 miles on it, put full synthetic in it and cut her loose. I built it for 5500 rpm so we'll see. Details on my build thread.
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Just curious.. .have you been researching the ZDDP levels in the synthetics? We have been finding that only the higher weights of Mobil1 have ZDDP levels in at least the 1200 ppm range; the lighter weight synthetics have reduced ZDDP levels, just like all the other lighter oils. I think my son has settled on a 5W50 Mobil1.
 
nm9stheham said:
Just curious.. .have you been researching the ZDDP levels in the synthetics? We have been finding that only the higher weights of Mobil1 have ZDDP levels in at least the 1200 ppm range; the lighter weight synthetics have reduced ZDDP levels, just like all the other lighter oils. I think my son has settled on a 5W50 Mobil1.
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I have not researched the ZDDP levels but was thinking of an additive anyway just to be safe. I will check it out, thanks for the heads up.
 
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.
 
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....
 
Well I did'nt really want to get into it, but since you asked, there is no way I'd put 4 barrel pistons in a driver. Our family has had 273 Barracudas since the early 70's. In every conceivable configuration. From a 284 duration, to Commando, to used 340, to an Isky E-4 cam. 10 years ago, I swapped a set of 675 heads onto the 67 2 barrel 273 short block so my brother could run it on regular 89 gas. For the previous 30 years with 920 closed chamber heads he had to run premium gas. I always run Felpro head gaskets as they always sealed and would not blow, even on 340's. The engine has over 300K on it and still runs like a top. It has the Commando cam and valvesprings. It will get 20 mpg with the original intake and AFB. It has also run with a 72 340 TQ and an adapter. It has plenty of torque and used to cruise at 100 mph out west all day long. It runs the original 67 904 but was never allowed to shift on it's own. Rear is an 8 3/4 with 3.23 power lock original. I am able to tune with the best of them. The Op does not need to pull his engine apart. Will it fry the tires like a 440? No, but it will have plenty of power and he can drive it anywhere, and he will be able to afford it. I'm assuming an early A. Never has it had light oil, synthetic or not. That is why it still runs great 40 years and 300k on the odometer later.
 
toolmanmike said:
The 65 heads use smaller bolts ant a different angle than all other LA engines. Edelbrock made a D4B for the 64-5 273's.
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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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