273 rebuild

[Baxtman]

Hey guys. I need some advice. I have a 65 Barracuda that I am restoring. I want to build up the 273 engine a little bit. I'd like around 250 - 300 hp, but want something that idles nicely. My main question is what to do about the heads and which cam to choose. Any help would be appreciated.

 

[toolmanmike]

Look through my build thread. I didn't dyno my engine but if the 273/4 barrel engine had 235 horse mine has 250. If you have a 2 barrel engine you will need to build it as a 4 barrel. Headers and a nice exhaust are a plus. tmm Use the link below.

 

[DartVadar]

A cam a bit bigger than stock will make more power and still idle good. Headers, good intake and carb and mid 9 compression ratio with stock rebuilt heads should get you there.

 

[Mopar Tim]

The 273 heads are a good choice, if a 4bbl 273 comp. should be good as well. Cam and headers not a bad upgrade to get more power. Dont over cam or over Carb. 273 is a small engine, needs to be setup right . RRR advised me on cam choice, It seems it was the right choice with the miles I have on the car so far. Strong puller to 5k. Have not reved past that yet, still new. Stock converter. http://www.hughesengines.com/Index/p...k&partid=30395 :burnout:MT

 

[RedFish]

Your largest headache will be exhaust. Clutch linkage or power steering will require more aspirin and research. This applies to the early A-body with any V8. You are in the right forum though, read read read. Good luck

 

[273]

The factory heads are good for 300 plus horsepower but that said cam and head flow is the main power ingredient as long as the intake, exhausted and CR are there to support it. So you could just cam her up but it's easier to over cam a 273. The best way is though more head flow like how the new hemis and LS motors do it that's why they have so much untapped power and they get away with big power numbers with pretty small cams (driveability). So either port you heads like 1 wild and crazy guys sticky or if you can't port, magnum heads with block notches would be a good second choice with good custom cam with lots of lift and short on duration. Something like .470-.500 lift and below 270 duration.

Don't forget about gearing the main ingredient when it comes to small engine performance, the main reason people say they can't hang with the bigger boys. Since torque is proportional to engine size so is gearing requirement. So if you want the performance of a 300 hp 360 with 3.55 gears, which a 360 is 32% bigger a 273 is gonna need around 32% more gear which is 4.69:1 that's why to most people a 273 is a dog. Obviously you don't have to run that much gear but performance is gonna drastically be reduced though. To me 3.91-4.10 is the minimum performance gear for a 273.

 

[4spdragtop]

Some good info in here. TMM's thread is a good read. I put new cam n lifters in my 273. I'll post more info once I get to laptop.

 

[nm9stheham]

The 273 heads are a good choice.....

Should one assume that you are saying the early 273 closed chamber heads are a good choice? The later ones were open chamber....lower compression. The OP should also be aware that the earliest year (or 2) intake manifold bolts and their angles into the heads are different; I think the change to the later style was in '66 but someone should verify that.

 

[AJ/FormS]

Hey guys. I need some advice. I have a 65 Barracuda that I am restoring. I want to build up the 273 engine a little bit. I'd like around 250 - 300 hp, but want something that idles nicely. My main question is what to do about the heads and which cam to choose. Any help would be appreciated.

This is full of trouble.
-First is the word restoring; Ima guessing you mean resto-modding.
-Next is the "little bit"; 250 is a little bit extra for a teener, 300 is a little bit extra for a 360.
Since the factory rated the 273-2bbls at 180hp, a little bit would be 10 or 15 percent so that would be 18 to 27 hp. you are targeting 70 to 120hp. That is not a little bit. That is a 39 to 67 percent increase.
-Then is; "that idles nicely". What does that mean? Nice and lumpy? or nice and smooth? Or nice like a racecar.
-And finally;why are you targeting 250/300?
I'm not trying to be an a$$. I'm just trying to get a grip.

 

[toolmanmike]

273 threads always start out this way. lol

 

[Mopar Tim]

Should one assume that you are saying the early 273 closed chamber heads are a good choice? The later ones were open chamber....lower compression. The OP should also be aware that the earliest year (or 2) intake manifold bolts and their angles into the heads are different; I think the change to the later style was in '66 but someone should verify that.

Yes the closed chamber heads are good choice for the 273. 66 273 heads on have the newer bolt angle. Dont over cam engine and keep the stock 273 valve sizes. dont over carb engine either. Real EZ to make engine a dog with low torque.

 

[273]

This is full of trouble.
-First is the word restoring; Ima guessing you mean resto-modding.
-Next is the "little bit"; 250 is a little bit extra for a teener, 300 is a little bit extra for a 360.
Since the factory rated the 273-2bbls at 180hp, a little bit would be 10 or 15 percent so that would be 18 to 27 hp. you are targeting 70 to 120hp. That is not a little bit. That is a 39 to 67 percent increase.
-Then is; "that idles nicely". What does that mean? Nice and lumpy? or nice and smooth? Or nice like a racecar.
-And finally;why are you targeting 250/300?
I'm not trying to be an a$$. I'm just trying to get a grip.

I don't think the OP is asking to much .9:1 - 1.1:1 hp per cid which would be like asking 325-400 out of a 360

A decent cam, 4bbl intake and headers should be right around 1:1. Look a the D dart engine you could get the same performance with a less crazy modern cam grind and the factory 4 bbl intake is an hp killer.

 

[Mopar Tim]

I will tell you building a good running 273 is a a little different then a 318. you can lose low end torque real easy.

 

[273]

I will tell you building a good running 273 is a a little different then a 318. you can lose low end torque real easy.

That's what gears are for lol

That's true but only after a certain point. Most stock engines don't have a lot to be desired performance wise, lots to be gained in the idle to 5500 range in both torque and hp but after that you don't lose torque just move it up the powerband leaving a hole between idle and usable torque that needs to be filled with gears and more stall.

 

[Mopar Tim]

That's what gears are for lol

That's true but only after a certain point. Most stock engines don't have a lot to be desired performance wise, lots to be gained in the idle to 5500 range in both torque and hp but after that you don't lose torque just move it up the powerband leaving a hole between idle and usable torque that needs to be filled with gears and more stall.

This is all true. I have yet to get a good run on my warmed over 273. But it seems to run real good. 66 dart still not put all together yet. Close tho.

 

[toolmanmike]

Mine is a mild build with a Isky E4 cam and worked over heads. I advanced the cam timing a few degrees and it doesn't crank much past 5000. It scoots pretty good with a 3:23 and I like the way it runs. I have read so many threads where guys built engines for maximum power and they don't have fun driving them, too rough idle, no power brakes, really bad mileage......etc. Not every engine needs to be maxed out to be fun.

 

[Mopar Tim]

Mine is a mild build with a Isky E4 cam and worked over heads. I advanced the cam timing a few degrees and it doesn't crank much past 5000. It scoots pretty good with a 3:23 and I like the way it runs. I have read so many threads where guys built engines for maximum power and they don't have fun driving them, too rough idle, no power brakes, really bad mileage......etc. Not every engine needs to be maxed out to be fun.

Just what I was getting at. :burnout:MT

 

[DesertRat]

Can't stay quiet even when I know better. TMM did a great build on his! I got a lot of advice on mine and learned a lot. The stock 4V setup rated at 235 HP was a beautiful factory setup and hard to improve on without a fat checkbook or cubic inches. I landed on the following-right or wrong this is how I am building it. It should be component matched for 5500 RPM if I did my job.
.040 bore with Egge 10.5:1 pistons.
stock heads cleaned up with hardened seats and 3 angle valve job and modern guides/seals.
Thin metal head gaskets to keep the CR up-fuel be damned!
Eddy LD4B with the small runners for air/fuel velocity.
Stock exhaust manifolds with heat risor valve removed and coated.
Dual 2 1/4" exhaust with free-flow mufflers.
Lunati vodoo hydraulic cam with comp springs and retainers matched to cam, stock shaft rocker setup and new pushrods.
(my research turned up added lift starts to work against you above .465" on these little guys) MP windage tray.
Holley 4V starting with the factory primary and secondary jetting.
O2 sensor for tuning fuel setup after break-in.
Stock distributor with Pertronix conversion and good plug wires.
TDC locator when setting up timing setup and degreeing cam 2 degrees advanced.
My machinest is a friend of mine and had build several chebby SB's for me and balanced the rotating assy and resized the rods and installed new rod bolts.
That will be my engine build, the cam and carb issues I am thinking about but I have everything bought and on the shelf and one kind of has to draw a line at how many components he buys twice.
My drivetrain is an 8 1/4 SG with 3:73 gears and will have a built 904 with stock converter and Transgo stage 2 kit and gearvendors OD.
Not looking for a lot other than a reliable-streetable highway driven nice daily driver.
My $00.02 for what it's worth------DRO
Good luck with your research/build!

 

[Baxtman]

To be more precise, I like enoughh horsepowert that when I put my foot in it, it moves
. But, I want to be able top pull out of the garage without the engine dying because it's too much cam. I have made this mistake with other cars and I don't want to repeat. The car is a 4 speed manual. I am unsure about the gear ratio. I was considering a Comp cam with a power band as low as I can find. I am trying to keep the car as close to original as possible.

 

[66fs]

The plusses of a 273 are: high piston height, even in 2 barrel engines; factory mechanical valve train; forged crank; closed chamber heads. They have high flow heads in comparison to cubic inches. They rev quick and high. nm9stheham is correct that the 64 and 65 heads have a different intake bolt size and angle. 66 and up are the same as all other LA (273, 318, 340 , and 360) engines. I would be looking at a solid cam, springs, and lifters. I have run the stock 4 barrel, 284 duration TRW, a stock 340, and E-4 Isky cams. They all had plenty of power, especially in a 64 4 speed Barracuda. Do you have a 4 barrel intake?

The minuses are: clutch, even with the 10 inch scalloped clutch mine is starting to slip in high gear after 5,000 miles, and that is with the small Isky E-4 cam; the 7 1/4 rear will most likely give up the ghost soon after making 250 to 275 HP, depending on how you shift.; Factory exhaust manifolds, but should be fine for what you want, with either custom Duals or 2 1/4 straight thru single exhaust. Cubic inches, but it makes up for lower torque with rpm range, easily up to 6,000 rpm;

 

[Baxtman]

The engine had been rebuilt by Sexton racing sometime wayback. When I tore it apart it had hydrolic lifters and some bent pushrods. Another of the cam lobes was worn way down. It does have a 4 barrel, that I am replacing with a Holley 650cfm. I was looking at Comp cams CL20-208-2 with hydraulic Flat Tappet. Power range adv is 800-4800 RPM
Advertised Duration: 252, and Lift: .425. From what I can tell, this seems to be the best choice I can find. However, stock I think this engine had solid lifters and was changed to hydrolic. Any thoughts?

 

[66fs]

... I was looking at Comp cams CL20-208-2 with hydraulic Flat Tappet. Power range adv is 800-4800 RPM
Advertised Duration: 252, and Lift: .425. From what I can tell, this seems to be the best choice I can find. However, stock I think this engine had solid lifters and was changed to hydrolic. Any thoughts?

A "65" 273 would have a solid cam and valve train, but it is now 50 years old. Obviously it was changed at some point. I would look at the CL 20-220-3, http://www.summitracing.com/parts/cca-20-220-3/overview/make/dodge , for close to Commando specs at .050 but, I'd go a step up to CL 20-221-3, http://www.summitracing.com/parts/cca-20-221-3/overview/make/dodge . I'd also borrow an adjustable pushrod, http://trendperform.com/, to check the length, since you had bent pushrods. Get the correct length pushrods. Check your valve springs to be sure they will work with whatever cam you choose. If you get your valve train sorted out, it is a beautiful thing to wind a 273 up to 6,000 rpm. Also do not be afraid to call Comp Cams, Isky, Racer Brown, or any good cam company and tell them what you have and what you want to do. If you are honest and know what you want to do with your car, you will be very happy.

 

[roccodart440]

The 2 cams aforementioned are

comp 206@.050/.425/110lsa
isky 216@.050/.425/108lsa

If you want to be in that realm of camshaft and stay hydraulic, I'd be more inclined to the melling 23203 or the crane 693941

Melling 214/224@.050, .444, 112LSA

Crane 216/228@.050, .454, 112LSA

 

[76440NY_nTX]

Baxtman,

Are you going to go back to a mechanical valvetrain or keep it hydaulic? I'm about to start a 273 rebuild and am just getting the project plan and budget laid out. My project is a '66 Plymouth Belvadere. I know, I know, not an "A" body, but at least I'm keeping it in the family

 

[toolmanmike]

Can't stay quiet even when I know better. TMM did a great build on his! I got a lot of advice on mine and learned a lot. The stock 4V setup rated at 235 HP was a beautiful factory setup and hard to improve on without a fat checkbook or cubic inches. I landed on the following-right or wrong this is how I am building it. It should be component matched for 5500 RPM if I did my job.
.040 bore with Egge 10.5:1 pistons.
stock heads cleaned up with hardened seats and 3 angle valve job and modern guides/seals.
Thin metal head gaskets to keep the CR up-fuel be damned!
Eddy LD4B with the small runners for air/fuel velocity.
Stock exhaust manifolds with heat risor valve removed and coated.
Dual 2 1/4" exhaust with free-flow mufflers.
Lunati vodoo hydraulic cam with comp springs and retainers matched to cam, stock shaft rocker setup and new pushrods.
(my research turned up added lift starts to work against you above .465" on these little guys) MP windage tray.
Holley 4V starting with the factory primary and secondary jetting.
O2 sensor for tuning fuel setup after break-in.
Stock distributor with Pertronix conversion and good plug wires.
TDC locator when setting up timing setup and degreeing cam 2 degrees advanced.
My machinest is a friend of mine and had build several chebby SB's for me and balanced the rotating assy and resized the rods and installed new rod bolts.
That will be my engine build, the cam and carb issues I am thinking about but I have everything bought and on the shelf and one kind of has to draw a line at how many components he buys twice.
My drivetrain is an 8 1/4 SG with 3:73 gears and will have a built 904 with stock converter and Transgo stage 2 kit and gearvendors OD.
Not looking for a lot other than a reliable-streetable highway driven nice daily driver.
My $00.02 for what it's worth------DRO
Good luck with your research/build!

Thanks for the kudos and great information. I still want to build a killer 273 but to get it there it would cost thousands of dollars and be so radical that it isn't fun to drive. All the drag racers I know that have screaming small blocks leave the line at 8,000 and get run down by a big cube engine that doesn't break 5,000 r's (I can't believe I said that).

The plusses of a 273 are: high piston height, even in 2 barrel engines; factory mechanical valve train; forged crank; closed chamber heads. They have high flow heads in comparison to cubic inches. They rev quick and high. nm9stheham is correct that the 64 and 65 heads have a different intake bolt size and angle. 66 and up are the same as all other LA (273, 318, 340 , and 360) engines. I would be looking at a solid cam, springs, and lifters. I have run the stock 4 barrel, 284 duration TRW, a stock 340, and E-4 Isky cams. They all had plenty of power, especially in a 64 4 speed Barracuda. Do you have a 4 barrel intake?

The minuses are: clutch, even with the 10 inch scalloped clutch mine is starting to slip in high gear after 5,000 miles, and that is with the small Isky E-4 cam; the 7 1/4 rear will most likely give up the ghost soon after making 250 to 275 HP, depending on how you shift.; Factory exhaust manifolds, but should be fine for what you want, with either custom Duals or 2 1/4 straight thru single exhaust. Cubic inches, but it makes up for lower torque with rpm range, easily up to 6,000 rpm;

Great info here too. If you build a powerfull 273 nad keep the 10" flywheel, find yourself a multi disc clutch or find a clutch shop that can beef up the pressure plate for more grip.

A "65" 273 would have a solid cam and valve train, but it is now 50 years old. Obviously it was changed at some point. I would look at the CL 20-220-3, http://www.summitracing.com/parts/cca-20-220-3/overview/make/dodge , for close to Commando specs at .050 but, I'd go a step up to CL 20-221-3, http://www.summitracing.com/parts/cca-20-221-3/overview/make/dodge . I'd also borrow an adjustable pushrod, http://trendperform.com/, to check the length, since you had bent pushrods. Get the correct length pushrods. Check your valve springs to be sure they will work with whatever cam you choose. If you get your valve train sorted out, it is a beautiful thing to wind a 273 up to 6,000 rpm. Also do not be afraid to call Comp Cams, Isky, Racer Brown, or any good cam company and tell them what you have and what you want to do. If you are honest and know what you want to do with your car, you will be very happy.

The 2 cams aforementioned are

comp 206@.050/.425/110lsa
isky 216@.050/.425/108lsa

If you want to be in that realm of camshaft and stay hydraulic, I'd be more inclined to the melling 23203 or the crane 693941

Melling 214/224@.050, .444, 112LSA

Crane 216/228@.050, .454, 112LSA

Yes, Yes, Yes! I think the Isky E4 cam is a great replacement for the original 273 cam. You can stick it in a stock automatic car and have no idle or low vacuum problems. It will rev to 5000+ and still get you mileage on the highway. I have not tried any other cams but I am sure they will give you extra power. The stock hypo cam was a bit bigger than the 2 barrel cam but any of the above mentioned sticks will do a nice job with your 273. A 4 barrel is a must. You can benefit with a dual exhaust and/or headers as well. A good ignition won't gain big horsepower but it will make the small block more efficient. I tuned my distributor and it made a big difference in how peppy it ran. Lighter springs/ quicker advance and total around 35° is the key. Lots of threads here on FABO about that..Don't overbuild your 273. If you want a street animal, build a 408 stroker. (I can't believe I said that. I am a huge HP 273 fan) LOL tmm