Slantsix64
Well-Known Member
oh okay thanks for the input i have a floor shift
273 upgrade intake and cam
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What car? In my opinion, 273's were made to scream! Weiand or Performer. If early A, go with the 2.25 straight through single exhaust and original manifolds. Isky E4 or Racer Brown ST-1.
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65Val
Average Length Member
I would also block the heat crossover passage in the intake to keep the Eddy carb cooler
First let's start out with what you have, obviously a 67 273-2 barrel with a floor shift 904 and a 2.93 gear. Those 180 horse 2 barrels have 8-1 compression at best, They also have a single point distributor, and small tube single exhaust. They also have a smaller cam than the 4 barrel engines. The solid-lifter camshaft sported 248/248 degrees advertised duration and .415/.425-inch lift, compared to the two-barrel engine's solid-lifter cam with 240/240-degrees duration and .395/.405-inch lift. The 4 barrel engine also had stiffer valve springs.
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Actually, compression was closer to 9.0.
Yes,rated at 8.8-1 but like all other engine ratings I would guess closer to 8-1. I have never seen anyone prove that the HP engines really had 10.5-1 either.
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Small engine. It needs a small intake, small carb, small cam, efficient exhaust, and I would add a basic electronic ignition. Those things and a reasonable rear gear and it should run well. LD4B intake, 500 cfm carb, Isky E4 cam (absolutely nothing bigger than 220 ° @ .050) 2 1/4" duals with a H pipe or the HP single system, and a Mopar electronic ignition, or my favorite, A Pertronix conversion in a stock point dist. with a modified curve. In fact, I would do the distributor re-curve first and see what you have. You may be surprised how much better it runs. You can always re-curve it after you do all the rest. That made the biggest difference with my 273 and I had the stock dual point.
Slantsix64
Well-Known Member
thanks for the response ya well this is what i shall do 500 cfm 1403 dual exhaust 2.25 with stock manifolds(and take out the heat riser) upgrade to 73 and up charging system with mopar ecu. put a new timing chain run that sp2p eddy intake see how i like it (iam more of a torquer). and drop the 3.55 out back. ill do a before and after WOT video of the barracuda. also thanks for all of the advice .i don't believe theres any bad or good advice or opinons thanks you once again FABO!!
Most get the building torque equation wrong. Building torque is the same as building hp (since there basically the same thing torque and rpm = hp ) is air flow. Engine with big roller cams huge ports big carbs make more torque than engines without. The problem once you start adding lots of airflow is you start moving the powerband (or torque curve) further away from idle. And that's what we're really talking about with low end torque. Most stock low performance engines have an idle to 4500-4800 powerband. Most engines can move the top end of the powerband to around 5500 without altering down low too much.
So the trick is deciding how much cam, heads, carb, etc... you can go before you start moving the bottom of the powerband away from idle and start needed deep gears, stall etc..
The only really way to add torque is gearing
since most engines will fall into 1.1:1 to 1.3:1 lbs-ft per cid torque is pretty much fixed. To equal the average 3.55 equipped 360 you'd need about 1 ratio lower (4.56) not saying to go with those gears but the deeper your willing to go the better also can add deeper 1st and 2nd to help out.
273, it is more of the cam's fault where the rpm band lays. The addition of the mentioned parts without a larger cam or properly sized cam could be a huge mismatch. But even if the added parts were only a mild set, like bowl ported heads with 1 size up in valves, a small 4 bbl. and RPM intake, there would be no real loss of torque to put a frown on the face. It "should" all be good and upwards in power every where.
Of course, extreme parts like fully ported Victores and Dominator carbs would be silly and foolish. And not counted here today.
Of course, extreme parts like fully ported Victores and Dominator carbs would be silly and foolish. And not counted here today.
I didn't get in on this thread early on. I bet I read the first post a dozen times to make sure what he wanted out of his 273. It is so easy to over do a 273 just because of it's size and easier to go the wrong direction with a bad combination of parts. I am pretty conservative when it comes to these small blocks. If you want something that roasts the tires get a 340, 360, or build yourself a stroker. If you just want your present 273 to run a little better go easy on it and pick the right parts.
Yea man, you got it. The previous posters are in the ball with good advice
IMO. Cam selection is more critical IMO. The best 4bbl. intakes would just simply be small port units. A carb no larger than 600 cfm and headers if you wished but a good dual exhaust would seal the deal for a nicely rounded package.
He could do well even without a aftermarket torque converter or a higher gear ratio. (More gear equals torque release, not more engine torque.)
IMO. Cam selection is more critical IMO. The best 4bbl. intakes would just simply be small port units. A carb no larger than 600 cfm and headers if you wished but a good dual exhaust would seal the deal for a nicely rounded package.
He could do well even without a aftermarket torque converter or a higher gear ratio. (More gear equals torque release, not more engine torque.)
Well said
With my 273 there was a noticeable difference with changing the performer manifold to the ld4b. Again from my experience, letting my motor breath was a big part of getting the most out of a streetable motor. Tons of great advice on this thread. Combination etc.
For me, intake and exhaust opened the motor up. Yes, it is not a screamer. It sounds mean and I get good hp to the wheels.
For me, intake and exhaust opened the motor up. Yes, it is not a screamer. It sounds mean and I get good hp to the wheels.
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Toolmanmike I think your engine is a perfect blueprint for most people building a 273 and probably even the OP. And yes it's probably best to caution on the small side when picking cam, carb etc... for a 273.
The only reason I wrote what I wrote is it seemed like a few were saying here and on other threads. Small carbs, heads, cams etc... build torque which is false. They might be the right parts for the job especially if you want a powerband like a truck engine. But being too cautious can leave a lot of power on the table for no reason.
The gearing thing I meant torque can be equal to the ground not at the engine.
The only reason I wrote what I wrote is it seemed like a few were saying here and on other threads. Small carbs, heads, cams etc... build torque which is false. They might be the right parts for the job especially if you want a powerband like a truck engine. But being too cautious can leave a lot of power on the table for no reason.
The gearing thing I meant torque can be equal to the ground not at the engine.
4spdragtop
Well-Known Member
Im not happy with my choices when building my 273. 4 summers with it and want more power.
Above advice with cam and carb (not too big) is good.
My 2bl.pistons are killing mine.
Above advice with cam and carb (not too big) is good.
My 2bl.pistons are killing mine.
Your cam is killing you. You would need 4.10 or lower gears to make that thing go.
I would agree. Comp recommends: "" SOLID: Great in 340 & 360 with 9:1 to 9.5:1 comp., 650 to 750 CFM carb. and 3.55 to 3.91 gear. Largest cam to use with stock converter.""
Yes, stock converter in a 340/360.
I did what to include some information about helping the motor to breath
Exhaust - the stock Y on my car was 1 3/4" that was collected into 2 1/4" pipe. The commando motor I believe was 1 3/4" collected into 2 1/2" (not 100% sure on that)
The 4 bbl intake was a low profile mixed single/dual plane. Some what limited based on the hood/air cleaner clearance. I could not find the actual specs; carb height and intake/exhaust port size. (side note - weight was 49 pounds)
Both of these are dual plane
The performer 2176 has a carb height of 4.63"with port .97"/1.95" which was really a 318 (all purpose intake) (weight is 21.2 pounds)
The ld4b has a carb height of 4.9" with port 1.05"/1.95" which was designed for the 273. Weight is 22.5 pounds)
That changing to dual 2 1/4" exhaust and better intake is a big help to these motors
Exhaust - the stock Y on my car was 1 3/4" that was collected into 2 1/4" pipe. The commando motor I believe was 1 3/4" collected into 2 1/2" (not 100% sure on that)
The 4 bbl intake was a low profile mixed single/dual plane. Some what limited based on the hood/air cleaner clearance. I could not find the actual specs; carb height and intake/exhaust port size. (side note - weight was 49 pounds)
Both of these are dual plane
The performer 2176 has a carb height of 4.63"with port .97"/1.95" which was really a 318 (all purpose intake) (weight is 21.2 pounds)
The ld4b has a carb height of 4.9" with port 1.05"/1.95" which was designed for the 273. Weight is 22.5 pounds)
That changing to dual 2 1/4" exhaust and better intake is a big help to these motors
I replaced the exhaust on my 66 Dart when I rebuilt the HP273. Somebody had replaced the exhaust crossover with a small diameter 2 barrel pipe. I should have measured but I would guess 1 3/4". The Accurite LTD system was much bigger. Yes, the intermediate pipe on the HP exhaust is 2 1/2" through a low restriction Hemi type muffler with a 2 1/4" tail pipe.
She can scream
Slantsix64
Well-Known Member
So this is my final set up 273 stock cam lbd4 dual plane 500 cfm eddy .86 primary .90 secondary rear end ratio 3.55 7 1/4 dual exhaust 2.25 to the back stock manifolds electronic ignition. Heres a little video of the tire smoking and brake check ha. Thanks for every ones advice on here gained some good results!
1967 barracuda 273 Burnout
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