Low Torque from 440BB and troubleshooting/solutions

[1971 Challenger]

Hi Folks,
I need some help to make decisions on how to raise my torque. I'm not a gearhead so bear with me please. I have a 71 Challenger I bought a year ago. Unfortunately, I don't know everything about car's build. It's a 440BB (allegedly rebuilt - when is ?), Torqueflite 727 - 3 speed auto, Edlebrock performer high intake, headers, a big cam. I replaced the Holley no choke race carburetor with a Sniper 2 EFI, but the latter's not relevant to the original issue. I have 3.23 gears and I believe a stock torque converter. When I floor it, I just don't feel the torque. Factory specs on the engine as y'all probably know is ~385hp and 500 ft-lbs Torque, notwithstanding the mods. I've had cars from 500-650 ft-lbs of torque so I know what it should feel like. I understand the cam will increase HP but lower torque. I also understand my tall gears are optimal for speed and the highway. In the process, with my drop-out transmission, I considered upgrading to a 4th gear for better cruising performance.

As far as my goal, I'm not going to be drag racing the car. Overall, it drives fine but has no punch. I'm just looking for a better launch when I need it (), kind of middle of the road. So I originally looked into the 40L60E with a 3.73 gear change and besides being a sacrilege to put it in a MOPAR, it's evidently not reliable either. The A518 I saw on these boards had specs of only 400 ft-lbs (?). These boards also referenced 'gear vendors' which looks like a great overdrive solution but can still keep the stock 3-speed performance.

So how do I start with troubleshooting my issue in a methodical way?
1. Evaluate the engine to see if it's just tired and worn out? How please? It seems to drive and sound fine so I don't suspect this is the problem.
2. Start with a 2200-2400 stall converter?
3. Throw some moderately shorter gears aka 3.55 or 3.73?
4. Keep the present 3.23s and install gear vendor transmission add-on? They say it will improve the performance to some degree.

Any thoughts on how to tackle this improvement and suggest possible solutions would be greatly appreciated.

Thanks everyone, Chuck

 

[pschlosser]

I've driven several 440 cars over the years, and I can share a few thought about what I think I know.

Sometimes, engines can have all the right parts, and just don't produce the power you would expect. They may have a better intake, higher CFM carburetors, header exhaust, perhaps ported heads, maybe a long duration camshaft with lots of lift. It's all got to work together to be really great.

The stock 440-4 and 440-6 cars, 727 auto transmission, factory exhaust, sure grip differential and 4.10 gears perform pretty nicely. most are still 12 second cars, though. What I learned from 4.10 differentials is the stock 440 has lots of torque and horsepower above 4000 RPM.

With 3.23, they don't feel as torquey and they tend to smoke the tires. They have plenty of torque at and above 2000 RPM, but spin the tires unless you can get them to hook up. If you're goal is to go fast, like a superbird/daytona going 220 MPH, then 3.23 may be fine. But not if you want to be quick.

It may be easiest for you to try out some higher gear ratios before you get into engine tear downs and rebuilds. I would only go with a higher stall after you confirm the rest of the engine is running in top shape, and if you want to sacrifice some street drivability for better quarter mile times.

DO run a compression check on your engine, but unless it's burning oil, it is what it is, and should be producing decent power at that displacement level.

 

[6PKRTSE]

Without you knowing all of the specs of your engine it is just a guessing game for us. If the so called rebuild is just a gasket job and repaint on a later smog 440, your horsepower is way less than the 385 you think with only 7 or 8:1 compression. Sure, a 3000-3400ish converter and 4:10 gears would help.

 

[540HemiCuda]

BEFORE you do anything, you really need to identify the core problem. If the engine is the problem, transmission and gear changes would be band-aids at best and possibly more expensive than addressing an engine issue.

A few pulls on a chassis dyno would not be expensive and would tell you if the engine was putting out a satisfactory amount of power. From there, you can make the proper decisions.

.

 

[mopar jack]

I would check the initial timing. I have seen 440s with timing set to 2° that can't get out of their own way but when set between 10 and 16° will smoke the tires.

 

[Ricks72Chlgr440]

Give us the current idle timing and max timing shown on your timing light. Running a compression test is also a good idea. The 3.23 gears should be plenty for street/highway driving. Also, you might want to check the kickdown linkage to ensure the trans is shifting at the proper time. I install a Fairbanks shift kit into all the 727/904's that I've had. The shift improvement is wonderful and not harsh. I have my kickdown set such that at 25 or 30 and I floor it the trans will go down into first gear and really pull. If your trans shifts too quickly into 3rd the low speed performance will suffer.

 

[Challenger RTA]

Good info above. Before I throw gobs of money at it. I would diagnose where the enige is at. 1 As mentioned compression test. 2 leak down test. Then do a vacuum diagnoses. If in spec check distributor for vacuum and advance. Vacuum leak? Then proceed through all tune up secs. Does the sniper control spark. Check battery voltage. Low voltage low spark. Battery,alternator,coil and wiring.

 

[540HemiCuda]

The OP said it had a 'big cam', so at least some of those vacuum readings will not apply and confuses some of the rest. Also, a 'big cam' will like a lot more and earlier ignition lead than a milder one. Timing should be set for total, which for most big locks is often somewhere around 32* to 34* and should be 'all in' as soon as possible without spark knock in high gear. Usually, that is by 2,500 +/- with 3.23 gears. With lower ration gears, the engine will tolerate a faster curve. I have the timing 'all in' by 1,600 with my 3.91s. Our big blocks really respond to a fast curve unlike the small blocks.

Of course, if the compression is compromised, the combo is mismatched, or other mechanical problems are present, no amount of tuning will help.

Given the OP's inexperience and lack of hard information on the engine, getting the car into the hands of a seasoned muscle car mechanic may be the best, if not the only way forward. That is not meant to hurt feelings, it's just that it is very, very hard to diagnose engine issues over the internet. There are just so many possibilities in a situation such as this.

.

 

[1971 Challenger]

Understood. My thoughts exactly. Yes, I too considered a dyno pull to see my baseline. Thanks.

BEFORE you do anything, you really need to identify the core problem. If the engine is the problem, transmission and gear changes would be band-aids at best and possibly more expensive than addressing an engine issue.

A few pulls on a chassis dyno would not be expensive and would tell you if the engine was putting out a satisfactory amount of power. From there, you can make the proper decisions.

.

ks.

 

[1971 Challenger]

Agree on engine baseline and the compression/leak test but barring satisfactory results, I understand I could still be having underlying issues

The OP said it had a 'big cam', so at least some of those vacuum readings will not apply and confuses some of the rest. Also, a 'big cam' will like a lot more and earlier ignition lead than a milder one. Timing should be set for total, which for most big locks is often somewhere around 32* to 34* and should be 'all in' as soon as possible without spark knock in high gear. Usually, that is by 2,500 +/- with 3.23 gears. With lower ration gears, the engine will tolerate a faster curve. I have the timing 'all in' by 1,600 with my 3.91s. Our big blocks really respond to a fast curve unlike the small blocks.

Of course, if the compression is compromised, the combo is mismatched, or other mechanical problems are present, no amount of tuning will help.

Given the OP's inexperience and lack of hard information on the engine, getting the car into the hands of a seasoned muscle car mechanic may be the best, if not the only way forward. That is not meant to hurt feelings, it's just that it is very, very hard to diagnose engine issues over the internet. There are just so many possibilities in a situation such as this.

.

The OP said it had a 'big cam', so at least some of those vacuum readings will not apply and confuses some of the rest. Also, a 'big cam' will like a lot more and earlier ignition lead than a milder one. Timing should be set for total, which for most big locks is often somewhere around 32* to 34* and should be 'all in' as soon as possible without spark knock in high gear. Usually, that is by 2,500 +/- with 3.23 gears. With lower ration gears, the engine will tolerate a faster curve. I have the timing 'all in' by 1,600 with my 3.91s. Our big blocks really respond to a fast curve unlike the small blocks.

Of course, if the compression is compromised, the combo is mismatched, or other mechanical problems are present, no amount of tuning will help.

Given the OP's inexperience and lack of hard information on the engine, getting the car into the hands of a seasoned muscle car mechanic may be the best, if not the only way forward. That is not meant to hurt feelings, it's just that it is very, very hard to diagnose engine issues over the internet. There are just so many possibilities in a situation such as this.

.

on both the engine and possibly the transmission, albeit it shifts well?

With regards to vacuum, I failed to mention a much larger vacuum pump was installed along with two cannisters to compensate for the large cam so I don't suspect there any issue there but appreciate the feedback. No feelings hurt at all. That's why I'm here. Y'all are super helpful and knowledgeable.

 

[pschlosser]

With regards to vacuum, I failed to mention a much larger vacuum pump was installed along with two cannisters to compensate for the large cam so I don't suspect there any issue there but appreciate the feedback. No feelings hurt at all. That's why I'm here. Y'all are super helpful and knowledgeable.

Its time to post an image of that engine bay. let's see what you got.