Low speed torque and driveability ?

[ir3333]

Cruising around town 1400 -1600 is where i noticed throttle response was lazy.
Compare the 256 with the 268. and the 256 wouldn't make as much torque as a stock cam below 2000. The graph
doesn't show the diifference below that but it is even greater. I did have a stock 340 with the generic replacement
Melling 340 cam at .204 / .214 duration. That thing would pin you in your bucket seat at any low rpm and would break
the tires loose at low speeds as well. 3.23:1 gears

 

[Newbomb Turk]

What happens when an engine makes more power when you increase the air temperature?

I'd say it's a case of piss poor carb parts selection and tuning.

 

[273]

Cruising around town 1400 -1600 is where i noticed throttle response was lazy.

How do you know it's cause of torque and not say something like overlap ?

Compare the 256 with the 268. and the 256 wouldn't make as much torque as a stock cam below 2000.

I don't know about that, possibly

I doubt the 256 would give up much it's got slightly more @ fifty duration, less advertised, similar lift, on a 110 lsa which should give better low end torque than 340's lsa.

But yes we don't have any dyno evidence down under 2000 rpm so it's a bit of guess work.

The graph

To me don't look like these much difference down low

doesn't show the diifference below that but it is even greater. I did have a stock 340 with the generic replacement
Melling 340 cam at .204 / .214 duration. That thing would pin you in your bucket seat at any low rpm and would break
the tires loose at low speeds as well. 3.23:1 gears

How much torque do you need at 1500-2000 rpm before it's. Not lazy ?

Say there's an amount eg. 300 lbs-ft does that mean a large displacement engine can never be lazy no matter the size the cam ?

Sure it's not the overlap the engine is not like running there?

How long does your car spend under 2000 rpm at full throttle ?

View attachment 1716233453

View attachment 1716233454

RPM Operating Range:1,000-5,200
Grind Number:XE256H
Cam Type:Hydraulic Flat Tappet
Lifter Style:Hydraulic Flat Tappet
Camshaft Series:Xtreme Energy
Usage:Street/Performance
California Proposition 65:WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov
Advertised Intake Duration:256
Advertised Exhaust Duration:268
Intake Duration at .050 Inch Lift:212
Exhaust Duration at .050 Inch Lift:218
Intake Valve Lift:0.447
Exhaust Valve Lift:0.455
Lobe Separation:110


If you look at this 360, @ 2500 the stock 2bbl cam makes about 330 lbs-ft and the xe256h & xe268h makes about 380 & 370 lbs-ft respectively a good 40-50 lbs-ft over stock cam, at 2000 rpm the stock 2bbl cam is still about 330 lbs-ft, the other aren't dyno'd down there so it's a guess but the dyno graph you provided didn't drop off there so I'd it safe to guess there still a positive gain possibly not.

I could be wrong and it's all about the torque especially since we got to guesstimate and piece together what's happening down there but I not seeing any overwhelming evidence saying so.

Graph starts at 9:45

 

[273]

Here's the 3 400 hp 318's

Mopar 318
RPM	HP	TQ
3,000	190	332
3,500	241	376
4,000	286	376
4,500	321	375
4,900	357	382
5,000	363	381
5,500	388	371
6,000	398	348
6,200	400	339
6,500	393	318

Junkyard Jewel 318 Power Curves
RPM	TEST 1		TEST 2		TEST 3
	Torque	HP	Torque	HP	Torque	HP
3,000	334.9	191.3	354.1	202.3	349.1	199.4
3,500	360.7	240.4	378.2	252.0	380.7	253.7
4,000	376.6	286.8	402.3	306.4	401.5	305.8
4,100	379.3	296.1	402.4	314.1	401.6	313.5
4,500	374.0	320.4	402.5	344.9	400.1	342.8
4,600	374.0	327.6	403.1	353.0	400.6	350.9
4,700	373.5	334.2	400.6	358.4	408.0	365.1
5,000	363.9	346.4	389.7	371.0	402.0	382.7
5,500	344.0	360.2	368.3	385.7	386.5	404.8
5,900	331.1	372.0	347.1	390.0	361.4	406.0
6,000	328.3	375.0	344.0	393.0	353.8	404.2
6,100	319.4	371.0	339.2	394.0	347.8	404.0

RPM	TQ	TQ	HP	HP
	BASE	PORTED	BASE	PORTED
3,000	335	335	192	192
3,200	342	340	208	207
3,400	351	356	228	231
3,600	365	369	250	253
3,800	374	379	271	274
4,000	379	384	289	293
4,200	378	383	302	306
4,400	375	383	314	321
4,600	376	382	329	335
4,800	375	386	343	353
5,000	372	384	354	366
5,200	367	383	363	378
5,400	361	379	371	390
5,600	355	374	379	399
5,800	350	371	386	409
6,000	345	365	395	418
6,200	341	360	402	425
6,400	329	345	401	421

 

[273]

Stock 2bbl with headers vs 4bbl headers and xe262h

TORQUE SUPERFLOW 901 DYNO-TESTED AT WESTECH
RPM	BASE	MOD 1	MOD 2
2,000	292
2,500	287
3,000	287	338	336
3,500	272	335	340
4,000	248	326	330
4500	218	309	319
5,000	188	285	296
5,500		250	258

 

[273]

Magnum stock cam vs mild 265 hydraulic roller
Both about 400 lbs-ft at 3000 rpm

 

[273]

477 hp 318

RPM	TQ	HP
2,500	337	161
2,600	350	173
2,700	357	183
2,800	357	190
2,900	356	196
3,000	351	201
3,100	345	204
3,200	339	207
3,300	343	216
3,400	356	230
3,500	371	247
3,600	385	264
3,700	396	279
3,800	404	292
3,900	410	305
4,000	415	316
4,100	418	327
4,200	420	336
4,300	422	345
4,400	421	353
4,500	420	360
4,600	421	369
4,700	425	380
4,800	426	390
4,900	427	398
5,000	427	407
5,100	427	414
5,200	426	421
5,300	425	428
5,400	423	435
5,500	421	440
5,600	419	446
5,700	417	453
5,800	415	458
5,900	412	462
6,000	407	465
6,100	401	466
6,200	397	469
6,300	393	471
6,400	390	475
6,500	386	477

 

[273]

If you look at all the 318 builds there all making 332-356 lbs-ft at 3000 rpm more than the stock dyno numbers on these graph for the 318 and a small margin for the 340 and 360. With comps xe262, xe268, xe275, 280 and fairly big solid roller in the 477 hp 318 making 337 lbs-ft at 2500 rpm which is still higher than stock 340, and would assume this should be the lazest one at low rpms ?

Unless all these engines take a super massive nose dive under 2500 rpms which I highly doubt for most of them.

 

[273]

360 stock 2bbl to 4bbl headers and xe262h

Torque
RPM	1	2	3	4	5	6
2000	357.3	376.9	346.7	356.8		349.6
2200	350.7	370.9	347.9	351.3		345.8
2400	349.8	367.5	355.9	353.1		350.4
2600	351.5	367.1	359.5	352.6	361.0	353.8
2800	358.8	374.1	367.1	357.7	359.7	361.0
3000	370.1	388.0	373.6	363.2	364.1	371.9
3100	371.7	390.6	375.9	366.0	369.3	375.6
3200	371.2	390.7	376.0	368.7	375.7	381.6
3300	371.3	390.3	377.1	368.8	381.0	389.6
3400	367.8	388.9	374.1	368.7	386.3	396.1
3600	361.2	381.7	369.2	367.0	390.8	400.1
3700	357.7	375.0	367.1	363.3	391.8	400.6
3800	349.9	370.4	363.6	358.7	386.9	398.0
4000	342.8	357.8	354.9	348.3	380.3	394.0
4200	331.0	346.3	344.9	337.6	383.1	389.5
4400	316.4	329.1	329.0	325.1	378.1	385.5
4600	295.7	311.0	313.3	310.5	368.2	375.6
4800	286.5	293.8	299.8	290.7	355.1	363.3
5000	270.9	278.7	282.0	272.4	342.7	351.9
5200		330.3	337.8
5400	311.8	321.7

 

[273]

Stock 273 Commando

Only about 280 lbs-ft at peak

 

[a-bodyguy]

I'd say it's a case of piss poor carb parts selection and tuning.

100% right
ive run all those cams including the 471 street hemi and the 484
the xe268 is stronger then the stock 340 cam across the board if the car is tuned right
having it in the 68 340 with nothing more then a stealth and a tuned 650 dp its nit even close
85k all stock 14.3 @97 mph
100k bottom end now new top end 268 same intake carb much much quicker and faster its not close
Tune the setup instead of blame the cam
that includes timming

 

[273]

Basically the 380hp crate engine

On The Dyno5.9LMagnum
RPM:	TQ:	HP:
3,000	407	233
3,100	406	240
3,200	406	248
3,300	409	257
3,400	411	266
3,500	413	275
3,600	414	284
3,700	415	293
3,800	416	301
3,900	416	309
4,000	417	318
4,100	419	327
4,200	420	336
4,300	419	343
4,400	419	351
4,500	419	359
4,600	418	366
4,700	416	373
4,800	413	378
4,900	409	382
5,000	405	386
5,100	401	390
5,200	397	393
5,300	392	396
5,400	387	398
5,500	381	399
5,600	375	400
5,700	367	399
5,800	361	399
5,900	354	397
6,000	347	396

 

[273]

Mopar Performance 360 cid 380 hp rated

RPM	TQ	HP
2500	380.6	181
3000	402.9	230
3500	415.1	277
4000	437.8	333
4100	439.5	343
4500	437.1	375
5000	416.3	396
5400	398.6	409
5500	388.6	407
6000	343.9	395

 

[1971 CY Dodge Dart]

My 71 Dart is a turd until a minimum 1500 RPM. Stock 340 and 3.23 rear gears. But I think my converter stalls at less than 2000 RPM so the converter is the first thing to address. Gears will stay due to the amount of highway miles it sees.

 

[273]

360 build

Dyno Test
Horsepower				Torque
RPM	Test 1	Test 2	Test 3	RPM	Test 1	Test 2	Test 3
2600	172.7	N/A	166.1	2600	348.9	N/A	335.6
2800	190.6	196.6	183.9	2800	357.7	365.8	245.1
3000	204.3	207.5	197	3000	357.7	363.3	345
3200	190.1	226	216.2	3200	359.6	370.7	354.9
3400	237.6	242.4	235.3	3400	367	374.5	363.5
3600	258.3	267.7	253.1	3600	376.8	390.6	369.3
3800	281.4	281.8	274.9	3800	388.9	389.4	379.9
4000	299.6	310.1	297.1	4000	393.5	407.2	390
4200	319.1	313.8	314.4	4200	399.1	392.3	393
4400	320.8	329.4	328.5	4400	383.8	393.1	392
4600	354.5	352.7	352	4600	404.8	402.7	401.6
4800	359.5	379.4	375.4	4700	397.2	420.2	408.4
5000	377.4	392.3	389.4	4800	393.4	415.2	410.7
5200	378.8	396.5	401.6	4900	399.8	410.6	412.2
5400	390.3	401	411.7	5000	396.4	412	409.1
5600	384	399.1	420	5200	382.6	400.4	405.7
5800	387	392.3	426.5	5400	379.5	390	400.5
6000	369.2	391.8	430.2	5600	360.2	374.3	394
6200	370.2	377	423.3	5800	350.5	355.3	386.1

 

[273]

473 hp EQ headed 273

Only makes 255 lbs-ft @ 3500 rpm and looks like it peaks at 330 lbs-ft @ 4800 rpm

 

[273]

A 655 hp 242/248 @ 0.050" solid roller 446

431-448 lbs-ft at 2500 rpm how big of a cam, how much torque you'd have to lose to have a lazy 446?

DYNO RESULTS
SUPERFLOW 902 ENGINE DYNO
STP CORRECTION
TESTED AT WESTECH
446 RB MOPAR
HORSEPOWER
RPM	T1	T2	T3
2,500	213	213	205
3,000	291	288	268
3,500	361	360	342
4,000	422	420	412
4,500	481	484	484
5,000	534	538	548
5,500	586	590	605
6,000	617	626	641
6,300	632	640	655
6,500	625	635	647
TORQUE
RPM	T1	T2	T3
2,500	448	448	431
3,000	510	504	467
3,500	542	540	513
4,000	554	552	541
4,500	561	565	565
5,000	561	565	575
5,300	565	568	577
5,500	560	564	577
6,000	540	548	561
6,500	506	512	523

LegendT1. Indy two-plane intakeT2. Indy two-plane intake with a Wilson 1-inch tapered spacerT3. Indy single-plane intake

 

[a-bodyguy]

My 71 Dart is a turd until a minimum 1500 RPM. Stock 340 and 3.23 rear gears. But I think my converter stalls at less than 2000 RPM so the converter is the first thing to address. Gears will stay due to the amount of highway miles it sees.

Stock 340 verter stalls over 2k
anything under 2k doesnt even matter
tune the setup
my 340 268 650 dp 3.23s dead stop punch from 850 rpm smokes the tires instantly tach jumps to 5500 stays there then 15 feet on the 1 to 2 shift at 50ish mph if i so choose
now 3.91s will smoke 1st and 2nd 5800 rpm if i want

 

[OldmanRick]

Aren't all these posted torque charts run at WOT? To me, drivability means nice/smooth bottom end acceleration with the least amount of throttle opening.

I'm still sticking with my ''big inch/long arm theory.....

 

[273]

Stock 340 verter stalls over 2k
anything under 2k doesnt even matter
tune the setup
my 340 268 650 dp dead stop punch from 850 rpm smokes the tires instantly tach jumps to 5500 stays there then 15 feet on the 1 to 2 shift at 50ish mph if i so choose

That's what I'm wondering, there decent dyno evidence that at least to 2500 rpm most these engines should be ok torque wise, so 1,500-2,000/2500 rpms maybe in question. Even with a stock stall realistically how long your spending under 2500/3000 rpms a fraction of a second maybe 1-2 at most during a full throttle run, even when you pass or merge car should drop down a gear be at 2500/3000 rpms.

 

[1971 CY Dodge Dart]

Stock 340 verter stalls over 2k
anything under 2k doesnt even matter

What do you mean anything under 2000 rpm doesn’t matter? If the stock stall was around 2400 rpm and mine stalls around 1800 rpm that’s a problem.

 

[ir3333]

I agree, it's the duration. As OldRick suggests, strong acceleration from lower speeds...even at part throttle.

 

[273]

Aren't all these posted torque charts run at WOT? To me, drivability means nice/smooth bottom end acceleration with the least amount of throttle opening.

I'm still sticking with my ''big inch/long arm theory.....

What I'm getting at more say stock cammed 2bbl 360 makes 330 tq @ 2500 rpm with 4bbl headers makes 373 tq @ 2500 rpm add a xe256 & xe268 and still makes around 375 tq say a xe275h drops down to 350 tq @ 2500 rpm, an xe285h say 325 tq @ 2500 rpm why is the 275 and 285 and maybe the 268 will usually be considered less drive friendly and stated cause will be considered the loss of torque.

Now you could say well we don't know what's happening torque wise idle-2000/2500 rpm which is basically true. But generally like you said we'd be at part throttle at those rpms to do normal driving and the engine will only be making a fraction of the available power it will be making what's needed which even a /6 is capable of doing unless when you drive a /6 it's floored the whole time. So even if you loss torque down here you generally wouldn't be using it anyways.

I'm just saying that the so called driveability might be other things than just torque.

 

[273]

I agree, it's the duration. As OldRick suggests, strong acceleration from lower speeds...even at part throttle.

The whole thing I'm getting at is torque the main/whole culprit ? As most would say or is there other factors that play a huge or bigger role ?

Obviously what we consider driveability and what part of driving has a huge effect, cruising, passing, spirted driving, from stop to full throttle and cruising to full throttle are all different in what were exactly comparing.

Like you said earlier you find a xe268h cam a dog compared to stock 340 cam, your saying cause of loss of torque, I'm saying maybe, maybe part of it but I don't think so, all those dyno's I posted low end torque don't seem to be an issue, but were generally not seeing under 2000-3000 rpms so hard to say for sure, but if there is an issue I'd say it's probably other things which I was hoping to get to the bottom of.

If it is mainly a lack of torque that would be fine I just don't see how.

P.S. Aj say 340 cams have terrible bottom end


An engine needs very little hp most of the time.

At 1313 rpm hp is 25% of torque.

Tq. hp.
100 = 25
200 = 50
250 = 63
275 = 69
300 = 75
325 = 81
350 = 88

At 2626 rpm an engine need half the torque to make those hp numbers.

 

[a-bodyguy]

What do you mean anything under 2000 rpm doesn’t matter? If the stock stall was around 2400 rpm and mine stalls around 1800 rpm that’s a problem.

no its not a 340 tuned right smokes the tires at 1800 not just spin smoke if not
somethings wrong with tune not the verter or cam