What would it take to make 1.44 lbs-ft per cid ?

[273]

I'm wondering what would it take to make a pump gas 365 engine make about 526 lbs-ft @ 4,000 rpm and 514 hp @ 5,900 rpm basically a very similar power curve to the Trick Flow 408 in the dyno graph I'm using as a theoretical goal, doesn't have to use any of the same parts just probably make a very similar power curve basically what heads and intake and what mods would need to be done to them to reach the VE% & efficiencies to have very similar power curves at similar rpms as this 1.29 lbs-ft per cid 408 or as close you think you could get?

A decent 365 should be able to make 450 lbs-ft so needing to find 76 lbs-ft more.

https://www.motortrend.com/how-to/408-inch-budget-mopar-westech/

 

[ch1ll]

Higher compression and a tunnel ram.

 

[PRH]

Off the top of my head, I’m thinking the highest TQ/CI combo I’ve ever built came up a bit shy of 1.44/ci…….it was 1.417.

A 14:1 572 with cnc ported Indy heads, a TR and a .800” lift roller cam.

It seems like those numbers are much easier to achieve in theory……..than in actuality.

I’m talking n/a on gasoline.

 

[273]

Here's a 365 with 1.28 lbs-ft, 468 tq @ 5,100 rpms & 537 hp @ 6,500 rpm, similar efficiency as the 408 1.28 vs 1.29 tq:cid.



Pump gas W2 537 hp 365.
https://www.motortrend.com/how-to/mopp-0408-w2-offset-rocker-heads-configuration/

Cam Specs*
Custom Comp Solid	Intake	Exhaust
Lobe number	7131	7132
Advertised Duration (@.020")	272	276
Duration @ .050"	243	247
Duration @ .200"	157	161
Lobe Lift	361"	366"
Theoretical lift @ 1.5:1 rr	542"	549"
Theoretical lift @ 1.6:1 rr	578"	586"
Lobe Separation Angle	108
Installed intake centerline	106

Port Flow Summary Flow Tested by Steve Dulcich Westech's Superflow 600 Flowbench (with FlowCom) All tests at 28" water depressionsion
IFT	Intake	Exhaust
050	32.1	24.2
100	62.5	54.5
200	132	115
300	188	170
400	236	197
500	272	209
600	300	213
700	314	215
Peak flow with pipe	230*

3,000-7,000 rpm peak hp if 6,500 rpm

Dyno ResultsDTS DynoTested at JMS
RPM	Torque	HP
.000	392	224
.500	390	260
.000	424	323
.500	453	388
.000	463	441
.100	468	453
.500	464	486
.000	453	517
.500	434	537
.000	397	529

 

[273]

Higher compression and a tunnel ram.

I imagine the average 365 pump gas with tunnel rams are falling short of 1.44 tq:cid.
But I imagine they both could help in the quest.

 

[PRH]

1.3 TQ/CI isn’t really that hard to do.

1.4+ is very rare here.

 

[remytherat]

Yeah I mean nitromethane and a 6-71 would probably get you there.

 

[273]

Off the top of my head, I’m thinking the highest TQ/CI combo I’ve ever built came up a bit shy of 1.44/ci…….it was 1.417.

A 14:1 572 with cnc ported Indy heads, a TR and a .800” lift roller cam.

It seems like those numbers are much easier to achieve in theory……..than in actuality.

Only a handful of the higher end builds that have been dynoed here have topped that mark.

I would believe that to be so, 1.20-1.29 lbs-ft per cid seems to be reasonable goals a lot should be able to get with parts that are available to us you see some hitting 1.30-1.35.

Basically I wanted to see what it would take for a 360 to act similar to an average efficient 408, I'm just wondering what the extra step are required to get more up to the 1.35-1.45 range I have a vague Ideal but you never hear what in particular.

 

[Hysteric]

Combustion Efficiency....

 

[273]

Here's basically a combo that closely accomplish the goal, problem is it don't really answer the question why/how ? It's vague what made this hit 495 tq and the W2 one only make 468 tq ?


It makes the same hp at the same rpm 515 @ 5,900 rpms but it's a bit shy in the torque department 495 tq @ 4,800 rpms vs 526 tq @ 4,000 rpms, The 371 is making 1.33lbs-ft per cid, would've been 1.37 tq:cid if was a 365.

371ci Mopar Small Block - Deadly Weapon​

SKMFX builds a budget iron-headed 510hp small-block Mopar

https://www.motortrend.com/articles/1208phr-371ci-mopar-small-block/

RPM	TQ	HP
2,500	401.5	191.1
2,700	408.4	202.1
2,900	426.2	235.3
3,100	429.6	253.6
3,300	430.8	270.7
3,500	425.3	283.4
3,700	431.3	303.8
3,900	444.9	330.4
4,100	461.2	360.0
4,300	473.9	388.0
4,500	486.1	416.5
4,700	493.7	441.8
4,800	495.0	452.4
4,900	494.3	461.1
5,100	491.9	477.7
5,300	485.9	490.4
5,500	480.7	503.4
5,700	470.9	511.1
5,900	458.4	515.0
6,000	450.9	515.1
6,100	441.5	512.7
6,300	424.1	508.7
6,500	402.9	498.6

By The Numbers371ci Mopar Small-Block
Bore:	4.060 inches
Stroke:	3.58 inches
Displacement:	371 ci
Compression ratio:	11.3:1
Camshaft:	COMP Cams hydraulic roller
Camshaft duration:	246/ 244 degrees at .050-inch tappet rise
Valve lift:	.648 inch
Rocker ratio:
Piston rings:	Perfect Circle 116-116-316
Piston:	KB Icon
Block:	Mopar 360 LA, production
Crankshaft:	Eagle
Rods:	Scat I-beam
Cylinder head:	EngineQuest Magnum
Intake valve diameter:	2.08
Exhaust valve diameter:	1.60
Intake manifold	Weiand
Carburetor:	Holley 750 HP
Header:	Schoenfeld stepped primary
Ignition:	MSD 6AL2
Damper:	CAT
Fuel:	VP Racing VP100

 

[273]

Combustion Efficiency....

Thanks Jesse

 

[PRH]

Here’s how I see it, in practical terms…….

However much fuel that 408 was using to produce its peak TQ, you’ll need to use at least that much with the smaller cubes.
But without a dramatically different head/combustion chamber, you’re going to need to turn the smaller engine to a significantly higher rpm to efficiently mix that fuel with enough air for proper A/F ratios.

The two engines aren’t going to have the same power band.

 

[PRH]

Nothing special bracket race SBC 383.
12:1, ported World sportsman 2’s(flow 280), roller cam, cleaned up SV, 1-7/8 x 2 x 3.5 headers.

Cam A made 490tq/599hp(1.28/1.56)

Cam B made 478tq/588hp(1.25/1.53)

Cam C made 509tq/608hp(1.32/1.58)

Only the cam was changed between tests.

These cams were all big enough that you could have started reducing the duration numbers a bit at a time and the TQ/CI numbers would have gone up……until you reached a point where they were just “too small”.
If the goal were simply make the TQ/CI numbers go up, you probably would have found a point where smaller headers payed off.
I doubt that by just changing the cam and headers you could reach 1.40, but I think 525ft/lbs(1.37) seems within reach.
The negative side of that is it would have probably lost 30-50hp in the process.

 

[ch1ll]

Here’s how I see it, in practical terms…….

However much fuel that 408 was using to produce its peak TQ, you’ll need to use at least that much with the smaller cubes.
But without a dramatically different head/combustion chamber, you’re going to need to turn the smaller engine to a significantly higher rpm to efficiently mix that fuel with enough air for proper A/F ratios.

The two engines aren’t going to have the same power band.

Yes, more rpm. Thats why I said tunnel ram. Both engine builds he posted used RPM airgaps. If he can’t get there with the ram alone, porting both heads and ram needs to be done.

And higher compression to increase efficiency. With aluminum heads he should be able to pump gas it at 11.3-11.5 to 1.

 

[Ant]

The easy way to make 1.44 lbs-ft per cube is with the use of nitrous oxide.

 

[PRH]

I had forgotten about one that beat the 1.40 mark here recently.
358” SBC for a road race car.
Dry sump(iirc), cnc ported 18* heads, solid roller about .700 lift, ported intake.
Made 509tq@5600/619hp@6700(still 603hp@7700).
That’s 1.42/1.73

 

[273]

Here’s how I see it, in practical terms…….

However much fuel that 408 was using to produce its peak TQ, you’ll need to use at least that much with the smaller cubes.
But without a dramatically different head/combustion chamber, you’re going to need to turn the smaller engine to a significantly higher rpm to efficiently mix that fuel with enough air for proper A/F ratios.

The two engines aren’t going to have the same power band.

I totally agree.

I'm just trying to figure out what it takes to build in the higher tq:cid ranges, cause ultimately I'm toying with the idea of building a mid/high 11's (don't want roll bar) 273 for my Valiant and like make peak under 7,000 rpms, more like 6,500 rpms if I can. Right now I got 360 380 hp crate.



Here's a 273/292 that makes 473 hp @ 7,900 rpm , but only makes 334 lbs-ft @ 7,100 rpm
Tq:cid is only 1.14 lbs-ft so lots of room for improvement.

 

[PRH]

I’d say the first thing you want are really good heads for the application.
In your case, something like a ported EQ head would seem about right.

Then, I look at it as, the worse the induction/heads are, the higher the CR you’ll need, the hotter the cam, etc.

Fundamentally though, I would just use parts that make sense for what the intent of the vehicle is……and not get hung up on the numbers.

 

[273]

Yes, more rpm. Thats why I said tunnel ram.

The point was to build with better efficiency not higher rpm, that 371 accomplished building the same peak power at the same rpm as the 408, both 515 @ 5,900 rpm but down on peak torque 495 tq vs 526 tq , 4,800 rpms vs 4,000 rpms.

And higher compression to increase efficiency. With aluminum heads he should be able to pump gas it at 11.3-11.5 to 1.

That would be fine, but is the cr of the 515 hp / 495 tq 371, maybe a tunnel ram might of made the difference.

 

[PRH]

if I’m not mistaken that 371 was at least somewhat built with the EM testing parameters in mind.

Part of the big TQ is from the smallish cam.
In those contests, it needs to strong right from the start.

 

[273]

if I’m not mistaken that 371 was at least somewhat built with the EM testing parameters in mind.

Part of the big TQ is from the smallish cam.

Besides the cam, I guess what I'm getting at would they spent a great deal of time and effort getting the velocities just right since both the 371 and the 408 are both making 515 hp @ 5,900 rpm they would have to be displacing similar fuel and air at peak hp anyways ? If so any idea what they would've been shooting for?

 

[PRH]

Well, the description of the 408 implies low buck…….which doesn’t coincide with tons of head r&d.
(After reading the article the engine appears to have TF heads)

I’m sure plenty of time was spent on the 371 heads for the contest.

RPM heads that flow 270 will easily make 550hp+, using any easy on parts Chevy lobe SFT cam and iron 1.5 rockers.
That’s with zero velocity r&d.

 

[PRH]

Unless you can find where someone has already built the combo you want, and has it documented well enough that you can follow the recipe…….then you’re going to have to build it how you think will work…….and see what happens.

 

[273]

Unless you can find where someone has already built the combo you want, and has it documented well enough that you can follow the recipe…….then you’re going to have to build it how you think will work…….and see what happens.

Ultimately if I decide on the 273 route, I plan on building a flow bench and play around with different factory heads and cams etc.. until it's dialed in (R&D) for me.

 

[PRH]

The MT 408 build isn’t exactly what I’d consider super budget friendly with a solid roller and TF heads.

Somewhat comparable build……
410”, 10:1, bowl blended RPM heads, easy on parts .600 lift roller, Victor 340, street Q 850 carb.

524tq@4700/538hp@5900.
Start of pull: 3900 = 496tq
End of pull: 6400 = 531hp