I need schooling - old vs. new engines

[Ricks70Duster340]

I have a Blueprint Engines 408 in my '70 Duster (w/Quick Fuel 750 VS) that runs great yet has a choppy idle. I also have a 2021 Challenger with a 392. The Challenger has more advertised HP & torque yet has a dead smooth idle and gets ~ 23MPG if I'm easy on it.

Besides the fuel injection being more efficient, why would the newer engine be so "tame" while delivering such smooth power on acceleration? Thanks guys.

 

[Sr4440]

A few things, FI, which you noted, adjustable cam timing, more efficient combustion chamber, variable intake runner length, reduced drag due to thinner piston rings and reduced fiction due to roller cam. These are just off the top of me head.

 

[Super-Cuda]

To be brief.. High powered integrated computers analyzing every facet of engine management including timing, air fuel ratio, shift points and even ambient air temperature. That together with computer designed aluminum cylinder heads with variable camshafts and engine blocks and multi speed transmissions. As far as Im concerned, technology at its best. Chev-LS , Ford, Coyote, DODGE, Hemi. All great powerplants.

 

[go-fish]

Lobe separation angle.

 

[go-fish]

I'm inching closer and closer to getting a 3G Hemi for my e-body project.

 

[abodyjoe]

I have a Blueprint Engines 408 in my '70 Duster (w/Quick Fuel 750 VS) that runs great yet has a choppy idle. I also have a 2021 Challenger with a 392. The Challenger has more advertised HP & torque yet has a dead smooth idle and gets ~ 23MPG if I'm easy on it.

Besides the fuel injection being more efficient, why would the newer engine be so "tame" while delivering such smooth power on acceleration? Thanks guys.

in the simplest terms. modern technology...

better machining, more knowledge and engineering, computers adjusting everything in milliseconds, 6,8,10 speed transmissions... etc... etc... etc.

 

[mgoblue9798]

Lobe separation angle.

This. It has more effect on the rumpity rump cam sound, or lack thereof, than anything else. More overlap, more lope.

 

[George Jets]

Your cam choice has everything to do with your choppy idle.

Pushing your power band up the scale in exchange for valve overlap at low rpms.

 

[67Dart273]

Very difficult to compare the two since the engine designs are completely different. Even though a 3G is not a "true hemi" it is still a hemi design, not a wedge. Football to baseball and all that

For example, I was astounded a few years ago to find that a 3G hemi only wants low 20's for total advance, while a typical wedge wants 35 ish and in some cases more than that

 

[RustyRatRod]

I have a Blueprint Engines 408 in my '70 Duster (w/Quick Fuel 750 VS) that runs great yet has a choppy idle. I also have a 2021 Challenger with a 392. The Challenger has more advertised HP & torque yet has a dead smooth idle and gets ~ 23MPG if I'm easy on it.

Besides the fuel injection being more efficient, why would the newer engine be so "tame" while delivering such smooth power on acceleration? Thanks guys.

Modern electronics.

 

[MopaR&D]

Along with all the technology features mentioned, the biggest improvement is port flow in the heads. Computer-aided flow modeling has allowed for much better port shapes that allow massive amounts of airflow while still having decent velocity. G3 Hemi 5.7 Eagle heads flow over 310 cfm on the intake side from the factory. I can't think of any factory head from any older pushrod V8s that flow anywhere near that much, aside from maybe the G2 Hemi or Ford Cleveland but those had lackluster port velocity.

Combustion chamber design and valve timing are also huge. Everyone poo-poos the G3 Hemi for not being a "true" hemispherical chamber but those quench pads on the sides make it so much more efficient than a true Hemi at lower RPMs (<3500). The shallower valve angle also improves "tumble" flow (like swirl but along a different axis of rotation) which again increases turbulence inside the cylinder during the intake and compression strokes and thus efficiency. IIRC ideal ignition advance on a typical G3 Hemi is around 22-28* thanks to the efficient chambers and dual spark plugs per cylinder.

 

[RustyRatRod]

I can give this example. I go help my friend Matt every now and again. He does high end restorations. Sometimes, he gets one that wants EFI and some other bells and whistles added to an already finished project. The few times I've helped with that, they were all lumpy cammed. When the EFI was added, it calmed the idle down drastically. One customer even swore and be damned we recammed it. We had to show him where there no witness marks on any engine fasteners and even then he had a hard time swallowing it. I prefer lumpy. lol

 

[cpearce]

Along with all the technology features mentioned, the biggest improvement is port flow in the heads. Computer-aided flow modeling has allowed for much better port shapes that allow massive amounts of airflow while still having decent velocity. G3 Hemi 5.7 Eagle heads flow over 310 cfm on the intake side from the factory. I can't think of any factory head from any older pushrod V8s that flow anywhere near that much, aside from maybe the G2 Hemi or Ford Cleveland but those had lackluster port velocity.

Combustion chamber design and valve timing are also huge. Everyone poo-poos the G3 Hemi for not being a "true" hemispherical chamber but those quench pads on the sides make it so much more efficient than a true Hemi at lower RPMs (<3500). The shallower valve angle also improves "tumble" flow (like swirl but along a different axis of rotation) which again increases turbulence inside the cylinder during the intake and compression strokes and thus efficiency. IIRC ideal ignition advance on a typical G3 Hemi is around 22-28* thanks to the efficient chambers and dual spark plugs per cylinder.

True story, an untouched Eagle head outflows a worked set of W2 heads, and can be had over the counter for much less cost. Technology has really changed in head flow and engine management. I do believe there is a place for both.

 

[Owen 340+6]

Im all for the radical shaking the car at idle and thumping her heart out. Just a nasty choppy idle is just peaceful to me. Then when you stand on it just blows the tires off. im no drag race so for me spinning IS winning much rather listen to a nasty old school than a new school engine idle. But I will be the last to deny how incredible these newer engines are when built

 

[67Dart273]

I can give this example. I go help my friend Matt every now and again. He does high end restorations. Sometimes, he gets one that wants EFI and some other bells and whistles added to an already finished project. The few times I've helped with that, they were all lumpy cammed. When the EFI was added, it calmed the idle down drastically. One customer even swore and be damned we recammed it. We had to show him where there no witness marks on any engine fasteners and even then he had a hard time swallowing it. I prefer lumpy. lol

I wonder if you could "change" that by modifying the timing curve right at idle

 

[RustyRatRod]

I wonder if you could "change" that by modifying the timing curve right at idle

I'm not sure. That's a really good question.

 

[AJ/FormS]

I wonder if you could "change" that by modifying the timing curve right at idle

Yes; with a stand-alone programmable timing module.
Put a scanner on your modern EFI car and watch what the factory does to your timing. It is a real eye-opener.

 

[Owen 340+6]

One way to fix all that crap, and it has 4 barrels.......

 

[mvh]

I guess I'm on the other side of this issue. I want smooth power when I put my foot down — I couldn't care less about a lumpy idle, in fact I hate the shaking. To each his own.

 

[MopaR&D]

I guess I'm on the other side of this issue. I want smooth power when I put my foot down — I couldn't care less about a lumpy idle, in fact I hate the shaking. To each his own.

My Duster has a moderately lumpy idle and it does get annoying in lots of stop-and-go traffic. It's like my engine is nagging me that we're moving too slow and I need to give it more throttle lol. It drives great at low RPM and smooths out as soon as you touch the gas pedal but I definitely wouldn't want the idle to be any more rough than it is for a car that gets driven on the street a lot. It does sound cool as hell though and I always get compliments about it. Pros and cons to everything lol.

 

[DionR]

Don't forget the addition of coil-on-plug or coil-near-plug on modern motors. Hot Rod did an article years ago about adding CNP to a SB Chevy and as I recall it added power compared to the traditional distributor and single coil.

 

[MidnightSwinger]

Lobe separation angle.

Yep.

 

[go-fish]

Don't forget the addition of coil-on-plug or coil-near-plug on modern motors. Hot Rod did an article years ago about adding CNP to a SB Chevy and as I recall it added power compared to the traditional distributor and single coil.

I had thought how wonderful it would be to add an MSD crank trigger to run COP on an LA. MPFI and a nice LSA. I researched the parts and looked at other shortfalls of the wedge. It just doesn't make sense to do if you look at how easy it is to just get a 3g Hemi. Way not worth it to stick with LA.
Now, I love the LA and I have put mega dollars in building 2 of them and put good money into building a few others. However, for my 'cuda I really want that ability to drive across country and get decent fuel mileage making level power.
The design limitations of the LA and wedge engines makes it where it has to keep it from eating itself the more power you make. With modern engines you can make power at higher levels before the inefficiencies start catching up with it. It's really about efficiency of design. Everything was designed beautifully from the get go. There has to be a lot of re-design with older engines to make them efficient and have big power.

 

[Rat Bastid]

I had thought how wonderful it would be to add an MSD crank trigger to run COP on an LA. MPFI and a nice LSA. I researched the parts and looked at other shortfalls of the wedge. It just doesn't make sense to do if you look at how easy it is to just get a 3g Hemi. Way not worth it to stick with LA.
Now, I love the LA and I have put mega dollars in building 2 of them and put good money into building a few others. However, for my 'cuda I really want that ability to drive across country and get decent fuel mileage making level power.
The design limitations of the LA and wedge engines makes it where it has to keep it from eating itself the more power you make. With modern engines you can make power at higher levels before the inefficiencies start catching up with it. It's really about efficiency of design. Everything was designed beautifully from the get go. There has to be a lot of re-design with older engines to make them efficient and have big power.

What are the shortfalls of an NA wedge compared to an NA Hemi? That’s crazy talk.

 

[go-fish]

M

What are the shortfalls of an NA wedge compared to an NA Hemi? That’s crazy talk.

Maybe shortfalls was not the right word but would you not say there are improvements made over wedge engines in the 3G design? I mean, port floor, mains, oiling, ....?