lightest 3.0+ liter 4 stroke engine

Bizon said:

if there were 4 aluminum block/head engines with the same 2.5L of displacement but in OHV v4, OHV v6, OHV inline-4 and SOHC inline-4, which would be the lightest?

I'd guess a v4, but maybe that's not right.  Is the only reason most 4 cylinder engines are inline is due to cost or are vibrations more difficult to manage in a v4 configuration?

For a given displacement: More cylinders = more weight, and longer crank/cam shaft(s) = more weight. If I had to guess the weights: OHV V4 < OHV I4 < OHC I4 < OHV V6. The biggest question mark in my mind would be between the OHC I4 and OHV V6... Well, that and balance shafts for the I4's when you're talking 3+L displacement.

Cost is certainly part of it. Two smaller heads are more expensive than one larger head. There are vibration concerns too.  However, I am of the opinion that most attempts have also made critical errors in regards to the latter issue... So I can't (yet) speak to how fundamental the issue is or isn't.

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Pete. (l33t FS) said:

I have an idea that keeps going around of running just the right bank of a 5.3.  Replace the left cylinder head with a blanking plate, block off the left side water pump passages.  ITB intake arrangement.  Keep the odd fire crank because why not.

If you can make 550hp-ish from a bolt ons 5.3, then 270hp-ish is perfect for my purposes.  And as a bonus, you only need to buy ONE cylinder head! 

Also been done with SBC's... And what better blanking plate than the head from a flathead, including dummy plugs/wires to complete the look?

How about a USAC GM Chevy 4 cylinder.  Wait, it is only 2.7 liter. 

However, I don't think it could be a street engine.  Mechanical FI, runs on alcohol.

And dry sump.

Pete. (l33t FS) said:

I have an idea that keeps going around of running just the right bank of a 5.3. 

I always thought there should be an inline 2.4, 2.7, or 3.0 LS motor in GM cars/trucks.

Porsche made a 3.0L DOHC 16 valve 4 cylinder that weighs 385 lbs.  

Pete. (l33t FS) said:

I have an idea that keeps going around of running just the right bank of a 5.3.  Replace the left cylinder head with a blanking plate, block off the left side water pump passages.  ITB intake arrangement.  Keep the odd fire crank because why not.

I've seen guys do similar things with the old Pontiac Trophy-4, the half-a-389 slant-4. There was a guy running one at Bonneville using one of the really high-end aftermarket cylinder heads and Hilborn injection on alcohol. 

There was also Mickey Thompson's awesome little digger where he took a Trophy-4, then cut it in half lengthwise to make a 97.25ci slant-twin, and then installed a blower off a Detroit 3-71 with a single Hilborn injector and ran it on nitro.

How about a 330lb, 5 liter, 500hp v-twin? I remember seeing articles in the 80s about the bike built around this one:

https://thekneeslider.com/5000cc-v-twin-motorcycle-engine-for-sale/

The cooling system would add weight, so maybe air-cooled would be better.

https://m.youtube.com/watch?v=ND4EA0dnAM8

In reply to NickD :

Spending time working on and driving a '62 Tempest has admittedly been part of this idea.

It's a shame there are no good cams or rods and pistons for the 2.2 pushrod engine.  The head in that looks really, really nice.

paddygarcia said:

How about a 330lb, 5 liter, 500hp v-twin? I remember seeing articles in the 80s about the bike built around this one:

https://thekneeslider.com/5000cc-v-twin-motorcycle-engine-for-sale/

 

The cooling system would add weight, so maybe air-cooled would be better.

https://m.youtube.com/watch?v=ND4EA0dnAM8

How about a 6.8L 2-cylinder.  Unfortunately, it makes 32 hp and redlines at 1000 rpm.  Also weighs about 2000 lbs.

Curtis73 (Forum Supporter) said:How about a 6.8L 2-cylinder.  Unfortunately, it makes 32 hp and redlines at 1000 rpm.  Also weighs about 2000 lbs

"It weighs nearly as little as the horse whose power it tantalizingly approaches!"

Pete. (l33t FS) said:

 

Curtis73 (Forum Supporter) said:How about a 6.8L 2-cylinder.  Unfortunately, it makes 32 hp and redlines at 1000 rpm.  Also weighs about 2000 lbs

"It weighs nearly as little as the horse whose power it tantalizingly approaches!"

 

I rebuilt one once.  The pistons are the size of a 3lb coffee can.

Nissan VQ35, maybe? I think they're around 300#

In reply to Pete. (l33t FS) :

Back in the mid-80s, Hot Rod built a GM 2.0 pushrod engine with 200hp on pump gas and naturally aspirated with dual webers.

Hayabusa based V8, they claim 96 kg (211 lbs) here: https://www.h1v8.com/maxi-v8---specs.html

this isn't 3.0L, but I wonder what a LLV (Vortec 2900) Aluminum head/block inline-4 weighs.  my guess is the LLV weighs more than a VQ35.  I'm guessing this because I haven't seen a light inline-4 with >2.5L yet.

RX8driver said:

Hayabusa based V8, they claim 96 kg (211 lbs) here: https://www.h1v8.com/maxi-v8---specs.html

is this engine used in a specific class of racing or did they design it for no specific application?  the specs are nuts!

3.0l NA V8

• 200lb Long Block

• 90 degree V8, flat-plane crank

• 84mm Bore x 68mm Stroke

• 4 Bolt Main ARP Studs

• 10,500 peak rpm

• 460hp and 280ft/lbs

Bizon said:

this isn't 3.0L, but I wonder what a LLV (Vortec 2900) Aluminum head/block inline-4 weighs.  my guess is the LLV weighs more than a VQ35.  I'm guessing this because I haven't seen a light inline-4 with >2.5L yet.

https://www.millingtonengines.co.uk/new-engines/

The 2900 is probably not very light because it's a giant engine.

The vast majority of inline fours are under 2.5l because there are some pretty bad vertical shakes in the inline four.  Consider that the pistons are all at 90 degrees from TDC/BDC at the same time, but they are lower in the stroke than halfway due to rod angle.  The heavier the pistons (bore) or the further down in the stroke they are (stroke) the more there is a strong vertical shaking force as the engine's center of gravity moves up and down.  Which is where counterrotating balance shafts come in to play. But those are expensive, and need engineering, easier and cheaper to just make the engine smaller and add turbo as necessary.  Or say screw it, make a V6, they can pay more for a bigger car to house the mess.

How heavy is a VQ35?  It has all sorts of things going against it: it is a DOHC engine (heavy) and it is a V engine (more weight) and has timing chains (the covers add mass and bulk in addition to the weight of the drive itself) and it has variable cam timing (more weight) and it has a giant intake manifold (weight, weight, weight).

Bizon said:

RX8driver said:

Hayabusa based V8, they claim 96 kg (211 lbs) here: https://www.h1v8.com/maxi-v8---specs.html

is this engine used in a specific class of racing or did they design it for no specific application?  the specs are nuts!

 

3.0l NA V8

• 200lb Long Block

• 90 degree V8, flat-plane crank

• 84mm Bore x 68mm Stroke

• 4 Bolt Main ARP Studs

• 10,500 peak rpm

• 460hp and 280ft/lbs

I believe it originated as a project with Radical for a more powerful motor for their track day cars. The Radical SR8 uses a version of it.

Anyone mentioned the Isuzu V6 from the late 1990's; all-aluminum construction, 75 degree V angle, 215hp for the 3.2 liter indirect injection version.  Came in vehicles like the Axiom and Trooper.  Kind of the swan song for Isuzu's "car division".  Supposed to be really lightweight. 

pres589 (djronnebaum) said:

Anyone mentioned the Isuzu V6 from the late 1990's; all-aluminum construction, 75 degree V angle, 215hp for the 3.2 liter indirect injection version.  Came in vehicles like the Axiom and Trooper.  Kind of the swan song for Isuzu's "car division".  Supposed to be really lightweight. 

My employer was a Honda tech during the timeframe when those were rebadged as Honda Passports.

He doesn't have much to say about them, under the "if you don't have anything nice to say, don't say anything" clause.  I have heard mention of many engine failures before 40k miles, and the trials and tribulations of the valvetrain when they were out of warranty.

Would a rotary count? 20b's are pretty light for their true displacement (4.0L). Otherwise, I think the lightest obtainable engine would be a sprint car 4 cylinder. They're not actually 3L, but they say they're making 350hp and I don't even think they run a transmission so you save weight there. If ability to afford one doesn't matter, I would think it'd be hard to beat Judd's F3000 motor.

https://www.racecar-engineering.com/racing-tech/gm-chevy-midget-engine-more-than-half-a-v8/

The Toyota 2GR-FE is a 3.5L V6 that makes 295-314 hp at the flywheel stock and weighs in at 359 lbs.

Alex Wilhelm, one of the innovators in the MR2 2GR swap community, managed to squeeze 360 hp at the flywheel out of one with a tune, some minor modification and exhaust work.

https://wilhelmraceworks.com/blog/2gr-power-gains

In reply to The_BIG_Texan :

I forgot to mention, Lotus uses a modified version of the 2GR-FE with a supercharger on the Lotus Evora GT 430 which puts out 430 hp.

Supposedly an aluminum block, 8.2 deck Windsor with aluminum heads can get down to 350ish pounds and you can make those 363 cubic inches.

In reply to white_fly :

Rotaries are remarkably heavy.  They are metal-dense, with very little airspace inside, and a lot of the metal used in that density is thick iron.  Consider that people do V8 swaps without really changing the weight of the car.

Logan at Defined Autoworks constructed a 4 rotor engine that weighed less than a stock 3 rotor engine, just by using aluminum side housings and some other simple lightweighting mods.  Big expense, but big payoff.

Note that the Millington Diamond engines I keep pointing out make way more torque than most 3 liter engines, or 2 rotor rotaries, or even 3 rotor....

DaewooOfDeath said:

Supposedly an aluminum block, 8.2 deck Windsor with aluminum heads can get down to 350ish pounds and you can make those 363 cubic inches.

8.2 deck Ford 90 Degree V8s are kind of odd because the iron blocks are more like sheetmetal-thin lattices of metal surrounding the crankcase and water jacket.  The 5.0 blocks weigh around 135 pounds empty, which is comparable to many four-cylinder engines and almost half as little as many "normal" V8s.  Even the heavier 302 blocks had a tendency to calmly split in half when pushed to over 450hp for any length of time, as they first started to find in Trans Am racing after Ford stuck Cleveland heads on the 302 so it could actually breathe well enough to make power (Boss 302).

Aluminum blocks are not all that much lighter, so nobody really bothers except to prove a point.  When going for big power, people go for 9.5 (Windsor) or 9.2 (Cleveland) height blocks anyway, and who knows what combination of Windsor or Cleveland oil pan rail or front cover or oiling system or cam journal or cam height is used.

Yeah, you can get 8.2 deck aluminum blocks with 4.125" bores like a Chevy 400 and make a really huge small block.  (I have heard of as large as a 3.6" stroke in an 8.2 block.  That and a 4.185" bore make for a 396ci engine)  But imagine how much lighter the engine could be if you used a 3.5" bore and didn't have all that metal inside.