I think that a truck Norris for the 8.1 would need 12 more degrees intake and the same spread that the 5.3 has between intake and exhaust with an appropriate balance of overlap and LSA. The heads don’t seem to be in need of porting, just more cam and springs to spread the curve out by flattening the torque curve and allow the torque and back pressure to rise more gradually and let it rev to 6200-6400 with a rising boost curve. A T6 with a 1.32A/R should be in the 8.1 s wheelhouse a 5 inch pipe out, and on the 5.3 maybe would prefer a T4 inlet on a 1.25 A/R and the Truck Norris for it and a 4 inch exhaust after pipe . To equalize the velocity and the boost curve rise and back pressure curve desired for each. The reversed manifolds and 2.5 crossover for the 5.3 with the two regulators for each , but the 8.1 using the long tubes with the 3 inch crossover to the T6 volute. This would equalize the velocity and each to my guessing would be on equal footing to make their best power apples to apples. The 8.1 and 5.3 at the same boost would allow each to produce their best performance. The 8.1 would make more power if the NA power is optimized to the same degree as the 5.3.
@@fenatic7484 Vizard has a 496 BBC making 717 bhp and 711 lb-ft. It has a 105* LSA, 236/240, 0.690" lift and it "idles like a Cadillac". The 8100 will be down on power and torque, but it'll be much better than the ZZ502 cam.
In a lightweight car the 5.3 would be close to edging out the 8.1 ina dragrace but I think the 8.1 would still take the smaller motor. On the street, the 8.1 would be alot more fun to drive
Assuming a 2000 RPM drop on the shifts, the 5.3 makes more average power. Also, torque breaks transmissions. That said, drop a cam in the BB, and it's no contest
Sheeeeit that 8L has the wall in its plenum still there. Remove that wall from the 8L plenum and smooth the mold lines and casting trash and the 8L can actually breathe. It’s easily an extra 20whp. With a cam an FI the real limitation would be
My application is very weight sensitive, so I would go with the aluminum 5.3 over the cast iron 8.1. That's 415 pounds for the aluminum 5.3 compared to 557 for the 8.1 truck replacement engine, or 602 for the 8.1 complete engine. Source : 2022 Chevrolet Performance catalog pg. 14.
Whichever motor has a driveline that is closer to optimized will win, if they're both optimized then they'll be about even but the greater average power of the 8.1 probably wins.
@@HioSSilver1999 if that was true diesel dragsters would be the top dogs. HP is how much work you can do tq tells you how hard you can twist without slowing the engine down. Now having power over a broader curve helps especially with older tech but in a world that 10speeds is normal you can get away with a more peaky curve
@@mddunlap03 I'm not denying there is some extreme ends of this..... But at the same time a small peaky engine in these trucks isn't gonna work well in the same configuration.....of which that is the question here. These a10s help every engine they're behind. If you multiply more tq by more gear you get more tq than you do multiplying less tq by more gear. There's also tq management in the programming of these a10s. Of which more tq still gers managed more than less tq. But you also run into heavier components with more tq which will reduce acceleration. I mean a 4l80 is gonna kill a 5.3 acceleration wise. But a 8.1 will laugh at that long first gear. Just so many different combos.....but in the end if both are right tq will win.
Congrats on 200k... I would guess that the 8.1 would get out front maybe to the 1/8th but then the 5.3 will gain ground and go around it... Bench racing at it's finest 🤣
Need to see what the 8.1 does with a Raylar cam, I know the heads run out of breathing room at about 4500 but I'm interested in that torque. Those are diesel numbers!
When horsepower is similar, more torque wins the race, provided traction isn't an issue... That amount more torque generates far better acceleration at higher speeds.
If you gear the 5.3 to make the average torque output "EQUIVALENT" at the rear wheels to the 8.1, It should accelerate the same as the 8.1! It's all about (TORQUE TIMES the GEAR RATIO EQUALS ACCELERATION!) Example 600 lb/ft at 4000 RPM= 800 lb/ft at 3000rpm IF YOU INCREASE OVERALL GEAR RATIO by 25%!!!!!!!!-!!!!
Of course the 8.1 if it gets traction would eat the 5.3 with the same gearing, and if you change gearing for the 5.3 it should run close to or equivalent to the 8.1! all you have to do is multiply the torque at every RPM level "times" the overall gear ratio till you find a ratio increase that makes average torque equivalent!!! and changing the ratio by that amount should deliver equivalent acceleration!
I generally agree but I would like to also have Dino pulls have a time to achieve max rpm. The faster an engine can wrap up to high rpm. Exotics for example with flat plane cranks can rev to rpm so much faster than American V8s. Race car vs drag car rpm range and use. There is not much info in this area on the web because so many variables are involved.
Just a thought, torque is the ability to do work . Variables variables what if, can I do this 🌪 to make my small block compete with a big block, Yep! But... what if you give the big block as much love and attention, is no replacement for displacement a thing of the past because of boost? I think not. GM Ford Ferrari Ducati Harley-Davidson Triumph ect ect bigger motor more power every year, marketing ploy? Why not just make more power with a smaller motor then. I'm not so sure all of us in the comments section are smarter than all of those people but.. you never know, one thing for sure though- more with less- turbo LS- is friggin killer! 0h oh twins on a 427 FE 🤘🤤
With more torque couldn't you just run a longer gear for top end? Since the big block can't rev as long? Seriously, you guys probably know more than me. I'm just a body man, haha
my 8.1 allison truck runs so great towing heavy stuff just stock, they really did such a good job designing it just the way it was. A lot of people in the past had tried to use them for something they're not. So cool to have the LS head technology on a big block
The cam is needed to let that python out into the Anaconda it is. Being able to get er done from 2800-6200 is going to open up a new door. I wish I could have a cam ground for my FE with a 351W-LS and lighten up my 391 steel 3.79 crank and stroke it by offset grinding to allow my 105 block to 4.1 bores and 3.89 stroke, a.050 offset and a bore at the minimum would be .170 non thrust, . 230 minor and.250 major for 410.88 ci . It is a3 web block in the mains. I have ARP studs and a strong iron CapSaddle for the center 3 mains. It is like a brute strength girdle the ties the center 3 together in the thrust fore and aft and prevents cap fretting on that axis and has what are essentially claws over each cap on the side to side axis. There is room for cam sized dowels to be put into the caps and block to further prevent fretting. With the great pulse balance of the LS firing order and reduced vibration helps oiling and return. And the 5140 forged stock steel rods with ARP bolts are a very sturdy 410.88 ci engine at 1.128 hp per ci which it would with a 236/240@.050 hydraulic roller would be 463 hp easily and using iron early style C6AER heads with 428 CJ valves. At 12 lbs of boost is 830 some FWHP. And with a T4 7875 2nd Gen . I think it would move my 65 Galaxie 2 dr Ht down the road and the strip E85 if I must but my 16 gallon aluminum fuel cell would either need a bladder or another cell all together. But man I really hope that I can do this, even if I am blind enough to not drive, but my son can. The 394 with 10 lbs could do 725 FWHP and I believe with a 1.25 7875 and the L 2291F*20 4032 alloy pistons and good rings that I built loose for power. I could likely pull the headers and put a pair of passenger side log manifolds facing forward with a 2.5 crossover with a 7875 Summit turbo $ 429with one 10 lb sprung valve under it and an air to air cooler with a boost hat over a referenced 750DPvwith a Holley Street Dominator ( nice short runners) that flowed 268 cfm through the manifold and head. It should be all right and not scatter, it has 6600 rpm springs,,but 6200 will be its best. Mighty tempting thoughts.,I wish someone made adapter plates for an FE to 6.0L iron manifolds to face forward to make such a scheme viable. Those are great pieces! Run a 4-5 inch pipe down to a flange for two 3 inch pipes and I actually have an X pipe and I could run each 3 inch pipe straight out in front of the rear tires. Would the 3 inch X pipe help with back pressure after the turbo? I almost forgot I had it., but the two pipes could allow it to make the X pipe really efficient. No mufflers just straight back and out. Thoughts?
It would be really interesting to see both of these combos in the same car with the same transmission do a quarter mile drag race. Great video Richard of course both engines would need different gearing. I would guess a 3.55 gear for the 8.1 and maybe a 4.10 gear for the 5.3.
Well I think that Steve B said it best, you are giving up so much at the gear change so the 8.1 will 9/10 times beat the smaller displacement 5.3. Again no replacement for displacement. That’s for the video!
My brothers stock 8..1 avalanche is stout . we use it too haul two vehicles at a time. . one on the random trailer and have a receiver welded on the rear . and we connect a car dolly for the second car to rind on
8.1 if it hooked up would et better however yes the 5.3 can match it with gears but you will probably have to rpm the 5.3 500 past peak that's drag racing 😊
TMI /FYI . In some cases torque increases by almost 10% for every pound of boost i.e. this 8.1 And horsepower increases by almost +/- 10% for every 1.5 pounds of boost NOT A RULE ONLY SOMETIMES! (AS BOOST INCREASES > THE RATE OF TORQUE GAIN DECREASES BY the INVERSE of the PRESSURE INCREASE "PSI" ÷ TOTAL "PSI" ) Unless some other LIMITING FACTOR AFFECTS this TREND! EXAMPLE = TURBO REACHES FLOW LIMITS! Adding one pound of boost when you already have 20 delivers proportionately less power gain THAN Adding 1 pound of boost at 5 pounds of boost!!!!!!!!!!!!!!!!!!!!!! RULE#2= The horsepower required to overcome wind resistance increases at the cube of speed Not the square!!!! Tmi fyi SO;--- TORQUE = ACCELERATION / HORSEPOWER = TOP SPEED!??! kind of. No MASAKO I Switched from Engineering to psychology after 86 credit hours TMI! ( Phyc students 80+% female! ) and I'm a male.
To answer the questions asked in the video, the larger engine would be inclined to accelerate faster from a stop, due to the massive disparity in low RPM torque. With the right gearing, sure, the 5.3 could then give that big block a good run. Once the 5.3 gets spun up into its power band, it should really start pulling just as the big block has hit the limit of it's useful RPM range. It is always always always all about gearing
Keep it going Richard. So many of your videos are nostalgic because I remember the Hot Rod mags they were in. You brought all that knowledge over with this series and you made me and probably many others buy parts and hit junk yards.
the 5.3 will be faster. My daily is an old BMW 530d they are capable of obscene torque stock with bolt ons, problem is it just shreds the tyres. but not much horsepower(about 300hp on a good day) So if you remap to the limit across the board you have a car that smokes and burns up the tyres then falls on its face.. My map is set up with a low peak torque figure and an attempt to carry it fairly flat to the red line, result is a car that has no smoke, but more importantly lets the weight shift and gets the power down. The downside is it feels less fun and lively compared to an agressive remap, but in the real world, cause it puts the power down, its actually pretty nippy.
Which car would be quicker? Most likely the 8.1. Which car would be faster? Most likely the 5.3. Quicker implies time. Faster implies speed. The low end torque of the 8.1 (as long as you can maintain traction) is going to get the car moving much quicker. The RPM speed the 5.3 is producing the power is going to allow the car run faster.
Gearing and trans the same my moneys on the 8.1. You will shift earlier but you will almost always be in a better power band due to the TQ. If you can optimize gearing and trans in the 5.3 only I would go with the 5.3 as you can optimize the gearing in order to get into the high HP power band faster and stay there when shifting at a higher rpm. just my opinion
I would imagine that everything being the same with the car (weight, perfect traction, etc). The big block would definitely prevail in the 1/8th mile, but hard to say what the outcome would be in the 1/4 mile. Does the small block have enough time and rpm to creep forward after that? 🤔
The difference would be in the driveline. Gearing, stall speed and stall ratio would decide things. Given the torque curve of the 8.1, if it can get out and stay out it'll win. The only thing is the weight.
Love the 8.1 content. Think an aftermarket cam in the 8.1 would have been more fair comparison with the 5.3 TN cam. Please do that next! Then normalize for displacement hp/ci or liter. Your 1/4 mi question, seems like average horsepower divided by weight would be the best indicator of e.t.
For the love of God modify the 8.1L plenum to remove that weird wall on the inside. That would further level the field against a cammed smaller block. Also why no cam in the 8.1?
@@richardholdener1727so a cammed FI 5.3 can make similar horsepower power as a stock block 8L standing on one foot with one hand tied behind its back? It’s cool vid if that’s what you want to show. I enjoyed it greatly. Why not uncork the 8L and really show just how much of a difference there is? Even without a cam that plenum mod is known to make an additional 20+ whp without a tune. With a cam the gap opens incrementally further. Oddly enough the 8L trades some torque for this bump in HP iirc.
Both motors will be just as fast in the 1/4 mile, only the 8.1 will start quicker but then stall while the 5.3 will start slower but catch up, the power curves say so. (Sorry I use the translator 😅)
7:55 in and the STOCK 8.1 is matching the BOOSTED 5.3 up to 3500 rpm and hangs until almost 4000rpm. Boosted, the 8.1 at 3000 rpm is making 470hp, while the 5.3 is making 290. LOL Driving around normally and pulling I know which vehicle I'd rather be in! Gotta love displacement! That 8.1 must feel like diesel torque with healthy gas hp. Nice.
Build 2 cars and find out. Or build one car and just swap the engines. I'd like to see the race. Theoretically the 8 1 would take the first 1/8 and the 5 3 should almost catch the 8.1 at the stripe! Sounds like a good TV show. Engine Masters look out!
The question of if putting them in the same car reminds me of a Hot Rod Mag article from 20-25 years ago where they build “nearly identical” BBC and SBC (both 408”, same compression, nearly exact same cam specs, same carb, similar heads/intake/headers. With them as slide to the same as possible, the BBC made a bit more power and even more torque. When tested in the same car, the BBC that made about 25 more hp (they were just shy of 500hp if I recall correctly) ended up running 0.2-0.3 sec quicker in the quarter; much of that time being at the launch. Despite weighing more, the extra torque got the car out of the hole considerably better. Keep in mind, the car was a 1970 Nova (if I correctly recall) that had decent tires, suspension bolt ons (Cal tracs I believe), and a converter (forget if TH350 or 400). Given a similar test between the 8.1 and the TN5.3, it’d really depend on the car setup as to which would be quicker; though I’m apt to believe the 8.1 would have the advantage in most cases. The 2 cases where I see the 5.3 having a chance is: 1- The car is so traction limited that the 8.1 can’t utilize its huge torque advantage 2- The car is highly optimized for both combos, and converter/gearing allows the TN5.3 to overcome the torque disadvantage by staying closer to its peak HP number during shifts. The #1 example is where I could see the TN5.3 actually winning. The #2 example I see more as the TN5.3 evening the deficit, but not likely overcoming it. Ultimately, the more traction the car has, the more the 8.1 can utilize its huge torque advantage. I could see them going through the traps at nearly the same speed, but the 8.1 would short track (60ft, 330) quicker when traction isn’t an issue, giving the 8.1 a lower overall ET. Edit: That said, the 8.1 would make for a good sleeper with how mild it’d sound. The TN5.3 would sound cooler since it’d have a little bit of lope.
Running the numbers in a 3500lb car I get 130mph. 4.10 gear for 5.3, 3.00 (custom?) gear for 8.1. At 3000 rpms the 8.1 gets 17% more tq to the tire. Equal at 4k. 5k rpms the 5.3 is putting out 30% more. Gearing has a phenomenal impact. Personally on the street, give me the 8.1 with a 2200 stall.
With an automatic with a torque converter with good shift extension, there might not be that much difference between the two. The big block would get out of the hole better if not traction limited, but the converter could help the 5.3 stay in the power after shifts.
Makes me think I want to turbo my 8.1 in my Holiday Rambler RV. Looks like all I would have to do is run 80 lb injectors and an S475 turbo and WALA....800 lb/ft of torque...I bet I would get better gas mileage as well. I don't think my allison 1000 would like it though - its only rated for 625 lb/ft
Same gearing 8.1 would win short races but the 5.3 would run around it on the top end. Optimized gearing 5.3 could possibly edge out the 8.3 while still having more top end.
let's look at this from a different direction: what about a tow truck application? a truck norris cammed 8.1 with a zf5spd running 7lbs of boost would pull as well as duramax. using a 3.73 gear. a 5.3 combo would need 5.13-5.5 6 gear and more boost to have the same pulling power. I tow a 40' 15000lb travel trailer so i think like that. imagine a Kodiak with an 8.1 setup with an allison 6spd auto. slight mpg problem vs. diesel, but if you only use it 4 or 5 times a year....
If we ignore weight and other things I say it's going to be exacly the same depending on the torque curve. Because gearing is literally making these 2 engines the same. 631ft-lb at 4400 makes 530hp and 434ft-lb at 6400rpm makes 530hp. If we apply gearing then it's going to multiply the torque and divide rpm at the same wheel speed. Let's say the wheels spin at 800rpm, the 4400rpm gets a 5.5 gear ratio so it will have 3480ft-lb at the wheels and the 6400rpm gets a 8 gear ratio gets 3480ft-lb at the wheels and they will have the same exact hp.
@@CjCurrin I hope this doesn't freak you out or anything , but when I saw your name it gave me goosebumps , one of my best Friends in the World was..."CJ" (Charles James) Curran , he passed on way to early about 5 years ago , shortly after I acquired a 2000 Corvette I'd been wanting for a very long time , got a random tag from DMV & put it on the Car & paid no attention to it , shortly after , walking up my driveway I glanced at it and it started out "4CJ" ! I'm glad he's letting me drive his Car , sorry again if this is weird but I felt compelled to share this , good luck to you with your LS , mine is the BOMB !
The extra 150+ ft lbs is great but I honestly think it loses to the 5.3 simply from the extra 150-200 lbs of additional weight…. The 8.1 would be an amazing tow package. That’s diesel torque on very low boost. Impressive 🤘🤘🤘 Richard, you’re the man. Keep the content coming brother
Try it with a proper cam . They left the stock cam and valve train in the 8.1 . That cam alone upped the horse power to 425 on the 5.3 which is only 310 stock .
@@philthelawnman right . I work in the maritime industry. They use a lot of those 8.1 in marine applications. Mostly air (fan) boats . Let me tell you . They sound nasty when equipped properly 😎
But you would not run the same turbos on different displacement engines. Let say they are both 10:1 compression engines with both Built Bottom ends and equipped with proper Turbo Camshafts, Heads and Torque Converters. I would bet that the BBC would run a larger Diameter Turbo and make a lot more power than the LS 5.3. Don't get me wrong, I run a stock 5.3 in my 2011 Sierra1 and it has a Whipple on it so I am more partial to the 5.3. But dollar for dollar as far as upgrades, the safe bet is the BBC as far as Power.
Horsepower defines top end mph, torque defines the first part of the quarter mile, so same vehicle, trans, driver rear gearing and zero tire spin,(I know not real) the 8.1 would accelerate off the line faster, and gain the lead, same horsepower would mean that it would win, because the 5.3 does not make more hp to create enough of a top end charge, even considering the weight advantage, but the trick is getting perfect traction, so it’s probable that real world, the 5.3 would win, due to not blowing the tires off at the line as bad and lighter weight for a little faster speed through the traps But on the blacktop dyno (funometer) the 8.1 would be more enjoyable
can we thrash one of these 2.7 dual volute turbo motors from GM??? im impressed with 348 ft lbs at 1500 rpm from a 4cyl... but what can you do to hot rod them??? they are a touch lighter than a 4.8.... tiny car lil motor making good power would be fun ... and semi cost efficient???
The only thing that a big block can do that an LS can’t do better is that gnarly exhaust noise a cammed big block makes at idle. I’d only use one if it were significantly cheaper and was going in a muscle car cruiser/tourer or towing rig build. 5.3 can go in pretty much anything, they even made fwd versions of the 5.3 so fwd LS swaps aren’t out of the question. 8.1 is cool but if I wanted a go fast engine I’d go LS and if I needed a towing engine I’d go 12 valve. If I was building a 442 or a Classic Cadillac I’d think about it but only if it were cheap and easy.
Traction might be harder to come by with all that low end torque in the big block. Plus with the same gear you may run out of rpm in 8.1 setup. The 8.1 will need a rear gear change (higher gear lower numerically).
Average torque/ time = acceleration. Bb wins every time. This of corse means torque measured at the wheel. That 8.1 need a mercury outboard cam. Anyway 502 based dragsters are the standard these days don’t see many 325 running with the big boys.
I mean they are both just air pumps. The 5.3 just has to spin faster to move the same cfm. The 8.1 is going to be much lower pitch on the exhaust because the engine is spinning slower. Personally I would much rather the torque. Hp is pointless unless you are pinning the pedal. And towing I'd rather have less rpm and less strain.
5.3L vs 8.1L drag cars with equal HP: Same gearing: 8.1 will win because it will deliver more torque and the same HP to the tire. It will 60' better, step out ahead to the 330' and 1/8th mile, and then maintain it's lead on the back half. Higher gearing on the 5.3: ET will be very close because the steeper gearing multiplies the torque of the 5.3. AT THE TIRE, torque and HP will be the same.
How I think there are 2 different inertia factors, the first one vehicle mass (8.1 is heavier), but there's another inertia an that's rotational inertia (the inertia of the crankshaft and gears to rotation) there was said that a reduction of 1lb of rotational inertia equals to about 7lb of vehicle inertia so that could be a good influence in a race, In this aspect 8.1 has a lot more torque to accelerate rotational mass and needs to accelerate the same mas to only 2/3 the speed an Ls engine needs to, before achieving the peak horsepower, if the 8.1 can put that faster torque in the ground in my opinion should win
great video! as far as your question, there isn't a right answer because there are too many other variables in the drivetrain, suspension, and trans / torque converter choice IMO
Along the same lines as changing the gearing for the 5.3, could you not just get a cam for the 8.1 so that it makes power at rpm instead of rolling over.
LS with complimentary gearing ove the big block. Weight is a thing.... cutting weight gains more in a 1/4mile than HP.... its just harder to do after a certain point.
all about gearing and shift points keep the small block in its power band by the end of the 1/4 it would be right there as well as less weight with the SBC
As long as there is enough traction the 8.1 even with a taller (numerically lower) gear would win, but a shorter gear for the 5.3 stands a good chance on a lower traction surface. The 8.1 would need a serious tire. Lol.
Truck gets the 8.1 and car gets the 5.3… but only because of fitment and weight ☝️. That 8.1 is a beast. Looking forward to seeing some carb testing with it.
same car over and over the 8.1l will send it faster, rpm is time it takes more time for the 5.3l to make the power to equal the 8.1l tenths of a second matter!!
Flash back to 2005-2006 where supercharged E55 AMG's were pitted against V10 M5's. Both made around the same peak HP on the dyno, but the M5 would rev out to 8500. Where the E55 were done at 6500. The 1/4 mile results were decisive the E55 would win every time probably because of its massive torque advantage. 8.1 wins if it doesn't snap something with that torque.
Well you should tell us which on is better for a street drag car power and money comparison all the graph is cool but never a good conclusion on all this ls based stuff
all MPH calculators spit out a HP number not a torque number. If HP is the same and gearing is the same, they will be the same. Weight and all being equal
