Small Block vs Big Block

I had posted a video of my new best a few days ago..and in that thread someone mention small blocks are always faster than Big Blocks.. that comment has had me thinking for a few days. We no that small block wedge.. has tons of R&D because of NASCAR and Pro Stock truck.. I don't know that much about the big block Max effort wedge heads.. what is the real answer . The most power per cubic inch..

I do believe that there is no replacement for displacement , and big makes a lot of sense for a lot of reasons.
If you have an artificial ceiling.......make 800 h.p with each and the big block will be easier on parts , maintenance and maybe even the wallet.
But taking each platform to the top of the heap , big block would have an advantage on the time slip and maybe on the bank account too because there are more " shelf " products available.

The big block always wins...if you can get it to hook. Bigger bores, wider bore spacing, taller decks all make more power.

Let's say you build two engines, both 400ish CID. The BEST you can hope for on the small block is a 4.250 bore. On a BB platform you can easily go 4.500 with a much shorter stroke. Now you can shorten the decks (saves weight amongst other issues) and you'll have bigger valves and room for bigger ports. Plus, you can RPM the piss out of it and RPM makes horsepower.

All one needs to do is look at Pro Stock (or what's left of it) and see they run the biggest bores with the shortest stroke and RPM (until NHRA killed that).

It's simple physics really. The BB wins every time. Unless you want to talk Modified or Comp eliminator stuff. Even then, small displacement BB architecture has advantages unless you can get the car light enough to benefit from the SB architecture.

cubic dollars vs cubic inches.

cubic inches wins in both the wallet and on the track.

When I see what these small block guys spend on just convertors it makes my hair fall out.

I was looking at the rule package 4 nmca.n/a 10.5.. they call out big block Chrysler gets a weight break but yet they do not give the small block Chrysler a weight break.. so is there a cylinder head deficiency for the big block. I think at the highest level Australian Pro Stock small blocks make the most horsepower per cubic inch they are at 3 or maybe even slightly above.

N/A 10.5 RULES.. these rules are somewhat to help keep the field level..

Big,,,,small,,10k rpm...Never made much a difference to me.I caught HEMI-ITIS on the starting line @ National Speedway back when there were at least 3 legal dragstrips on Long Island.All the real fast cars had spark plug wires coming outta the valve covers!!I knew at age 12/13 what I had to have one day.Took almost 30 years but............

If you go by HP per cubic inch, historically, smaller displacement engines have had the advantage (up to a point). It is easier to make smaller engines more efficient.

It was done in the early Pro stock days when they started destroking the 426 Hemi to make it more competitive with NHRAs cubic inch to weight formulas. There were even some 383 blocks modified to accept Hemi heads so they could achieve smaller displacements, better bore/stroke ratios and overall lighter weight.

Old Modified Production and some newer sportsman classes also follow that pattern. i.e.: At the same level of execution, using 10 lbs per cubic inch, a 300 ci engine in a 3,000 lb car would tend to be faster than a 350 ci engine in a 3,500 lb car.

As pointed out, when there are no specific rules, max displacement will provide the best results.

EDIT/ADD: Interesting NMCA rules to help make a variety of combos competitive. Just gotta figure out what will work best for you.

Head flow and RPM, add lots of cubic inches

If you go by HP per cubic inch, historically, smaller displacement engines have had the advantage (up to a point). It is easier to make smaller engines more efficient.




If you go horsepower per cubic inch then you aren't truly answering the question which is faster.

Well....technically he did. As I pointed out and Myron added to (very well I might add) when class racing on a pounds per CID the smaller engine in a lighter car is almost always faster. It's easier to make a 3000 pound car with a 300 CID engine out run a 3500 pound car at 350 CID.

The smaller engine will RPM more, be able to use more gear and effectively move the car quicker. It's all about the levers.

I should have been my dad. Modified Eliminator was the SHIIIIIIIIIIIIIIIIT.

I was just trying to point out that finding the optimum combo gets more complicated than just getting, as he mentioned in his original post: "The most power per cubic inch."

NMCA is obviously trying to even the field by actually helping the bigger inch engines with their formula to allow more diversity and help racers with existing combos.

This (big vs. small) was transformed from rumor/gossip/opinion over 100 years ago. Dr. Lanchester's formula to predict outcome of a 4-stroke engine is still accurate, where:
B = bore diameter
S = stroke length
N = number of cylinders
C = a constant representing quality of materials and fuel energy value.

HP = B^1.65 × S^.5 × N × C

As you can see, displacement is far less valuable than large bore and more cylinders. Note that there is no factor for valve mechanism or number of valves. A significant flaw: no correction for mandatory parasitic loads which are disproportionately high for small engines: water pump, oil pump, cam drive, ignition.

In the LB/HP classes, they usually make the car as light as allowed and build the engine accordingly.

Which makes more power, more power per CI, which is faster, etc., are all very different questions with different answers. Is this a max effort project, budget, reliability, index, rules, ???.

A bigger engine needs to make enough power/CI to make it worth carrying the extra couple hundred pounds (unless you are in the aluminum block club) on the nose of the car.

Mostly it comes down to personal preference. If it was all about the "best option", we'd all be running Big Chief 632s or some such thing.

Clinton Cranston best machine built big block, NA wedge style head, over 1200 hp. Enuff said ! Lol

My nitrous cammed combo with a 1050 carb and C23 ( not very conducive to make NA hp, should make over 1000 with a 1200 carb and c14) only made 915 NA...lol , but can take 600 or more of nitrous....lol

If you had a race class which was NA, 2800 lbs, door slammer and no cubic inches what do you think guys would build? I bet there wouldn't be a single SB car in the lanes. People would show up with mountain motors. It would basically be IHRA Pro Stock.

SB engines win if there is a weight break or a cubic inch limit or something along those lines. If there aren't any size limits then guys are going to show up with big engines.

Have a car weight? Figure out what cubic in small or big block you can run.

Have a certain cubic inch engine available/planned? Figure out how much the car has to weigh. Don't know if that includes driver or not.

10.5" slicks "might" be a hindrance under some conditions/situations.
Big blocks do put more weight on the nose.

NMCA 10.5 rules

These are answers to the simple question of "most HP". If the question is "most HP per CI" or "most HP per lb of engine weight", then it gets more complicated.

Original post was basically comparing a wedge small block to a wedge big block. Horsepower per cubic inch I understand that an 800 cid Mountain Motor hands down is going to make more power and potentially go faster than any small block.. that's not what I was referring to I'm curious to know about Max effort big block Chrysler wedge heads not predator can valve or hemispherical headed Motors... so if someone was going to do a Max effort big block wedge semi conventional what would be the cylinder head of choice and how much power per cubic inch would it make

N/A hp/cube is easy. The smaller the motor, lighter rotator, more rpm, the more the HP. Bracket race maybe a different story. Big block, lower rpm, lower maintenance. My bet is a 900HP small block will not go 300 passes with nothing but lash and oil changes. Not to mention it would probably have less torque. Lets face it, the wedge big block head development is light years behind the small block stuff. That being said, they can run pretty decent. I'd love to have a 9000 rpm stick car. It's more work and $ than I can keep up with. Anybody that's a real power junkie uses boost. Variety is what makes all this stuff interesting.
Doug

Wasn't there like a B-1 cylinder head that was used in Pro Stock back in the day that could make some big horsepower on a wedge..

Being a wedge (closed chamber, quench, parallel valves inclined at a small angle to the bore axis, just like the 1949 Cadillac and Oldsmobile) isn't the problem.
The LS makes the common observation that "engines are more successful as they approach hemi design" a far stretch - the hemi is, by the away, many decades older, Harley-Davidson since 1926. The iron Sportster and Chrysler 392 are remarkably similar (both 1957) and both to WW1 aircraft engines.
Kaase remarked years ago that the correct intake valve was the biggest one you could fit, and the exhaust valve gets whatever room is left.
"All big blocks have inadequate valve area" (Vizard).

I've been running big block mopar for all most 40 years the problem there's very little RD I think the hemi got all the Rd in the early years I worked a machine shop for 15 years I cut up more 906 and 915 heads to look at core shift my 67 gtx with 512 with steel heads went 12.20 and drove it every were B1s a good set flow 400 in the intake I ran B1s up to 5 years ago they haven't changed that much my 588 with B1s from best made 1050 hp and went 8.20 at 2800 pounds I now run a set of heavily port Indy 600-13 XXX head with the help of Mike Sanders Chuck from Best and Tod Goodwin these heads flow over 500 on the intake and 390 on the exhaust we are still learning this combo the motor has made well over 1200 hp and 900 ft pounds of torque we raised the in and the ex a 1/2 inch cost come into a factor I've been very lucky to get the help to keep racing Mr Sanders and Best Machine can't say enough

On a Big block Mopar there isn't a head available that can make the HP/ci comparable to small blocks, that's just a simple fact.
N/A power, RPM is king and the available heads don't have the port cross section

Put a B1 head on a 400 inch BB and it will kill any SB. Every. Single. Time.

Yeah I think Mazzolini had a 383 with B1 heads a few years back. 8500 rpm shift points or something crazy like that. I don't know what the power level was but I'm sure it was up there. A combination like that would be a good match for a big inch SB with killer heads. The inches are about the same and the head flow would probably be roughly the same. The big block has larger bore size and room for bigger valves so it might hold its own. Probably comes down to who is building the engine and who is paying the bills.

If any of you small block guys are looking for any of these beasts just go on Facebook. Seems to be a fad going on now to have someone build you one, dyno it, and sell it. Take your pick and bolt it in. Lol

. This is an interesting idea how short could you get a deck on a big block.. and would the head work on this short of a stroke motor

Mazolini first 417 C.I. B1 motor was bought from Koffels which had been in there Comp eliminator car, it was a KB block with 4.5 bore and a stroke short enough to make that C.I.. He put in his 1964 Savoy SS car to make it into a SS/BM, he would shift it right at 8600 RPM, if he miss the shift by 150 RPM it would pull one or more of the 5/16 bolts that held the T&D rocker stands out
His second motor had a set of B1-MC heads on it and it was smaller, 411 C.I. I think he still has that motor
Short stroke, large bore, big heads

The big block has larger bore size and room for bigger valves so it might hold its own

This^^^

In theory this may be true, but a B1 headed 400 would be challenging getting the valvetrain to live past 10K RPM

Finding a block would be a challenge these days I'd think as well. On paper you'd be right.

Deck height would want to be 9" or there abouts.

It's not a combo that hasn't really made its place in Super Stock or Comp, the destroked Hemi 99 engines in Comp have seemed to be replaced by the P5 stuff

Thanks Clinton!! Your doing all the R&D to make a reasonably price big HP big block,Sold by BEST!!!

An impressive combination for sure. However if it was such a great engine why is Bob or one of his group running it anymore?

I think the first one got sold to a friend( plumber?) of Bobs who may still be racing it.
He still has the other one with the M.C heads, he had a lot of trouble with those head killing the rear exhaust valve springs in one run due to poor coolant circulation
I have a set of M.C. also, I hope mine don't do that on a Koleno block

A 400" big bore, short stroke, 10,000RPM big block is a pretty exotic piece for most people reading this.

A single 4 and correctly sized heads won't need 10k. 8500-8800 is a pedestrian RPM today and that should be all it would need. Also, cam timing would be relatively short. That's also a bonus. The better the head, the less timing you need to get the same RPM.

O.K. here is my opinion on the subject.

Take a 440CID Small Block with W8 heads and put it up against a PSO B-1 Headed 440CID Big Block

Combos would look like this

Small Block

4.00" Stroke
4.185" Bore
9.580" Deck Height

Big Block

3.40" Stroke
4.530" Bore
9.980" Deck Height

If you run a KB block on the Big Block you will even have a lighter engine than the Small Block

Pocket book would feel about the same....empty

I believe the Big Block would out power the small Block by at least 200HP

I agree - if the heads work, the cam can be less violent.
Reasons why down-sizing an engine by stroke reduction doesn't always track: it throws anything you learned w/r/t chamber shape, dome shape, spark advance, plenum size, and especially cam events over the cliff. You're walking on new thin ice.
A traditional hemi (deep section, they're not actually a "half sphere") is a liability without enough displacement to keep the piston shape out of the chamber during overlap. Back in the day, de-stroking a 354 or 331 to get 300" (Bonneville etc.) failed in favor of DeSoto engines with smaller chambers and longer strokes.

There was a big block wedge that ran N/A 10.5 Out here on the west coast it was owned by Chris.i thank it ran low 8s..not sure how big it was. maybe some one would remember..

A gen 3 hemi is a small block, and they sure make a lot power for not much cubic inch.

An all out W8 headed small block will make peak power at around 10K, willmake around 2.7-2.8 HP per cube. I don't see a B1 original head matching the HP/ci at under 9K. They're a 30 year old head design. I think the fact that they weren't ever really taken up in Super Stock or Comp Eliminator if fairly telling. I think we're going to have to agree to disagree on this one

That’s what I hear.

Ever hear this?
"What hits is history, what missed is mystery".
Winners get more press than losers.

I keep hearing about these fast gen 3s where are they

That Smith guy is building one but it’s a Pro Mod I’ve been told.

Why is there a B1 headed big block in you "heads up" car ?
Was that just "easy button" for you ?
LMAO !

Unfortunately far a few between right now,

NA 392-440CI G3 hemi will make 700-750 Flywheel , stock block Ported Apache heads STOCK VALVE TRAIN. and .640-.650 lift cam. same short block with ported Eagle(or 6.1) heads will do 600-700.....can't say it's cheaper and over 800hp in the G3 platform is definitely not cheep.

My opinion $ for $ a 451-500 B block based combos is the best bang for the buck, Non Hemi type build.

440CI(SBM)vs 440CI(BBM)vs 440CI(G3HEMI) again my opinion your best HP/CI is going to be the SBM, reason being the siamese exhaust port on the W8/W9 head has better cooling between the ports than any of the BBM heads I've ever cut apart....the G3 is limited in Valve lift in its stock form and to over come it is too pricey to kept inline with cost HP/CI of the other 2.

Just repeating something I heard that Herb Mcandless said decades ago, "you will need a 600 HP big block to drive past a 500 HP small block",or something VERY close to that, it's been a long time and I've thought about it over the years and I thought he followed it up with "And you can't leave 600 HP turned on for very long without doing non engine related damage" I spose when you think it through, the small block is probably going to leave the line harder [less torque turning the tyres] around 200 lbs. less weight on the front of the car, Maybe a 904 instead of the 727 and the big block is going to still need a bit up it's sleeve to drive by.......I thought it was still and interesting statement!

It still comes down to the fact that you can give some guys 700 horsepower and another guy 550 horsepower and if the 550 horsepower guy is a track tuner he would kick the 700 horsepower guys butt. Some guys get hooked up on numbers but can’t do anything with them.

wheres all the FAST smallblock mopar heads up cars??

don't get me wrong, id rather have a smallblock because they are so much easier than a tractor size motor bigblock, all big and goofy...but I just don't see it?? Meanwhile small block chevy and ford are right there....Again must be the R&D going into the more popular engines. Meanwhile im trying to race in a a heads up class (Ultra street) with a 30year old dinasour cyl head big block...LOL.

I don't know anything about boost, but its a lot easier to get 600hp nitrous through a 540 or bigger engine than through a 440 (smallblock)

To overcome the Gen 3’s valvetrain shortcomings you need to splurge for the T&D/Jesel stuff? What kind of lift can you get from them? How does a similar high end T&D/Jesel set up cost for W8 heads?

I thought in comp Eliminator which is heads Up Racing. Had quite a few small block Chryslers..

oh and I know of one small block mopar on the West Coast that went to the semifinals . In Ultra a few times in the nmca west Series..

Robs . Late model Challenger is a beast in 275 Pro with a 3 gen Hemi..

COMP, honestly I don't care...lots of rules and hp/ci so big block small block not that defined? Rob Goss, yea your correct there !
But in Josh's race and in Ultra, X275, Grudge...where are they? Hey I like smallblocks myself, but im too broke and just took the "easy button" Big BLock with B1's, everyone keeps telling me how great of a combination it is...LOL

is it a 4.70, 4.80 car? 5 sec cars are first round losers at Cecil county monthly race. The front runners are 4.70 and even 60's. After first round its all pretty much 4 sec cars, A lot of small block Chevy and Fords, but no small block Chryslers

Whitedart has be 5:30 on motor I’m sure he could run 4:7-4:8 on spray he and Brett have both those small block making some awesome power

Do you really understand what your saying?? These guys are making awesome NA hp, BUT its not that easy to just bolt on a plate and pick up 6tenths in the 1/8 let alone carry the weight and run on the 275 tire that Ultra street requires.
Maybe I shouldn't comment on this topic because im looking at it only from my narrow minded view of heads up small tire race cars. AND in that im saying where are all the fast Mopars...There are none ! THE only fast small tire car so far we can name here is Rob Goss.AND yes its a smallblock, but its a gen 3 hemi, not the "smallblock" that I think the OP was referring to.
Small block cars, I can say the ones I see that are wicked fast, Leon, Bill May...and ??
even at that im sure imleaving people out that are fast, but what do you consider "fast" I ask that because this is moparts...LOL Fast to me is 4.XX and even that I don't think Bill or Leon have done.

Flame on ! !

heres the original post....
my answer to this cube for cube, I would have to say..Smallblock will make the most HP per cube.

We know there not going to throw a kit on the combob they have now but with some changes they could be close to what your saying

under West Coast rules you would have to weigh 3500 lb limited to two solenoids and a dash 4-line not a cheater line... I used to drag the big block shitro let's on spray.Completely different rules and I don't think this is about power adders we all know that your car is badass and leave it at that.

... in my opinion my car is not fast enough I will continue to work on it and it was never the subject it was small block vs Big Block.. there is a s*** ton a four second small Tire cars in this country only a handful of fast N/A cars.. look at the heads-up classes back East you will have five power Adder classes a total of God knows how many cars and only one naturally-aspirated class with maybe five cars or 10 why is that
.

power adder is the "easy button" LOL
NA takes a lot more finesse and you have to actually use ALL the power you have. It is rare to see people go really fast NA because its a lot more work (at least my opinion) It is sad that more people don't race Mopars heads up. WIth the tall deck height and great heads available I just don't understand why you don't see more Small block mopars… It seems to me to be a way better platform than a big block. AND thanks for the compliment, but I consider my car slow, for now at least

Some of the fastest mopar door cars I have seen in person have been SB powered with W series heads. One was a 70 Challenger that had a repurposed older Nascar engine. He changed the cam and made a dual 4 sheetmetal intake etc. The sound this engine made turned heads the moment it hit the water box.

Any heads up stuff is a money pit. But N/A heads up, wow? Comp and Aussie Pro Stock have the most powerful SB's in the world. The cost isn't even on the same page as anything being discussed here. Neither is the longevity. There hasn't been a B-1 in Comp for years. There have been a scattering of SB Mopar but shortage of good blocks is an issue.
Doug

That's why there are limits on turbo and blower size: to keep you buying those $$$ N/A parts.

And those $$$ n/a parts would be?

Really - you don't know what I mean?

I just like this sound 🙃

https://youtu.be/QfiwYYn4KQA

love the sound of it too

That's how it should sound. Like old modified eliminator stuff. Very nice.

that is only part of the rules, the rest of the rules dictate the required weights for big block as well as small block combinations.

To keep the field level Big Blocks have to weigh more than small blocks at the same cubic inch.

SMALL BLOCK BASE WEIGHT (max cubic inch 470)
300 = 2400 + Over 300 add 1.25 lbs. per cubic inch
340 = 2450 + Over 340 add 2.50 lbs. per cubic inch
360 = 2500 + Over 360 add 2.75 lbs. per cubic inch
380 = 2555 + Over 380 add 2.70 lbs. per cubic inch
400 = 2609 + Over 400 add 2.65 lbs. per cubic inch
420 = 2662 + Over 420 add 2.60 lbs. per cubic inch
440 = 2714 + Over 440 add 2.55 lbs. per cubic inch
460 = 2765 + Over 460 add 2.50 lbs. per cubic inch
470 = 2815
BIG BLOCK BASE WEIGHT (max cubic inch 640)
440 = 2860 + Over 440 add 2.60 lbs per cubic inch
460 = 2900 + Over 460 add 2.55 lbs per cubic inch
480 = 2940 + Over 480 add 2.50 lbs per cubic inch
500 = 2990 + Over 500 add 2.45 lbs. per cubic inch
520 = 3039 + Over 520 add 2.40 lbs. per cubic inch
540 = 3086 + Over 540 add 2.35 lbs. per cubic inch
560 = 3133 + Over 560 add 2.25 lbs. per cubic inch
580 = 3178 + Over 580 add 2.10 lbs. per cubic inch
600 = 3220 + Over 600 add 2.00 lbs. per cubic inch
620 = 3260 + Over 620 add 1.80 lbs. per cubic inch
640 = 3296

Even with the deduction of 125 lbs the big block still has to weigh slightly more than the small.

Not sure if I agree but the example of the N/A class would suggest that Big Block are quicker per cubic inch.

Love the sound of a high winding small block

these rules are somewhat to help keep the field level

So, the best engineer using the best parts and most experience and driving skill shouldn't win?
Level field: heads up.
Anything else: give your friends* an advantage. NHRA started doing it in the 1950...

* important sponsors, people with money - like NASCAR

In any MAX EFFORT deal power per cube is ALWAYS going to be a SB end of discussion. Anyone who thinks different is in denial period!! It aint just a Mopar thing it is a thing for all. Look no farther than a class like Comp or NA 10.5

Ultimate NA power, again MAX EFFORT it is always going to go to the BB hands down end of discussion!!

As for NA10.5 rules. those weights listed are just the BASE weights. There will be adds and minuses depending on combo. They get way more into the weeds than most on Moparts will care to know. Rules are in place to try and level the playing field and in our class are ever evolving, as racers are ever pushing.

A BB Chrysler only gets a weight break for a TRUE wedge head. A 600-13 head would actually get a weight penalty for its NON STOCK bore space, we also have a weight structure tier that takes into account distance from the deck to the intake port. As most everyone runs heads that are extensively modified from stock.

Chris went 8.40's in the Cuda with the B1. Eventually I went 7.90's at 171 with the same engine after some updates at 2975.

Al is correct. HP/CID will always favor the SB. BUT... At equal displacement the bigger bore will ALWAYS make more power. Always. I don't even know why this is argued.

If you can run a small displacement BB or a big displacement BB I'm picking the BB every single time. I don't give a single crap what the HP/CID is.

I'll always take the biggest bores, the widest bore spacing and the biggest intake valve I can get. That makes horsepower. And horsepower always wins...if you can get it to hook.

Look at the turbo guys switching to big singles. They don't have to pull as much power out down low as the big single turbo doesn't make as much power down low.

what Bore,stroke combo are the top fuel Hemis?

Fuel is a liquid bomb. Fuel hates big bores. Fuel engines use small bores and long strokes because of the detonation prone nitro.

What the hell does a blown fuel burning engine have to do with a N/A anything?

Just asking..

Most are as follows:

4.200" bore

4.500" stoke

499CID

But again they have nothing to do with HP in a N/A motor


55lbs of boost running 100% Nitro

The cylinder wall need to be extremely thick to make sure they stay round and they don't break.

One Cylinder makes more HP than most complete N/A engines

Not many 1100Hp 400" Big blocks out there. Quite a few 1100hp small blocks out there, just saying. Also FWIW other makes have SB stuff that is a wider bore space they can work with as well.

Yep. Just like everything else Chrysler, you're screwed. The bigger bore spacing GM spaced stuff will beat all comers.

Are you saying 1100 HP NA stuff using Chrysler architecture? Pretty impressive.

. In Australian Pro Stock the small block Dodge has been at the top.. Bob book has built some pretty impressive ones as well.. there is room in a certain aftermarket block to do a 4 500 inch bore space. Sbm.... and a set of W8 could be manipulated

I forgot about the down under guys.

. Did Chrysler do 4.500 bore space in NASCAR.
I want to say it was around the time Sterling Martin was driving the Coors car I thought I read something along those lines. I think it was quickly band if my memory serves me correctly which it rarely does

Not many guys have the budget to build some of these engines a few of you are using for examples. High dollar high maintenance stuff for a few races a year

r6 block is 4.5 BC I'm doing one now, R6P8

Erin Elliot , has gone 1200 with the R5P7 Larry Wallace has had some good luck, And Patterson racing

You can take the R5 to 4.250" bore, the steam holes keep you from going any larger….but would you dare…….. best bet is to stop at 4.20/4.22,
4.185X3.75(413CI) Great combo ...for any one who wants to spend the coin.... it will equal any power out put of the same CI RO7/X or SB2
R5 can take a 3.75 stroke and still have cylinder wall length to support a typical piston skirt , a 4.000" stroke will fit, issue there is rod ratio and urber short hockey puck piston……. And it makes for a short lived “race engine”

R5 block and P7 heads With 4.310" Nikosil liners and boring the mains to 2.500", to give you some more crank overlap a 467CI is possible and has been done and will make enough power to turn a top fuel Blower at 8k and have a few 100 to spare.



With out a doubt the larger the bore the better with a wedge, canted valve and Hemis, don't seam to care as much, less chance of shrouding the valve...one thing we all can agree on is the larger the Intake valve the better.

When you change the bore pitch, you shorten the list of inherited characteristics. Like valve size and position, chamber shape, port config.
Oh wait - it's everything.

There would be a point of deminishing returns in regards making the highest hp per cube, I recall it being somewhere in the 3-400 cube range. I can't recall exactly.
Whilst a big bore is always better in terms of airflow, it's not the case when it comes to friction. There is a presentation on YouTube about it, one of the Cup guys presented it at a AETC or something similar. Very interesting

FWIW I had a BB that made 2.64 per cube. Oh did I mention it was a 99/06 Hemi Compared to some of the comp stuff that's just for beginners. I know of more than a few right at 2.8/2.9 that are in the 350-360" range

a big bore is always better in terms of airflow...
... and carries with it new problems w/r/t combustion chamber shape, charge energy loss, swirl, quench, mixture direction bias, flame front propagation, etc.

Smaller cylinders with very high B:S ratios make the most power, but the parasitic loads are not scaled, so a 90" V12 isn't as much better as you may suppose.

I have wondered about the parasitic loss due to big bore with short stroke versus small bore with a long stroke
I've always though that RPM was RPM ,no matter what the bore and stroke was for the same C.I. motor
I understand the N/A Pro Stock type motors use a large bore(4.625+) with a short stroke to meet the rules of 500 C.I. but how much of that is to get the bigger valves in the heads versus running a 4.350 bore with a long enough stroke to make 500 C.I.?

I'm sure there are frictional differences between those choices, I'm just not up on them, perhaps someone can help?

For the friction aspect, the long stroke would be at a disadvantage due to the higher rod angularity in the case of the SB (side loading piston more)? Longer stroke would also have higher piston speed, also increasing it's friction. Wonder how close to a wash it would be (BB vs SB friction)?

. I have a goal of 2.55 per cubic inch on the next W8 motor.. obviously dynos very. But 2.55 on the tool that we use is going to be tough

For anyone that may have been interested, the section about efficiency starts at around the 10 minute mark.

https://www.youtube.com/watch?v=rBZCnG1HwDM

the long stroke would be at a disadvantage due to the higher rod angularity
But... that's rod ratio-dependent? Don't all BBC have short rods (stock 454: 1.53:1)?

Longer stroke would also have higher piston speed, also increasing it's friction.
Reduced by the smaller wall contact area?

BBC 454 is 1.53 ,BBC 427 and 396 were 1.636 SBC 400 1.466.

I thought all three early BB Chevy type motors ran the same length rods
Wasn't the 396 motor the smallest bore with the same stroke as the 427 and the 454 increased the stroke from 3 3/4 to 4.0 inch stroke with the same 4.250 bore as the 427 had ?

Same rod, inherited from the 348 W engine in 1958.
3.76" & 4.00"

Fwiw all BBC use a 6.135 C to C connecting rod
…………396/402......……...….427/454
bore 4.094/4.126..............4.250
stroke 3.760...........……….3.760/4.000

... wish I'd said that.
Oh wait...

Yes you did, I just thought I'd clarify the rod length,...I see you still have not fixed the Hemi Magnum info for the 6.4 on your http://victorylibrary.com/mopar/m-table-c.htm#Boss chart...Thank you for all the other correct info in that chart

Sounds like a way to slip in a KB alum block and still get a weight advantage. Mega block is way heavy, KB not so much.

The KOS Demon I bought from Mike Robbins had the original motor. 4.500 bore, 3.81 stroke. Huge 47cc B1 heads with 1.7 Jessels, 16-1 and 300* cam. The first time I took it into the water box it had no rev limit chip and I was used to my 416 SB, so I just mashed it in 2nd and watched the guy who tells you to go open his eyes as big as silver dollahs. Next time I asked him what he was looking at and he said it was gonna blow. So that burnout I actually looked at the tack and saw 9300 right away. Mike said he shifted at 8600 or something.

I will sell it BTW.

My goal is to be less wrong than the Supreme Court.
I'm winning.

Is that with you being the judge or someone who is not biased

Well we are going heads up all motor racing this weekend I will report back how many Big Blocks and small blocks they're were

Good luck this wknd

. Thanks man going to need it

I have a reliable method of avoiding rude remarks: stop helping.
Did you think my questions are answered here? Not in many years.

For those not sure about the Supreme Court thing, explain:
Kelo
Citizens United
Batson
Dual sovereignty
FISA

When I built my first W2 340 I concluded that a 340" motor turning 7600 RPM was as "BIG" (in terms of pumping air..ie, at the same relative VE) as a 440" motor of the time turning 5800. Back it those days (late 70's early 80's) Mopar people were just starting to routinely pull their 440 wedges and swapping in 340 and 360" "giant killers"...In Cudas, road runners, I even remember a 67 Charger. at 7600 my W2 was peaking, by 5800 most BB wedges of the time were already nosing over or else they had comparatively narrow "light switch" powerbands. We didn't have bolt on BB heads that flowed 380 back then, I doubt few flowed much over 290 with a lot of port work and wafer thin or epoxied ports. Back in those days the quickest cars were BB Chevies and Cleveland fords and Hemi's but there weren't really that many Elephants around.

Air flow and efficiency determine how BIG a motor is, how much air it can move efficiently is generally more important than static displacement. And we're just talking naturally aspirated here....Turbos are a whole 'nother level and less, generally speaking smaller/lighter engines are more thermally and volumetrically efficient overall.

To steal a phrase from virtually every judge I have seen on television series from the 60's , " one more outburst like that and I'll clear the court. ".
After careful deliberation , I enjoy reading your input and addition to the posts on here.
You are right a lot more than I am. ;-)

Are we done with the political stuff now? Is everyone bored and stuck inside because of the weather?

People share their opinions/experiences on here, take them for what they are worth. Some are more theoretical opinion than practical application. I prefer to live by the moto that its all theory til its put into practice. Ive been in and around this business for a very long time and seen some great ideas fail miserably and some folks throw things together that have no right to even work, that work very well. We learn more from mistakes than successes sometimes.

BTW Shiloh 2.55 per cube is a great goal. Build it smaller and shoot for 2.6

this point a few people always seem to forget,

Knock down some score boards for us Good Luck

Love you Jeffery ......seriously have a ton a respect for Poly and his Library

. I have made more mistakes broke and ruined more good parts by trial and error myself sometimes I wonder what I'm doing... . 2.6 would be great just really depends on how generous the dyno is to me that day.

Do us be racing dyno now
Flog that motor and car

My actual field is divorce law...

Most of the reasonably intelligent racers I know plan out their build around the rules, with the chassis first, figure out how light they can afford to make it, then figure how many cubic inches that they can run at that weight.

one local guy I know just couldn't get his SBC light enough within the rules, at 275-something radial class and this was a 3 stage nitrous car running 4.8's. Now he runs a 582 BBC, and is working on making 4.5's. S/F....Ken M

I have never been divorced , but have witnessed several from the sidelines.
It always seemed to me that the only people who make out in those deals are the lawyers.
Good call. lol
I did see a big block cause a divorce once.
The fellow took out a second mortgage to fund an ex pro stock motor for his car.
She didn't understand.

by the way some guys act toward you, i believe it !

Cab pretty sure I've done that Dynos are tools for sure and some of the numbers I have seen on here I'm gonna say a LOT Of them are REALLY happy.

Those aren’t HAPPY dyno numbers. Those are highly influenced numbers raised by the coefficient factors elevated by the elasticity ability of the elaborate materials used in the production of rubber timing belts.

okay PolyBurgeracer. John you shot way over my head I think this post is getting to us all I feel like divorcing my Dyno

There are some cars out there that will never show an engines true potential as well. Usually the loose screw behind the wheel is the main problem

Not what you think.
New York State Courts paid me to MAKE lawyers do what they were paid to do.
Fun!

Now if we could just force the U.S. Government to force elected official to do what they are suppose to do which is to serve the public and protect us all from waste and lies

Hey I’m right here and can see this!

https://www.hotrod.com/articles/hrdp-9808-chevrolet-engine-block-challenge/

408 bbc vs 408 sbc both with 9.6:1 static compression ratio.

On the dyno and track.

I assume the results of a 400 B mopar vs 400 LA would have similar results?

Air flow makes hp. You can make as much hp with a 565 in motor as you can make with a 632 in motor. the small motor will be faster than the big motor due to reduced torque on small tires much easier to launch.