Big Block vs Small Block

Wreckage

George

CURRENTLY BANNED
Yes I have spoken to 1, he doesnt care if the car is a 302/351 or a 511+

This is why i wanted to work out whats the better motor choice.

List of wants?

Faster average speed
Best possible acceleration 0-100km/h, 100-200km/h 200-300km/h (an engine that accelerates hard all the way)
A car that handles phenominaly well
A car that can be driven on the street normally with a fist full ready to go if you so choose to 'use' what its got (btw im the kinda guy that would drop the gear back when I wanna go hard rather than just press the pedal further, its a manual for crying out loud not an automatic)
A car that would not be too harsh on fuel because its built 'crazy' n thus only good for the track n nothing else really without it being stupid.

I plan to get the GT40 built with supercar suspension

The engine choice (whether BB or SB) would have all the parts neccessary (brakes, suspension, whatever else) to utilize the capability of the engine

If I go BB, it would be a BB that is built propperly to utilize a broad power band, and geard to make use of the top end speed. It will also be sitting with a 6 speed manual box. The BB would be running an alluminium block, titanium conrods, n I remember fibreglass used on an engine aswell (wasnt sure if that was rockers or something else) but the engine would be very light even as a BB.

So that would be a 600 HP 650 ft/lbs torqued monster, as that kind of torque is gonna do some serious 0-100 times etc.

On the other hand

SB, alloy block, etc (all the same as the BB) making it even lighter again compare to the BB. Rev limit around 8500rpm. THis engine would have less torque than the BB though, I see that = slower 0-100 etc.

However, if 650 torque is stupid for a car as light as this 1 is as its not going to be very controlable considering it comes on 500+ at 2000rpm which is basicaly just off idle... then that cars gonna be ice skating all the time? Then its smarter to push the torque up the RPM band by going a small block, then u can comfortably drive between 1000-4000rpm without frying tires, and when u wanna nail it, just drop gear, pop it up 5000+ and its gonna pull like mad.

So i almost know what im after... just few things to nut out like whether or not 500 ft/lbs at 200 rpms means the car cant go slow at that stage or not.

But again the BB is gonna be way cheaper on maintenence and last forever in comparison to the SB as the SB is gonna be wild and a SB will be anything but fuel friendly.

I know ppl running 502ci stroker BBs pushing out 575 HP at 20MPG on a 850cfm Holley carburettor. Thats in a heavy muscle car. Car has around 630 ft/lbs torque. The guy said its hard to cruise cause the tires constantly wanna chirp... n thats in a 3600lbs car... whts that gonna be for a 2000lbs car?

A SB would be lucky to see 15mpg at that power. So I kinda sway towards the BB unless ofcourse the above makes that much TQ too hard to drive with as it comes on 500+ at 2000rpm.

Then id rather just make this car totaly light even with alloy SB, make the power band as wide as it can be made, and get as much TQ It can get without it being TOOMUCH tq where it rather than making the car better, it makes it worse.

Given I want the 6 speed... would that dictate in any way given all the above SB or BB?

O yeah, engine is gonna run EFI aswell, the best available (whatever best is, but thats what its gonna have).When I get this done I want it done with the best of everything. Doing the car once, mayswell make it exotic like with serious parts that will just last and last and last.

Would a roller motor be of any use? I heard that stuff lasts forever and strong as nails.
 
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J

Jon Briggs

I would go with a 351W alloy roller block with a custom cam to be honest. All forged bottom end and pistons, some 225 AFR heads, rev it to about 8000rpm. Any more and you need to go for solid lifters. Have the heads ported, along with the intake and exhaust manifolds. Stick 50mm individual throttle body injection on it. And get the engine as low in the chassis as you can. If money is no object then go for a dry sump set up.

Keep the car as light as possible, with a nice torquey high revving engine. Don't get too sucked in about numbers (Torque & HP), its great for willy waving in the pub, but in the real world means next to nothing. I wouldn't get too excited by top speed either, theres not many places in the world your going to get to it. And do you really want to do 200mph in a car you have built in your shed?

Just my opinion.
 
I

Ian K

G-man, here are my opinions on your "wants":

"Faster average speed" - this is a push

"Best possible acceleration 0-100km/h, 100-200km/h 200-300km/h (an engine that accelerates hard all the way)" - more displacement, so either a BB or a nice SB stroker

"A car that handles phenominaly well" - probably a SB

"A car that can be driven on the street normally with a fist full ready to go if you so choose to 'use' what its got (btw im the kinda guy that would drop the gear back when I wanna go hard rather than just press the pedal further, its a manual for crying out loud not an automatic)" - Again, displacement - so either a BB or a nice stroked SB, however, no matter what you choose, you better seriously rethink about down shifting. With a high torque motor, you will destroy most transaxles. Which goes back to my first point - figure out your transaxle options first.

"A car that would not be too harsh on fuel because its built 'crazy' n thus only good for the track n nothing else really without it being stupid". - again, anything will go here. A high revving small block can still be driven at lower RPMs, and get significantly better fuel economy than a BB. More displacement means more fuel. Higher revs means more fuel. So, really, it's a push.

It will also be sitting with a 6 speed manual box. - again, a high torque big block may not fit with a 6 speed transaxle. The closer ratios may not work well at all.

"SB, alloy block, etc (all the same as the BB) making it even lighter again compare to the BB. Rev limit around 8500rpm. THis engine would have less torque than the BB though," - again, this is a generalization. Levy Racing makes a nice 351W stroked to 408 pushing 633HP/613 lbs ft ...

"However, if 650 torque is stupid for a car as light as this 1 is as its not going to be very controlable considering it comes on 500+ at 2000rpm which is basicaly just off idle... then that cars gonna be ice skating all the time? Then its smarter to push the torque up the RPM band by going a small block, then u can comfortably drive between 1000-4000rpm without frying tires, and when u wanna nail it, just drop gear, pop it up 5000+ and its gonna pull like mad."- And now you are starting to see things a bit clearer.

"But again the BB is gonna be way cheaper on maintenence and last forever in comparison to the SB as the SB is gonna be wild and a SB will be anything but fuel friendly." Again, generalizations.

Ian
 
F

Kevin L

G-man said:
I remember fiberglass used on an engine aswell (wasnt sure if that was rockers or something else) but the engine would be very light even as a BB.
Click to expand...

With all your talk about building the best and supercar, I think you need to stretch your thinking. I recommend you invest in a carbon fiber engine block to compliment your carbon fiber chassis, CF body, CF wheels, CF tires, CF driver, etc.

In fact, I hear they are now making CF pushrods, valve springs, crankshaft, and flywheel. Just go CF on the entire car; heck who wants Aluminum or that old tech titanium. If you look hard enough, they may be able to make a driver out of CF as well.

I can't wait to see this car come together, it is really going to be one of a kind.

Kevin
 
Wreckage

George

CURRENTLY BANNED
Kevin :laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh::laugh: @ CF driver.

I know the enzo/Zonda/Koenigsegg etc run carbon fibre on the actual engine (not much of it) but where usable (believe its the exterior), thats all I intended. Otherwise Titanium I love cause I had the experience of seeing it/using it, that metal is stronger than most metals and yet when I held it in my hand, its like a paper. Its umbelievable stuff. The unusual grey colour it is, looks absolutelly beautiful. If a Titanium block existed, that would be awesome but I doubt it does and I doubt the cost would be even worth it considering Alloy is strong enough, thus Titanium beomes simply overkill as is of no extra use except ofcourse that cool colour.

I like to use Titanium as a 'dress' article, when most things are chrome, borderlining with titanium just makes the chrome pop out even more. Looks very nice.

And thank you IAN. I was hoping at least that part u said im seeing things clearer was was right.

See, things r starting to come together now. Wouldnt of happend had this post not started. I just throw out 100 scenarios out there which as replies come gets my mind around certain things in a direction thats actualy 'real' n thus I kinda start getting the whole thing. Appreciated.

O btw

http://www.youtube.com/watch?v=oGQqV0zgrag&feature=related

I only ever found 2 on youtube that had this sound. Whats that due to? The 180 degree exhaust setup or what?

Would that sound be gettable out of a Big Block? Cause that to me is the perfect sound. The other video was a '351 chevy' according to the topgear in newzealand thing... i thinks he meant 351W or C from ford... unless a 351 chev does exist? Far as I knew there 350's and Mopars are 360s.

Having said that, going back in memory, I remember sitting in a valiant charger probbably 6 years ago. Was a 360ci SB stroked to 412ci with 550hp. That thing was crazy. I still remember him coming around the bend n then saying "Hold ur seat" put his foot on it, the automatic kicked a gear back and the front nose started lifting.... That thing sounded bloody awesome aswell. Car was a bright yellow (like a lemon - not the gold colour sort of lemon but the fluro yellow sort) with white interior. I remember falling inlove with that color combination. The whole car was just 'wow' inside and out with a beautiful chromed up 412 stroked SB that really put u in the seat something crazy. Yet while cruising it had no issue of wheel spin as the power came on 'later'. I honestly felt like there was nothing in that car until he said hold ur seat.... WWWWWWOOOOOOWWWWWW. To me, unless theres GRIP (running street slicks 335 wide which ofcourse will be costly excercise) theres no point in having all that torque of a BB, thus having more HP/less TQ from the SB would be better. Usable power/torque vs tire anihilating.

just found this

http://www.youtube.com/watch?v=TQtwpm3p7Ak&feature=related

I spoke to fellow mopar people about that, as to me thats the best sound of any engine I ever heard (426 ci hemi) however, they believe that it was a race built small block that was making the noise in the background, not the charger. Could a sound like that be gotten out of a Ford? With a sound like that driving down the street, i doubt id be concernd with tq lol.

And going with a SB, why a 351W stroked or why a 351C stroked, whats the difference between the 2 other than built in windsor vs Clevland?
 
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R

roaldin

If you want the wild roar that turns into a howl then 8 stack induction and crossover exhaust, open with megaphones. Nothing else will come close. Difficult to get past the authorities though. ;)
Cam etc makes a difference as does pipe size etc. This thread should be called subjective opinion wanted, or perhaps keep up with the moving goalposts... ;)
BB is better, SB is better, I feel like I'm watching someone on a swing... ;)

Tim.
 
R

roaldin

I have built a few Clevelands in my time, I have never built a Windsor (edit: forgot, I did part build a 289) although I had one built for me for my GT. Basic difference is that the Windsor, especially the 302, is physically smaller and I think lighter generally. The Cleveland was considered a more modern engine but these days with all the aftermarket possibilities I think it's much of a muchness. The factory Cleveland head varieties were markedly different to the original Windsor heads (the boss 302 was a Windsor with Cleveland heads) but once again modern parts have equalized those differences pretty much I think. Anyway there are people here with a lot more experience with both than I have so I'll leave it at that and hope I didn't make too many silly mistakes. :)

Btw, someone referred to the Cleveland as a "mid block", I like that, I think it's a fair description.


Tim.
 
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Wreckage

George

CURRENTLY BANNED
I sent an email to a racing team here in australia.

Asked them Big Block or Small Block and they pretty much said

"What about meet half way and get the 351?" (medium Block)

And then proceeded to say a car as light as the GT40, its a no brainer which engine (refering to using the 351 and definately NOT a BB in a car like that) as the SB is a more responsive engine to the BB which is what you want in a car designed for handling.

are RPMs dertermined by CI capacity or block (big or small).

Cause say you had a small block producing 454ci. Will the RPMs be the same as in a Big Block 454ci.

Would the torque/Hp etc be the same as CI is what matters not size of the block or does the block itself play a role in everything so a SB 454 is not neccessarily the same as a BB 454.

I ask that cause if its the CI, then whats the point in stroking a SB thats designed to rev etc when u just eliminated what it was designed for by turning it into a BB so to speak.
 
R

roaldin

Uh Oh, this feels like a can of worms...

Here goes - There are a number of factors. Main among them are ability of the bottom end assembly to endure the forces acting on it and the ability of the valvetrain to "behave". I won't go into what that means because this could get to be a very long thread indeed.
Bottom end forces were part explained earlier - piston speed and mass determines the force that it and the rod etc must endure. There are other forces and vibration etc that must also be taken into account.
BB or SB it comes down to the same issues, and different combinations will give different results. I really wish it were as simple as you'd like it to be.

When it comes to power and torque I think you misunderstand what they are. I suggest that instead of trying to make what has been said fit your concept of what they are, that you discard your understanding completely and read again as though you had never heard those words before.

FWIW and definitely IMO - I Like the idea of a BB in a GT40, just because deep inside I think there is something attractive about the American "just use a bigger hammer" ("yes but why don't they use a screwdriver, it is a screw after all" I hear the rest of the world cry ;) ) approach, but to me the SB makes more sense, especially in alloy, because to me a car is not just an engine it is a dynamic thing "living" in a dynamic environment. I believe the SB equipped car is more likely to suit more of that general environment.
It is always tempting to go for more more more but sometimes you have to be rational and think how much is enough and what compromises am I making to allow more more more in the engine.
I think a decently built SB can give you more than you'll realistically need. I do not however criticise those who have chosen BBs because I think I understand why.
Anyway, after that decision is made it gets more complicated - what spec's...? ;)


I am tempted to ask how old you are? I like your enthusiasm but I think it may have moved ahead of your willingness to properly study your subject.
I don't think it's the questions so much as the "I don't really want to understand, I just want simple answers" responses that have annoyed some (Excuse me for putting words in mouths), it is hard to figure out how to respond and be truly helpful.
I for one am also worried about advising someone that may be a tad naive on any aspect of how to make a fast car, so I am trying to stick to providing information rather than advice. Please be careful with whatever you do. High performance vehicles can be dangerous things.

If you want to play in the deep end you really need to know how to swim.

I wrote the opening and closing sentences especially for Alan. ;p



Tim.
 
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roaldin

Simple answer to what affects rpm limits - Stroke; component mass, design and materials; number of cylinders - the list goes on. My rb26 (2.6 turbo) spins to over 8000 straight from the factory; My neighbor's 1.6 Hyundai would likely explode if he tried that.

In your 454 comparison (A SB based 454 is not a BB, it is still a SB.), bore, stroke, materials etc all being equal, they would still likely have differences such as rod length to stroke ratio that would have an effect on characteristics and things like side loads on pistons.
Are you realising that this is a complex subject and that you are getting the answers you are because simplistic answers may do more damage than good? ;)

If size and weight didn't matter then a BB could do more at the extremes, but they do matter and the extremes are probably way more than needed for most purposes. It is all about balance and compromise. Achieving balance is IMO the most important goal for any car, be it road or track.


Tim.
 
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Z

zollis

are RPMs dertermined by CI capacity or block (big or small).

Cause say you had a small block producing 454ci. Will the RPMs be the same as in a Big Block 454ci.

Asked by George in post # 69.

The appropriate answer I can not give because words fail me. Perhaps the moderator should help out.

Z.C.
 
R

roaldin

When it got to wanting a hard accelerating rolling 200 - 300 kph vehicle and then fuel economy became a priority I wondered... :)


Tim.
 
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