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496 vs 540 BB?

30K views 61 replies 24 participants last post by  Whittaker 
#1 ·
Hello - I am in the planning stages of building a BBC for a 71 SS. Using a low deck block, my builder has suggested using a 4.25 stroke crank and building a 496 with mini-dome pistons, shooting for a 10.1:1 compression ratio. He has the crank, rods and block, but has not sourced pistons yet. My goal is a street friendly motor with an occasional blast down the 1/4. Hydraulic roller cam, TH400 trans, 12 bolt rear (gears undecided).

Since the block has not been finished yet, I am wondering if we should shoot for 540 cubes using the same crank with a 4.5 bore. Is there any distinct advantage to the 540 over the 496 aside from 44 additional cubes?

Thanks,
Rob
 
#2 ·
As you may/may not know, you won't be able to get a 4.5" bore out of a factory short deck block...that would require purchasing an aftermarket block. This additional expense would be your only consideration when deciding between building a 540 and a 496...all other components would cost the same.
I'm assuming that your using a 454 block because you've mentioned building a 496.
 
#3 ·
Since you probably can't get that kind of bore out of that block, and you want to use that block, it's kind of a moot point, but the advantages of a 540 versus a 496 are numerous. For one, displacement. More displacement: more power. Another would be further unshrouding of the valves which helps with improved dynamic head flow during operation.

Other advantages (versus, say increasing stroke to make that displacement rather than bore) is improved higher RPM performance.

Ultimately a 496 should make a '71 a plenty fun ride. If you end up utilizing a hydraulic roller cam, there are a number of issues with those and RPM. Check out both AFR's website and Comp Cams (www.airflowresearch.com and www.compcams.com respectively) because RPM above 6000-6500 can get spotty. Comp has a new kind of Conical spring made of Ovate wire that has helped improve higher RPM performance on the big block hydraulic rollers as well as a company named Sherman Racing that modifies hydraulic roller lifters to handle increased spring loads for higher RPM spinning (they can be reached through www.wolfperformance.com).

Hope that helps,
Ryan


kacp-o said:
Hello - I am in the planning stages of building a BBC for a 71 SS. Using a low deck block, my builder has suggested using a 4.25 stroke crank and building a 496 with mini-dome pistons, shooting for a 10.1:1 compression ratio. He has the crank, rods and block, but has not sourced pistons yet. My goal is a street friendly motor with an occasional blast down the 1/4. Hydraulic roller cam, TH400 trans, 12 bolt rear (gears undecided).

Since the block has not been finished yet, I am wondering if we should shoot for 540 cubes using the same crank with a 4.5 bore. Is there any distinct advantage to the 540 over the 496 aside from 44 additional cubes?

Thanks,
Rob
 
#4 ·
Unless you are going for all out power, that 496 will easily achieve 600 hp/tq, and be a blast to drive, keep your expense down including drivetrain expense.

No doubt that the 540 would be best for all out power, but unless you have the money to build the supporting cast for it, then that 496 will be all you will need, and still generate that ear to ear grin....
 
#5 ·
JMHO, but I can't imagine being able to use all the HP you can get from a good pump gas 496 on the street anyway. You should be able to build over 600hp easily. The 540 has the cool factor for a street driven vehicle, but it is overkill for most people. If you want the ultimate street strip engine, and cost is not a concern, build the 540. If you want close to the ultimate, and want to save $1800+, build the 496.
 
#6 ·
Thanks for all the quick replies. Sounds like the 496 should be plenty and cut an additional 2K plus out of the price by avoiding a new block and all that extra machine work. 600/600 was pretty much my goal for this one.

After I typed the note, I figured you could not get 4.5 bore out of a factory block...but it's all about learning :)
 
#9 ·
I'm hoping mine is close. Its a 489 with 781 iron ovals mild port and valve work, 2.19/1.88 SS valves, Performer RPM Airgap intake, Holley 870 Street Avenger, (get a double pumper), 1 7/8 headers, 10:1, MSD distributor, MSD 6 AL box and wires. I have just added a hyd roller cam, from Cammotion. It is .618/.630, 240/249 on a 112 LSA it is a billet cam with the pressed on iron gear.

If I had the chance to do mine again and was only $1,800 away from a 540, I would have done it. Shafiroff http://www.shafiroff.com/ has some killer 540 packages.

It puts down more power than I really can use with street tires and tight suspension
 
#10 ·
wildman926 said:
Unless you are going for all out power, that 496 will easily achieve 600 hp/tq, and be a blast to drive, keep your expense down including drivetrain expense.

No doubt that the 540 would be best for all out power, but unless you have the money to build the supporting cast for it, then that 496 will be all you will need, and still generate that ear to ear grin....
I agree with this statement! :D
 
#12 ·
The 540 would easily blow away the 496 if for no other reason, the larger bore and unshrouding of vavles. But as stated, you can make 600 by accident with a 496. I would not use a hydraulic roller in anything but a truck. You will need some fairly hefty cam specs to do what you are looking to do, and a hydraulic is not the way to go.
 
#15 ·
Don't see how 600/600 is that tall an order from a hyd roller 496 motor with decent heads. Not dyno'd yet but from comparison to some published dyno'd motors, my 454.030 motor with GMPP 2.25/1.88 heads, 10.3/1 CR, 233/236, .600/.610 112 LSA hyd roller, Air Gap, 870 combo is probably in the 550/550 range. Can tell you, it is a handful on street tires.
 
#16 ·
adamrharris said:
does anyone have a dyno proven 600hp 600tq 496 combo that they can post the components and specs? must be pump gas friendly (91 octane)
=
Why yes I do :D

489, 10.0 compression, Brodix RR Rect port heads, Brodix modified dual plane intake, Holley HP 1000, Isky 252/260 solid roller, 2" headers.
RPM HP Torque
3100 315 533
3500 369 553
4000 440 577
4500 511 596
5000 561 589
5500 599 572
6000 613 536
6500 602 486

Peak power 614 @ 6200 Peak torque 597 @ 4600

This is on a very honest dyno,,, mine :)

 
#17 ·
Mine pulls easy to 6K and thats where she is set to shift. I have no problems with the new Morel lifters and springs set up right. 6500-7000 on the street isn't going to get me much more, maybe at the track.

Solid rollers in my research could have gained me some power but I didn't want the hassel or changing springs each season or even every other season. Maintaining your spring pressure reliably with very aggressive ramps and high lift just was not what I wanted.

Hyd rollers are in all but one of the most common GM crate engines. Even the 620 HP 572 has a hyd roller. All Gen 6 502s and 454 are hyd rollers.

Shaffirof even offers their Ultra Street 540 with a hyd roller. Must be OK for them.

I made a very small sacrafice to be able to set my pre-load and forget it for quite a while. I drive it hard and I have no regrets. Also no issues of smoked cam lobes on break in. Not to worried about the oils not having the zinc and other additives.

I agree on the Gen 6 502 idea. I'd skip the rebore. I'm pretty sure there are pistons out there for that. Isn't that how Pace or one of the other GMPP made their 534 before the 572 was out. That way I'd have a couple of times to bore it later. I break things.
 
#18 ·
We had a 9.2:1 CR 540 with an UltraDyne hydraulic roller do pretty good on the dyno. I'm sure a 10+:1 496 would do very close, especially on 91-octane. The 540 was on 87-octane(Boat engine.....).
Cam---UD 288/296HR14, 236/244@.050, .600".600" valve lift, 114 LSA.
RPM-----Torque---BHP
1500-----505------144
2000-----522------199
2500-----539------257
3000-----555------317
3500-----577------385
4000-----599------456
4500-----625------536
5000-----625------595
5400-----613------630
5500-----594------622

Steve at Lunati-662-892-1526, or Tim at Bullet/UltraDyne can make you this cam. Masters at HR12/HR16...
Or I can make you a 233/241 with .638"/.638" valve lift......
All these are hydraulic rollers, billet cams, EverWear gears.

UDHarold
 
#21 ·
I would have gone with UDHarold but he was between gigs and Lunati could not grind one a 112 at the time they didn't have the masters or something and it took about 2 weeks to get back to me aafter lots of phone tag, but Steve was very nice.

I ended up at Cammotion and I'm/was very happy with their tech and customer service folks. I'd reccomend them if your looking their web site has a feature where you plug in all your cars particulars and they will make a reccomendation off of that.
 
#22 ·
Well guys, I have to say after almost completing the 540 install in my 70, i would have gone 496. The motor ran $11,400 and necause none of the mark IV parts really swapped over, about an extra $1800 in parts. I think a good evenly hp:ci motor 496 would run about $6000-$7000.
 
#23 ·
JC70SS said:
Well guys, I have to say after almost completing the 540 install in my 70, i would have gone 496. The motor ran $11,400 and necause none of the mark IV parts really swapped over, about an extra $1800 in parts. I think a good evenly hp:ci motor 496 would run about $6000-$7000.
Strange. :confused:
Used a Merlin III block for my 540 project when building it two years ago. Had no problems using Mark IV type components.
Curious as to what items caused the additional $1800 expense??
 
#24 ·
JC70SS, chances are that sometime in the future you'll begin to seriously wonder what 632 cubes is like :D. You have a better block with a much longer life expectancy and more hp and tq that come with unshrouded valves in deep breathing big bore blocks.
 
#25 ·
JC70SS said:
Well guys, I have to say after almost completing the 540 install in my 70, i would have gone 496. The motor ran $11,400 and necause none of the mark IV parts really swapped over, about an extra $1800 in parts. I think a good evenly hp:ci motor 496 would run about $6000-$7000.
I'm definitely curious about this one too...particularly about the 1800 in parts over and above the extra 2K for the block. Which block did you use? I am still mulling over the Merlin block - no commitment yet to go one way or the other with my builder...

Rob

(Yes I have two usernames...one at home, and one at work - just noticed myself)
 
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