496 vs 540 BB? - Chevelle Tech
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post #1 of 62 (permalink) Old Jul 14th, 06, 1:35 PM Thread Starter
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Rob
 
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496 vs 540 BB?

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
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post #2 of 62 (permalink) Old Jul 14th, 06, 1:52 PM
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Re: 496 vs 540 BB?

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.

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post #3 of 62 (permalink) Old Jul 14th, 06, 2:01 PM
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Re: 496 vs 540 BB?

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


Quote:
Originally Posted by kacp-o
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

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post #4 of 62 (permalink) Old Jul 14th, 06, 2:24 PM
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Re: 496 vs 540 BB?

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....

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post #5 of 62 (permalink) Old Jul 14th, 06, 3:55 PM
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Re: 496 vs 540 BB?

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.

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post #6 of 62 (permalink) Old Jul 14th, 06, 4:00 PM Thread Starter
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Rob
 
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Re: 496 vs 540 BB?

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
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post #7 of 62 (permalink) Old Jul 14th, 06, 4:15 PM
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Re: 496 vs 540 BB?

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)
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post #8 of 62 (permalink) Old Jul 14th, 06, 4:34 PM
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Re: 496 vs 540 BB?

Quote:
Originally Posted by adamrharris
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)
Close. Link 586/600.

Belongs to Britt. (PURS)

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post #9 of 62 (permalink) Old Jul 14th, 06, 5:48 PM
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Re: 496 vs 540 BB?

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

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post #10 of 62 (permalink) Old Jul 14th, 06, 7:27 PM
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Quote:
Originally Posted by wildman926
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!

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post #11 of 62 (permalink) Old Jul 14th, 06, 7:39 PM
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Thumbs up Re: 496 vs 540 BB?

Imho, I figure that you can use a stock, 502 block bored .030" over to make it a 4.50" bore and then use a rear crank seal adapter so that you can use an inexpensive Mark IV 496 rotation assembly from Ohio Crankshaft Co. to build a CHEAP 540 motor!!

It WON'T be a race motor, but should still be one heck of a street motor, again, imho!!

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post #12 of 62 (permalink) Old Jul 14th, 06, 9:27 PM
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Re: 496 vs 540 BB?

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.
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post #13 of 62 (permalink) Old Jul 14th, 06, 9:36 PM
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post #14 of 62 (permalink) Old Jul 14th, 06, 9:42 PM
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Re: 496 vs 540 BB?

Quote:
Originally Posted by mr 4 speed
I'd go for the 496 and some aftermarket heads..throw in a big flat tappet solid
Exactly what I did...

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post #15 of 62 (permalink) Old Jul 14th, 06, 9:50 PM
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Re: 496 vs 540 BB?

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.
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