Traditional Big Block or Supercharged LS3?

6

68/70Vette

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I've been working off and on on my 70 project car for many....many years. Many years ago, the way to go for HP was to use a big block. I have an aluminum BB and heads....not populated yet with rods, pistons, cam. When I bought it many years ago, the crank and bore configured it as a 454. I have plans to bore/resleeve it to 502 cubic inches with goal of 600 HP.

But with the passage of years, if I were starting out today, I'd be looking at building up a LS3 short block with stronger than stock internals. Maybe if the bucks were there, a ZR1 short block ( a LS3 short block with steel crank, titanium rods, etc). Pretty much stock LS3 heads and a supercharger lets you pick the hp you want...600, 700, 800, 900...just pick the supercharger pulley diameter. And the engine would be very light. Using a centrifugal supercharger, the car would be very docile on the street and not much more of a fuel burner than a stock engine. Putting one of these engines in a C3 would involve customizing the motor mounts. Also, for a really large HP, you might want to consider a iron version of the LS3 block.

But for acoustics, a powerful classic BB with minimal exhaust will be a unique beast. Would you consider replacing a BB with a performance supercharged modified LS3?
 
I have a 74 with it's original 454 built with a cam, headwork, headers through magnaflow system, edelbrock air gap with an 870 holley, msd ignition. There is no shortage of torque to drive in 4th without shifting very much if desired, or just nail it and go from 30 to 70 in a few blinks. The old school style big block also has a classic hotrod look and sound to it that matches the lines of a vintage c3. A well done big block looks much more impressive to me than an LS. The trend today is LS conversions, I like to be different, and still prefer old school power, but than i'm 66 and old school myself. Be different, Aluminum big block.
 
I"m 68.5 and would go LS in an instant, if anything happened to this engine.....

but it's just a L98 type build.....I note the comment with BBC about not bothering to shift....I think that's funny, as that is the way I drove the '72 when putting TPI on it, second to forth, had to be a steep hill before I bothered with first...muncie and 336 rear....GOD I'm lazy....

:drink::gurney:
 
If your goal is 600HP, then you have your answer....if your wild after 700 or higher, then you also have your answer.

But I can't figure why anyone would want that kind of power for the street.
 
Big cube LSX!!! Building a 495LSX here, modified LS7 heads, Lift .669" intake .677" exhaust
Duration 264* intake 271* exhaust @.050" on a 110* cam, carbureted setup, front drive distributor..blahblahblah...... should easily make close to 750/800 NA

with 1" set back adapter plates it's a bolt in deal with stock motor mounts
 
69427 said:
If it's just for the street, what's the point of either engine?

But if ya gotta do it, go with the LS engine. It's a cheaper replacement once you grenade it.
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Forgot about that!!! About driving the car on the street......something like pulling onto the freeway from an on-ramp....its exhilerating to go from 30 to 75 mph in ..what less than two seconds. You have to go to a drag strip or road raceway to take advantage of the power.

One thing about an LS supercharger...either centrifugal or roots type, they are relatively compact. I have a centrifugal blower on my 08 LS3. It fits pretty easily under the hood in existing engine space. I produces 580 rwhp which is probably about the limit for a stock nodular iron LS3 crank. I've been meaning to take it to a drag strip or raceway...my excuse lately has been I want to wait until the weather cools down a little.
 
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If you have a real aluminum BB that's the way I would go. You just don't see big blocks that much any more. Sure, you could ultimately make more power with the blown LS3 but like others have said, the trend seems to be LSx motors in classic cars. Now if it were me (and we're just playing 'spend money you don't really have' here), I would build a nasty roller PFI big block with side pipes the size of sewer lines.
 
I don't see money savings with the LS motor. If you didn't already have the block and heads - maybe it'd be cost effective.

The large an item, the more robust. I had a blower on a SB 400, and it'd constantly blow head gaskets - because there wasn't enough material (and cooling) between cylinders. With small architecture, you'll always run into the fundamental material strength problem; and the lack of space to --- hmm, how to describe --- put in a margin for error. The SBC was ~750 hp (okay, 751.3) @6400 - the next motor I built was a 455 Buick, NA, 812 hp. Granted, there was much done via halo girdle to make it strong, but we never had head gasket problems, block flexing problems, or head lifting problems.... which we had in abundance with the SBC.

If you can fit the larger block, by all means, put it in your car, it at 600 hp will last 100k.... if not, LS it and plan on 50k rebuildings.

With all that said, the LS3 motor is its own beast - but it requires titanium and big revs to get 600 hp.
 
clutchdust said:
If you have a real aluminum BB that's the way I would go. You just don't see big blocks that much any more. Sure, you could ultimately make more power with the blown LS3 but like others have said, the trend seems to be LSx motors in classic cars. Now if it were me (and we're just playing 'spend money you don't really have' here), I would build a nasty roller PFI big block with side pipes the size of sewer lines.
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Paying 5 bux/gallon for the privilege.....:gurney::hissyfit::banghead:

:drink:
 
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