Big Block -or small block?? 1994 K1500 GMC

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Vettepilot

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Hi guys,

Thanks to the price of fuel, my plans/goals are changing...

I am working on culminating my multi-year effort at owning a big block C4, and putting a nice 454 in my '87 Vette. Cool.

Also, I am fixing up a 1994 GMC 4x4 pickup. That too was going to get a (very mild) 454, but with the fuel situation, I've decided to rebuild the Vette TPI motor, and put it in the pickup. I will use the stock TPI, rebuild the aluminum heads, new rings/bearings, and install it with long tube headers in the pickup.

I'm guessing some gains could be had over the 35 year old TPI smog cam though. I'm looking hard at this one:

Note that I would use stock rockers, so lift would be more around .515 than Comp's 1.6 rocker stated .550 lift.

Torque and gas mileage the goal on this one. What say you all??

Ah, one more thing on that subject. In such a mild, 5000 rpm max build such as this, do you think the header upgrade is worth it, or just use the Vette "wanna be" headers???

Lastly: Back to possibly going with a big block. With 9.5:1 compression, a super mild cam, headers and well tuned fuel injection, I wonder what mileage a 454 would get in a half ton 4x4 pickup with overdrive??? If it would get 16, and the small block say 18, I'd probably go with the big block. That monster torque is SO cool!!

Vettepilot
 
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b454rat

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I've only ever had 1 truck that I can remember that was a small block, 3/4 ton. I don't really remember gas mileage, but I know that it wasn't horrible, but not great, but had no power. I have a CCLB with a 350, runs amazing, but it's alot of truck for not alot of motor. I also have the trucks in my sig, and no surprise, they have power. And just because you have a smaller motor, doesn't always mean better mileage. If it came down to a couple MPG difference, big block all the way.
 

Vettepilot

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Yeah, but think about that. If it takes "X" power to move "Y" car down the road at "Z" speed, the big block is going to make that power with less throttle opening. Efficiencies come in to play and create differences, but it's definitely not as clear nor simple as the big block is just inhaling more air. Now at full throttle; yes.

Vettepilot
 

0xDEADBEEF

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There's a reason they don't use big blocks with intake restrictions to meet fuel economy standards. It doesn't work.
 

b454rat

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Yes normally big block and fuel mileage don’t go together. But, if you have a 10k pound truck with a small block, and the same truck with a big block, the big block will prolly got same mileage and pull better. Being he wants a big block in a 1/2 ton, I doubt it will do better than a small block, but the smiles per miles will be higher with a big block.
 

0xDEADBEEF

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Unless the BBC is more efficient at extracting mechanical energy above its weight penalty for the same amount of air and fuel as the TPI, it will never get better mileage. I doubt that, but I don't know. The newer big gas engines I could see that being a possibility because of the extra decades of R&D (and they are lighter), but again I don't know.
 

The_Family_Tahoe

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Turbo or supercharge the tpi and you will have small block mileage with big block power on tap. In order to keep the mpg up you will have to keep it out of boost, but the potential is there for both mileage and power using a small block with boost.
 

Vettepilot

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Well, I don't expect to ever get the same fuel mileage with a big block vs a small block. That's an unreasonable expectation. All I'm hoping/wondering is if I could get acceptable mileage out of a big block, so that when needed/wanted, I could get those SMILES per gallon the big block offers. If I could get, say 16 mpg or so highway out of the big block, I could live with that. I would even be willing to drive a bit slower to get that mpg, and enjoy that big block! It would be SO worth it!

I ran numbers through Desktop Dyno last night. Yeah, I know, it's not real accurate, but it is good for comparisons, and I've built several quite good engines with it's assistance. Anyway, yes, that Comp cam would be a good move for a Corvette TPI engine, gaining an average 10 pounds or so of torque and nearly 20 horsepower, while not changing the curve hardly at all.

But, of course, the big block JUST CREAMS any reasonable small block, with 35% more power, and positively brutal torque!

Anyone here think I could get 16 mpg out of a 9.5:1, mild, well tuned EFI big block in a half ton 4x4 with overdrive??? (It's the stupid low compression of stock big blocks that kills them. I got 12.5 mpg out of my last truck, a Blazer with a 500+ horse nasty a$$ big block...)

Actually, I once super-tuned a customer's bone stock 1972 big block 1/2 ton 2wd pickup and he got just over 18 mpg- carbureted!!

???

Vettepilot
 
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