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Old 04-08-2012, 12:29 PM
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Torque Differances

I've been looking at different build ideas for a truck engine (5200# empty) with a 2000 rpm cruise and 4 spd manual.

I have a smog 350 now. It looks like heads/cam/headers would get me in the 350 ft-lb or so range at the flywheel.

What would a similar streetable build on a 383 gain?

To give me a better idea of the gains, how much torque gain is needed before much difference is noted?

Is a 383 known to do better, worse, or the same on mpg?

If I built a 350 as described above would I notice any better mileage over stock (10 mpg).

I'm considering this in the next year or so and want to think of all of my options.

As an idea of what I do when I load this truck to work, I have scaled @ 9000#. I don't do this often, but when I haul dirt or wood, I load all I can.

I haven't hooked a trailer yet, but according to the owners manual, it is rated to tow 12000#.

Thanks for the insight.
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Old 04-08-2012, 12:33 PM
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You are well into BBC territory. Just saying.
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Old 04-08-2012, 12:40 PM
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What year truck? If you want to go with the small block then the 383 would be the way to go for towing and hauling. You could also install a NV 4500 to give you an overdrive transmission too. That would help keep gearing low enough for towing yet keep the RPMs down for normal driving.
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Old 04-08-2012, 12:46 PM
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I figured I was close, but considering I do a lot of unloaded or light loading, how bad would my mpg suffer going to a big block?

I was thinking being a little underpowered and going for a better mpg might serve my needs better.
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Old 04-08-2012, 01:25 PM
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Quote:
Originally Posted by Hoyt71
I figured I was close, but considering I do a lot of unloaded or light loading, how bad would my mpg suffer going to a big block?

I was thinking being a little underpowered and going for a better mpg might serve my needs better.
That could be. I'd say if you were hauling as much as not, use the BBC and eat the mileage difference. If you haul considerably less than 50%, and/or the truck is also a DD, the SBC could save you over the long haul, especially considering you already have a SBC engine. What gives me pause personally is the comment that when you haul, you HAUL. That's taxing on a SBC.
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Old 04-08-2012, 01:31 PM
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As cobalt mentioned it really comes down to how often you tow a decent load. It isn't hard to get 430-440tq out of a very mild 383 which if you tow occasionally would be more than enough but if you tow almost everyday then your real best bet would be a diesel. If this is not an option then a mild 454 can easily make 550tq.
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Old 04-08-2012, 03:04 PM
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Is my research correct on the 350 or is it a little conservative?

Is a 383 inline with a 350 on mpg? How much would I look at giving up with a 454?

Where does a 383 tend to make it's power (rpm)?

Not arguing, but looking at my Chiltons manuals it looks like sbc makes 270-350 depending on year and bbc are all around 400 on torque regardless of year. I know the ratings changed in the early 70's. Is there more difference than paper shows?

Is there anything to look for on a bbc when looking for one?
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Old 04-08-2012, 07:23 PM
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I guess it really depend on how much money you re going to put into, if all you want is a factory motor then yea you might only end up with 300-350tq from a abc and 400-430tq from a bbc. But with either of these motors a little extra money can go a long way. Most times when you actually build/ rebuild a motor with mild perfeomance in mind you actually end up getting better gas mileage than what you got from the factory because the motor is now more efficient.

I don't think it would be hard at all to build a mild 383 that would make 375-390hp and 440-460tq but still get you 12-14mpg as long as you don't have a lead foot. And a mild budget 383 like this could be built for 2000-3000.00.

A mild 454 built could easily make 400hp and over 500tq but you wouldn't likely see better than about 7-10mpg and this too would cost around 2000-3000.

What kind of money are you trying to spend, what gears are in the truck, what transmission, and what size tire are you running.
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Old 04-08-2012, 08:26 PM
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I'm running a factory 4 spd manual in a 78 3/4 ton with 3.73 gears and 235/85/16 tires. 55-60 mph is 2000-2200 rpm.

I will be on a budget but it is still undecided. If my best bang for the buck and balance of power will be 2-3K then that is what I will try to plan for. That is the range I was considering.

I looked into trading trucks, and I think I am money ahead to build what I need.

If you've read my other posts its looking like I need to do some work before I break something.
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Old 04-08-2012, 09:09 PM
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I would go with a 383
I would look though the junkyards for a 5.7L 350 vortec complete motor, buy a 3.75" stroke crank, Kieth Black 18cc dished pistons, externally balanced harmonic dampner, have all the necessary block work done, new bearings, hyd roller cam around 212-218 degree duration at .050 maybe .475" lift, have the vortec heads machined to handle .500", cleaned and rebuilt if in budget have the bowls and valve guides ported a bit, you will likely be able to reuse the factory lifters, rockers, and pushrods, buy a vortec bolt pattern edelbrock performer rpm intake and a 650-750 vaccum secondary carb, look on eBay for a HEI distributor, melling standard volume oil pump.

This combination would be good for around 340-360hp and 425-430tq and would likely get you 12mpg or better. And should be able to be built for around 2000-2500.00
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Old 04-09-2012, 05:16 PM
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Quote:
Originally Posted by Hoyt71
I've been looking at different build ideas for a truck engine (5200# empty) with a 2000 rpm cruise and 4 spd manual.

I have a smog 350 now. It looks like heads/cam/headers would get me in the 350 ft-lb or so range at the flywheel.

What would a similar streetable build on a 383 gain?

To give me a better idea of the gains, how much torque gain is needed before much difference is noted?

Is a 383 known to do better, worse, or the same on mpg?

If I built a 350 as described above would I notice any better mileage over stock (10 mpg).

I'm considering this in the next year or so and want to think of all of my options.

As an idea of what I do when I load this truck to work, I have scaled @ 9000#. I don't do this often, but when I haul dirt or wood, I load all I can.

I haven't hooked a trailer yet, but according to the owners manual, it is rated to tow 12000#.

Thanks for the insight.
Many years ago when I had a 78 half ton I took the 9 miles to the gallon 350 out and put a 454 into it that also got 9 miles to the gallon but was a whole lot better runner in the mountains.

Bogie
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Old 04-09-2012, 09:07 PM
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Was it stock or modified? Are bbc heads good or do they have issues like the sbc?
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Old 04-10-2012, 08:11 AM
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Swap in a complete newer drivetrain, fuel injected with a heavy duty trans. I don't care if its ford, chevy, or dodge. Gas or diesel. Swap it in and go. Spending the same amount of money on 50 year old technology is silly.
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Old 04-10-2012, 10:08 AM
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Quote:
Originally Posted by ap72
Swap in a complete newer drivetrain, fuel injected with a heavy duty trans. I don't care if its ford, chevy, or dodge. Gas or diesel. Swap it in and go. Spending the same amount of money on 50 year old technology is silly.


i agree with this slightly by i also disagree with it as i have a GMC 2500HD with the LQ9 6.0. these are rated at 345hp/385tq, the truck has a 14bolt with 4.10's in the rears and the 4L85E transmission with external trans cooler.

2 summers ago my family and i decided that we would take my father-in-law's 32ft camper up to the Shenandoah Valley for a vaccation. my truck did great towing up and down the hill on the way to the mountains, but going up the switch backs of Lewis Mountain was another story. i had the truck in second gear doing 3500rpm and it was all she could do to keep 30-35mph. in this truck my transmission normally runs about 160-170 during the summer in stop and go traffic. by the time we go to the top of this mountain my transmission was sitting about 225-230. i pulled the truck over once we paid the toll to get onto Skyline Dr. and sat there for about 30min to let the transmisson cool off. i will admit though that the camper is about an 88' model (very well kept) and we had my bed loaded and the camper loaded with everything that the 7 (my family and my sister-in-law's family) people would need for a week. i'm sure i was towing about 9000lbs possibley more. i decided that after that year i would never tow that camper back up a mountain. since then i have towed a car trailer, horse trailer, and even that camper and as long as i dont have to go up mountains i'm fine. but if i towed things on a regular basis, i would either want a diesel or a more powerful engine.
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Old 04-10-2012, 10:52 AM
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??? Swap a Ford or Dodge powertrain into a 34 year old Chevy and make it cost effective?

Not going to happen in my area.

That and I have no interest in such.
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