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Interesting find: 5.7L-7.8L V6, and a 11.5L V12

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thunderbird1100

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Yeah, you saw it right, a 7.8L V6 was produced by GM in the mid 60's for heavy duty trucks.
It produced just 206hp @ 3200rpm and 400tq @ 1400rpm. CR was 7.5:1 and it weighed 925lbs. Obviously the engine was 2v/cylinder OHV. Redline: 3200rpm.
Its little brother, the 5.7L V6, produced just 155hp and 288tq. Redline: 3400rpm. Weight: 860lbs.
They made a 11.5L V12 which was basically two 5.7's welded together. It produced 250hp and 585tq. Redline: 2400rpm. Affectionaly called the "Twin Six". It requires 16 quarts of oil. Weight: 1485lbs.

The beast:
Image

The 7.8L:
Image



Modified by thunderbird1100 at 12:44 AM 5-12-2006
 
#3 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (thunderbird1100)

Quote, originally posted by thunderbird1100 »

They made a 11.5L V12 which was basically two 5.7's welded together. It produced 250hp and 585tq. Redline: 2400rpm. Affectionaly called the "Twin Six". It requires 16 quarts of oil. Weight: 1485lbs.

It's no wonder why they were soon replaced by diesels. A modern Cummins will produce more torque with only half the displacement. Those old heavy-duty gas engines were pretty gutless (if you're old enough to have ridden in those gas-powered school buses, you will know what I mean).
 
#4 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (thunderbird1100)

If you go back evern farther, look at a Corbin racer.
1910 Corbin 12.7L Racer
4 cylinder, 12.7 Liter, 110 hp, 4 spead tran
The flywheel was around 400 or more pounds. Very different I guess.
 
#5 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Soul Man)

Quote, originally posted by Soul Man »
It's no wonder why they were soon replaced by diesels. A modern Cummins will produce more torque with only half the displacement. Those old heavy-duty gas engines were pretty gutless (if you're old enough to have ridden in those gas-powered school buses, you will know what I mean).

How old would you have to be? When did the transition to diesel take place?
 
#7 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Soul Man)

Quote, originally posted by Soul Man »

It's no wonder why they were soon replaced by diesels. A modern Cummins will produce more torque with only half the displacement.

I was always wondering about this, why is it, that many countries were still using gas engines while Diesel technology was already available. An example might be Germany after the war, where US Army vehicles were reztofitted with Diesel engines by Henschel. Another country that stand by gasoline engines was Soviet Russia. There are some crazy stories floating around the Net about the (horrible) fuel consumption of Russian trucks with gasoline engines.
 
#8 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Dommer)

I'm 30, I used to take the school bus until I was 7. So I guess the carriers started switching to diesel from the mid 1980s.
The clearest memory I have of gas-powered busses is a ride from a field trip. The driver had to take an onramp that was quite steep, and the engine was revving so slowly I was afraid he could not make it to the top of the hill.
 
#9 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Soul Man)

Quote, originally posted by Soul Man »
I'm 30, I used to take the school bus until I was 7. So I guess the carriers started switching to diesel from the mid 1980s.

I think the gas engines in use by the late 70's/early 80's were the newer 7.0L V8 truck engine...
 
#11 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (DoktaJoch)

Quote, originally posted by DoktaJoch »
Another country that stand by gasoline engines was Soviet Russia. There are some crazy stories floating around the Net about the (horrible) fuel consumption of Russian trucks with gasoline engines.


Just guessing here, but gas is more volatile than diesel, and it won't gel in the tank, stranding you somewhere in Siberia.
 
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#12 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Soul Man)

Quote, originally posted by Soul Man »

It's no wonder why they were soon replaced by diesels. A modern Cummins will produce more torque with only half the displacement. Those old heavy-duty gas engines were pretty gutless (if you're old enough to have ridden in those gas-powered school buses, you will know what I mean).

Back in the 80's the school buses I got to ride in were powered by Ford's 302, Chevy's 350 or Dodge's 360, all of them converted to propane.
At the end of the 80s they started getting diesels, and by now, most of, if not all, are diesels.
 
#14 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (thunderbird1100)

Very cool. I wonder what a good engine builder could do with one of those- I'm sure the weight penalty would be too great, but it would be fun to see how much you could squeeze from one.
 
#15 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (HarryC)

Quote, originally posted by HarryC »


Just guessing here, but gas is more volatile than diesel, and it won't gel in the tank, stranding you somewhere in Siberia.

You can get a different blend of diesel(or add additives) that lower the freezing point by quite a bit, just as a note.
 
#17 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (kerridwen)

I can remember gas-powered busses with manual trannies back in grade school. Those were the days.
Image
 
#18 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (Dommer)

Quote, originally posted by Dommer »

How old would you have to be? When did the transition to diesel take place?
It still hasn't in some places based upon budgetary constraints.
 
#19 ·
Re: Interesting find: 5.7L-7.8L V6, and a 11.5L V12 (thunderbird1100)

Quote, originally posted by thunderbird1100 »
Yeah, you saw it right, a 7.8L V6 was produced by GM in the mid 60's for heavy duty trucks.
It produced just 206hp @ 3200rpm and 400tq @ 1400rpm. CR was 7.5:1 and it weighed 925lbs. Obviously the engine was 2v/cylinder OHV. Redline: 3200rpm.
Its little brother, the 5.7L V6, produced just 155hp and 288tq. Redline: 3400rpm. Weight: 860lbs.
They made a 11.5L V12 which was basically two 5.7's welded together. It produced 250hp and 585tq. Redline: 2400rpm. Affectionaly called the "Twin Six". It requires 16 quarts of oil. Weight: 1485lbs.

The beast:
Image

The 7.8L:
Image


Modified by thunderbird1100 at 12:44 AM 5-12-2006

Would those have been used in trucks to run PTO's and maybe hydralic units? Almost 600 ft/tq is still enough to pull stumps and heavy loads, or be used as work trucks were they sit and idle while running excessories.
 
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