'76 Cadillac Acceleration

[R Schroeder]

Some info I dug up.

Cadillac Coupe de Ville, model year 1970, version for North America (up to September)
4-door coupe body type
RWD (rear-wheel drive), automatic 3-speed gearbox
petrol (gasoline) engine with displacement: 7729 cm3 / 471.7 cui, advertised power: 279.5 kW / 375 hp / 380 PS ( SAE gross ), Torque net: 712 Nm / 525 lb-ft (see horsepower and torque curve)
characteristic dimensions: outside length: 5715 mm / 225 in, wheelbase: 3289 mm / 129.5 in
reference weights: shipping weight 2109 kg / 4650 lbs base curb weight: 2170 kg / 4784 lbs
how fast is this car ? top speed: 206 km/h (128 mph) (theoretical);
accelerations:    0- 60 mph 8.1 s    ; 0- 100 km/h 8.5 s (a-c simulation); 1/4 mile drag time (402 m) 15.9 s (a-c simulation) (see detailed performance data review)
fuel consumption and mileage: average estimated by a-c: 26.1 l/100km / 10.8 mpg (imp.) / 9 mpg (U.S.) / 3.8 km/l


1978 Coupe Deville  425

0-30 mph (s):
4.7

0-40 mph (s):
6.6

0-50 mph (s):
8.6

0-60 mph (s): ********
11.2

0-70 mph (s):
15.4

0-80 mph (s):
20

0-90 mph (s):
26.3

0-100 mph (s):
36.8

But you also get a nice ride in my Honda CR-V. It will do 0 to 60 in 8.4 seconds.

I wondered why I dusted off the Chevy Silverado last week.

You also have to remember the 70 has 195 more horse power, so the 425 I have isnt that bad , at 180 hp.

[Scot Minesinger]

If you test a perfect 1979 Cadillac (180hp) and a perfect 1970 Cadillac (375 hp) on a dyno, the 1970 will not be twice the power of the 1979.  I remember driving a 1979 Cadillac in 1979 and they were quick enough that no one would complain about lack of power.  Plus the 1979 Cadillac is lighter than a 1970 Cadillac.  The 1977 Cadillac seemed fastest of the three 425 engine years. 

Now OK the 4.1 horsepower rating (140hp or so?) is overstated and a 1970 Cadillac will test twice the horsepower on a dyno and run rings around it if it is powering a SDV in 1982 for example.  I well remember the difference between my Grandmother's 1973 Cadillac SDV and her 1982 SDV with a 4.1 when driving them.

[R Schroeder]

Scot, I would be proud to own either car. They both have more than enough power to have a nice drive in the country.
Roy

["Cadillac Kid" Greg Surfas 15364]

Where are we going with all these numbers guys? The original poster was wondering if his car was accelerating like it should, and he was going to run some tests for comparison.
Regarding the actual horsepower of a '70-472 I believe I saw documentation that the actual NUMBER was somewhere around 285.00.  Horsepower is not what moves our cars, it is torque.
My '73 with a very tired, oil burning 472 ran the quarter mile in 16.2 seconds at just about 90 mph. So what.  That has nothing to do with the numbers for the 76 in question.
The large chamber (74-76) motors were designed to provide large amounts of torque at low speed, smoothly and keep producing it all the way to top speed. No muss, no fuss, just move the iron up to highway speeds at least better than the rest of the traffic of the day..
Lets wait to hear from Jeff when he gets a chance to get some numbers.
Greg Surfas

[Jeff Moffo]

I didn't forget you guys and thank you all for all the info you all have proposed. If you saw the weather in NJ  and the copious amounts of salt that cover our roadways, you'd understand why the old girl is still in hibernation. Can't wait for spring!

[Smedly]

I remember as a kid (my dad had 2 76 sdv. ) going from stop light to stop light laying black rubber all the way around the block that the high school my sister went to was located. Just because one of the teenage boys at the school "chirped the tires on his fire chicken. The only mod to this car was the removal of the cat. I don't think if the car works properly anyone would complain about acceleration. (traction maybe but acceleration NO)

[Scot Minesinger]

Sheldon,

That is all I meant to say, that the Cadillacs of the 1970-79 decade enjoyed wonderful power.  Some were faster than others, but all very nice driving cars.  Same can be said for the 1960's too.  The horsepower ratings were not all equal (or indication of acceleration feel), after all an early 1950's Cadillac (with say 220hp) will not keep up with a late 1970's Cadillac with 180 hp rating.

[Jeff Moffo]

I am enjoying the discussion you guys have and have learned so much from all of you.   The car definitely rides terrific.  And I know these cars had great torq as I owned another for several years.  I don't want it to be a race car by any means, just want the thing to move the way it should from a dead stop.  Even at cruise, if I accelerate, I have no problem getting it going.

I am eagerly awaiting when I can get the car back on the road and first test the new vacuum advance I installed.

I also pulled the No. 1 spark plug, and the thing was in near pristine condition, so there are no problems there.    I "fixed" the spark plug wires, and routed the wires a bit better with the respective wire separators/holders seeing the wires were all over the place, and at one junction feeding the odd cylinders, they were bunched up and held together with a twist tie. 

When I get the car started, I will also check to see how the vacuum reading is on it, just to also be sure the exhaust (cat. con) is not clogged.

[James Landi]

Hi Jeff.. I wonder what the vacuum spec. is for your model car at idle.  I have worked with older engines, and there is a very specific range (most are 17 on the gauge @ idle). With a vacuum gauge, you can also tell if your car has leaky valves ( a power robber), as the needle will look like it's vibrating as you accelerate the engine in neutral.  Might be a good investment for you, given all of the vacuum hoses that run to the engine, and it may provide you piece-of-mind, as well.
they are not very expensive and likely worthy of consideration as you move forward.     James (Mr. Shadetree mechanic)

[waterzap]

My 78 is sloooowwww too. Smooth and starts easily, but can slow to accelerate. On the highway its fine though.
And takes forever to warm up. So disributor / and / or carb could cause this slowness?
Such a nice car. Just wish it would be a bit more peppy. Almost too slow to drive in traffic. Once up to speed is fine, but speeding up, slowing down is painful.

[James Landi]

Waldo--- urge you to read the entire thread-- a bunch of great suggestions from many members that you can easily use to diagnose for that problem, and can make a tremendous difference without costing much money.   

[waterzap]

Will do. Thanks

[Jeff Moffo]

I will check the serv manual when I put the vacuum gauge on it to see where the reading should be!

[bill06447]

My 78 was a slug when i got it-then again, it had only traveled 20 something miles in the previous six years. Fresh fuel, new EGR, HEI module, plugs, coil, cap, wires, etc also had to reroute the vacuum advance lines to their proper connections on the temperature switch, car is very responsive now. Fuel may cause big problems especially if the car is driven sparingly, modern gas is crap after 30 days.

Bill

[Smedly]

Scott.
My comment was made in general toward the original post was not intended to anyone specific.

[Scot Minesinger]

Sheldon,

Yes understood.  Thought your comment was so right and better expressed than I wrote.  Just wanted to say you nailed it.