Imagine a 500cid with PFI!
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500, 472, 425, 368 Discussion, Imagine a 500cid with PFI! in Cadillac Engine Technical Discussion; I was thinking about this earlier, if a 1976 500cid made 400 lb/ft of torque with the primitive EFI setup, ...
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    Question Imagine a 500cid with PFI!

    I was thinking about this earlier, if a 1976 500cid made 400 lb/ft of torque with the primitive EFI setup, (was that throttle body injection?) what kind of power would it make with a modern Port Fuel Injection setup?

    Heres some things I was considering:
    350LT1 with PFI: 260hp/330 lb/ft
    Dodge 8.3 V10 with PFI: 500hp/525 lb/ft
    8.2 EFI: 215hp/400 lb/ft
    6.8 V10 w/ PFI: 362hp/457 lb/ft
    1993 Ford 460 with PFI?: 250hp/410 lb/ft

    With a good PFI setup, I'm estimating that it could make around 350hp and 550 lb/ft. What do you guys think?

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    terrible one's Avatar
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    Re: Imagine a 500cid with PFI!

    I was going to run a MPFI system on my built 500, but decided against it.

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    Re: Imagine a 500cid with PFI!

    The low compression 500 makes about 300/490 with a carb. FI on a stock/stockish manifold won't give you much of a gain in power. It'll help economy out a bit though. I'd say a Bulldog would be great with FI, maybe worth 30hp or more... just a guess though.


    BTW the EFI 500 was indeed MPFI. I'd avoid all the old factory FI stuff really if I were to go FI. Run a megasquirt, new injectors, make some rails, etc...

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    Re: Imagine a 500cid with PFI!

    yeah, no way any fuel injection system is going to add 135hp/150ft-lbs torque just not happenening on anything near a stock engine

    Keep in mind, the big block Cad was designed in the 50's while most all the other engines you mentioned were 90's designs.... not very fair to compare stock for stock

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by davesdeville
    . I'd say a Bulldog would be great with FI, maybe worth 30hp or more... just a guess though.
    A Bulldog would be way too much for anythign even near stock. Probably the only thing to do is just get an originial FI manifold, or modify one.

    Either way I don't think it's worth the gain, not even in fuel economy. If you really want good mpg don't drive anything this heavy with this big of an engine.

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    Re: Imagine a 500cid with PFI!

    Oh BTW,

    The "primitive" EFI setup was multiport, not TB.

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by terrible one
    Oh BTW,

    The "primitive" EFI setup was multiport, not TB.
    Oh ok I remember learning that in my vehicle services course, but I forgot the system, I thought Throttle Body because that one seemed like it had been around the longest, so logically it would seem like it would work.

    Did they use Throttle Body Injection on the early 4.1's or was that multiport too?

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by Night Wolf
    yeah, no way any fuel injection system is going to add 135hp/150ft-lbs torque just not happenening on anything near a stock engine

    Keep in mind, the big block Cad was designed in the 50's while most all the other engines you mentioned were 90's designs.... not very fair to compare stock for stock
    Oh ok that was just a rough estimate.

    I just got those motors because they are powerplants similar in size to the Caddy 8.2L

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    Re: Imagine a 500cid with PFI!

    HT4100/4.5 was TBI until 1990, then the 4.5 was PFI and all 1991-1995 4.9 was PFI.

    I personally think sticking FI onto a BB Cad isn't worth it... I dunno, I like the Qudra-Jet and have no issue on it... when talking the cost of all the stuff, the complexity and more... its just not worth it to me.... plus keeping it carbed is half the fun

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by I~LUV~Caddys8792
    I just got those motors because they are powerplants similar in size to the Caddy 8.2L
    Most of the power gains are as a result of improved airflow (better flowing cylinder heads), improved combustion through careful shaping of the combustion chamber/piston crown, and modern cams giving more valve lift and lifting the valves faster.

    People think EFI is such an incredible thing nowadays because the average Joe public is comparing his new EFI car to an old out-of-tune, needs a rebuild (for the engine and the carb) carb'd motor. Also, the majority of EFI motors have ovderdrive trannies while the majority of carb'd motors do not. The overdrive itself gives big improvements both in acceleration (because you can run a lower final reduction) and fuel economy (because of the OD). If you had two versions of the same car that were identical in every way except for one having a carb and the other having EFI, I'll bet you the average driving public wouldn't notice that much difference.

    EFI will gain you some fuel economy, some throttle response, and some power. Emissions will be reduced as well. The biggest gain you'll probably see is in cold starting, but even that isn't a huge gain if your Q-jet has a properly-working choke.
    Keep in mind that all the gains would only be after fully tuning the EFI setup, and that's going to take time. To get it really good I'm told you really must go to a chassis dyno and spend at least a day on the EFI tune.

    Now, I do think you could get those power numbers from a Caddy 500, but you'd have to add ported cylinder heads, a revised camshaft, 10:1 compression, and a freer exhaust/intake to the mix along with the EFI. Basically, the things that those newer motors have to begin with.

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    Re: Imagine a 500cid with PFI!

    This series of engines was designed to make about the same amount of power as previous smaller higher compression engines. By the mid '60's GM knew that leaded fuel would be phased out requiring lower compression. They also knew that exhaust emissions would become an issue. Cadillac didn't want to sell underpowered cars....just yet. They took all the best features of V8's designed up to that time. Several were borrowed from Chrysler. Look at a 472. Intake valley pan, external oil pump up front and distributor up front where it can be easily serviced. All copies of the raised block Chrysler powerplants. Cadillac took it a few steps further. High Nickel casting made for more strength allowing more modern casting techniques. This allowed for a light engine that would survive use. A Cadillac 472 only weighs around 75 Lbs more than the heviest Chebbie 350. Chebbie cut weight in later years resulting in core shifting troubles. Remember all the '78/9 schmalblock Chebbies eating the #7 cam lobes? Cadillac cut weight on the 425 and 368 without them falling apart. Cadillac also thought about the engine as installed in the cars. Where the spark plugs would be and how difficult will it be to replace them. Another great thing was the heater hose outlet directly at the cylinder head. This was the most modern V8 for many years. Manufacturers waited years to get back to V8 design as the V6 was supposed to save the world.
    In 1968, Cadillac also was able to advertise 30% fewer gasketed joints in the all new series of engines. No more exhaust manifold gaskets or paper intake manifold gaskets. No starter shims were needed for these higher tolerance blocks either.
    These engines really do not compare to other brands directly because the Cadillacs make less power in stock form for the cubic inches. This was by design. The Cadillac engines of the era also have the ability to deliver impressive fuel economy if driven properly.

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by terrible one
    A Bulldog would be way too much for anythign even near stock. Probably the only thing to do is just get an originial FI manifold, or modify one.

    Either way I don't think it's worth the gain, not even in fuel economy. If you really want good mpg don't drive anything this heavy with this big of an engine.
    No. The reason a bulldog is considered "too big for the street" is because it has a lot of plenum (and runner for that matter) volume, so the carb can't "see" a good vacuum signal from the engine. Not a problem with FI.

    The second argument is weaksauce. I like driving a big ass car with a big honkin motor in it. If I don't want to compromise and get a small car, why should I have to? Why shouldn't I try to get the best mileage I can out of my big honkin motor?

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    Re: Imagine a 500cid with PFI!

    Oops. Then I guess you could get a bulldog.

    You don't have to compromise with a small car. Who doesn't like getting the best mileage that they can? I'm just saying that no matter what you do, you won't get very good mpg out of your 70's Caddy. I was also saying that although it would improve your mpg, EFI isn't worth the money IMHO.

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    Re: Imagine a 500cid with PFI!

    Quote Originally Posted by terrible one
    Oops. Then I guess you could get a bulldog.

    You don't have to compromise with a small car. Who doesn't like getting the best mileage that they can? I'm just saying that no matter what you do, you won't get very good mpg out of your 70's Caddy. I was also saying that although it would improve your mpg, EFI isn't worth the money IMHO.
    What do you consider good mileage?

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    Re: Imagine a 500cid with PFI!

    Is it possible to get something like 14/22 mpg in a 500?

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