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500, 472, 425, 368 Discussion, How many horsepower does 472 engine has by current ratings? in Cadillac Engine Technical Discussion; The HP numbers for most mfgrs are lies anyway. The 472 in 1968 and 1969 was rated at 375 HP ...
  1. #16
    steelybill is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    The HP numbers for most mfgrs are lies anyway. The 472 in 1968 and 1969 was rated at 375 HP @ 4400, which is likely above valve float on those stock springs. And the listed torque is 525 ft lb @ 3000 RPM. The torque numbers are likely about right. Compression ratio is listed as 10.5:1 for those years, but dropped to 8.5:1 in '71 & '72.

    The torque is where the power is it seems. Modern small engines list a lot of HP, but not much in torque.

  2. #17
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    Re: How many horsepower does 472 engine has by current ratings?

    Quote Originally Posted by Fleetwood70 View Post
    Good to know that it still has about 300hp,
    What I don't fully understand is why 472ci in 1974 has only 205 hp, and 500ci has only 190hp and 360 lb-ft in 1976. Yeah I see it has lower compression ratio, some emission stuff, but, that sucks.
    The compression ratio was actually raised in '75/'76 compared to '74...

    1974.......... 8.25:1
    1975.......... 8.5:1
    1976.......... 8.5:1

  3. #18
    kilog55 is offline Cadillac Owners Member
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    Re: How many horsepower does 472 engine has by current ratings?

    Quote Originally Posted by Tiny Huge View Post
    Just a small piece of info , The 472 and 500 are sought after for pick up swaps.the torque is good the "Roll on power" makes it well worth the extra effort .
    indeed i have a 472 in my 68 F250, i didnt do the swap but it was well done.

  4. #19
    fuknuz is offline Cadillac Owners Member
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    Re: How many horsepower does 472 engine has by current ratings?

    iv heard alot about the car companys actually posting lower power rating than what the motors actually put out. did cadillac also do this in the late 70's and i got a 79 425, seems to have alot more pull than 180hp and 300ft/lbs. had a 350 in my truck b4 i put the 425 in it, ~250hp and ~300ft/lbs with sum goodies and it couldnt touch the hevier 425. And my 425 is not close to factory power bc my carb is junk and having timing issues

  5. #20
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    what happened in the mid to late 70s was exactly the opposite of what happened in the 50s and 60s. Mfg's were quoting less horsepower so as to seem more responsive to 70s fuel crises concerns.

    either way, a high compression 472 or 500 today won't be producing the horsepower it did in 1970 because of the modern fuels (see my previous post on this), but will still produce some impressive torque (although that is still hampered by modern fuel). if you look at the ports in cylinder heads of modern high performance engines you'll find them MUCH smaller than on old time engines. you just don't need those huge, yawning ports and valves anymore..

  6. #21
    otherworld is offline Cadillac Owners Member
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    Re: How many horsepower does 472 engine has by current ratings?

    Why would a smaller carb help?

  7. #22
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    Quote Originally Posted by otherworld View Post
    Why would a smaller carb help?
    Because of todays street fuels. A huge carb, on an engine that really doesn't generate huge horspower will only cause it to bog and dump gas, not make power. We know, that it takes 1CFM to make 1 horsepower. Simple. So a 472 making about 375 hp on the street would only need about a 400 CFM carb or so, not some enormous 1000 CFM fuel bucket. Throttle response on the street with the smaller carb would be noticeably different and milage would be better by far.

    I've seen guys in low compression, mild cammed smog monster late 70s' early 80s' Camaros put giant 1000 CFM holley double pumpers on them and then wonder why it stalls, seems to accelerate slower, and sloshes gas like crazy. Easy - there isn't enough "engine" to utilize all that fuel.

    Look at the ports on the current crop of High Performance Chevy engines in the 'Vettes and such, and you'll see MUCH SMALLER openings than on the older engines. Why? Because with current fuels, you just don't need those huge ports anymore. Take a new Z06 and dyno it, then take a vintage 427 powered 'Vette and do the same. the dyno doesn't lie, the newer 'Vette on pump gas will be making WAY MORE power than the 427 tri-carb car.

    Same for cadillac - the gas now is WAY DIFFERENT than in 1970. That '70 472 or 500 won't be making the same power it did 40 years ago, in it's stock configuration. It can't because the 2011 fuel is nowhere near as volatile as 1970 fuel was. Heck, you can even SMELL the difference between modern fuel and (if you could find it) 1970 fuel.

  8. #23
    fuknuz is offline Cadillac Owners Member
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    Re: How many horsepower does 472 engine has by current ratings?

    is there any additives we could add to help?

  9. #24
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    Quote Originally Posted by fuknuz View Post
    is there any additives we could add to help?
    I have little faith in "witches brews." Octane booster may help quell the knocking but taking the old Q-jet and putting in a box while fitting a more modern carb will definitely bring more smiles per mile.

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    fuknuz is offline Cadillac Owners Member
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    Re: How many horsepower does 472 engine has by current ratings?

    what do u recomend? i got a 79 425 with a q jet off a 80 something chev truck. with the q jet being a variable cfm carb im sure iv got a good cfm/ci/hp ratio. what would i look for in a carb for it to b "more moddern"?

  11. #26
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    Quote Originally Posted by fuknuz View Post
    what do u recomend? i got a 79 425 with a q jet off a 80 something chev truck. with the q jet being a variable cfm carb im sure iv got a good cfm/ci/hp ratio. what would i look for in a carb for it to b "more moddern"?
    I'd absolutely get rid of the Q-jet and install a Holley, Edlebrock, or Barry Grant carb of no more than 390 CFM. You can buy them with the smog fittings all ready to go. I'd also upgrade ignition, the old GM HEI was good in its day, but can't throw the flame like a new MSD or Pertronix can. More flame power means more fuel burned to make power not dumped in the exhaust.

  12. #27
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    Re: How many horsepower does 472 engine has by current ratings?

    Doug, I don't necessarily agree with a couple things you said....just want to throw my thoughts out there, this is not gospel, just my observations.

    First, the Q-Jet is a fine carb, and it works well with a stock motor. It's not necessarily as easily adjustable as a Holley with a heavily modified motor, but for stock motors, I can't see how changing out the carb is going to do anything for performance, and may possibly hurt it.

    You said that modern fuel isn't as volatile as 1970 fuel... I have no doubt you're right that modern fuel is different and has less energy, in part due to the addition of ethanol, but more volatile fuel isn't necessarily the answer either. 87 octane is more volatile than 93 octane, but cars with higher compression, especially carbureted cars, have no choice but to use higher octane fuel or dial back timing to avoid detonation. A richer mixture on the stock carb might be the answer to modern fuel. The correct way to check this is to measure A/F ratio.

    As for guys putting 1000 CFM carbs on their cars and wondering why they don't run well, are less responsive, use more fuel, a lot of guys go big with things like carb and cam and expect the car to instantly have 200 more horsepower from 1,000 to 6,000 RPM. They may be getting more horsepower up top, but generally speaking, the more you get up top, the more you give up down low. It's all a trade-off. The best solution is a well-designed package. A stock 472 was a very well-engineered motor, and in the WORST case, it's still CLOSE to being set up properly for modern fuel. It's not so far off that a carb half the size of the original is appropriate.

    As for the modern LS motors, there is a WHOLE LOT of technology that they use to improve performance, they're entirely a new design from the old Chevy small blocks. The modern LS7 valves though are BIGGER than even on the old 427 L88 motors, and are designed to work with the whole package. Just like the old Q-Jet on the 472. The 472 was set up for it, and going and randomly swapping parts like the carb isn't necessarily the best way to improve performance. A smaller carb might increase port velocity, but may also provide less fuel, and while it may provide better throttle response down low, may hurt top end performance. Again, richening up the mixture may be the simplest solution and would retain the factory carburetor that the motors were designed for. There is something nice about having a stock motor with a stock carb that can be adjusted via the factory service manual techniques.

    Also, the HEI...that was designed to help the motors run better on the leaner mixtures of the mid-'70s. A side-benefit was no more points to replace. Some say that they notice improvements with HEI, other say HEI is pretty unnecessary on an older motor. My stock low-mile '70 472 still has an original Q-Jet and points, and runs EXTREMELY well. I've spent the time to tune and adjust it properly. Again, these things are my observations and thoughts, I'd be happy to discuss it and am open to new ideas if I'm missing something.

  13. #28
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    The Q-jet was a great carb. For 1968. So advanced was the design, it served well into the 1980s before being sidelined. That is one heck of an admirable record. However, things change. It just can't adequately atomize the fuel like a more modern street carb can. The dyno doesn't lie - I saw an Olds 455 make a 20hp jump with just a carb replacement. I work quite closely with the speed shop across the street from my machine shop. I've seen cars go on the dyno and not make anywhere near the HP they were rated at 40 years ago, even though they were running tops. The old 472 family of engines were way advanced for their day, and were capable of huge horsepower and torque. They can still make big power today. Can you still run a Q-jet? Sure. Will it be maximizing the fuel used? Nope. You'll need a more modern carb to atomize the fuel better. I know some folk that won't get rid of the Q only because of originality. I understand that completely. But you're gonna lose some HP and torque. Plus a reduction in milage.

    As far as fuels go, modern street gas doesn't have the toluene, MTBE, Benzines, and other things that 1970 fuel did. Take a whiff of Cam2 fuel and the highest octane pump gas - your nose won't lie either, you can tell the difference. It's not scientific, but it proves a point.

    Onto the modern HP motors. The LS7 Chevy has huge valves, but the ports in the heads are nowhere near as large as the old 454 squareporters were. Much smaller in fact. Why? It doesn't need that enormous opening. The whole engine is a packge - yes - you are most correct. A package designed to run on 2011 unleaded pump gas and make big power.

    I also know that the old points type and early gen HEI systems don't throw the fire the way a modern system would. Simple physics, the hotter and bigger the spark, the better the fuel will burn. No two ways about it. When I swapped out the old Motorcraft points system in my 67 Thunderbird for a Pertronix system, the difference was noticable from first start. The engine simply lit up with more authority and much less cranking. Throttle response was way better. The smaller carb greatly improved that as well as milage.

    Even if you were winding your 500 out to max RPMS and ultra high speeds, unless you've got it tuned for 800-1000 hp, a smaller carb would not hurt much. A stock engine? 400 CFM would not starve it at all. Mildly tuned? 5-600 CFM would be MORE than enough. The big fuel buckets should be reserved for radical engines that are wild in their state of tune. Few folk run these on the street.

    I know that one of the Cad engine builders runs wild 472s and 500 with HUGE carbs and they make torque and HP that is simply unreal. But few of us Cad enthusiasts have our cars in that state of tune. With my two hearses, I just wanted a bit more "punch" but not have it rattling the windows when it goes by.

    By no means am I the final word on this. I've seen what the dyno says and I've seen cars updated and post impressive performance and milage gains. I was convinced.

  14. #29
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    Re: How many horsepower does 472 engine has by current ratings?

    I'm not disagreeing with you necessarily on the carb, but if someone is going to swap the old Q-Jet out for something new, it's not just a matter of unbolting the old, bolting on the new, and you're set. While the Q-Jet may not be the latest technology, or even necessarily yesterday's latest technology, it was still engineered as part of the complete engine package by Cadillac. For those who are building a motor and are willing to put in the time to engineer and then maintain it for top performance, obviously the Q-Jet isn't going to be the answer. For those who want pure originality, the stock carb set up the way the factory did is obviously the way to go. Am I right though that the stock carb could also be optimized at least for the chemistry of today's gas, to do better than an untouched carb, but without resorting to a modern aftermarket carb? I know I'm beating a dead horse at this point, but I think the reason the Q-Jet finally did go away was because carburetion went away, not because the factory found a new better carb. Wasn't it one of the very last carbs installed on production cars? If I'm not mistaken, the last two of these were the Olds 307 and the AMC 360 (in the Grand Cherokee...NOT the Chrysler 360) around 1991. Not sure if the 360 was using the Q-Jet, pretty sure the 307 was using the computerized one, for idle reasons.

    As for cars not making the HP they were rated at, they used to be rated at gross HP. I don't know what a '70 472 made at the wheels versus the flywheel in 1970 versus 2011, but there is a large grey area and it would be hard to nail a specific number down. It's not really an apples to apples comparison to say that, in 2011, a 40 year old car doesn't make the power it was rated at 40 years ago. Some of this is dyno variance, some of it is rating variance, some of it is fuel, some of it is age and wear. I still contend that, if you took an old motor that was in good condition and either use 1970 type fuel or adjust the factory carb for today's fuel, your dyno numbers in 1970 would have been at least close to your dyno numbers today. Excluding of course for the drying and aging of parts that are subject to drying and aging, which isn't possible to exclude for in reality, the car doesn't make less power simply because 40 years of time have passed for the carburetor. There are other variables. Likewise, if the factory had a 2011 carburetor that atomized fuel better in 1968, the 472 may have been rated at 400 horsepower from the factory, instead of 375. Fast forward to 2011 and modern fuel versus old carb setup would have the same detrimental effect in either case. Having said this, I recently built a 1970 Chrysler 440-6, using oem carburetors. It was rated at 390 HP from the factory, and it put out 392 HP on the dyno jetted for and using modern fuel. I thought this was kind of cool.

    As for me and my car, I am into the originality...to an extent. I plan cam and head work eventually, but I'm going to do it the hard way and use the stock carb and distributor, adjusted where it makes sense. I like making things difficult for myself, and a lot of people can't understand how people like me reach for performance in some ways, while leaving it on the table in other ways. For now, the car's only got 72k miles, and even with points, as long as the carburetor isn't dry, it will start up on the first try with less than a second of cranking. If it started any quicker, it would just be running all the time. I do maintain it very regularly.

  15. #30
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: How many horsepower does 472 engine has by current ratings?

    As far as optimizing the ole' Q-jet, I don't know. It "might" be able to be tuned accordingly. But remember that it's a 1967 or '68 instrument. Things have changed RADICALLY since that time. I know that for Ford carbs there is a place that allegedly tunes them to run properly on unleaded pump gas, but I have had no experience with them. The best I can tell you is "maybe".

    But for me, a more modern carb, even out of the box, is a better bet, and with slight tuning and jet adjustments, you can expect the old 472 to run like the good old days. I know this, as I've seen it.

    Look, the Q-jet was an amazing piece. Truly. It was so good, even Ford was buying them and using them. It handled all the emissions requirements of the day, and provided fantastic performance. But a lot of miles have gone under the tires since then.

    I remember the Olds 307 using it up thru '87, not sure about the AMC 360. I "think" that some Chevy/GMC trucks had it up thru 90 or so but then that was it. Injection was in, carbs were out. But even if injection hadn't taken over, it would've eventually be retired long before now. Time marches on.

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