: My 472 has trouble breathing... 74 Cadillac Sedan Deville.. just purchased

01-31-11, 02:38 PM
Wow.. my 472 is really running rough.. feels like it's cutting out when I give it gas.... Now to be honest.. JUST picked it up.. I bought it because the Cadillac was clean and straight. The guy I bought it from didn't know a whole lot about cars.. he only put a very few miles a year on the thing and only during summer. I'm going to be systematically going through things (mainly fuel related) as I believe this is the problem. Could be crud in the system, carb, etc.

BUT what I'm getting to.. I read that the '74 Caddy was plagued with a horrible emissions related system due to the lack of a catylic converter. The following year WITH the converter I hear they had more performance. Now that I no longer need emissions on this car.. what is the best way to "clean things up" engine-wise so I can get better performance from this thing? Would prefer to keep stock intake, carb, etc. if possible. What emissions components can I remove and still have a good running (or soon to be good running) engine with a little more pop?

Much thanks,

01-31-11, 11:50 PM
Cutting out when you give it the gas.... my first bet would be the excelarator pump in the carb...

02-01-11, 08:09 AM
yeah, but it cuts out (never dies) as it's idling too... Also saw where mice had been on top of that engine at one time.. with all those hoses on that thing (can't believe the amount to the carb alone), could be something was nawed on.. although I didn't see anything. Need to pull carb and see what the deal is.

02-01-11, 08:11 AM
Back in the day, many many carbs were rebuilt due to burnt points. I would do a tune up first. You can check the accelerator pump by looking down the carb and moving the throttle. that's a very common failure too as was already mentioned.

02-01-11, 09:05 AM
Everybody jumps on the carb first before verifying that everything else is operating as it should. '74 dosen't have points, HEI. These engines have miles of vacuum lines, as you have already noted, and several vacuum motors, or dashpots. Get out your Mightyvac and start testing your vacuum signals and dashpots to ensure they are all operating correctly. Check for cracked vacuum lines. A cracked diaphram in the vacuum motor ( dashpot ) on your distributor advance will cause the reaction you describe.

02-01-11, 02:56 PM
Yes! I'll do that. Looking at that motor yesterday.. can't believe the amount of vacuum lines. Crazy!
I'll do the checking you suggested.. sounds like a good place to look. All good suggestions! thx.

02-01-11, 09:10 PM
In 1974 the HEI was a option and not all the cars had it ... most had points...

02-01-11, 09:14 PM
I coulda swore '75 was the first year for HEI that's why I automatically blamed the points. I guess we'll let 73super settle it haha.

02-02-11, 08:01 AM
I've got points...

02-03-11, 08:59 AM
I forgot, '74 was a transition year. I had a '73 with the first generation HEI in it, throws me off at times. So, do check your points setting and your engine's state of tune.

02-03-11, 07:53 PM
Before you remove ANYTHING, get it running right first. The 472 in the 74 had some good things and some bad things. First of all, you probably have a load of crap in the fuel system, the tank, lines, pumps, carb, filters. This is VERY common on older cars. The quadrajet carburetor is a complex instrument and if there's a load of varnish and garbage in it, you're going to have problems. Also check the distrbutor cap for cracks - very common on pre '75 cars.

02-16-11, 09:24 AM
Well just an update... It turns out that it WAS the carb. I put the rebuilt unit on there, replaced a few vacuum lines, added an in-line glass fuel filter close to the carb... fired it up and wa-la.. She's purrin' like a kitten now! I think that glass filter was a good idea.. I can see the fuel pump isn't pushing much fuel through there.. so may have to look at that too. Anyway.. took it for a run yesterday and it's running MUCh better.

So there ya go. Thanks for all the advice/suggestions/help.

Butch W.

02-16-11, 09:43 AM
74 is one of my all time favorite years. The HEI, as you've discovered, was an option. Some have it, some don't. For some reason, a lot of Eldorados have it. I may suggest that eventually you replace the Quadrajet with a Holley street performer or similar instrument. As I've said elsewhere, the Q-jet was a great piece in its day, but today's low volatility fuels present a challenge. You may also want to update the ignition. The more energy you can blast through the spark plugs, the better todays fuels will burn.

02-16-11, 10:16 AM
Well put. Yes, I have been looking at the Eldelbrock intake and carb setup.. but just wanted to get this thing in good running condition for now.

Most of the problems this car has could have been alleviated if the guy would have driven it around once in awhile. 57K orginal miles and he said since 2006 he's only been putting about 100 miles a year on it. Ugh.. seals dry up, leaks start happening, and of course all the crap in the fuel system.

I'll go through it.. after it's functioning to where I'm satisfied I'll go ahead and start thinking about the upgrades you're talking about. Yes, the HEI ignition setup would definitely be a good way to go as well.