There are a few guys who have done it on the impala ss forum. Stingroo is currently putting one in his wagon.

 

If you're only getting 6 mpg from your 425, there's something wrong. Even around town, this engine should be returning 10-12 mpg, and 15-17 mpg on the open road. Not stellar, I admit, but still. I'd personally address the issues with your 425.

 

The above is oh so very true. The 425 is one of the very best of the last true Cadillac engines.

 

Sting better post a link in the picture thread....or else....lol

 

lol That is not a Cadillac Forum approved project. No fun to be had here for that type of stuff.


Yes - you could LS swap it pretty easily. You could run a carb'd 6.0 and have a Cadillac worlds faster than GM ever intended, but then you get to go through the brakes, rear end, steering.... it never ends. As Smoky the Bear says: Only YOU can decide how far you want to go with your project and how much money you want to throw at it.


...well, those weren't his exact words, but I paraphrased.

 

I do love that 425 cubic inch under the hood of my 79 Coupe deVille... and yes I will be addressing the issues with it. The car has been taken care of for the most part over the years. The second owner had a fleet of cars and I think was having trouble keeping up with all of them. So she does need a complete tune up and I'm also going to completely rebuild the carburetor... I don't believe it's ever been touched. It brings back so much nostalgia when I get those secondaries to open up --love that sound!

I wouldn't mind having the fastest 79 Cadillac Coupe deVille to torment my neighborhood a little more... but really would keep the LS1 or 2 stock and dare I say quite. I would even keep catalytic converters...

It's just something I was thinking about, between the 3 cars I have I don't have the money for that project... yet!

 

Do not go through the Q-jet carb until you have gone through a complete tune up procedure at least once. The Rochester Q-jet is one of the most reliable units on your engine. Get a Service Manual for a '77 - '79. The described settings are similar throughout these three years ( with a few variations, but any will work on a base line ). Understand and follow the procedure as described, but, before you do, check all the vacuum hoses for leaks and cracks. The vacuum systems on these engines are extensive and have a major influence on how well your engine runs. Check all vacuum canisters and the dashpots that they hold the proper vacuum for the required amount of time. You would be surprised that people often go through the carbs when the dashpot motors are the main problem. Also check out your distributor. Sticky mechanisms, worn flyweight parts, and rust can effect the mechanical advance. A little dab of lithium grease will go a long way. Don't forget the Vacuum Advance canister.
Then go through the settings for your Q-Jet. Get out your feeler (gap) gauges and check the settings. Hope you have a lot of patience, because the procedure can be tedious. If all your support units for the vacuum system are working properly, you should be able to get at least 16 mpg.

 

Ive alsways wondered what one of these would do on a 425.

http://www.summitracing.com/parts/hly-502-20s/overview/

But then the Qudrajet has an outstanding reputation.

As far as taking a 425 out, that's a giant step Backwords.

 

Taking an ancient, carburbureted 425 cubic inch boat anchor out and putting in a modern all-aluminum power plant with fuel injection and the latest technology is a step backwards?

But dropping $1200 on an ancient TBI-based fuel injection setup is a possible alternative?

Yep. There we go. We're still on the Cadillac forum. :lol:

 

Bruce has been working with the factory injection system for the 425 for a long time now. He has been tweaking it in an attempt to get mpg over 20. This system does get the 425 better mpg than the Q-Jet, ( I think Bruce last recorded 19 ) but it is complex and needs understanding if you are going to install it on your car. The TBI system was the corporate answer ( experiment ) that soon was overshadowed by other more efficient means of fuel induction ( Tunnel-Port, EFI ). Perhaps the offering by Summit will give more than the Q-Jet without the complexities of the factory injection system, but the engine still has to be tuned-up and properly set up to get you there.

 

The whole problem is sort of like this......................

Mustangs, Cameros, Firebirds and Corvettes are highly collectable......................but the New Ones are a whole lot BETTER.

We RWD Cadillac collectors don't have a lot of options, as there will never be another one made, so a better new one is not going too happen.

The 425 was a Fine Power Plant, only reason I suggested projection was a direct replacement for the carburetor, which should increase mileage and power slightly, as well as driveability and cold starts.

As I see it, it wouldn't be worth the costs and trouble to try and make the car a 2014 running car. At least that's not why I collect them.

IN my 1990 , on trips I have gotton as good as 24 MPG in my "throttle body" 350 Brougham, and even by modern standards that's exceptional.

 

A new whiz-bang powertrain in an old car is a fine experiment but there's nothing wrong with learning how to make original equipment work to potential.

Young folks will always write off what they will never grasp. Easy.

 

Ah, there it is. NOW this is the Cadillac forum.

 

 

:lol:

Well played, good sir.

 

The 425 is not a boat anchor. No, it's not super-powerful or ultra-efficient like a modern engine. But it is smooth, reliable, and it's what the car was built to have. It's a big part of what defines the car's character. Changing the powertrain (or suspension, or interior, etc.) fundamentally changes what the car is. It may bear a passing resemblence to its old self, but it's no longer the car it was built to be. If you want a new car with a modern drivetrain and all the goodies, buy one. Why try to force an old car to be something it never was nor was meant to be? I mean it's your car and you can do whatever makes you happy. I just don't get buying a car and radically altering it into something totally different. It seems pointless to me.

 

It was the end of an "era" that will never again be repeated.

 

Stinkpoo had a mid 90's Fleetwood once upon a time, that's how he found us, bump that torturous thread to find out his engine solution for that poor car.

 

Hey! Ray's a good guy, and a sharp car enthusiast. He and I may not always agree on what to do with a car, or even what makes a good car, but I have total respect for him.

 

'Specially a non-running car with a bad title that was going to be repossessed, but that's another story.

Anywho, OP's thread was pretty clear on the intent here. It hasn't been done on this forum, but it's been done in several similar cars on the Impala SS forum and LS1Tech, and I can't think of anyone who has regretted their swap.

 

That's only because they haven't pulled up next to me at a stoplight.

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I'd love to see this swap happen, thats the stuff that floats my boat. 3 months ago, I was close to buying a 49 Caddy with the intent of putting a modern fuel injected motor in it to make it my daily driver. That would have been a dream, real old school style but reliable and less expensive to keep running if driven 7 days a week. I still hunt craigs for a 40s/50s caddy every week, its probably gonna be my next project.

Have you seen Cadzilla?

 

I'd love to see this swap happen, thats the stuff that floats my boat. 3 months ago, I was close to buying a 49 Caddy with the intent of putting a modern fuel injected motor in it to make it my daily driver. That would have been a dream, real old school style but reliable and less expensive to keep running if driven 7 days a week. I still hunt craigs for a 40s/50s caddy every week, its probably gonna be my next project.

 

If you want to do a conversion, I have no problem with that. I have done my share of them. If you plan to do a conversion take time to study what has to be done to before jumping into the fire and getting burned BADLY. I have converted Firebirds to Chevy drivetrains. After the first one, I knew what had to be done on the ones that followed. I kept notes on the first one and had something to refer to so I could inform the owners what expenses they would have to expect on theirs. The worst was a Olds Cutlass to Chevy. There were many unexpected items which needed to be exchanged. The smartest thing I did was to procure a Chevy complete of like design. Gave me the chance to study everything as I dismantled the donor. When you consider a swap, don't forget linkage, there are pieces you need from one that weren't necessary on the other.

 

Cadzilla has a 500 in it. It was initially built with injection, but they put a carb on it for the Power Tour. Saw Cadzilla (and the pair of matching Harleys) at the Performance World show in Toronto. Wow, I'm getting old. I had that poster on my wall. Remember those few months in the late 80s/early 90s when Hot Rod did centerfolds?

 

I guess Bruce's resistor trick didn't work for them either.

I remember the original writeup.

Missed seeing ZZ last Saturday night. They had to cancel due to Dusty hurting his hip. Jeff Beck had a great set though.

 

Fun story about Cadzilla:

I have seen the real car, and I have seen a replica that, according to Hot Rod Magazine editor David Frieburger, is BETTER than the real one, because of interior design/fitment. It is still 100% to scale and uses the same design elements. I'm actually going to meet with the owner here in the next couple of weeks and feature it on my website.

That car looks so badass.

 

And Stinkpoo is still the guy who chopped up his repossessed Brougham which still smells funny when I see, or smell, his tens of thousands of postings here.

 

^ yeah I'm hoping they don't cancel the portland ME show on the 27th. We have 2nd row tickets for that one.

 

Do you wear ear plugs?

Both shows i went to this past weekend had the house sound way too loud.

Saw Joe Walsh at the Borgata in Oct 2012 ans it was 99 percent fine not too loud in the third row.

 

Saw them a couple of years at the NAC in Ottawa. They were very good, and the sound was amazing (as is everything at the NAC). No plugs needed (and I do wear them for concerts at hockey rinks). I missed seeing them in Maine on their double bill with Skynyrd at the Scarborough Downs over by the Maine Mall.

I hope they make it for you... but I've read elsewhere that Dusty's injury is bad.

 

Yeah I read that, too. Hope he recovers. If not in time for the show, then at least soon after.