How to tune a 1977 Cadillac Eldorado for performance?

[6219_Rules]

My 1977 Cadillac Eldorado Biarritz is a beautiful car...in wonderful original condition with only minor maintenance at 78000 miles...but it is a performance dog. It is not that it is terrible. It does 0-60 in about 11 seconds which is pretty poor. The real problem is when on the highway, trying to pass or avoid a situation at, say, 60 miles per hour, when you floor it the car goes enemic and just stalls. The car has a good, big block V-8, 425 cid with a four barrell carburetor. The engine has been hampered with emission control systems, catalytic converter, PCV filters, etc.. but it should not be THIS poor. So what I would like to do, is use the original components and improve the performance a bit.

I was thinking of an improved four barrel Eberhardt Qjet, dual exhaust with a performance catalytic converter. I am not looking to hotrod the car, simply raise its performance potential within the engineering architecture that keeps the car original for 1977. In other words no NOS or new headers etc.

Another point, how would this effect the car's show quality? Would this hurt its chances for the CLC events? I don't want to damage the potential value of the car.

Thank you!

Randall <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

[cmj]

having owned one of these beast at one time it should not do that. I would try rebuilding the carb and make sure that the catalytic converter is not plugged up. That causes all kinds of performance problems. Also check pcv valves etc and just make sure everything is in good working order. When I had mine I lived in CO at 5000 feet and even there had no performance problems. No problem passing people even at 75 mph.

[6219_Rules]

Oh OK, thanks CMJ. It sounds like my son might be right. He thinks the kickdown switch might be bad. I Will check on the PCV (I had thought of that one <img src="http://www.aaca.org/ubbthreads/images/graemlins/smile.gif" alt="" /> ) and the catalytic converter. I was planning on either rebuilding the carb or buying a new one.

However I am curious why I should not do the improvements...is it for the originality? If so, I certainly will not do it. I believe in keeping them as original as possible. What did you think of the cars you owned? Do you think a Biarritz will be a valuable representation of the marque?

[cmj]

The 77 Eldorado was a good example of the excesses of the early 70's at about 5000 lbs, forget the exact weight, but it was the heaviest. the problem with it (is my opinion only) is that it isn't much more than a dressed up Oldsmobile Toranado. This does help in the parts dept as a lot interchanges. If my memory serves me right there was a fuel injected version that would be more desirable. In 1977 they were still simple enough that a person could still do a lot of the work at home also

[6219_Rules]

I like this model, and I would HATE the fuel injection...not because its bad but because it is so expensive to work on. I am pretty happy with this car as it is. It is a big, comfortable car with some flash and nice amenities. But like most 70s cars, it lacks something almost indefinable that leaves me still hankering after a 60 or 56 Cadillac. Maybe it is just me. <img src="http://www.aaca.org/ubbthreads/images/graemlins/crazy.gif" alt="" /> <img src="http://www.aaca.org/ubbthreads/images/graemlins/crazy.gif" alt="" /> <img src="http://www.aaca.org/ubbthreads/images/graemlins/crazy.gif" alt="" />

[6219_Rules]

Here was some suggestions by Matt Harwood on CLC.

More power is easy, and keeping it stock appearing is entirely possible. There are several levels, so you can decide how deep into the engine you want to go. Some of the basics you have already mentioned--better carburetion and exhaust. Instead of duals, I'd suggest a larger diameter single exhaust without a catalytic converter--perhaps a 2.5" to 3" exhaust with a nice quiet muffler (this is a Cadillac after all). Most people won't notice the increased pipe diameter, and if you use a stock resonator at the end, nobody will ever know.

Port the heads. Cheap horsepower and it can really make a difference. You can even do it yourself--just be careful not to go into water jackets. You could also have your local machine shop take a few thousandths off the head to raise the compression a little bit (I think these cars are 8.5:1, and it could probably handle closer to 10:1 with good gas). Upgrade the cam at the same time, and I'll be that these two mods would yield 50-60 real-world horsepower and probably and equal torque. Once it's all back together, nobody will ever know.

Driveline improvements--a higher-stall torque converter will make it feel snappier off the line, and a shift kit will improve shifts (providing either of these items is available for the FWD TH425).

If you really want to go radical, drop a 500 in there and do the same mods, upgrade the pistons to get some more compression, Extrude Hone the intake and exhaust manifolds, and add all of the above.

Is this a show-caliber car? If not, I wouldn't worry about originality. It is YOUR car, do it the way YOU want. It isn't particularly valuable (sorry--I mean that in the best possible way), so I don't think there will be many purists objecting to your changes if they are visible.

Here's what I did on my '76 Eldo convertible when I rebuilt it:

+ .060" overbore (515 cubic inches or thereabouts)

+ Reground stock camshaft

+ hardened pushrods

+ rebuild Q-jet (I would go with the Edelbrock today, but it wasn't available when I did my car)

+ port & polish stock heads, intake manifold and exhaust manifolds (all by hand). Shaved .100" off head to bump compression to approx 9.7:1

+ Exhaust from a '73 Eldo (no catalytic converter, 2.5" tubing, off-the-shelf at the local auto parts store and it was a direct fit)

+ recurved HEI distributor with hotter coil

With those simple mods, the car was a VERY different animal. I could run down much faster cars at will, and it would launch HARD and pull forever. It felt like a freight train hammering along. I pegged the speedo (120 MPH if I recall), and it was still pulling like I was going 50. None of these mods affected reliability, driveability or appearance. I used premium fuel (ouch!), but the performance was nothing short of amazing, especially considering it weighed 5200 pounds. More than a few kids in Mustangs and Camaros were startled when the big boat walked on them.

Hope this helps.

--

Matt Harwood

Cleveland, OH

My thanks to Matt for his and the others suggestions.

One thing I found might be a source to the problem (besides the obvious catalytic converter issues and possibly plugged exhaust systems) was the kickdown switch may either be broken or stuck. That happened on my son's 1972 Eldorado which made it appear as though the transmission was failing completely. So that is another possible area to investigate.

I am not sure I want to go to such lengths to jazz up the car's performance, but I do think some of the ideas will help give the old girl new life!