A question for the other car people on the board....

[sld72382]

I have a question for my fellow car people here....

Say you bought a car that you always had a desire to own. Either because you had one previously and had to give it up, or you were always drawn to that model of car.

Only problem is, thanks to all the government-mandated smog controls of that model year, the engine produces less power than some of today's 4 cylinders. You find a company that specializes in that era of motors that can build around the original engine block with new components (heads, internals, new carb, exhaust etc) and give it way more HP than stock. Or, you can rip out the original engine and dress up a nice crate engine for the same cost as an original engine rebuild.

Now here's the kicker: The model of car you bought is a rare, little-known trim level that is rumored to be 1 of 150. Knowing this, would you keep it numbers matching but rebuilt or replace the original with a brand new powertrain?

[mathnerd]

We're purists in this household. I'd keep the original engine block. Actually, I don't know that I'd do anything to increase the HP at all, since the reduced HP is one of the quirks of the original engine. Not all cars have to be fast.

[sld72382]

You would if it's a 7.0L V8 with only 180HP. I'm talking about the ones in the 77-79 Cadillac Devilles.

Great engine but heavily choked down thanks to the new emissions regulations that went into effect in '77. Basically a de-bored 500CID from the previous years.

MTS specializes in being able to turn what was basically designed to be a low-rpm motor with enough torque to move a huge heavy car into something with a little more grunt.

Link: http://www.powerblocktv.com/episodes...ngine-build-up

If I was to go with option A, they would be the people I call....

[mathnerd]

But the thing is, one of the things that makes a particular car that car is all the little quirks that came along with it. If you change anything substantial, it's not really that car any more.

But, like I said, I'm a purist*. I would put up with lack of HP to have the car exactly as the manufacturer designed it, warts and all.

*All bets are off if we're rebuilding a car for racing purposes, but then if we're doing that, we're not going after that car, we're going after a car that can win.

[ADeMartino]

If you plan to drive the car a lot and seriously desire the extra power, I'd go ahead and find an older, less 'emission controlled' engine for it - an old pre-smog 472 or 500, for example. By the same token, I'd also keep the original engine stored someplace safe so that, if the urge ever strikes you, you can swap it back in and easily return the car to original spec.

Also, I'd take that 180-hp rating with a grain of salt. There was a shift in how engines were rated in the 1970s (1974 I think?) that resulted in much lower numbers than had been common previously. That 180 horsepower was probably about 250 horsepower or even more if it was measured using the old system.

[csquared]

The real question is: Are you looking to make this car a collectible to sell later on for top dollar, or are you looking to make the car something that you want to own?

[sld72382]

The real question is: Are you looking to make this car a collectible to sell later on for top dollar, or are you looking to make the car something that you want to own?

Funny that you say that.

My take on "numbers matching" depends on the car and what I wanted to do with it. Would I resto-mod a 1970 Hemi 'Cuda that was already in pristine condition? Probably not. Would I resto-mod a 'Cuda that only had a 340 and needed some work? Absolutely!

If the car was going to be driven and not sit in some museum setting, then yeah I would probably resto-mod it with new engine/trans/suspension etc as well as other things to make it more drivable. I would probably keep the original engine and trans stored somewhere so if I ever wanted to go back to stock, I can. OTOH, if the original engine has been proven to be bulletproof and can handle abuse, I would probably just keep the original block and build off of that. The '87 Buick Grand Nationals are a good example of that.

BTW, about the HP ratings: in 1971 the ASE made all car companies re-rate all the engines in NET instead of GROSS. That's why a lot of the HP figures dropped dramatically after '71. Of course, it was a more accurate statistic.

[Chromatix]

You would if it's a 7.0L V8 with only 180HP. I'm talking about the ones in the 77-79 Cadillac Devilles.

That *is* pretty pathetic. For comparison, the 1960s-70s version of the Tatra 603 engine was a 2.5L V8 making just over 100hp. The 1950s version made just under 100hp. All of that being air-cooled, and therefore lightweight enough to mount in the *back* of the car without completely destroying the handling. The car's state-of-the-art aerodynamic styling meant that 100hp was enough for 100mph - it just took a while to get there.

[ADeMartino]

BTW, about the HP ratings: in 1971 the ASE made all car companies re-rate all the engines in NET instead of GROSS. That's why a lot of the HP figures dropped dramatically after '71. Of course, it was a more accurate statistic.

Okay, 1971, then. Thank you for the correction. If I remember correctly, the big Caddy 500s were 'only' rated at about 350-360 horsepower, even before the change to net horsepower figures. As a rule of thumb, 'net' figures tend to be about 2/3 of the old 'gross' numbers, so this would put the 500's output in the 240-250 horsepower range.
That 180 horsepower number doesn't sound so bad in comparison.

Of course, advertised horsepower figures are for Madison Avenue types and insurance salesman. If you're motorin' in a big Caddy-Wack, what you want from the engine is big heapin' gobs of torque at fairly low RPMs - and those big 500s could deliver that in bulk.

If the 7.0 is indeed just a small-bore 500, then a real 500 should bolt right up to your frame mounts and transmission.

Also, if you don't plan on taking this on the freeway a lot, you might want to consider a change of axle ratio. Lots of those late-1970s cars had really low-numbered axle ratios in an effort to improve fuel economy from large engines. A raise to something a little more aggressive - say, 3.23:1 - will give you a major shot in the arm without an engine swap or excessive engine speeds. Remember to have your speedometer re-calibrated.

[Arcus]

If you plan to drive the car a lot and seriously desire the extra power, I'd go ahead and find an older, less 'emission controlled' engine for it - an old pre-smog 472 or 500, for example. By the same token, I'd also keep the original engine stored someplace safe so that, if the urge ever strikes you, you can swap it back in and easily return the car to original spec.

This is what I would do, but I would also put some thought into a much newer engine for the reliability.

If you do the engine swap, keep that motor. Even if you don't put it back in, the car will be worth much more if you have the matching numbers.

[Seshat]

Just chiming in here with what's already been said:

A collector will want to be able to restore it to pristine. So do what you want/need for you, but keep the engine and other significant parts.

Which parts are significant? Ask a collector.

[Antares]

I'd keep it original.

[TheSHAD0W]

My opinion? If you want the car for looks and will be driving it occasionally, then keep it original. If you're going to be putting lots of miles on it, then you're better off renovating it; it's not going to keep a value after you beat it up over the years.

[protege]

As long as you don't plan on stuffing in the infamous V8-6-4, you should be fine. That thing was a piece of shit

But seriously, if the car is pretty rare now, I'd probably keep it original. Cars that have been modified, are sometimes very difficult to sell on later. With that said, if you do choose to modify the vehicle, don't do anything that you can't switch back later. Keep the original engine nearby.

And yes, I do own a car that's been modified a bit. When my MG was built, it came with emissions controls all over the place. An air pump and various hoses sapped quite a bit of horsepower. 44 years on, many of those parts are now unavailable. Not surprising actually--quite a few owners yank that stuff off.

Most of the other mods aren't so easy to spot. I fitted an electric fuel pump instead of the mechanical one; the distributor has an electronic ignition module which does away with points and condenser; the speedometer cable is a longer one from an overdrive-equipped car (which allows me to do away with the troublesome 90-degree connector at the transmission); poly bushes in the suspension; and a bigger oil cooler is fitted. Oh, and there's an "unleaded" cylinder head as well.

...and I know everyone is going "uh, didn't he say to keep it original?" Well yes...and no. Most of the tweaks I've done could be easily undone. Many of these things were also done by the factory in period. They make the car more reliable and easier to maintain. Plus, unless you *really* know the cars, they're invisible

[GreaseMonkey]

Lifelong mechanic and classic GM owner / enthusiast here. I can't believe I didn't find this thread earlier!

What most of the others here have said is correct- the car will be worth more the more original it is. Even so- don't hold your breath waiting for ANY late 70's Detroit sedan to become a serious collectible. There's still too many of them around, and their quality / performance deficit vs. their earlier counterparts make them less desirable in the marketplace, keeping values fairly low.

There are many things you can do make the car much more safe and enjoyable to drive, while keeping its original flavor. Swapping in an earlier 500 motor ( rebuilt of course ), painted in the same shade as your original engine, is a good start. Edelbrock makes an aluminum intake for these engines. You could have the runners extrude honed for better breathing. Paint it factory "GM Corporate Blue" and no one will know the difference. That aluminum intake will also shave some weight off the car's nose. A good 3-angle valve job with some bowl blending and mild porting will improve output without hurting driveability. Add a mild performance cam. The stock exhaust system on these cars is a joke. Replace the puny 2 1/4" single stock pipe with a 2 1/2" or 3" single along with a high-flow catlytic converter and a low-restriction yet quiet muffler like the Dynomax Super Turbo "Hemi" muffler.

In the handling department, some large aftermarket sway bars from Addco or Global West, along with some good-quality gas shocks like Bilstein or KYB will vastly improve the car's road manners, retaing a comfy ride without being quite so floaty. Thanks to GM's parts-bin engineering, many parts from other, lesser GM vehicles will fit these Cads. A new set of heavy-duty coil springs made for a 77-79 Chevy Caprice with the police / taxi package will help too. They even make a fast-ratio steering box for GM B-bodies to replace the sluggish factory unit.