Newbie 1970 Convertible - Impala Tech
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post #1 of 7 (permalink) Old 06-06-2016, 09:09 AM Thread Starter
CMH
 
 
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Newbie 1970 Convertible

Hello everyone. I'm new to the forum, and to Impalas. I've had a few classic Chevys in the past; 1970 SS RS Camaro, 1972 SS El Camino, 1976 Corvette. I've always been interested in the big Chevys and I am looking at a 1970 Impala Convertible right now. Are there any common problem areas to focus on? Certain areas prone to rust? It has drum brakes all around, is it relatively simple to do a disc conversion? Thanks Everyone!
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post #2 of 7 (permalink) Old 06-06-2016, 09:16 AM
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A '70 Impala should have Disc Brakes on the Fronts already. Are you sure they are drums?

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post #3 of 7 (permalink) Old 06-06-2016, 09:44 AM Thread Starter
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Yes they are drums. I did some research and looks like front discs were standard on some models, but not convertibles.
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post #4 of 7 (permalink) Old 06-06-2016, 09:59 AM
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Welcome to the Team!

In 1970 disc brakes were still an option. An expensive and rare option using a part that was made for only two years and is not reproduced. In 1971 and up to their going Metric in 1985 the disc brakes used were the same as every other GM product as the larger full floating single caliper wasn't proved to be required so to cut cost GM dropped that larger caliper and the special wheel hub from production. The correct single caliper disc brake caliper was only used in 1969 and 1970.

The earlier Corvette four piston fixed bridge disc brakes with their thicker rotor off of the Corvette used in 1967 and 1968 also fits the 1969 and 1970 model years and they are reproduced (but you have to buy the parts from a Corvette reproduction house which drives the price up).

As far as rust goes the climate from where the car comes from is the deciding factor. If you can find a project car from the desert southwest it will be rust free but the interior will be reduced to dust from UV damage. If you find a car from the Northeast the interior will be dirty but fine; however there won't be much left of the car and frame as it will be a collection of rust holes held together by Bondo and paint.

A car from rural Michigan or Wisconsin will have been put up in the winter months when they salt the roads around the cities and stored in a barn when not in use so it has been out of the weather most of the time. It will have been exposed to normal rain fall and since GM designed the car to only last for seven years it will need replacement patch panels, new trunk and floor pans or quarters to repair the normal rust.

1971 through 1973 where the biggest heaviest B-bodies made by Chevrolet. Most will have a SBC 350 or a SBC 400 under the hood just to get it to move on down the road. The gas crisis of 1973 spelled the end of big cubic inch engines and heavy cars as people couldn't get gas at all, or it was rationed to just seven gallons (a fill up for an empty VW gas tank but a drop in the bucket for a 28 gallon tank in an Impala). Because of this a lot of these car years went to the crusher once they were traded in on a new four cylinder powered Chevette or a Vega (which worked out well for them on the second gas crisis in 1976). This makes finding parts cars difficult.

Big Dave
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post #5 of 7 (permalink) Old 06-06-2016, 10:11 AM
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Quote:
Originally Posted by CMH View Post
Yes they are drums. I did some research and looks like front discs were standard on some models, but not convertibles.
That's pretty interesting as I know most of the Bel-Air cars had Drums, but always believed "all" the Caprice and Impala cars got Discs in '70.

But anyway, as Dave has indicated, a direct swap for an original set-up, part for part, would be from another '69 or '70 Full Size Chevy car only.

They are getting pretty hard to find though as they are also a direct bolt on for all '65 to '70 Full Size Chevys as well.

Bill

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post #6 of 7 (permalink) Old 06-06-2016, 11:20 PM Thread Starter
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Thanks Big Dave! It has been a southwest car from the factory. Any other things to check out that are common problems on this year?
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post #7 of 7 (permalink) Old 06-07-2016, 07:32 AM
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Nope. 1970 was the end of the muscle car era. Your engine still had a Net HP rating due to it having the same compression rating as the earlier muscle cars (which is probably going to be problematic with today's low octane gas as even regular gas in 1970 was rated at 94 octane and high test at most pimps was at least 98 octane with some pumps offering 104 at the pump). High compression is free horsepower which is why starting in 1954 Olds started an octane war with every higher static compression engines until every car offered by all manufacturers on the road in 1970 had at least 10.25:1 static compression; which is too high for today's gas with a cast iron head.

Brakes were then and even more today barely adequate for the average speeds found on today's roadways. The interstate system was started under president Eisenhower; but it took five to seven years after he was replaced by president Kennedy for the first concrete lanes being opened to the public connecting cities in the late sixties. Speed limits have climbed steadily on all roads even though your car was designed to stop safely only from an average speed of 55 mph. Don't forget it is a large heavy car with soft suspension so even if the brakes work, wheel hop can increase stopping distance.

If you plan on driving it a lot be sure your front suspension is up to the task (replacing worn ball joints and tie rods ends and linkage) as well as all suspension bushings, and that you have good working brakes. Then you can tackle the rust issues.

Big Dave
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