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New to the forum and new to me 1970 521


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Hola, y saludos a todos 😊

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I ended up buying a 1970 521 from a friend, which, drives great, other than the breaks being a little sketchy πŸ˜… (maybe I'm not used to all drums? Idk) eitherway way, drives great and my kids love it.

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Me being me, I already started wondering what all are common "upgrades" or aesthetic touch ups all of you are doing without messing too much with it? I'm familiar with Datsun Z cars, but am new to the truck community, figured there's a few of you who can tell me the do's and don'ts, of course, any inputs would be greatly appreciated.

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Cheers 🍻 

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Brakes are a common upgrade. There are a few kits out there for brackets, and then they use late model calipers and rotors. It's a huge upgrade. The stock drums do not work well if they aren't constantly adjusted.

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I think the most common mods are lowering the truck, and some people do wheels. I think the stock wheels are pretty classy if done right. They don't leave much room for wide rubber though.

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The above. Get it running and stopping properly, specially stopping. Drum brakes work great but need to be maintained for even stopping. Front discs are almost zero maintenance and maximum performance.

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Lowering, yes in moderation if just for transportation. The more you lower the more bump steer is introduced and steering geometry is affected negatively.Β 

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The 521 came with 6:00 X 14 and 6 ply sidewall tires. Extremely stiff sidewalls because... truck. Today if mostly used for transportation, that would be something like 205/75R14 car tires, the important thing is the diameter for what ever you choose. Keep it 26" so performance and speedometer are not affected.

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Looks? well the 521 looks best with natural patina and wear. It's a work truck.

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To put a finer point on this, let me say that the 521 uses a single master cylinder for ALL the brakes. This means that a leak anywhere in the system results in a loss of hydraulic pressure for ALL the drum brakes. Regular maintenance and drum adjustment 2 to 3 times a year is essential and visual inspection for any damage and leaks. Naturally having a properly working and adjusted parking brake is paramount as a secondary means of stopping in the rare possibility of hydraulic failure.

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Cars and all trucks after the 521 had a dual master cylinder and the front and the rear hydraulic systems were completely separate. A failure in one, while reducing braking performance, did not result in complete failure. Β 

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3 hours ago, Stoffregen Motorsports said:

Aside from making sure all steering, suspension, brake, cooling and fuel systems are in good shape, the top three mods for an old truck like this would be :

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Dual circuit brake master

Weber DGV

Electronic ignition (like a pertronix)


The stock hitachi is a better carb than a crappy DGV.

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If both are in good condition the Weber has more CFM so from a performance standpoint it will outrun the Hitachi top end. From a drive-ability standpoint, the Hitachi is better. Because the Weber is a progressive carburetor stepping 'into it' a little too fast can result in poor low speed off idle performance, specially on a 1.6 liter engine, whereas the Hitachi is a vacuum operated secondary that responds to engine load demands rather than the driver's foot. The Hitachi is very complex (more to go wrong) compared to the Weber but it is designed to fit and work with the L series stock air cleaner where the Weber fits everything made and requires an adapter to mount on the intake and a small air filter.Β 

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I've driven an L16 Weber 510 and yes you do have to drive it. Feels like it's about to fall on it's face if you gas it too soon and there is a learning curve but soon you get the hang of it. Weber is 32/36 vs. 30 followed by 34 as needed on the Hitachi. You can feel the tip in point on the Weber so all that's needed is get it rolling and use your ass dyno to find your sweet spot.

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20 hours ago, mainer311 said:

Not to mention the "dead spot" issues with the DGV at throttle tip-in because of the poor progression circuit. It's not a good "fix" for anything unless your original carb is junk, which is not likely.

Weber fixed that with the 5A. Where have you been? Oh yeah, avoiding DGVs for the past 25 years.

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2 hours ago, Stoffregen Motorsports said:

Weber fixed that with the 5A. Where have you been? Oh yeah, avoiding DGVs for the past 25 years.

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No they didn't. I had a 5A.Β The butterfly needs to open too far to reach the first progression hole, and you get a sudden inrush of air causing a lean condition. It's all over the internet.

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7 hours ago, datzenmike said:

Accelerator pump is intended to ease the lean transition from idle to primary use. If the pump volume is properly adjusted. I was more concerned with the sudden opening of the secondary


Not quite. Accelerator pump if for when the butterfly snaps open and you need that squirt of fuel, but the accelerator pump doesn’t activate soon enough to cover the lean tip-in. The only way to solve it is to drill an extra progression hole.

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