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Door and Trunk Poppers

Story & Photos By Jim Clark (The Hot Rod MD)

A popper that raises the decklid or opens the door enough to get your fingers in and open them may seem like a small item to be concerned with, but are necessary on many vehicles that have shaved the handles off the doors or decklid.  These are custom touches that add to the smooth look on a custom or hot rod, though defeating the practical function they provide.

Doors on a custom car with the handles removed only need a small popper that pushes them out.  However, cars like early hot rods that have decklids without spring-loaded hinges need one that is pretty strong so that they can lift their heavy decklid.

My roadster has a trunk latch from a ‘70s era Datsun 510 with a spring that does not push the decklid up at all.  The decklid is heavy enough to stay down without a latch but that offers no security for contents in the trunk.  The trunk lid on Tom McMullen’s ’32 roadster had no latch and was originally equipped with a small vinyl strap to pull when opening it.  It was pretty crude but we never had any trouble with it coming open under any operating conditions.  His second ’32 high-tech roadster and my ’32 hiboy were sister projects and both are equipped with that same Datsun latch.

Tom used a coil spring to raise the decklid on that 2nd car but I wanted something with more control over the popping mechanism.  The best one that I was able to find was the one from Watson’s Streetworks.  It has a long enough push rod and a stronger spring than ones made for doors.  Unfortunately, it has a maximum pressure of 15-pounds at full compression so I had to find a way to modify it by replacing the spring.

Building hot rods seems to require all kinds of adaptation of components for a given vehicle even when something is available from a good source.  First I modified a door latch from Ace Hardware that would work on doors but it was too short to install a longer spring.  The one from Watson’s Streetworks has a longer barrel and worked out just right once I made the spring interchangeable.  The photos show the processes needed to modify the short and longer push rod versions.

In the center of the decklid there is a small vinyl tab that was used to open the trunk lid on the original Tom McMullen ’32 roadster.  We never installed a trunk latch and it never came open, even at 168 mph on the dry lakes.

A coil spring like this one on the hood of my old Ford van could be used to pop up the trunk lid on an old hot rod with a heavy trunk lid.

The coil spring on the van lands in this pocket riveted to the cross brace.  It acts as a guide and could be used on a decklid or trunk threshold.

This ball catch from Ace Hardware can be converted to create a shallow door popper where there is limited space available in the mounting site.

The original ball catch has this spring-loaded ball and a strike plate with a recess in it.  The ball is held in place by a threaded retainer.

A carriage bolt and nut of the desired length for the poppers reach can be installed in place of the ball.  High points on the nut can be ground off if there is a clearance problem inside the barrel of the catch.

This is an exploded view of the popper showing the parts needed to make it function.  It looks like the nut is too big but it actually fits inside the barrel of the housing.  A different spring could be substituted if a stronger popper is needed.

For the heavy decklid on my roadster I needed a stronger popper with a long-reach pushrod.  This one from Watson’s Streetworks can be used with or without the mounting plate.  It includes the hardware and strike plate with adhesive backing.

This shipping scale provided a low-tech way to determine how much pressure the decklid would need to push it up when the latch was released.  The scale indicated that the decklid was exerting 18-pounds of downward pressure.

A bathroom scale could also be used to get a reading, though not as accurate as the shipping scale. 

The popper from Watson’s Streetworks exerts a maximum pressure of only 15-pounds when fully depressed so I had to find a way to change to a spring that would increase this.  Long spring on the right is the original one installed in the popper.  The other springs are alternative spring choices with thicker wire making them stronger than the original.

I ground down a hacksaw blade and cut the washer swaged into the popper base so that I could change to a stronger spring.  The barrel was tapped with 5/8-18 UNF threads to accommodate the threaded plug used to retain and set tension on the new spring.

Threaded plug allows the tension on the spring to be increased if more preload is needed.

Center of the latch was marked and a hole drilled in the threshold to accept the popper where the decklid aligns with the push rod.

Barrel on the popper is large so I had to fine-tune the size of the hole with a file.  A smaller hole would be needed if you decide to install the popper without the bracket.

Popper with the bracket installed was used as a template and mounting holes drilled.

It is difficult to predict exactly how much tension is needed in the spring so spacers were made to fine-tune the popping action applied to the decklid when the latch is released.

Popper was installed with bolts and nuts with the spacers in place to test the action when releasing the decklid latch.

Strike plate for the popper pushrod is installed on the edge of the decklid with the supplied double-stick tape.  It could be riveted in place or replaced with a larger strike plate if necessary.

After testing it was determined that these spacers provided the necessary elevation of the popper to open the decklid.

The modified popper is quite stiff but is what is needed to push up the heavy decklid on this early hot rod.  There may be a source for one that doesn’t need to be modified but I was unable to locate one after searching on the Internet.

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