Topic: Holley(R) Carburetor Accelerator Pump Rocker Arm Wear

[Dan Case]

Holley(R) Carburetor Accelerator Pump Rocker Arm Wear


Accelerator pump rocker arm wear:  Rocker arms usually wear into a "double hump" defect pattern on the surface following the cam. Wear is normal and is one of the weakest design feature of the Holley(R) carburetors that evolved from the first 4150 model created for Ford Motor Company.  At some point in time the wear will get bad enough to seriously affect performance. The issue is the once smooth steady streams of mechanical fuel injection during acceleration become on-off-on events. Countless users have suffered declining performance without a clue as to what was happening. The lever is the sacrificial part in the Holley design. Cams might be serviceable for decades but levers can were badly in just a few years depending on many factors. Fortunately most levers in most applications may be repaired successfully at least once and many may be twice. As long as they remain thick enough to not bend they are usable. It just takes a few minutes to rework one. I start with a file working lengthwise, all work must be lengthwise. Then I use 600 wet or dry sand paper to wet sand the surface lengthwise to get the file marks out. And finally I use a power buffing wheel to polish the follower surface.


Do not use oil or grease to lubricate the cam and rocker arm contact patches. Lubricants trap grit and grit will wear the plastic cam quickly.

[Scott302]

Dan,
How prevalent is this in the carbs you see?  Curious as I can still get those arms fairly cheap.
Regards,
Scott

[Dan Case]

Dan,
How prevalent is this in the carbs you see?  Curious as I can still get those arms fairly cheap.
Regards,
Scott

The wear pattern, to some degree, is normally in most parts that are originals to decades old carburetors unless they have been repaired before.

Many of the commercially remanufactured carburetors I have handled received new rocker arm levers during the process. An issue with originality is that some new parts that get installed are not the same as what the carburetors originally had.  Some world famous shops will send out a carburetor with a rocker arm that has been recolored with some type of finish or another without doing anything to the wear pattern they covered up with fresh blackening.

This for sure is not a how to but these rocker arms can have other problems also. The typical one is the finger over the plastic cam gets bent up into a curve or just up at an angle. Either way the angle change affects geometry and shot timing. The rare problem is the lever over the accelerator pump cover rocker lever is bent up (part is twisted). I just repaired a carburetor for a friend with both issues.  The carburetor was ?restored? by a very well known person.  The fine details of the rocker arm made me think it was a reproduction part including that it had zero wear from a plastic cam rubbing on it.  The carburetor had enough reproduction parts in it and two had serious functional / dimensional issues, both throttle shafts assemblies, that a low quality reproduction accelerator rocker arm lever with functional / dimensional issues would not be unexpected.  The bend and twist issues were easy to correct. (The carburetor had lots of functional problems, but looked nice.)