The Canadian Chevette Holley 5210C difference
(very interesting ! )
I recently received a carburetor from north of the border. It is a Chevette carburetor, Holley 5210C, list number 60113, original application 1986 Chevette ( Canada ).
I was very surprised to see an "adjustable" main jet capability built into this carb. Prior to this, I was only aware of the computer feedback US versions of the Holley variations ( 6510C, 6520C ) having this feature. As usual, this feature is a "secret", and not really designed to be "played" with. It is technically a factory pre-set adjustable part throttle screw, and usually best left alone. However, for the tinkerer, this is a wonderful way to change jet sizes ( on the primary ) without taking the carb apart, just turn a screw !
Here's how it works:
| Note the the carburetor depicted on your right. This is a shot of
the secondary side of the carb. I have left the vacuum diaphragm device partially in place
to help you locate the screw. On US computer feedback carbs, this screw is under a
hardened plug that is very difficult to remove. When I received this carb, there was no
plug in place. I do not know (yet) if this is normal. The screw is very difficult to turn,
and it has a "double D" head. I'll refer to this again later. I do not yet know if all Canadian Chevette Holley 5210C carbs have this feature, I'm sure to be finding out soon. Here's how this works. See the little hole that is pointed out in the picture to the right? That is a fuel feed hole that supplements the primary main jet. The primary main jet is intentionally "lean", and the auxiliary fuel "adds" to this by metering fuel through an orifice that is controlled by a tapered screw. The hole in the picture allows fuel to enter the adjustable jet below the pictured hole where the tapered screw is. ( You can see the end of the silver tapered screw by looking down this hole ) This is how you can "change" your main jet size by merely adjusting the external screw without having to take your carburetor apart. Pretty neat. Of course, you should keep track of your adjustments in case you need to return to your original setting. Here's another tip that might be helpful. Making a tool is required for the adjustment. It's not easy. If you don't have a tool, the "green" vacuum tube in the base of the carb is almost perfect for the job ! I don't really suggest using the one in your carb, although you could. Get ahold of one from a junk carb, ( they usually pull out rather easily. If yours doesn't , insert the appropriate size drill bit, so you don't crush it, and grab it with a pair of vice grips to pull it out. ) and slightly crush one end of the tube into a "D" shape with a bench vise. Crush the other end flat { if it's an extra tube}, and this will allow you to turn the screw, although with some difficulty. Like I said, this screw is hard to turn, and hard to get ahold of. In is "lean", out is "rich". Have fun, and don't forget to keep track of your adjustments. Although I could type a lot about this feature, I know that personally I have always taken advantage of the "secret" stuff like this that you never read about in books. |
 
|
| Hmmmm.... very interesting. Canadian Chevette Holley carbs don't
have a bowl vent. People have expressed confusion when I mentioned this before, and now I
know why. Holley never installed one ! Just a metal plate where the US carbs get an
electrically controlled solenoid for the bowl vent. Holley didn't even install the
3/8" tube off to the right in that main boss. Damn polluters....... J |
 |
