Hey everyone!
Long time lurker, first time poster.
I just landed myself a new (well, new to me) 73 Spitfire 1500 which is in pretty darn good shape, but with a few things that need attention. My goal is to get her solidly road-worthy by early September in time for a leisurely Labor Day trip up the coast to Portland, Oregon.
The kindly previous owner swapped out the ZS carb for a pair of SUs (HS4?) which appears to match the UK setup as far as I can tell. I'm happy with that choice and probably would have done the same.
I've been spending most of my free time going over her making a to-do list, and when I removed the two K&N air filters, I noticed that they were mounted upside down. On my SUs, there are four holes on the intake side - two for the filter mounting bolts, and two others spaced closer together. The air filter mounting plates have corresponding holes, but with the plates upside down, the other two holes are blocked. WIth my somewhat limited knowledge of SU carbs, I'm thinking that those two holes are static air vents to equalize the pressure on the piston. If that's right, it would seem that if they were blocked, it would interfere with the piston's operation.
Is there a reason why someone would want to block them like this?
Thanks! (having lurked here for a while, I'm really impressed with the level of generosity shown by everyone. I know that I'll have more questions and only hope that in time, I will be able to re-pay the community by contributing answers myself.)
Long time lurker, first time poster.
I just landed myself a new (well, new to me) 73 Spitfire 1500 which is in pretty darn good shape, but with a few things that need attention. My goal is to get her solidly road-worthy by early September in time for a leisurely Labor Day trip up the coast to Portland, Oregon.
The kindly previous owner swapped out the ZS carb for a pair of SUs (HS4?) which appears to match the UK setup as far as I can tell. I'm happy with that choice and probably would have done the same.
I've been spending most of my free time going over her making a to-do list, and when I removed the two K&N air filters, I noticed that they were mounted upside down. On my SUs, there are four holes on the intake side - two for the filter mounting bolts, and two others spaced closer together. The air filter mounting plates have corresponding holes, but with the plates upside down, the other two holes are blocked. WIth my somewhat limited knowledge of SU carbs, I'm thinking that those two holes are static air vents to equalize the pressure on the piston. If that's right, it would seem that if they were blocked, it would interfere with the piston's operation.
Is there a reason why someone would want to block them like this?
Thanks! (having lurked here for a while, I'm really impressed with the level of generosity shown by everyone. I know that I'll have more questions and only hope that in time, I will be able to re-pay the community by contributing answers myself.)