I run a 69 baja in SCCA Rallycross here in the Cincinnati area and I'm having a heck of a time keeping dust out of my carbs. I'm going through rings like you wouldn't believe. Pretty sure I roasted the latest set in about four runs, which is a total of around 4 minutes of drive time, plus maybe 15 minutes of idling in grid.
I recently upgraded to CB performance hex bar linkage so I have the better cast top plate/filter bottom, but I'm still getting a ton of dust into the carb and subsequent toasted rings. Currently I cant fit pre filters between the carb filter and the body, though I'm open to cutting the body back further if that's the other option. Otherwise I'm considering the CB sand system air box with hoses routed to some kind of filter box that I would mount inside the cab. I'm down to spend some money, but I don't want to have to do this again, also sick of changing rings.
Dirty carbs:
Gratuitous rally shot (this is from a "non dusty" day, rally this weekend you could'nt even see the cars it looked like out takes from the mummy or something:
On the rubber base of the top and bottom of the filter smear a fairly thin coat (but not too thin or too thick either) of grease on it for an additional seal. The picture shows traces of dirt travel on the base of the filter where the filter's light to no contact is allowing dirt transit.
As CWB said, run a washer beneath the base of each of the wing nut to spread the load out further on the top piece. This should help stop any localized distortion of the thin metal of the top caused by tightening or over-tightening the nuts. You aren't using a "split washer" under the wing nut are you? If so look at a flat washer as the split washer takes more tightening to flaten out.
Washers can be stacked going from the normal size on top and getting wider as the stack increases if you are really "yarfing" down on the nuts or you could make your own "load transferring washer"... any shape or size you want it.
By over tightening you can also cause the filter itself to distort in many directions including bowing the sides making a bad situation even worse.
I have the cb cast filter bases so I don't think I can bend them by tightening. The kit does come with some steel washers with rubber on the underside which seem designed to seal the mounting holes under the wing nuts.
I spoke to the people at RC2 and it seems like there is a filter that will fit my existing bases but I must have written down the number wrong because now I can't find it.
I have the cb cast filter bases so I don't think I can bend them by tightening. The kit does come with some steel washers with rubber on the underside which seem designed to seal the mounting holes under the wing nuts.
I spoke to the people at RC2 and it seems like there is a filter that will fit my existing bases but I must have written down the number wrong because now I can't find it.
Its not the AL base that deflects but the steel top/covers that can. The AL filter designs are less likely to deflect itself but still, too much compression pressure can still deform the filter element itself (ben there, done it myself) causing the top and bottom rubber seals not to have a full footprint.
I ride in the sand; the grease thing is something that we do as a normal precaution. We also use a slip over (https://www.bing.com/images/search?q=sl ... &FORM=IGRE) which does do a lot of good or at least some people think so.
I think I'll start with the RC2 filters and go from there. Pretty reasonable price and from talking with the sales guy they last for an entire Best of the Desert race which is probably equivalent to 3-5 years of rallycross.
If I ever get to the point with my engine where I feel like a plenum box would be beneficial I'll build that to run inside the cab and put some hardcore filtration on that.
Just making an air filter seal to the housing and the housing to the carb should handle anything you're gonna run across without fancy or expensive filter assemblies. You just need to pay attention to the basics. Gauze filters like K&N I do not recommend as they "make more horsepower" because they have bigger openings and thus let in more dust. If your filter is made to be oiled, then oil it! Just plain ol' paper filters will work just fine.
Richard
Lake LA, Mojave Desert, SoCal
Speed Kills! but then...So does OLD AGE!!
Tech Inspection: SCCA / SCORE / HDRA / ARVRA / A.R.T.S. OffRoad Race Tech - MDR, MORE, Glen Helen BajaCup
Retired Fabricator
'58 Baja with 955K Miles and counting
I'd advise against any type of filters that require oiling. Not many places to clean a silt filled filter in the middle of nowhere. Been there done that already. Keep the intake above the dirt and it will be ok.
Yeah but he's in the northeast and doing minute long autocross sections and the occasional rally. He's not racing in the dry silty desert. And I have used oiled filters for many years in the desert. On race cars as well as on daily drivers. The only time I ever encountered a problem with the filter silting up was at a Mint 400 race where they had miles of 2' deep silt beds. Just taking the filter out and knocking it against the ground and putting it back allowed us to finish the race with the inside of the carb clean.
Richard
Lake LA, Mojave Desert, SoCal
Speed Kills! but then...So does OLD AGE!!
Tech Inspection: SCCA / SCORE / HDRA / ARVRA / A.R.T.S. OffRoad Race Tech - MDR, MORE, Glen Helen BajaCup
Retired Fabricator
'58 Baja with 955K Miles and counting
I use the paper filter that is cleaned then oiled and with a gauze filter over it. There is a foam over filter I have seen used once in a while but not often so I am not sure of it's abilities.
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