The decision to make a custom dome filter is usually made when one of our Megaflow or JC70/JC71 filters simply won't fit due to lack of space, the need to have the fasteners in specific places or if the job is so peculiar that none of our standard range are even close to being suitable - I doubt any filter company would have an off shelf solution for a 1953 Bentley fitted with a 27 litre Rolls Royce Meteor V12!!!
There a few things we will need to know when ordering your custom dome:
What is the car being used for??
Circuit racing cars tend to run in fairly clean conditions so we can generally get away with a 10mm thick foam with good flow rates, however for rallying etc a 20mm thick foam is going to be more preferable to cope with the extra dust. Both 10mm and 20mm foams are available with a finer layer for more extreme conditions if necessary.
How much room is available around your rampipes??
A common problem we encounter is people fitting rampipes that are too long to allow enough room for a filter. We realise that some engine builders specify specific ram pipe lengths to achieve a desired torque curve, however there are limitations to what we can do. We can offer filters with either 10mm or 20mm thick foam and we recommend having a minimum of 25mm between the inside face of the filter and the end of the rampipe, although on some engines 40mm would be more desirable. We also need enough space to allow the filter to be fitted and removed so sometimes a compromise needs to be made between ultimate performance and getting a filter fitted which will extend the life and maintain the power of your engine. Typically the minimum clearance between the rampipe and bulkhead will need to be 60-70mm although this will vary depending on your installation and filter size (deeper filters will need more room to allow them to be fitted). Another thing to take into account is clearance with the bulkhead on some in line installations, it's quite common to find the rampipe on no.4 cylinder to be quite close, especially when full radius rampipes are fitted - depending on the amount of clearance, it may well be that a thin foam has to be used just to fit in and in some cases we have even had to design frames with aluminium end plates where clearance has been less then 10mm.
If you are using injection throttle bodies, will the fuel rail prevent a baseplate being fitted between the rampipes and throttle bodies??
The most common means of mounting a dome filter is on a baseplate sandwiched between the throttle bodies and the rampipes. Quite often though the fuel rail will overhang the mounting face preventing a baseplate to be fitted. there are a few different ways of overcoming this problem depending on the setup you have. The most common solution we use is to mount the baseplate on rubber grommet that grip onto the rampipes, this allows us to mount the baseplate at virtually any point along the length of the rampipes. Another method we have used in the past will depend on the style of your rampipes, if the flared end is relatively flat it may be possible to mount the baseplate directly to the end of the rampipe, either by drilling the flared end and bolting the plate in place or by using small straps or tabs to pull the baseplate up against the bellmouth flare.
What's the diameter of the rampipes and what is the port spacing??
Most standard Weber and Dellorto carburettors use rampipes that are around 65mm diameter at the flared end whereas most throttle bodies will have 85mm - 90mm diameter rampipes. This affects the overall length and size of the filter that's needed, it may well be that in some installations a switch from full radius rampipes to a more conventional style may be needed to make space for a filter to be fitted. The port centre measurements are quite important to get correct as this will dictate the overall length of the filter but also to ensure that the baseplate will fit correctly: 1mm -2mm out will make it impossible to fit!!!
What carburettors or what patter throttle bodies are you using??
We have dimensions for most common carburettors, Weber DCOE and Dellorto DHLA use the same pattern which is also shared with the majority of aftermarket throttle bodies. One to watch out for with side draught Weber 48's is whether they are DCOE or DCO'SP, visually DCOE and DCO'SP are very similar however the bolt spacing is slightly different (69mm PCD compared to 65mm PCD for the DCOE), all new genuine Weber 48 side draughts are now DCO'SP. Another common pattern on individual throttle bodies and some direct to head throttle bodies is a 4 bolt pattern using a 65mm PCD. For carburettors or throttle bodies that we don't have the dimensions for, we would either need accurate dimensions or a drawing, failing that we would supply the baseplate blank.
in order for us to be able to find out the kind of filter that you need, it would be helpful if you could tell us a little bit about you and your carTell us about your car