RX-2 vs RX-3 vs RX-4 vs RX-7 OMP
 

I'm working on adding a Sohn (Rotary Aviation) OMP pump adapter to my 1985 12A. I ran in to an issue where the Sohn pump adapter pushes the factory pump out to far and the lines to the carb are touching the water pump housing and getting hot. Also at issue is that because the lines are jammed up against the water pump housing and getting pinched.

I'm trying to find a solution but haven't come up with anything that works. I tried a RX-2 dual distributor OMP but the bolt foot print is not that same. I like the dual distibutor OMP design because the hoses are attached via banjo bolts.

Does anyone know if the RX-3 or RX-4 uses banjo bolts and the foot print the the same as the 1978-19985 12A?

others have blocked off the front cover oil passage and added a simple barb port fitting tapped into the stock OMP.

no adapters, no fuss.

I've read several of the write ups on modifying the existing pump. I might give that a try.

Any chance you'd be able to take pictures of the set up, issue, and the fix? I've been considering installing one for a while. Thanks and good luck

I built my own omp adapter to mount an s4 4port omp onto a 12a front cover.

Using a FC 4port in my rx-4, wanted to use the housing injectors as well as float bowl premix

I'll see if I can dig up some pics

Here are some pic of the crimped hoses.

http://i1133.photobucket.com/albums/...psbe7c2dc8.jpg

http://i1133.photobucket.com/albums/...psb76468d6.jpg

that thing is massive... you'd think they could shave it down a little bit more.

Can someone with an S4 water pump housing and a 12A do me a favor? I need to know if the S4 water pump down neck gives more room between between the OMP compared to the stock 12A water pump housing.

I would rather not have to purchase an S4 water pump housing before knowing if it;s going to give more room.

My last ditch effort would be to take a 12A water pump housing and modify the down neck to give more room. My thought was to cut the down neck off and clock it and weld it back on.

I have a 12a front cover and s4 waterpump housing, plenty of room for the omp with adapter