Precision Air mixture arm hits cowl scoop

I have an IO-320 with a Precision Airmotive fuel servo. I have the Van's 360 bottom cowl. The offset mixture lever interferes with the side of the cowl scoop. I have the kit to make a cut out in the FAB for lever movement and I can also make a new mounting plate that is offset to move the entire FAB to the right. This would not solve the lever situation, however. Should I buy a new "straight" lever to replace the offset? ($165) I have read that I might have to still fabricate a "bulge in the side of the scoop for engine movement. This is an updraft servo. I am open to any suggestions from those who may have had the same issue.
Thanks, Jim

I have the reverse mixture option and a straight mixture lever and I still have the same issue. The shaft and nut at the base of the mixture lever (which is there irrespective of lever shape or clocking) still comes too close to the cowling to accommodate the expected engine movement. The only solution I see is to, as you said, add a "bulge" to the cowling there to provide more clearance.

It is useful in creating a record of experience to specify whether the servo is reverse mixture (arm pointing up) (and whether vertical induction). I have an O-360 RV-6A with reverse mixture and an offset arm, vertical induction, and that arm interferes with the cowl.
The cowl cutout that Van's offers appears designed to create clearance for a downward pointing mixture arm.
Others have reported success with a reverse mixture arm that is shorter and with less offset - there is another thread that discusses this at length. It appears to me that a straight arm should work.
Precision has offered to exchange the arm for me for another for no charge.
On a different but related matter I mentioned in a post a few days ago to give people something else to think about - Van's says there should be no gasket between the servo and the FAB top plate. Many photos I see have a gasket.
Bill Brooks
Ottawa, Canada.
RV-6A finishing

Talk with Precision and see what they can offer

As Bill said,.. they have in the past offered to exchange lever arms.

Gotta send it in, before you get one back. BoyHowdy, at those prices it must be an airplane part.

As I recollect, I ended up exchanging mine. (still have offset/cutout of the FAB).

Contact Precision

I contacted Precision and they swapped out the offset mixture lever which came with my new engine for a straight lever.

With the straight lever, a new airbox mount plate I fab'd to shift airbox toward center, airbox cutout from Van's (I have regular mixture rotation) and careful bolt/nut selection, I ended up with nearly 3/4" clearance between bottom cowl and mixture bolt.

Mixture is even further away during engine start and stop (retracted up) but I'll wait until flying to see for sure if that is enough or I need to add the fiberglass bump.

Thank you Roee, Bill, Wallace and Allen! I think I will send my mixture arm in for a replacement after I call Precision. I will use the cutout piece from Van's to clear the arm, offset the FAB with a new mounting plate and see what I have at that point. It sounds to me like it should work. I appreciate your input - and this Forum. Have a great day.

Alan, Happy you are ready for your DAR inspection. Rubbing it in a little, eh?

Jim Sygitowicz

Picked up my new straight mixture arm yesterday. Great people to deal with at Precision Airmotive.

AF_Alan said:

I contacted Precision and they swapped out the offset mixture lever which came with my new engine for a straight lever.

With the straight lever, a new airbox mount plate I fab'd to shift airbox toward center, airbox cutout from Van's (I have regular mixture rotation) and careful bolt/nut selection, I ended up with nearly 3/4" clearance between bottom cowl and mixture bolt.

Mixture is even further away during engine start and stop (retracted up) but I'll wait until flying to see for sure if that is enough or I need to add the fiberglass bump.

Click to expand...

I did the same thing, only with a slightly offset arm, not straight. That way you don't have to move the FAB quite so far. I had plenty of clearance, but it was the only problem I had with anything on the aircraft not fitting right or working right when installed. Instructions could be clearer on this on. All worked out well in the end.

Same setup here

I swapped the arm, modified the FAB and also put a little blister in my cowl. Look at my build site to see the cowl mod. Www.n91rv.com