My Oriental's OS 40fp spraybar

I agree, it shouldn't be critical, probably only makes a difference in the needle's happy spot. And, right, most spraybars have a flat on the hex that lines up with the hole. I always mark it with a red sharpie before I start installing.
Rusty

On single holes I usually point them them straight down. Sounds like you are about there anyway.

There was an article somewhere by one of the engine gurus, who described the optimum location of the spray bar hole. Suction is strongest when rotated from straight down something like 15 degrees from center. I've seen that recommendation in other places, too. Just wish I could find where referred to.

Cribbs74 wrote:On single holes I usually point them them straight down. Sounds like you are about there anyway.

Yes, given the tilt of the venturi, I'm about 25 degrees off. I guess I should bench run it as Phil suggested. Probably ought to take a look inside in case of dirt too. I know one thing, these FPs are tough little buggers. I've also heard the they are not nearly as loving as the smaller ones. The 35 is amazing, always a 1-2 flip engine, the 25 is almost as cooperative.

All of which reminds me I have today's flight report to file. Guess I'll get to it tomorrow. It was a great day at the field, cloudless, mid 70s, 5mph wind, tops, blowing away from the sun.
Okay, one pic, them you gotta wait til tomorrow.
Flight of the .40 Ukey


Hey George, Thanks. You posted that while I was writing and arraigning pictures.
Rusty

Align your spray bar hole to the same angle as the venturi stack.  Unlike the POS Fox spraybar the Fp isn't generally as fussy. What it is fussy about is the o-ring under the venturi. Seeing that it's been in the engine for some time, it's more than likely compressed. You really should require a lot of thumb pressure to squeeze it down to install the spraybar. If not, this sometimes requires you to double them up. When they do come loose over time and from vibration, the through hole can become egged out in the venturi. When the case gets hot problems can develop.

George, Bob Zambelli wrote an article in Stunt News in regards to what you read. It's been passed around many times through other forums. Ken

Hi Ken. Thanks for the position info. I thought about the o-ring when I saw how thin it was, so I left it in place and added a Norvel gasket. It was hard to get on, but then I had to use my 14" channel locks to compress it enough to get the spraybar in place. That ought to do it.
Rusty

Ken Cook wrote:Align your spray bar hole to the same angle as the venturi stack.  Unlike the POS Fox spraybar the Fp isn't generally as fussy.

Interestingly enough, Ken, Horace Cain recommended replacing the Fox double hole spraybar with a single hole NVA from Enya, OS, and etc. This would help it to run more consistently and solved burping problems during stunts.

George, Bob Zambelli wrote an article in Stunt News in regards to what you read. It's been passed around many times through other forums. Ken

Ok, thanks, just couldn't recall but the explanation made sense, had to do with the airflow around the spraybar that suction was stronger if canted slightly away from bottom center in relation to venturi stack airflow direction, something like 15 degrees. So far, seems the McCoy's, OS FP and Enyas haven't been that fussy if pointed directly down in relation to venturi air path. I suppose with some engines, that if one had some fussiness, could rotate slightly to see if that improves performance in varying stunt positions. I've started doing that, seeing it did not harm and if improves reliability, I had nothing to lose and all to gain.