Too many variables, ideas/advice sought

[vmcurry]

My S2 GP2276 56 x 48 Sterba 34mm Revmaster carb gravity feed. 2 hr flight home. Next day running on 3 cyls. Stuck exhaust valve on #2 cyl. New valve and machine work. Flew 8hrs before exhaust valve stuck on #4. Life got priority(18 mos later). Now new pistons, cyls, and heads installed. Havent run yet. Observed what appeared to be too lean mixture before top overhaul. WOT with mixture full rich static 3000rpm, cant get any egt rise by leaning. Too many variables with all issues. Considering float type carb, fuel pump with either carb, prop mod possible because Ive never seen 3300rpm or higher, even in flight.

 

[Mytonic]

What EGT and CHT was the engine typically operating at? How many hours are on it? Do you know the compression ratio? A 56x48 is taking a pretty big bite for our vw's.

 

[Steve Stephenson]

Agreed. The propeller is part of the problem. 52 or 54-48 would let the engine wind up.

 

[Speed20]

I

My S2 GP2276 56 x 48 Sterba 34mm Revmaster carb gravity feed. 2 hr flight home. Next day running on 3 cyls. Stuck exhaust valve on #2 cyl. New valve and machine work. Flew 8hrs before exhaust valve stuck on #4. Life got priority(18 mos later). Now new pistons, cyls, and heads installed. Havent run yet. Observed what appeared to be too lean mixture before top overhaul. WOT with mixture full rich static 3000rpm, cant get any egt rise by leaning. Too many variables with all issues. Considering float type carb, fuel pump with either carb, prop mod possible because Ive never seen 3300rpm or higher, even in flight.

i have a 2180 with a prince 52x48 and I can’t break 3000 rpm static or straight and level. Thinking of a getting a Sterba 54x43 prop

 

[Mytonic]

I believe a 54x43 would require more HP to reach 3000 rpm than a 52x48

 

[Todd Loes]

Burning 100LL? There's an interaction with the lead that makes sticking valves far more common. Temperature of the valve and guide are players too. Oddly, "too cool" and "too hot" are both part of the problem (per some recent articles). I have an O-300 in a C172 and have had a valve stick on at least three different cylinders since installing said cylinders in 2017. Maybe I'm inventing a connection but it seems to happen after taking a long trip where I've burned several tanks of 100LL after having operated with mostly mogas in my local area. I'm thinking the deposits created by the 100LL hate the deposits created by the mogas.

 

[Steve Stephenson]

Try adding 100mL of mineral oil to your fresh engine oil but only if you're using non-synthetic. If you're using synthetic, try dropping to 0-30 full synthetic for a few hours.

I haven't had the kehones to try it with an airplane, but adding a small amount of transmission fluid to the fuel helps with valve sticking and carburetor operation.

Regarding the propeller, so much more torque is consumed as the radius increases. The pitch is also only part of the equation since the airfoil shape and overall propeller profile play their part too. 52 seems to be a sweet spot.

 

[John B]

52 x 48 sterba works fine on my 2276cc Sonerai IIL. I get about 3100 static and 3400 rpm level flight WOT.

 

[JondorB1]

54 x 48 for 2276 on Sonerai II LS, I get 3400 rpm WOT in flight.

 

[Speed20]

I believe a 54x43 would require more HP to reach 3000 rpm than a 52x48

I’m at loss already don’t know which way to go

 

[DeadRinger]

Find a prop you can borrow

 

[John B]

Keep in mind these numbers are general numbers unless everyone has calibrated their tachometers. Mine has not been calibrated and is an mid-grade automotive tach.

 

[kennyw]

I’m at loss already don’t know which way to go

Talk to Ed Sterba. I think he might be able to point you in the right direction.

 

[spankyscub1]

Marvel Mystery Oil instead of tranny fluid, works great so stickies here
Smells good too reminds me of AFX slot car oil

 

[Steve Stephenson]

I forgot about that stuff! lol. It does smell retro. Transmission fluid and Marvel Mystery oil are both mainly severely hydrotreated petroleum distillates (naptha). Hell, some transmission fluid is just highly refined mineral oil. Like Frank's Red Hot - you can put that $#*t in anything.

 

[Steve Stephenson]

I also forgot to mention that all of the above fluids have a laxative effect if swallowed - so maybe you DON'T want to put that stuff in "anything."

 

[DeadRinger]

I think old formula marvel had fig fat oil in it. I'm talking real old stuff 30's? I cant find a pic of the back of a old bottle but I'm sure I remember seeing it had like pig fat oil or something in it.

 

[Speed20]

Talk to Ed Sterba. I think he might be able to point you in the right direction.

Thanks that’s probably the best thing I could do right now

 

[vmcurry]

My gratitude to all who replied. Sorry, I dont get to sit down to my computer very often, but have read all today. FYI that first post of mine in this thread says 2hr flight home. I bought this from someone and flew home only to have the stuck valve next day. I use marvel mystery oil in crankcase and in gasoline, since I bought the plane. Only got to fly it about 10 hrs total before tearing down for top overhaul. I would like to get it flying again first. My priority is the carb. Tied down to test, Im thinking not enough fuel flow at WOT is why I cant get rise on egt. gravity flow and revmaster carb. I could buy new Zenith carb and modify intake plus add fuel pump. Has anyone used a pump with a revmaster carb? PS could i cut my prop down or must I get another?

 

[soneraifred]

Before you start making changes to the fuel system, you should try adjusting the carb to enriched the mixture at WOT. There should be no reason to install a fuel pump. I’ve flown my Sonerai IIL with POSA carbs, a HAPI UltraCarb float bowl carb, and the Monnett AeroCarb/AeroInjector, and they’ve all run fine on straight gravity feed. The Revmaster carb should also run fine without a pump. If you have any concerns about fuel flow, test the flow rate with a high nose attitude. For an 80 hp engine you should get at least a 10 gallon per hour flow rate. If you’ve got that flow at the carb, you should be able to adjust the carb to get fuel mixture you need.