model tech P-51 engine (91 4 stroke)
 

Just got model tech p51. Was planning on using Magnum 91 4 stroke. At the altitude I'm at that's usually not overkill for motor on this size of plane. However It will take some trimming to get this to work and the carb will be right up against the 1st firewall, crankshaft looks a little long also, spinner may have to much gap.
Anybody else put this size of motor in this plane?
Any suggestions would be greatly appreciated.
Thanks

model tech P-51 engine (91 4 stroke)
 

I don't think you can squeeze the Magnum 91 4 stroke in the Model Tech 46 P-51D as that engine is too long. My Saito 72 barely fits with a 1-mm gap between the carb and the firewall even though it has a small footprint, smaller than the OS 70 or the Saito 65.

You only have around 100-mm between the firewall and the front of the nose ring to play with.

RE: model tech P-51 engine (91 4 stroke)
 

thanks for this info, it helped me in purchasing an motor. I was almost going to get the .91 magnum 4stroke until i read this, although it is less than 100mm to the drive bolt. I ordered the 70 instead. Any issues with the 70?

RE: model tech P-51 engine (91 4 stroke)
 

I did end up using the 91 magnum. Barely fit but it worked out okay
they are a nice airplane and your 70 will fly it well.
scott

RE: model tech P-51 engine (91 4 stroke)
 

What size is this? I have a Saito 100 stuffed in a WM 40 size P 51 and a G2300 in a 60 size

RE: model tech P-51 engine (91 4 stroke)
 

man i wish i knew that, i really wanted that extra power. did you have to cut the firewall? maybe i will exchange it for the 91. I already ordered the 70.

RE: model tech P-51 engine (91 4 stroke)
 

Nope. The 100 is really crammed here. The 91 would be good

RE: model tech P-51 engine (91 4 stroke)
 

damn. i assumed since scottad didnt reply to richard l's post that the 91 is too big, that it was infact too big so he got the 70. I should have waited. Maybe tower will exchange it for me. I assume the 91 would give me alot more speed, i hear the 70 is nice in this plane but far from fast.

RE: model tech P-51 engine (91 4 stroke)
 

Hi Mike,
Sorry for delayed reply, just been away from computer. I put a magnum 91 in a modeltech p51 for my cousin. (It was just a plane I put together for him). he still has it, it was a while ago when i did but it didnt require any major mods just was tight, I do remember having to put the battery in the rear of fueslage to balance but other than that wasnt a big deal, I can't remember how the firewall was on that plane but I know I didnt have to change anything major. Anyway sorry for the delay
scott

RE: model tech P-51 engine (91 4 stroke)
 

ok we are building the plane and the 70 fits nicely. we had to cut out a tiny bit of firewall but not much at all. we also took off the choke thing for priming the engine by hand, is that going to be a problem? i would like to start this thing by hand so i dont scuff up my nice aluminum spinner but i dont know how i am going to do it without that choke valve. even if we left it on, the little allen rod that sticks out would be right into the firewall or behind the firewall so i wouldnt be able to get at it.

we are also having a problem with the throttle rod. he bows out and causes the throttle to change randomly depending on how the rod bows. we were thinking of replacing it with a tube or tube and cable. any suggestions, how did you guys get this to work??

thanks for your help with these two questions everyone, i appreciate it.

mike

RE: model tech P-51 engine (91 4 stroke)
 

i have the model tech P-51 with a YS 63 in it ,, it fits perfect and is fast too,, no balance issues either,,, the new 63 s should be even better,, at $ 239 it's not a bad deal..,;)

RE: model tech P-51 engine (91 4 stroke)
 

Hi Mike,

You can choke them by just plugging the muffler with your finger and flipping it over, (that is as long as your using muffler pressurized tanks) works real good, just flip it 4 or 5 times till your finger plugging the muffler until your fingers get's wet with fuel.

Also on the throttle cable, I can't remember what I did on my cousins, but you do need to get the bow out of it.
good luck
scott

RE: model tech P-51 engine (91 4 stroke)
 

thanks for the replies, i managed to get the throttle rod replaced with a tube/rod system and then built in supports for the tube, so it no longer bows. it required me to change posisitions of the rudder and throttle servo, this made a much better line up for the throttle and an ok one for the rudder too.

my biggest problem is the elevator linkage system, it is TERRIBLE! Those little white tubes that go in the outside tubes (already mounted in the plane at the factory) they bind like crazy, my hands are burned from sanding those tubes down for hours, then they would still bind, so i lubed the tubes with tons of vaseline, they still bind, so i repeated the process, hours later the rods were sanded down to thin little sticks and they still bind, it seems the action of pulling them apart the further the tube goes in the worse it gets. but replacing it with a metal rod isnt an option cause its two tubes and two elevator halves that are joined. please any assistance you guys can give, anything you might remember.... thanks

edit: i bought 2 rods to try, i havent tried it yet, i am going to combin the two rods together and then a third coming out the otherside to replicate the factory linkage. i dont know how i am going to connect all 3 wires together, they have to be spaced, so i cant just solder them all together at the ends, the 2 rods that go to the elevator need to be like an inch apart or maybe even 2 inches apart.

RE: model tech P-51 engine (91 4 stroke)
 

I replaced part of the elevator rods and its still terrible, i had to use the existing plastic tubes for part of the linkage so i could split into two rods.