Frank N821BF
Active Member
I have a Precision model MA-4SPA on a O-320-D3G in my 9A with dual Lightspeed ign. Can any one give me some feed back on rejeting.
Yes you can drill the main jet one or two drill bit size larger (or more if needed). You will need some new tab washers and gasket. You need to take the bowl off and main jet out of the body. The tricky part is the MA-4SPA jet is I recall it has a radius in the orifice, and when you drill it will make a sharp notch. How that affect the fuel flow who knows, but your may want to go in an carefully break that shape edge. Treat is like jewelery.Frank N821BF said:I have a Precision model MA-4SPA on a O-320-D3G in my 9A with dual Lightspeed ign. Can any one give me some feed back on rejetting.
Yea that is the GOOD part number #10-5217 (I think), and 50-80deg rise is a bit too lean but not horrible.Frank N821BF said:Thanks for the info. I have part #10-5217 ser# BL198084, when I was breaking in the engine it seemed like I could lean the engine, but as the oil consumption became less so did the leaning. My problem is at 75% when I try to lean even a small amount(1-2 turns) the egt goes up 50-80deg, then it drops off(LOP?) I did put a call into Precision and should get a call back tomorrow.
Frank
RV-9A 150+hrs
Depends on who you talk to. They are thinking liability. I remember 6, 7 or more years ago I called Precision about a MA-4SPA, and I thought the guys head would explode as he told me how terriable that idea was. That is the company line. However I am happy I did it.mahlon_r said:Re-jetting is not recommended by Precision or Lycoming.
Good Luck,Mahlon
With all those mods I think going to #37 is a reasonable thing to do. I think you sound just a tad lean but Mahlon says about right, and he knows more than I do. I would just say you may want to take the carb out and have it checked over. Make sure the venturi is in properly (correct hight), float and over all health is double checked. However with you HC pistons, EI, more fuel is not a bad idea. I have heard of several people needing to go over #38. So its a reasonable thing to do. You may need #36, but I would go #37 and make sure you have a radius/break sharp edges (subtle) in the jet orifice exit / entrance. I had to go into my O320 Carb twice myself. The results where I was very happy and cold get 150 rise in 75% cruise and the engine RPM went up 50 RPM when leaning during shut down. Disclaimer: Do it at your own risk. GScott DellAngelo said:I have been thinking about going to #36 or #37. Question is, should I? I think yes because I still cannot get a very big rise out of 1 and 3. This is leaning at 2400-2500 rpm and 4500 feet (FP prop). I do have 9:1 compression (H2AD pistons) and dual electronic ignition so "should be" in the upper 160's for horsepower. Thanks,
Scott #90598 - N598SD Flying - 23 hrs
It made a huge difference in my O320, and the engine run much better. Better and when I leaned I got EGT rise. Before it would just start to run rough.
My O-320 E3D with MA4-SPA 10-5009 has had a rough idle and I have had the problem up here on the forum. I've done everything possible to find the problem but it is still running a bit rough at 600-700 rpm. I saw you post here and one line got my attention: "It made a huge difference in my O320, and the engine run much better. Better and when I leaned I got EGT rise. Before it would just start to run rough". When leaning my engine I don't get the usual 50 rpm rise when leaning from 1000 rpm to cut-off. I've tried to turn the idle mixture screw out five turns and there is no change so I was thinking, maybe I should drill out the jet?
Lycon in Visalia ca, will wet flow your carb and based on your info of your motor and so on and will re jet and wet flow after and when I did it the costs was all of 213.00 bucks with shipping.. knocked 20 degrees the cht all four of them. Motor ran perfect just bolting on carb . Lycon I recommend