Champ Low oil pressure

[Eric Brown]

I have a 7AC with a newly overhauled O-200. Have a low oil pressure problem. Start up oil pressure is 50psi. When oil temp reaches 190, pressure is 20 psi at 2400 RPM. Idle pressure is 8 psi. Have reviewed Harry Fentons small Continental engines web page. The 5 items he recommends have all been done. No luck. To me, it seems that there is fixed open orifice in the engine that leaks hot oil. The oil pressure relief valve has been lapped and a new spring installed. Adding washers to the relief valve spring will increase the start up pressure, but when hot, it still returns to 20psi. Of the 8 small Continentals that I have overhauled, I've never had this type of problem. Anyone out there had a similar experience and know of a fix ?

 

[Bartman]

I don't know of a fix but the engine is freshly overhauled?

 

[Eric Brown]

I don't know of a fix but the engine is freshly overhauled?

Engine is freshly overhauled. All major pieces were refurbished by Aircraft Specialties, Divco, and a local CRS engine overhauler. Crankshaft main journals are -.020", rod journals are -.010". No generator, no vacuum pump. Camshaft forward drive gear is installed. I removed the accessory case to look at the oil pump. Applying air pressure to the pump showed some leakage around the cavity cover. Installed another cavity cover. Same leakage. I did what is not recommended and applied a small amount of Loctite 515 gasket maker to oil pump cavity cover. Air pressure showed no leakage. Reinstalled accessory case. Oil pressure still low. Currently running Shell 80 mineral oil.

 

[Bartman]

Is there any reason to think it's the wrong pump or a bad gauge?

 

[Bob Turner]

Double checked the main bearings? I am pretty sure the 020 bearings are well marked, but might be an idea to get some of that putty the hot rodders use to measure bearing clearances. As I recall, you are looking for around .006.

I can’t remember what it is called, but I may have a few strips around here somewhere.

 

[November67]

Plastigauge ?

 

[Eric Brown]

Yup ! Bearings were supplied by Aircraft Specialties under their STC. Bearing part numbers were double checked at install. Oversize was also clearly marked on the bearings. No Plastiguage was used.

 

[Bartman]

it's a simple system, it's probably a simple solution. I'll be curious to see what you figure out.