Hi,

I'm having trouble with my 305 TPI motor - I'd be grateful for any suggestions...

When the engine is first started the oil pressure is around 30 PSI at idle and upto about 50 PSI when the engine speed is increased - but as soon as the engine gets upto normal operating temperature, the oil pressure drops down to around 15 PSI right through the rev range.

I have changed the engine oil and filter twice now - the first time I used 5W 30 oil and recently I upgraded to 15W 40, this has made no difference to the oil pressure at normal operating temp (the pressure is slightly higher at cold with the thicker oil).

There are no knocking sounds from the engine - but when running on the 5W 30 there was some 'valve lash' type noise.

I have checked the gauge and sender and they seem o.k.

 

¿Check? What is this "check"?

If you replaced the sender; or if you hooked up an external oil pressure gauge, such as a mechanical one; and that's what your oil pressure really is, then I'd start saving up for a new motor. Or at least, a crank kit, if it doesn't smoke or anything and has good compression (rings OK).

If you did anything else, then you didn't "check" it; do one of those 2 things, so you know your reading is accurate.

I'd recommend 10W-30 once you get it straightened out.