slow to make oil pressure from cold

[brian stevens]

I have a 71 v12 etype , I have recently had the engine out for bottom end rebuild , crank grind , new shells , oil pump , complete clean , re assembled with new gaskets , rob beere canister oil filter , new fly wheel and starter. makes good oil pressure even when hot ,but when left for a few days on start up the oil light takes say 20 seconds to go out , I think the oil must drain back or something , I am using good quality 20/50 oil , any idea's

[MarekH]

Dear Brian,

The oil pick up is from two sources:-

1/ the middle of the sump via the main suction tube, and;
2/ the overflow which fills the oil and water heat exchanger.

Assuming all of the clearances are good and there is enough oil in the engine, it sounds as though there is a nice airlock in the latter as this is exactly what happens at first startup after a rebuild. I presume this is because that overflow won't get any oil until the relief valve opens or oil has circulated round.

The classic way to get around that for first start is to swap the oil sender for a connection to a garden insecticide sprayer filled with engine oil and prime the oil galleries first. If you then start it up and it still takes 20 seconds, then I'd worry that there are some O-rings missing or somesuch.

Fitting a mechanical gauge would also instantly tell you what the oil pessure is.

kind regards
Marek

[71 V12]

I think I would try refitting the OE filter and housing?

Good luck

Kevin