Slow to build oil pressure

I've got a '68 Sweptline that someone before me dropped a 440 into.

I did quite a bit of work on it in the first few months I had it to fix some problems (i.e. ended up replacing the worn out 906s for Eddys, replaced the Chevy [even Chevy PN] carb for a Holey 750 with electric choke, among a large number of other things). So I'm not sure if this problem has existed since day 1 or not.

The engine is really slow to build oil pressure. For the first few seconds (maybe 3 seconds) after startup the oil light is on and you can hear a knock.

What causes this? Oil pump, or just totally ragged out?

the 1st thing I would suggest would be to put a new wix filter on there. Some filters have a faulty drainback valve. Do you have a mechanical gauge to see what your psi is cold/hot. It may need a new pump or be worn bearings/lifters or both.

what weight oil? lighter oil will help.

I agree with the filter swap suggestion. When I got my 400 powered truck it would take 20+ seconds at 1500 rpm to maintain ANY oil pressure. It would build slowly to 60+ psi only if I held the throttle. If I let it idle it would drop back to zero. As soon as I put a good (Wix) filter on it was fine. Ill give you 1 guess what brand was on it before (orange and rhymes with "cram").

Pete

I had been using 20w-50 VR1 for the zinc (Valvoline). I decided to try 10w-30 (Valvoline). It didn't make a dimes worth of difference.

The only oil filters I use are Mobile 1. I get the big M301. If that thing doesn't work properly I'll eat my hat.

might be time for a new oil pump.
easy to replace on a bigblock.

Could be a bad oil pressure gauge too.

I don't have a gauge, so I don't know what the actual pressure is. ... but with the knock it does, I don't really need a gauge or light to tell me the oil pressure is a little low.

I'll pull the pump this weekend I guess and take a look at how worn out it is.

Thanks.

you might want to drop the pan and check to see if the pickup is not cloged. no flow no pressure.

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you might want to drop the pan and check to see if the pickup is not cloged. no flow no pressure.

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Pull the pickup and shake it.
Check the oil pump plate for wear.