Oil Line Size
 

I currently have #10 (about 5/8") running to my remoter filter. The fitting size for the Mercruiser oil cooler I'm installing is #8 (about 1/2"). Is this smaller line size OK?

Re: Oil Line Size
 

If you are using AN line, then there are #10 to 1/2" adapters available. That's what I'd use.

Re: Oil Line Size
 

I've always used -12 for engine oil, -10 for tranny fluid, and -08 for fuel. I wouldn't go below a -10 on motor oil. I don't know if a -08 would actually limit flow volume, I'm sure some Engineering types can recall the formula to figure it out though.

Re: Oil Line Size
 

Weird thing is I'm using a oil cooler off of a 454 mag and it has #8 inverted flare fittings built into the cooler so I'm thinking that's OK. I'm using this on a 400HP small block that I haven't had a cooler on in the past but I don't want to choke off the oil supply.

Re: Oil Line Size
 

Use #10 lines with 1/2npt fittings on your oil cooler and engine ports. The fittings are common and have a much larger i.d. than fittings for #8 lines.

Re: Oil Line Size
 

I can't use 1/2" fittings on the oil cooler. It is threaded for #8 fittings. I guess this is OK since it is off of a big block mercruiser but I want to make sure. Is anyone running #8 lines to there oil cooler?

Re: Oil Line Size
 

Strange, my 454 mag coolers had 1/2 npt threads. The system was plumbed completely with #8 lines and fittings but I don't think that's enough for a big inch engine or a supercharged application. You lose a lot of pressure going through 14 feet of hose, fittings, oil cooler, remote oil filter, oil thermostat.

Re: Oil Line Size
 

I use a -10 with 1/npt fittings on my cooler and remote filter.

Re: Oil Line Size
 

I used 12 you may get away with 8

Re: Oil Line Size
 

No stay with the 10s don't step down. It is possible for the filter bypass to open up when the engine is cold if the restriction is too great.

Roby