The Stovebolt Site Forums The Shop Area Engine Shop 270 ci pressure gauge

Hello all , just fitted a 270 into my 51GMC suburban , it has a oil filter fitted to the fire wall , to,which the oil pressure gauge is fitted on the return oil line , my question is
Is this the best place to get a true reading , the gauge seems to take a while to register and it doesn't get very high about 30 psi when cold ,lower when at running temperature any ideas anyone .

The correct hookup would be a street T coming out of the block on the front on the manifold side of the engine. A line with a limiting orfice goes to the filter which should be mounted on the pushrod side of the engine. Another line goes from the street T to the head to oil the rocker arms. The preferred place too draw oil for a pressure gauge is from the oil galley about 6" behind the exhaust pipe. It is an 1/8" pipe plug. If you have a filter without a restricted orfice, you could be losing too much oil through the filter and starving the engine. If you will sign up for this site, http://www.oldgmctrucks.com/ they have some very good pictures of how oil is routed in the discussion forums.

Ken, I've never heard that fitting referred to as a 'street T'. Where does that name come from?

Don't forget there's a restricted fitting going into the head to oil the rockers.

The oil line for the gauge should NOT be hooked to the oil return line. These filters don't really operate on pressure, more like gravity, hence the crappy reading on the gauge.

Jeff

Thanks Tim.

So a street T is just a combination male and female threaded T?

I learn something new everyday.

Jeff

Ok many thanks for that,I will remove the oil gauge pick up point from the filter return line and move it to where you,recommend below the manifold , my next concern is thIs oil line restriction you mention, my filter is just plumbed in from the oil gallery at the front of the engine directly to the filter housing using 1/4 copper pipe with out any restriction this now sounds wrong , where should the restriction go and what size should it be,

You can't get restricted fittings anymore unless you find one NOS, to my knowledge. You can take an inverted flare fitting, fill it with solder and redrill to the appropriate size. The original fittings were a compression fitting that had a conical tube nut that slipped onto the tube.

There should be a brass fitting both in the head and in the filter housing that will accept either a compression fitting or inverted flare, both with male pipe threads I believe.

I can't remember the size of the restriction, but it's got to be listed here somewhere, if not, http://www.oldgmctrucks.com/ will have it listed on the site in one of the posts.

Jeff

GMC used the same restrictor orfice for 20 years and was used on the 228 up to the 302. There are lots of people who have old engines laying around. Until you find one, I would just block the filter off completely. A filter was an option anyway. Running it without a filter won't hurt anything. It is a lot better than starving the engine for oil.

Thanks for that information I have disconnected the oil filter until I can find a restrictor not too sure where to look if some one can help I would be gratefully for any help in finding one