Mechanical Oil Press Gauge ?

[Big Kev-O]

I have searched the threads and I can find any information on what the pressure range is on a mechanical oil gauge. I think my oil pressure may be a bit low at idle. When it idles cold it is in the dead center. Once the engine warms up it is just under the second line. Cruising warm it looks good. My previous engine was a worn out 81 350 and the needle was always in the center. My current motor is a crate 350 I picked up from a "friend" who said it had about 40K miles. I downsized the cam when I got it and rebuilt the crappy chinese MSD streetfire HEI. When I installed the SF HEI it seemed to have alot more wiggle room than the GM HEI in the old 81 engine. Could the SF HEI be my culprit? Is this range safe?
Thanks.

[haysonj]

I have seen a few guys on here say you should have 10 psi for every 1000 rpm and it looks like you have 15 to 20 psi at idle which should be about normal. I have two gauges in my truck and the stock gauge seems to be a little lower than the after market one.

[n33k0]

My oil pressure reads similar to yours. I don't know where I got the info, but I think that gauge is a 60 PSI max, so each line would indicate around 0/15/30/45/60 PSI. That could be totally wrong, but that is what I have lodged in my brain somehow, and that would sort of make sense with the 10PSI per 1k RPM. When warm, my idle pressure sits just above the first line, and cruising pressure is where yours is marked. After a few minutes on the highway, my idle pressure will drop just below the first line for a few minutes, then return to the normal spot above the line.

[cleszkie]

The change in oil pressure could be attributed to the cam swap. The previous cam was probably seated in the cam bearings nicely, resulting in good oil pressure. When you swapped in a new cam, I am assuming you did not replace the cam bearings, so there will not be that good seating of two parts that have worked against each other for many miles. This could result in slightly lower oil pressure.

I also belive the wiggle in the distributor is due to the new cam. There is some slop between the cam dizzy gear and the distributor gear. Two slightly different wear patterns from two parts that have not been broken in together.

[Big Kev-O]

Originally Posted by cleszkie

The change in oil pressure could be attributed to the cam swap. The previous cam was probably seated in the cam bearings nicely, resulting in good oil pressure. When you swapped in a new cam, I am assuming you did not replace the cam bearings, so there will not be that good seating of two parts that have worked against each other for many miles. This could result in slightly lower oil pressure.

I also belive the wiggle in the distributor is due to the new cam. There is some slop between the cam dizzy gear and the distributor gear. Two slightly different wear patterns from two parts that have not been broken in together.

The cam I removed was the same brand and looked brand new but that doesn't mean much. The technician at Comp Cams told me I could swap it without changing beaings or valve springs. It was the first cam I have ever swapped and no I didn't replace the bearings. The rings above the distributor gear and the hole they rest in down inside the motor definatly have more play than other 350s I have messed with. There isn't any excess slop in the gear mesh, timing is steady.

Thanks for the help guys, I feel a bit better about driving it now.

[hamjet]

your preveous motor had different tolerences than this one. you can't compare two different engines with the same gauge. I don't understand what you mean by "more wiggle room", explain please...

[Big Kev-O]

When i slide the distributor down into the block it feels as if i can move the distributor around. I under stand the top hole in the manifold is not a tight fit by design but the bottom of distributor shaft seems to have room to move arount as well.

[hamjet]

Originally Posted by Big Kev-O

When i slide the distributor down into the block it feels as if i can move the distributor around. I under stand the top hole in the manifold is not a tight fit by design but the bottom of distributor shaft seems to have room to move arount as well.

You better switch back to the GM one, doesn't sound good. if its not tight fit at the bottom the camshaft/dizzy gears aren't fitting well together and you can strip or ruin the teeth on one or both. .EDIT, I'm not sure on the sbc, but on the 348/409 IF the dizzy is not the correct one you won't be getting oil to the top end, could have something to do with your oil pressure problem too..

[midniteblues]

Your oil p seems to be OK not great but not bad.
If your really concerned about it pull a valve cover and see how the oil is flowing out the rockers. Here a squirt is good and dribble is bad.
You didn't say anything about your intake.
I've noticed distributors fit much tighter in cast iron intakes than aftermarket aluminums. They usually have a oversized hole. And a lot of the newer ones have two hold down bosses.
You could always pull the diz out and measure/ mic it and compare the shafts to a oe hei.

Also if the collar on the oil pump drive broke it would move around a a lil' more than usual.
But Since yours is a newer engine I doubt it's broken.
I've found plenty of broken plastic collars in oil pans.it could have a metal collar also idk.

[68 TT]

Originally Posted by haysonj

I have seen a few guys on here say you should have 10 psi for every 1000 rpm and it looks like you have 15 to 20 psi at idle which should be about normal. I have two gauges in my truck and the stock gauge seems to be a little lower than the after market one.

GM says 7 psi for every 1000 rpm with 10W30 oil. Any more is just wasted HP turning the oil pump harder than it needs to be run. This is from the GM Performance Parts engine building guide book I have.

[68 TT]

Originally Posted by Big Kev-O

I have searched the threads and I can find any information on what the pressure range is on a mechanical oil gauge. I think my oil pressure may be a bit low at idle. When it idles cold it is in the dead center. Once the engine warms up it is just under the second line. Cruising warm it looks good. My previous engine was a worn out 81 350 and the needle was always in the center. My current motor is a crate 350 I picked up from a "friend" who said it had about 40K miles. I downsized the cam when I got it and rebuilt the crappy chinese MSD streetfire HEI. When I installed the SF HEI it seemed to have alot more wiggle room than the GM HEI in the old 81 engine. Could the SF HEI be my culprit? Is this range safe?
Thanks.

If you pull the gauge out of the bezel it will say what the pressure range is. I believe the ones I have seen say 80 psi on the face plate. You can always hook up a numbered pressure gauge in series with the stock one and use the numbers from it to know what the marks on the L-H gauge represent.

[68 TT]

Originally Posted by hamjet

You better switch back to the GM one, doesn't sound good. if its not tight fit at the bottom the camshaft/dizzy gears aren't fitting well together and you can strip or ruin the teeth on one or both. .EDIT, I'm not sure on the sbc, but on the 348/409 IF the dizzy is not the correct one you won't be getting oil to the top end, could have something to do with your oil pressure problem too..

If it doesn't fit snugly into the boss in the engine block then you are losing more oil past the distributor housing than the factory designed into the system. If you have a factory distributor then measure the diameter of the base of the distributor housing and compare it to the aftermarket one you have.

I have seen some aftermarket distributors that have a set of O-ring grooves cut into the base of the distributor housing that are meant to seal it to the block as the aluminum itself is not machined as a snug fit like from GM. Maybe yours is designed like that and the O-rings are not present.

[Racer382D]

What the hell is a dizzy?