Low oil pressure in a new motor?

[BigPoser]

Hey all,

Been a while since I've been in here and I feel bad about that, haha. So I put in a new Chevy Performance 350 crate motor in my 73 about 500 miles ago and haven't really driven it much since I had to get a new truck for work. Anyway, when idling I get a PSI of 7-10lbs once the engine is really warmed up. Not when cold. It is a 5 quart motor, and has 5 quarts in it. I am using the previous distributor though, if that helps at all.

What could be the issue? I'm in the process of selling it and don't want there to be any issues for a new owner.

Thoughts, suggestions, and advice are greatly appreciated as this is an area that I'm not familiar.

Thanks.

Brandon

 

[74 Shortbed]

There was a new crate motor in my truck when I bought it and it was the same way at idle, and only 45lbs running when hot, I put 20,000 miles on it before I tore the truck apart never had an issue still runs good.

 

[jetman]

Hey all,

Been a while since I've been in here and I feel bad about that, haha. So I put in a new Chevy Performance 350 crate motor in my 73 about 500 miles ago and haven't really driven it much since I had to get a new truck for work. Anyway, when idling I get a PSI of 7-10lbs once the engine is really warmed up. Not when cold. It is a 5 quart motor, and has 5 quarts in it. I am using the previous distributor though, if that helps at all.

What could be the issue? I'm in the process of selling it and don't want there to be any issues for a new owner.

Thoughts, suggestions, and advice are greatly appreciated as this is an area that I'm not familiar.

Thanks.

Brandon

Are you using the stock GM electronic oil pressure gauge or aftermarket mechanical?
Have experienced under reading inaccuracies w/ the stock gauges which have been verified via use of mechanical.

 

[BigPoser]

There was a new crate motor in my truck when I bought it and it was the same way at idle, and only 45lbs running when hot, I put 20,000 miles on it before I tore the truck apart never had an issue still runs good.

Oh man, that's exactly where mine sits when running too. Thought for sure it would be around 60 when cruising. Good to know, thanks.

 

[BigPoser]

Are you using the stock GM electronic oil pressure gauge or aftermarket mechanical?
Have experienced under reading inaccuracies w/ the stock gauges which have been verified via use of mechanical.

I have Dakota Digital VHX gauges in it so it is aftermarket.

 

[74 Shortbed]

Oh man, that's exactly where mine sits when running too. Thought for sure it would be around 60 when cruising. Good to know, thanks.

I think the most I've ever seen was 50 when it was cold and it dropped pretty quick, I wouldn't worry about it.

 

[74 Shortbed]

I have Dakota Digital VHX gauges in it so it is aftermarket.

I had Autometer mechanical in mine..

 

[87scotty]

to much can be just as bad as to little sounds like your in the good range

 

[Tranz Zam]

I'm sorry, but 7-10psi at idle is too low for me. Every healthy sbc I've had idles at a minimum of 30psi hot, and anywhere from 40-65 while on the highway.

I'd be keeping a close eye on it.

 

[87scotty]

Yea 7-10 very low i was meanin the 40 when cruising

 

[74 Shortbed]

Rule of thumb is 10lbs per 1000rpm, any more is just a strain on the distributor gear and robs power.

 

[jetman]

Your new VHX gauge set is prolly pretty accurate compared to the OE electric gauge set which I believe used an old style rheostat/bourdon tube style sender design. I agree with 74 Shortbed, your 7-10 at idle is fine.

I have factory gauges, in heavy traffic, pulling a heavy load the indicated pressure at idle approaches 1-2; used to worry but after 2 years I never give it a second thought.

 

[MikeB]

Rule of thumb is 10lbs per 1000rpm, any more is just a strain on the distributor gear and robs power.

Exactly. But I still don't like 7-10 at idle, even though it's probably not gonna damage the engine. Back in the day, it seems like a new factory 283-327-350 would hold 15 PSI at hot idle and 35-40 at 60 mph in top gear. That was using a USA-made Stewart-Warner mechanical gauge. The only new gauges I trust are AutoMeter (not AutoGage), and their full sweep mechanical gauge is probably the best. The cheap no-name gauges with 90 degree sweep from 0-100 PSI aren't very accurate at anything but mid-scale. And even then they could be 5-10 psi off.

BigPoser -- What weight oil are you running? If it's 10W-30 try 10W-40. That will probably keep the hot idle pressure above 10 PSI, while keeping the viscosity low for good oil flow on cold startup.

 

[74 Shortbed]

Exactly. But I still don't like 7-10 at idle, even though it's probably not gonna damage the engine. Back in the day, it seems like a new factory 283-327-350 would hold 15 PSI at hot idle and 35-40 at 60 mph in top gear. That was using a USA-made Stewart-Warner mechanical gauge. The only new gauges I trust are AutoMeter (not AutoGage),

Well, these days it's all about efficiency and fuel mileage, like I said more pressure takes power which in turn eats up more fuel, so anything they can do to save a bit they go for it. Yeah, they all idled at around 15psi back then my 74 does too and hot going down the road runs at 55psi, and all that can easily be changed with the spring in the pump, want more pressure just add an SAE washer to the spring and pressure jumps up, lower pressure put a weaker spring in.. Oh, BTW Autogage is Autometer just one of the many styles they have.

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[yevgenievich]

There are wide ranges and even it is in ok range, it does appear to be low. Factory 91 suburban hot idle shows 25psi on factory gauge with 140k miles. Factory 94 one ton shows hot idle of 10-15psi on factory gauge with 250k miles

Gm specifies generally absolute minimum:
Minimum 34 kPa @ 1,000RPM/ 5 psi @ 1,000RPM