Possible low oil pressure issue in 74 road runner 318…Can someone help tell me if this aftermarket gauge is electric or mechanical?

[tonyp25]

The T shouldn't cause any problems unless it is plugged. As long as the orifice of the T is close to the ID of the tube feeding the gauge, there won't be any delay.

For the heck of it I went down to the local auto parts store and bought a new sending unit. The gauge needle is sitting at the first dash line (picture below) after running for about 30minutes.

 

[HawkRod]

Alright so I hooked it up to the T. So I had both the harbor freight test gauge and cheap mechanical sunpro gauge hooked up (just ordered a nice autometer). It seemed like the mechanical one in the car wasn’t on very well so I tightened it down.

Anyways on start both gauges were above 45 psi. After it warmed up I let it sit and idle for about 30-40 minutes, the harbor freight was solid at 12 psi and the sunpro was solid at 18psi. If I gave it some gas it would jump to 25-35 psi.

I feel like the harbor freight being in the 10-15 psi range is low at idle when hot (though I read something online that said Plymouth/dodge originally stated it should be below 6-8 psi). The sunpro after it was tighten down was in the 20 range the whole time.

I guess we’ll see after I get the autometer. I’m still tempted to pull the T out and hook the gauge up so it’s the only thing connected. Not sure what you think of the current numbers it’s giving me. But it never dropped to 0 like the guy I bought it from was saying.

A rough rule of thumb is 10 PSI minimum per every 1000 RPM.

Having higher PSI on startup and then having it drop once the engine is warmed up is totally normal.

I assume this is with the 20w 50 oil. So with the numbers you describe, this is totally normal for an engine that is a bit "loose". In your case, probably a bit worn. I wouldn't worry about it at all. Drive it and enjoy it. At some point in the future the engine will want a rebuild, but if everything else is OK I'd say drive it.

 

[tonyp25]

A rough rule of thumb is 10 PSI minimum per every 1000 RPM.

Having higher PSI on startup and then having it drop once the engine is warmed up is totally normal.

I assume this is with the 20w 50 oil. So with the numbers you describe, this is totally normal for an engine that is a bit "loose". In your case, probably a bit worn. I wouldn't worry about it at all. Drive it and enjoy it. At some point in the future the engine will want a rebuild, but if everything else is OK I'd say drive it.

Really appreciate all the information and help! While I was back there replacing the sending unit I noticed (distbributor caps and carbs are new to me so bear with me) what I believe is maybe some type of filter hanging off the distributor cap without a hose on it…circled below. It should have a hose on it right?

This is probably a question for another thread but with how much luck I had getting the oil pressure gauge going on the dash, any idea where the tach and temp gauge sensors located? For instance I got the roadrunners *meep* *meep* horn going again just by cleaning the connectors.

 

[Fran Blacker]

Vacuum advance and a hose go to the carb. When you buy hose say it's for vacuum, wrong type hose can collapse. On oil pressure run it.

 

[tonyp25]

Vacuum advance and a hose go to the carb. When you buy hose say it's for vacuum, wrong type hose can collapse. On oil pressure run it.

Thank you! I’ll do exactly that….I also need to clean the carb though it is idling well (even if I can’t see the tach yet).

Any idea why there’s a hose connecting from the valve cover to the air cleaner? It seems to at some point spit oil in the air filter a little bit (unless it’s blow back from the carb making it dirty). Could I put a valve cover breather on it instead or install catch can?

 

[Fran Blacker]

PCV valve hose to carb base it looks like, it's if hooked up that way