I have a 239 flathead that has great oil pressure when it's first started but when the engine warms up I only have about 20 psi while driving and it drops to 0 at idle. I'm using a mechanical gauge. I've checked the mains and rods and they're good. I need to use this truck to pull a 68 mustang from ND to NC in feburary and wanted some advice on replacing the cam bearings. I use this truck every day and I never have a problem with it. Do I need to replace the cam bearings before I try driving it 1500 miles towing a car? I was told that running these motors with bad cam bearings won't hurt it and they would run for a long time that way. I don't have a lot of room in the garage to work on it or a lot of time right now to do it but if this is a MUST then I will find/ make the time/room. Any advice would be greatly appriciated.

 

The risk is that the mains will suffer from loss of pressure/flow because of the cam bearings. Do you know for a fact it's the cam bearings loosing the pressure? Or is this by process of elimination?

A high-volume pump might be the ticket here, even tho I am totally against using them on stock motors.... you could have one in in two - three hours...

 

This is process of elimination. I just don't know what else it could be.

 

Ross is right. Have you put a different oil press. guage on to verify? It's possible that th e bypass spring in your oil pump is fatigued allowing oil psi to bypass. I would change the pump first, as that is far easier than cam bearings.

 

An air bubble in the line to the mechanical gauge will give an erronious reading. You might try bleeding the line at the gauge. It can get messy so be prepared and do it while the engine is cool.
You Sir are a brave soul to attempt this trip! Where in NC are you going?Feb is a better time for it on this end, but not on your end or most of the trip.You do realize you'll have to cross some pretty serious mountains?

 

I put a new pump in it and I'm still getting the same readings. When I hooked up the gauge I just the line and hooked it up on both ends. I never bled the line. What do you do to bleed it?

AXracer, I've been told many times that I'm crazy. I just plan on taking it easy. Life wouldn't be any fun if you didn't challenge yourself. It's funny you wrote because we are headed to Raleigh. If you see a yellow 52 F3 driving around honk and wave. You'll know I got there!

 

You bleed the gauge line much like bleeding brakes. with the engine running crack the fitting at the gauge until all the air is out.
Let us know when you head out, we'll keep an eye out for y'all and have a big glass of sweet tea waiting! Sure you don't want to ship one or the other vehicle. I travel that route as far as Indy a couple times a year. My tow vehicle (2007 GMC PU with HD tow pkg.) knows I have the race car in the trailer behind it thru the mountains of WV, VA and northern NC. The hills are steep enough for the interstate to have runaway truck ramps with sand traps along them. The secondary roads are even worse so stick to the interstates. The weather can turn ugly in a hurry up there in Feb with ice, snow and freezing rain as well, but it usually doesn't last more than a couple days.

 

Sweet tea!! I'm originally from south GA and I love me some sweet tea. I haven't lived anywhere in the past 8 1/2 years that you can get sweet tea when you go out to eat.

I'm going to try bleeding the line to the gauge tonight and see how it goes. Thanks for the advice.

I'm rebuilding the brakes in the truck and I'll be pulling the car on a dolly and not a trailer. I don't think this trip will go too easy (it's an old truck) but I always hope for the best, plan for the worst.

 

Bleedig shouldn't make any difference, there is no way to bleed the bourdon tube inside. The air will simply compress to the same pressure as the oil.

On 8BA's the relief valve is in the pump, so I don't think it's that, since you replaced the pump (the new pump could be bad butseems a stretch if it behaves exactly the same). It might be worth rigging up a pressure pump and pressurizing the system with the intake manifold and pan off, to see if there's a gusher somewhere. It is rare but the oil distribution tube in the valve chest may be cracked or rusted. You could also pull the timing cover to see if the front cam bearing is gushing.

I wouldn't feel too bad with the pressure you've got except that you are going to tow with the truck. That puts a lot of stress on the engine.