Just got the gages on the F2 working, it is converted to 12V and has a cluster of S-W gages someone added long ago. The oil pressure sender measures 200 ohms with the engine OFF and decreases to about 50-100 ohms with the engine running at high idle about 1200 rpm, COLD. Does anyone know what it should measure? I'm getting a reading at the gage but it seems low. Seems like the resistance should change more than that. Maybe I should add a mechanical gage like on my Hudson? The engine runs well with no hint of knock or smoke.

The water temp gage appears to work right but there is an obviously new sensor on the cylinder head.

thanks again!

Tom

 

Tom,

Don't know what range the resistance should be, but sounds like the sender is working. If you have a mechanical gauge you could hook up temporarily to verify pressure, that's what I would do. I've always had more confidence in mechanical gauges than electrical anyway. What pressure are you reading at the gauge?

 

The gage reads low, 20 or so at fast idle right after startup, drops after warmup in 5 to 10 min. I think pressure is good because when the oil filter cap was loose there was quite a spray out the top of the oil filter!

I'm thinking the calibration must be off. Looks like a stock sending unit with an aftermarket 12V gage.

By the way, I was shocked that the starter spins the right way whether the truck is hooked up positive or negative ground. the gages only read correct one way (negative ground) however.

 

I agree the gauge is probably reading low. Most any engine at startup should hold 30-60 pounds of oil pressure. Unless you can find the correct 12V sender for your old SW gauge, I would change out the gauge AND sender...

 

That's probably what I will do. Does the sending unit have standard threads into the engine or is there a secret to removing it? Since it's a standard size gauge I will look for a mechanical replacement.

Thanks!

Tom

 

Tom,

I can't recall what the stock one looked like. I got rid of my old flathead some time ago. Most of the senders for newer engines require only a pair of vice grips to back them out. I think the threads might be pipe threads, but don't remember for sure.