The Stovebolt Site Forums The Shop Area Engine Shop 235 Hi volume/pressure oil pump

I was wondering if anyone has used or heard of a hi pressure oil pump for a 235? my truck only has about 9 lbs when hot at idle and about 25 at 3k rpm. It makes me nervous. i had a mechanic listen to it the other day and he didnt hear any bad sounds. any ideas would be welcome. Its a 57 block and has a oil filter installed. no idea of its age but no smoke when it runs down the road.

I wonder if your oil filter, which I assume is a bypass filter, has the required restriction in it.

I don't know. Its the can type that bolts on the manifold. How would i tell where the restrictor is? I can block it off and see if pressure comes up. My mechanic thought a restriction in the screen could cause it. Before pulling the pan I wanted to have a line on a good pump.

Low oil pressure is almost always caused by too much oil clearance at the bearings, rod, main, and cam bearings. A high-volume oil pump is like taking aspirin for the headache caused by a brain tumor- - - -it treats the symptom, not the cause. Once you drop the oil pan, check the clearances with Plastigage, and also look for any scoring or roughness on the surface of the bearings and the crankshaft.
Jerry

235 Hi volume/pressure oil pump

No such thing.

Back in the good old days, the "serious" chevy racing engines used GMC oil pumps. I've never seen any real data on the pump volume vs. pressure characteristics, but based on the gear dimensions the GMC pump might produce about 20% more volume than the Chevy pump. Probably not enough to fix your low oil pressure or to justify the oil pan modifications needed to use the GMC pump in the Chevy.

Tom Langdon, among others, says that there is no need, as the stock Chevy pump has plenty of capacity.

As Jerry says, the low oil pressure problem is probably excess clearance in some or all of the bearings. Or, it could be due to lack of a restrictor orifice in the bypass filter line. Plugging the filter inlet line (if it is a bypass) will show if that is a problem. Did the low oil pressure readings come on suddenly or gradually? The specification documents call for 30 psi at 1200 engine RPM.

Any machinist with more than three brain cells to rub together could fit a small block V-8 oil pump to a 235 in a matter of hours. It would be very simple to adapt the mounting flange and drive shaft with a custom-made bracket. I doubt if it would even be necessary to modify the oil pan. It's just not necessary to go to that extreme if you've got a stock pump in good condition and a properly-clearanced engine.
Jerry

What oil are you using?

cm

1. make the V8 pump tower a few inches longer, so the pump body doesn't strike the crankshaft counterweights
2. extend the V8 driveshaft a few inches
3. make a new custom bracket that attaches the V8 pump's top flange to... to... there's nothing there
4. make a new pressure outlet tube to the 235 pan rail that aligns with the V8 outlet... whoops! The V8 outlet goes back up through the top of the housing
5. make a new suction tube that aligns with the V8 pump port, and clears the crank, etc.

Right, only a few hours.

Just change oil to a thicker grade oil next time. In '65 Pontiac shop manuals said anything above 3 psi was enough oil pressure, in fact the light on the dash came on at 3 or less PSI. I would think for a older engine, your pressure is close enough. Even new they didn't have much more then that. Lucas oil products will thinken the oil and help the engine at start ups, its one of the few oil additives that really works.

Joe

Thanks for all the info. The engine has castrol 10w30 with a can of Lucas oil additive in it now. I bypassed the oil filter and the pressure came up about 5 lbs. cold. Didnt have time for a drive to warm it up. They had a nice show on horsepower about rebuilding a 235 today but I missed what the used for oil pump.Think I will pull the pan soon and see what it looks like in there. Thanks again for info

Bearing clearance changes (increase) are the NUMBER 1 cause of a declining oil pressure reading over time. The cam bearing clearances are generally the main wear area that causes the pressure drop. A sudden change (drop) in oil pressure means a major problem such as oil loss (leak), pump failure, gauge failure. A sudden INCREASE in oil pressure means a spun cam bearing or a clogged/restricted oil gallery.

I think I have seen references to a "Melling" pump for these sixes that is high volume. However, as Jerry says, a high volume pump is not the answer.

I don't know.... A 57 235 should be a full flow oil filter system already and have inserts not babbits, so your oil pressure should be between 20-30 lbs at 30 mph. When I rebuild 235's I always replace the old oil pump with a Melling high volume/low pressure pump. You really don't need high pressure in a 235. If your oil pressure in a 57 engine is running in the single digits it is either a wornout engine (main, rod and/or cam bearings are bad) OR the oil bypass in your oil pump is bad. Your oil pump is the backbone of your engine.

I thought my 250 oil pressure was a little low after rebuilding and using 10W30, so I tried straight 30 wt. Castrol and gained a few psi. I don't remember the numbers, and I don't think I'd trust the dinky little gage anyway, but the change is the important thing.
I also don't think you need 50 psi.

cm

I just checked the Melling website, and they only list one part number for the 235, the "M-45" pump. It's in their OEM listing, so I believe it's a standard-volume item. I'll update everybody when the conversion project is under way. Remember- - - -it takes a machinist to build an adapter!
Jerry

The Melling oil pump IS as OEM-- a high volume/low pressure oil pump--- that the 216 and 235's were designed to have.
The 235 had some variations in a few years (that's why you make sure of what you have).
Here are some links to different 235 "Melling" oil pumps

M-29

M-11

M-45

Those are all just stock replacemnt pumps, only difference is high pressure or low pressure engine application. No "high volume" pumps listed.
Full flow filtration for the 6 cylinders didn't start until 1959, even then, it was only on the 261. All 216, 235, and early 261 are bypass filtration, if equipped with a filter.
If you meant full pressure oiling, that started in '53 with the Powerglide 235, '54 on all others.

I caught most of that one, almost lost interest when they did the "DUB" Taurus segment in the middle of the show. It was intersting, though they're a bit confused on what the engine really came out of originally, and what the truck on the other show is as well. They kept calling the engine a "truck" engine, and even called it a "bus" engine at one point. But the serial number, T54Z, gives it away. It's a '54 Passenger engine, manual trans, built at the Tonawanda plant. That's why it had the fiber gear, trucks use aluminum gears. The truck that it came out of, the Classix project on Trucks! is a '51, not a '48 as they claim.

You didn't miss it. It's the stock pump, which you already have, and it's the largest one that fits.

A high volume pump is the answer for right now, unless you want to run it until you drive over the crank.

Not to hijack the thread but I caught the Horsepower show too and they made quite a few boo-boos.

1) They replaced the mains with the newer bearings without the dowels. The guy said they couldn't buy the older type and filed off the tangs!

2) They showed shims on the main bearings and described them as .009" to make "everything round".

3) They had a crack repair done on the head. One of the regulars then said that it was "pressure tested to make sure the valves sealed correctly".

4)They also showed a shattered timing gear which they claim that they broke trying to pull it off. Now that one I believe!

In the original show on the truck, they described the engine as a 216 and it was quite obvious it wasn't.

Hmmmm- - - - -no dowels, and no tabs, plus no crush fit- - - -that engine's going to spin the bearings in a very short time! What do these dummies do for a living? It's certainly not engine building! Now, if they checked the valve seating with a vacuum pump, I'd buy that.
Jerry

"What do these dummies do for a living?"

That's easy Jerry. They make TV shows, HA. Obviously accuracy or knowledge isn't one of their criteria. This is the place to learn about old Chebbies.