The Stovebolt Site Forums The Shop Area Engine Shop Do I have a full flow oil filter?

I have a '53 Chevy 3100 and the PO installed a 261 in it. I never met him and bought the truck at an estate auction after he died. He also installed an oil filter though I don't think the engine is set up for full flow filter operation. I know that if the diverter pin is depressed then it's full flow but my problem is that there is no diverter pin. Instead, it looks as though he tapped the hole and installed a screw - and the head extends beyond the block, of course. I've included links to photos below showing the pin before and after the engine was painted and would appreciate your expert opinions. Seems to be that the oil filter is eye candy only. Am I wrong? Thanks! https://www.dropbox.com/s/17s1lfve55ypg42/Engine%20painted%2010-2016.jpg?dl=0 https://www.dropbox.com/s/e4y1v1oi13aqdh9/IMG_3069.JPG?dl=0 https://www.dropbox.com/s/5xm53upkbp69h6b/Diverter%20pin.jpg?dl=0 https://www.dropbox.com/s/asjnjk4grm99trs/oil%20filter%20.jpg?dl=0

Full flow oil filter would have half inch lines from the block to the filter housing. What I'm seeing is a set up for a by pass filter.

Denny, that's really interesting. The 261's that I have in the shop have the dowel, the 1/2" threaded hole beneath them that yours does, and a 1/8" NPT threaded hole to the left of the 1/2" threaded hole. The 1/8" NPT hole is not connected to the oil galley and drains directly into the oil sump.

IMHO, the only real bullet proof way to tell what you have will be to pull the plug from the dowel hole. Not sure why it was added unless the dowel was drilled out for some reason. When you pull the plug, if there isn't something (such as a dowel) pushed in to block the oil galley, then you are set for bypass filtration. If there is a dowel behind the plug pushed in to block the oil galley, then you are set for full flow. Maybe the dowel was leaking and the plug was inserted to stop the leak? Regardless, I'd want to check to see what, if anything, was behind the plug.

And as Roy Rogers points out, a full flow should have 1/2" lines...but I wouldn't trust the size of the current lines to be the determining factor. I'd check behind the plug.

Matt

Could you get the case # above the starter? I have a '54 early '55 high mount water pump 261 setting in my shop, only set up for by-pass oil filter, no full flow ports drilled or tapped.

Early 261s did not have the 1/2" holes, don't remember what year this changed. Also this set up would only come with the bypass type filter, still a great motor for your truck!

1958-1963 261s had the capabiluty for a full-flow oil filter (1/2" ports on the block. Some 58-63 261s can be set up with by-pass or full flow (and if they came with no filter, they needed no filter. If a 261 ever had a full-flow set-up, it has to always ever after have a full-flow set-up (or have an external line connecting port holes).

Post head&block casting codes and date casting codes.

That engine in the first posts looks to have a by-pass oil filter and by-pass 3/8" lines and block ports.

Sorry that I forgot to post the casting codes. It's a 1960 261 block with a '56 235 head. The codes for the block are: 3769717, D 14 0 (April 14, 1960). Head: 3836848, C 14 56 (March 14, 1956).

So if I do have a by-pass filter, does it do much good? I guess there's no reason to remove it but I still change my oil frequently, ~ every 1000 miles or so.

Looks to me like the block has the 1/2" oil ports,but has reducer bushings in the block where the oil lines are. I would take that plug out and see what is there. That plug looks rather large to be replacing the dowel pin.

The by-pass filter works fine.

3,000 miles between oil changes would be fine.

Some people who do not drive 3,000 miles per year change their oil/filter every year.
When I live up north, I changed the oil/filter on my old trucks just before winter hibernation.

Oops, now this will get interesting.

Ok, now I'm really curious. I'll pull that plug this weekend & post a photo of what's in there. Thanks much for all your comments. This is so helpful.

Ok, guys, after many attempts with a long bar over a 1/2" wrench, I can't budge that plug. I don't want to heat it up as the engine is painted. I'm going to invoke the "let a sleeping dog lie" rule & assume that it's a by-pass filter. It's working fine & I learned some stuff from this thread. Thanks!

Your third photo is a by-pass oil filter. Someone might have used that incorrectly connected to the full-flow ports. Oil would flow through it, slowly, but at full pressure.

One other possible problem would be if the filter got plugged - that would stop all internal lubrication. If you use that set-up, you should place the oil pressure gauge line on the outlet side of that filter.

Denny, be sure to get it right- when first I got my truck, my 261 was set up with a bypass filter and it was a full flow engine... a low mile rebuilt engine that suffered oil starvation at the top end....all because the lines were too small.

Great points. I do have the oil pressure gauge line on the output side of the filter & watch it closely. I wish I could get that plug out but it won't budge. Thanks for all your input.

Denny, there might be an easy way to check. Do it outside so that you don't paint the walls of your garage with oil.

The circuit is reversed for the oil filtration when you push in the dowel. What I mean by this is that the flow for a bypass filter (dowel out) goes from the oil pressure gauge fitting (feed side) to the filter to the fitting in the block that drains to the sump under the dowel (return side). When you push in the dowel for full flow, the flow goes the other way. The feed side is from the fitting under the dowel to the filter (or not) to the return at the oil pressure gauge fitting.

Be prepared to shoot some oil everywhere, but you should be able to spin your oil pump with a drill with both of your existing lines disconnected. If you get a geyser from the oil pressure gauge fitting, the dowel is out and you are set for bypass. If you get the geyser from the fitting under the dowel, the dowel is in and you are set for full flow.

I mention 'or not' above because you don't need to have a filter with the dowel in the full flow position, but if you don't have one, you still need to have a 1/2" line connecting the two ends of the flow circuit or you will starve the engine of oil.

The shadetree approach given above might not be bullet proof, but I'd sure trust it more than just guessing!

Remember, if you try this test, you'll shoot oil everywhere out of the open fitting(s). I know from spinning one up and accidentally not having connected one of the lines!

Matt

I see no value in using a 1/2" line, if both "ports" on the block are indeed 3/8".

Denny, are those ports/holes 1/2" NPT or are they 3/8"?

After again reading Matt's post, I'd like to change my advice regarding where the oil pressure gauge line goes. It should be on the output side of that filter canister. If you indeed have it running/flowing full-flow, the output port would be on the right side of the canister/block.

Referring to Tim's post, the oil gauge connection location is the easy part that doesn't get confused...it is in the same place regardless of full flow or bypass! That is, if you use the 'standard' place to connect the oil pressure gauge...to the threaded hole on the lower left rear side of the engine. The direction of the pressurized oil is reversed (bypass is pressurized with an outward flow from the oil galley at that location and full flow is pressurized from the filter and has an inward flow toward the oil galley at that location), but the gauge doesn't know the difference or care about the direction...it just measures pressure! That particular fitting is pressurized with either type installation. Sure, there are other places you can connect the gauge, but no need unless you really want to make a change.

Matt

If I wanted to be sure my full-flow filter was not clogged, I'd want my gauge reading at the output side of the filter.

Tim the ports are both 1/2" with reducer bushings in them for 3/8" fittings. I like the idea of checking which port shoots out the oil, Matt, but I need more coaching on how to spin the oil pump with my drill. Thanks.

Denny, you'll need to remove your distributor. The bottom of the distributor shaft is ground to look like the tip of a wide blade slotted screwdriver. The blade on the shaft fits into the slot of the oil pump. That's what makes the oil pump work...a gear on the camshaft engages a gear on the distributor shaft to make it turn, and when the distributor turns, that makes the oil pump turn.

To engage the oil pump with the distributor removed, cut the handle off a long flat blade screwdriver with a large head and insert it into an electric drill. Stick the tip of the screwdriver into the slot on the oil pump and pull the trigger on the drill. That engages the oil pump and you'll pressurize the oil system.

Instead of using a cut-off screwdriver, you can also use the shaft off an old distributor (that's what I use) or you can take a length of 3/8" threaded rod or a length of 3/8" round stock and grind the end to create a flat tip.

If you search the topic on this website, you'll get lots more information about pressurizing the system with an electric drill.

Matt

Got it, Matt. Thanks. I'm going to convert to HEI soon & will check this when I pull the distributor.

I took a length of pipe with an outside diameter slightly less than the inside diameter of hole where the distributor goes. I then welded big washers on each end of the pipe. The washers have holes in them the same diameter as the shaft which engages with the oil pump (I used an old distributor shaft). This setup works on 216, 235, 261, small block and probably many others. The shaft is held in place very securely for worry-free spinning with a drill.

If you have an old distributor, just remove the drive gear.

Put the distributor into the block and turn the shaft a little until it drops into the pump's slot.

Then, you can use a socket attached to a drill to spin the oil pump.

Ok, this is probably a dumb question but wouldn't it be easier to simply disconnect one of the lines off the oil filter & turn on the engine? Seems to me that I'd see oil either spurting out of the line or the block depending on whether it's full flow or bypass. What am I missing?

I think you will find you have equal oil pressure at both ports the filter is attached to with that setup.

Yes, regarding Dave's post.

And, by placing the oil pressure line in the output side of the filter, you would get a reading that assures you that you do not have a clogged filter unit. That is where my 1960 and 1959 261's had their original oil-pressure line attached.

I remember you mentioning that previously.
Makes me wonder how any oil is filtered at all like that.
Maybe it only filters "snake oil"...
Carl

On most bypass filters there is no resistance to the flow on the outlet side, the oil just dumps back in the pan.
On this setup it looks like the filter will do nothing but fill up.
216's are where I learned what a waste of money filters are on them. There is only a pressure differential between inlet and outlet at idle.

Yes, but the oil filter add-ons helped to keep the dealerships in the black.