The Stovebolt Site Forums The Shop Area Engine Shop Full flow oil pressure question

Late 57 235 w/848 head.
I bought this motor from a gentleman who had it rebuilt from shop a few back(shop owner passed so now closed). Gentleman said he ran the engine in a pickup for a year or so, ran excellent, but wanted to go with a Chev 350. From the pic you'll note there is a spin on filter. I asked him if this mod was done complete? He had no idea. Said the old machinist did it as a upgrade. From the pic you'll notice the forward 1/8" port was plugged and a 3/8npt was drill next to it. The rear port was drill out to 1/4npt. From what I've researched, this appears to be full flow from the outside. They used 3/8" rubber hose. I would prefer either hard line or at least steel braided/teflon lined. I could even increase the house size, thinking I would get more/less restrictive flow.

Q:1- If you notice the IN/OUT arrows on top of the remote filter top, the IN comes from the forward plug on the block and the OUT goes into the 1/4" rear port that originally held the oil pressure to instrument gauge line. I've seen this mod calling the forward port as incoming pressure and the rear being drain. And I've seen others state the REAR port is the pressure and the forward port being the drain????? Does anyone know for absolute certainty which is which? Or does it really matter either way as some others believe?

Q:2- There is no "restrictor" in this setup. I've read some say not to on a true full flow and others say it's required so not to lose pressure and starve the system. Keeping in mind this engine ran for approx 3000 miles and the gentleman I bought it from seemed very honorable so lets presume that's not an issue.

Q;3- Is there a problem with me replumbing with larger lines?

Thank s in advance guys,

You'd have to pull the pan and see if the oil pump outlet is plumbed directly into that forward port and into the filter. Unless it is, that's not a full-flow filter setup. The line size is a bit restrictive IMO.

I wrote a long post, and the internet gremlins ate it. Yes, you have a full flow setup. The rubber lines are a disaster waiting to happen, and there has been some internal modifications to the block. Drop me a Private Message and I can explain the procedure in detail. There have been a few serious mistakes made on your engine that really need to be corrected before you try to run it.
Jerry

PM sent

Here some pics of the 235 I built years ago & converted to full flow. No longer running this engine, (grey engine) in storage now.
Put '59 261 in a few years ago. Had local NAPA build weather head hoses to spin on filter base (alpine green engine).

BC's steel lines are the safest bet. Less likely to blow out and drain all the oil out of the engine than rubber hoses, although hoses rated for hydraulic system pressure would be pretty safe. If the engine were disassembled, enlarging the tapping on the oil rail (rear one) would help with flow, but I wouldn't try to drill and tap that one larger with the engine together. I'd be afraid of getting metal chips into the engine bearings. Getting everything up to that point a bit bigger would probably be OK.

I would use CuNi because it’s easy to bend, flair and will easily hold the pressure.

Thank for all of your replies. Appears the orig builder did do a proper full flow mod. However, for whatever reason, enlarged the rear(drain) hole from 1/8 to 1/4, rather than 3/8 as many noticed. And drilling that out and retapping ( although a pretty easy job) would be difficult removing ALL the chips So I guess ill just roll with it and hope flow and pressure are adequate.
Thanks again for all the help

I hope HRL (Jerry) makes his comments public at some point. It could save someone from disaster.

I'm not particularly fond of doing the "full flow" modification to a stovebolt engine. With the right kind of bypass filter, the oil gets more, and smaller particles of debris strained out- - - -it just doesn't happen all at once. A full flow filter has to have filter media that's open-weave enough to allow a high volume of oil to pass through it- - - -enough to lubricate the engine properly once it gets through the filter. For that to happen, it must allow some of the smaller particles of debris to pass. I'm in favor of filtering oil a little at a time, and doing it with a filter media of around 1 micron. That's approximately the size media that's used in industrial hydraulic oil filters, or maybe Diesel fuel filters. To strain oil that well, the volume must be pretty low. A bypass filters system bleeds off a small volume of oil, sends it through a 1/16 inch restrictor orfice to avoid oil pressure loss, filters it efficiently, and dumps it back into the oil pan, or in the case of a spray oil engine like a 216 or early 235, sends it to the rocker arms. All the oil gets filtered eventually, just not every time it cycles through the oil pump.

Millions of stovebolt engines were sold with no oil filter at all- - - - -a filter was an extra cost option sold by dealers. That's why stovebolts (and other car makes) used flex lines to and from the filter- - - -it gave dealer mechanics a few options about where the filter got located, and gave a flat rate mechanic a quick way to install a filter after the car was sold, before it was delivered to the customer.

To make a stovebolt engine (except for later model 261s) a "full flow" filtered item, an internal oil passage must be plugged between the oil pump and the main oil gallery, and at least two holes must be drilled and tapped into the block. That's best done during a complete teardown to a bare block, so all the drill and tap debris can be thoroughly flushed away. It's not a project to be attempted by someone who does not have a very thorough understanding of the stovebolt oil system.
Jerry