The Stovebolt Site Forums The Shop Area Engine Shop 261 Full Flow Oil Filter Plunger

** I dropped my 261 engine mfg. date 01-1963 off at Allard Machine in Ennis Texas yesterday for a complete rebuild. While loading it for transport I noticed the plunger that is said what makes it a bypass flow or a full flow oil filter system was flush with the engine block. ** My question what should be the position of the plunger for a full flow oil filter?? I've seen it posted both ways {plunger in & plunger flush} for full flow. I plan on using an orig. full flow filter so I thought I had better ask the experts as to what position the plunger should be in for a full flow oil filter. Many Thanks To The Experts. Your Time And Effort Is Greatly Appreciated.

I am not an expert, marzac,

I have read here that on a full-flow 261 engine, you cannot (easily) go back to by-pass-only flow.
My somewhat logical conclusion is that pushing the plunger/plug inwards, results in full-flow filtration.

Wait to hear from others.

I have a 261 with full flow but I don't remember a plunger when I installed it in 2004. Is this a bypass valve so the oil filter is bypassed on cold startup? I have a NAPA 1072 spin on filter which has its own bypass valve.

To get full flow filtration, push the plunger IN until it bottoms, about 5/8" or so. It will be extremely difficult to move, and hammering on it with a big flat tipped punch and a BFH runs a distinct risk of cracking the block casting. I'd suggest drilling and tapping the plug, pulling it out of the block with a long bolt and a spacer, and either fabricating a new plug that's a very snug slip fit, or polishing the original plug a little. It would be wise to pull the plug out in any case, to do a very good job of cleaning out any sludge that has deposited itself in the passageways over several decades.
Jerry

You could not have picked a better machine shop than Allard's. I started using them in the 60's when Jimmy was a young guy working for his dad, Walter, who was a genuine genius. He invented the cam grinding machine that made racing cams possible. Before that each machine was set up to grind one kind of cam only for one engine only. He also built a half a sbc for his midget years before anyone heard of SESCO and his last midget engine was a Vega short block with a single overhead cam hemi head. He made it all from scratch including the hemi pistons. I bought a super modified from Jimmy and years later he bought it back to make a nostalgia racer (picture). One of the few places that have both an engine and chassis dyno.
Check out the wall of plaques and awards in the shop.

[img]https://i.postimg.cc/NyZxRcZT/winged-modified-001.jpg[/img]

Just had an idea- - - - -instead of hammering on the slide valve, how about using a big C clamp or a ball joint press to push it into the "full flow" position? With the oil pan off, that should be a good possibility, depending on the shape of the crankcase on the inside.
Jerry

** I failed to mention to Jimmy that I wanted the plunger positioned to the full flow oil filter position so I will visit him again today. When I dropped the 261 off at Allards Jimmy said he had not had a 261 in his shop for a long time but had rebuilt lots of them back in the day. After my first visit with him I have no doubt that Allards Machine Shop was a great choice for the over-haul thanks to a fellow Stovebolters recommendation.

I am not sure if you are building the motor as a restoration or not but I will just mention that the stock truck 261 oil filter had issues. Apparently the full pressure was sometimes too much for the hoses and they would fail spraying hot oil all over the place, including on to the exhaust manifold. If I remember correctly, it was not necessarily anything to do with the housing or filter itself, but with the hoses being too close to the exhaust manifold on the big trucks, the heat causing the rubber to fail, even with the steel shield. I have been told over the years that there was a service bulletin on this but I will be darned if I can find it. Just food for thought when it comes time to select some lines for the filter housing.

The original equipment in some years was a metal "stand off" tube from each port on the block (maybe started being used in later years). A heavy duty hose was used between the stand-off tube and the filter head.

I do not think that my 1960 and 1959 hoses had those stand-off tubes.

I think I might have used 3" stainless steel pipe as stand-offs?

I'd suggest using 1/2" X 4" NPT black iron pipe nipples in the block to clear the exhaust system, and "single braid" hydraulic hose for the flex lines. It's rated for 3000 PSI working pressure with hydraulic fluid, so engine oil pressure shouldn't bother it at all. Any hydraulic shop or farm supply store, and most NAPA stores can custom make that hose to any configuration you need.
Jerry