The Stovebolt Site Forums The Shop Area Engine Shop By-pass oil filter?

The PO installed a 261 block with a 235 head in my '53 3100. The oil filter canister doesn't drain when I change the oil so I suction it out. How do I know if I have a by-pass filter? See an image of it here: https://www.dropbox.com/s/btpy0d80orn5ohx/Oil%20filter%20cannister.jpg?dl=0

Thanks for any help!

The bottom return line looks like it's plumbed as a bypass filter. The pressure line that comes in near the top also appears to route like a bypass but can't tell by the pic. To be positive a pic of where the pressure line attaches to the block is needed.

The canister is a bypass type also.

Odds are it's a bypass filter but it could be "made" to look like one to try to look period correct.

Dave

It would be nice to know the year of your 261. If it is 1958-1962 you 'could' have a full flow system. If it's older, then it's bypass unless it has been specially machined. Very likely like Dave says its a Bypass system.

Lots of information about your engine here:

http://devestechnet.com/Home/TheVenerable261

I just added something I was very fortunate to stumble on. How long is the dowel pin that is pushed in to switch from bypass to full flow on the 1958-62 models? 1-5/8" woohoo!

The 261 is from a 58-62 model and that's why I'm wondering if it has a full flow system. Here's another picture: https://www.dropbox.com/s/pmql4hm2tlu78u0/IMG_2919.JPG?dl=0
Thanks much for your help!

Right now no. Its using the smaller bypass port. The port above where that hose is connected to the block is larger and it would have to be attached there for full flow. BUT.. that isnt all. There is a dowel pin above the larger connection. It looks like a round hole with a plug inside. That is the dowel pin. Look over the document I linked earlier to learn exactly what you would have to do.

Just for the heck of it, try to ID your engine.

Look-for and post-here the following codes:

1. Engine Serial Number
2. Block casting cde
3. Block date casing code
4. Head casting code
5. Head date casting code

It is supposedly possible to use either a full-flow or a by-pass flow oil filter (or, no oil filter) on a 1958-1963 261 engine/block.

Engine serial # F0421LB (Flint, April 21, 1960, C60 basr engine)
Block casting # 3769717
Block casting date D140 (April, 14, 1960)
Head casting # 3836848 (from a 235)
I don't have the head casting date yet

Yes:
F0421LB
F = Flint
04 = April
21 = 21st
LB = 235
Note (for others reading this): 1960 is not indicated/designated in this engine serial number, but the block date casting code indicates 1960 (as DJMTruck posted).

My casting code chart shows 3769717 as a 1958-63 261 block (3769716 is shown as a 235 block). My chart is probably wrong, because the 3836848 head is a 235 head used from 56-62, and the Engine Serial Number indicates base engine, 235.

3769716 is a 235
3769717 is a 261
Both are 58-62. The end date is arguable since I have a replacement block that is dated 1964, but they stopped putting them in new trucks when?

Numbers above were taken off engines I have in the shop.

Replacement blocks could be dated with years after the 1963 regular production end-of-261s used as regular/optional engine.

I believe that it's a 261 block as the casting number indicates, with a 235 head as it's number indicates. According to the 1960 Chevy Truck manual that I have, the LB suffix is a type designation indicating that it is the base engine in C-L-S 60 models. I will check the oil flow divertor ppin to see if it's pushed in for full flow operation. If it's flush, I'll assume that this is a by-pass filter. Thanks for all your help!

With those tiny oil lines, the engine wouldn't have survived the first test drive if it was set up for full flow filtration. There's a reason Chevy used 1/2" flex lines on the full flow filter.
Jerry

The oiling/filtering system of a 'late' 261 is a bit confusing as it could be set up for no filter or bypass or FULL FLOW FILTER! Depending, this is where it gets goofy; there is a pin on the side of the block near the rear 1/2" NPT hole and if this pin is 'IN' just over half inch she's FULL FLOW ONLY (must have a proper filter, no filter destroyed motor) that can handle this much oil, not the skinny lines in your picture. Now if the pin is 'OUT' meaning flush with the block it's not full flow filtering or any filtering.

I am just at the stage of starting my high oil pressure 235 out of a 1954 3100 (unknown history and not completely assembled). The engine had a bypass filter that looked like it was set up for a car of the period, but it was not hooked up, no T on the outlet just opening for oil pressure gauge. I had a bypass filter on the 216 I am replacing, same as the one from the first post, same line size and locations. This filter only has one small hole half way up the central post and filter sits in a 3 inch bath of oil. The supplied top cover gasket from the new filter cartridge was not large enough so I used the old one. Cranking the engine I noticed a leak at the lid of the oil filter.

I took the oil filter feed line and connected it to the return on the engine (no filter).

A couple of questions;

- should I be using this filter and these size of lines?
- what did a normal high pressure 235 in 1954 without oil filter look like? all internal passages?
- would a 235 of this vintage have the pin mentioned, I could not see it.

She did start and run after unknown years that is until the water pump gave out.

A couple of questions [regarding a 1954 235 engine];

1. - should I be using this filter and these size of lines?
2. - what did a normal high pressure 235 in 1954 without oil filter look like? all internal passages?
3. - would a 235 of this vintage have the pin mentioned, I could not see it.

1. You my/can use it.
2. There were two sizes and thus 2 GM/AC style filters (By-Pass Oil Filter Tech Tip) Any other AC or other manufacturer's by-pass filter could be used.
3. What pin; mentioned where? The 58-63 261 has a pin/plug - maybe that is what you are referring to? There are no pins like that on a 235 engine.

Any 216/235 can have (or, have not) a by-pass oil filter.

Once a 58-63 261 has a full-flow oil filter, it MUST have a full-flow filter OR it MUST have a full-flow line between the oil-filter ports on the block.

Thank you for the clarification.

Good luck, Nick D

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