The Stovebolt Site Forums The Shop Area Engine Shop 261 engine identification and oiling question

I picked up a 261 from a 1957 6400.

The casting number on the block is 3769925 which is for a 1958-62 261. The original color was yellow, indicating that it is a 1957.

It has threaded holes that are plugged for the oil feed line fittings inside the side cover.

It has 1958 and later solid lifters with the groove in them.

The rocker assembly is the 1959 and later version with the offset oil hole in the rocker arms and the short, pinched off oil feeder.

It had a drilled head bolt in the correct location to feed oil to a 1958 and later block that has a 1957 and earlier rocker arm assembly.

It had an auxiliary oil line from the oil pressure gauge fitting in the block to the fitting on the upper right hand center of the head.

I know that lots of these things can be mismatched over the years, but I have a few questions that I'm hoping for some help with because some of this doesn't make sense.

Did the later 261's with the oil feed inside the block casting still have the oil feed tube fitting holes threaded into the block but plugged?

Any reason for the drilled head bolt with the configuration described above?

I have heard that Chevy would continue to use some parts until they ran out or put new parts on the assembly line if they ran out of old ones as changes were supposed to happen with new model years. Is it possible that they ran out of 261's in 1957 and had to put the newer 1958 version into a 1957 truck? That could explain the yellow paint.

The other casting numbers on the block are CON3 and A104. I haven't decoded those yet.

Any help would be appreciated. The insides of the engine appear to be in incredibly good shape, so whatever was done appears to have worked well.

Thanks,

Matt

Got any photos of this engine? Would love to see original yellow color.

Perhaps the mismatch dated parts were replacements during the previous life of the engine?

The 58-62+ has 1/2NPT full flow oil ports on the side and a dowel pin that allows you to choose which you want, Bypass oiling or Full Flow. You can read alot about this engine here:

http://devestechnet.com/Home/TheVenerable261

That is a very good engine. Not sure why the parts are mixed and matched other than necessity at some point in time.

Your Date Code A104 indicates January 10th, 1964.

Does the block have a factory serial number stamped into the machines surface at the distributer? What is it?

Mike B

Sweet, here is a close-up showing some yellow underneath the Chevy orange.

http://s844.photobucket.com/user/matthewronaldsaunders/media/261/IMG_1318_zpsiifxozvj.jpg.html

Mike, I couldn't find the serial number on the machined surface next to the distributor when I looked earlier today but will check again when I have a wire wheel and a flashlight to help.

Deve, that is a great article and one of the reasons I began a hunt for a 261.

Sorry, I should have included in my initial post that this one has half inch fittings, but the dowel is flush with the block. It had a bypass oil filter on it. The top half inch fitting is a galvanized plug that was drilled and tapped to fit a smaller size to the bypass. Pix below--

http://s844.photobucket.com/user/matthewronaldsaunders/media/261/IMG_1316_zps15yuhzif.jpg.html

http://s844.photobucket.com/user/matthewronaldsaunders/media/261/IMG_1317_zpsgfshczrw.jpg.html

Thanks,

Matt

Yeah, lots of people have 261's configured for bypass filtration. That is exactly how it's done. Pretty exciting for you I am sure. Two issues if you decide to go with full flow filtration:

1) Going with 100% filtration, and push in that dowel, it is a blind hole and there is no easy way to pull it back out.

2) From that point on, the front outlet MUST be connected to the rear inlet. (even if through a filter). There is no capping off the outside lines.

I am a full flow fan so i do it and don't look back, but that's why I directed you to the article so you can decide for yourself. Have fun with your new engine Matt!

BTW, if this is a 1964 engine, it could very well be a replacement block and there may be no numbers on that Flat area beside the Distributor at all. That's how mine is.

Deve, I would rather go full flow. Is the dowel hard to push in? I don't want to damage the block. But if I can push the dowel in, I will go full flow.

It would make sense if it was a replacement block. I checked for a serial number again. There aren't any numbers on the flat machined area by the distributor. The block does not seem to have the yellow paint underneath that the rest of the parts like the valve cover and oil pan do.

Thanks for your help,

Matt

I have read alot about that. Some people on the internet felt it was dangerous and could crack the block. Of course this is one of those things that could happen.

Everyone who has followed these instructions so far have had good luck with no problems. Me and two other guys have been successful that I know of so far.

1) Use a very solid drift Punch that has at least a 3/8" flat end. The dowel is about 1/2 inch but is so close that 1/2 might be too large. Get a nice long punch and then use a large size hammer.

2) Mark the end of a screwdriver, safety wire, paper clip, whatever .63 or 5/8" from the end with tape. You need to be able to gauge how deep you are. You do not want to hit too hard when its already bottomed out.

3) Get a good grip on the punch, hold it centered on the dowel, and take about a half swing at first. See if it budges, then use your head on how hard you need to hit it to make it move.

4) When you get close to the mark, slow down and move it slowly. You have to be all the way in to cover the internal hole, so be sure you are exactly .63 from the edge of the block and the end of the dowel.

Heat will not help you because you can't avoid getting heat on the surrounding area, however, if you can't get it to budge, don't damage the dowel, rather heat it up and then try again. I didn't need heat and my friends who did it did not need it either. Good luck and be sure to let us know when you are done.

Deve, thanks. It was the stuff that I read on the internet about cracking the block that had me spooked. Your instructions give me the confidence to do it.

Thank you,

Matt

I gave up attempting to drive that dowel in on my '61 motor. Probably the best method would be to drill it out, also I was thinking of threading the hole so you could remove it at some point? I'm sure someone here has a better method re. moving this pin. Maybe pre68Dave will come along with his 2 cents?

Here's how I'm planning to address the situation when I build my Cadillac stroker engine. It will have two filter systems, a Frantz bypass filter to actually clean the oil, and a full flow spin-on filter to catch the rocks, marbles, bowling balls, and other big chunks.

My 261 block has the big ports and the dowel pin, which is currently in the bypass flow position. I'm going to drill and tap the plug so I can use a slide hammer to remove it, and then tap the hole for a 9/16" bolt all the way past the oil passageway. I will thread a bolt into the hole until it bottoms out and use some blue Loctite to retain it. There is a very simple way to swage an Allen hex hole into the bolt after cutting the head off so there won't be an ugly bolt head sticking out of the block, in case I ever decide to remove the threaded blockoff plug.

This procedure should ONLY be done with the block stripped down to bare bones so any chips from the threading process can be thoroughly cleaned up.
Jerry

Let us know how that drilling and tapping idea turns out. I am honestly curious because that dang thing is in there so tight I can't see threads holding up with the slide hammer. Then, how are you going to get both at the same time? (bypass at the same time as full flow)

What Chevy could have done instead is to just thread the hole and use an allen set screw with the proper length to turn it out flush (bypass) or in all the way for (full flow).

As it is, the dowel passage is 1-5/8" long. The dowel itself is 1 inch long. There is really no reason that plan won't work. (except that 1 inch is TIGHT - ask JiM)

If I can knock in the dowel, I will convert it to full flow with a new spin on filter assembly and will probably leave the original bypass oil filter for looks. Kinda gives me belt and suspenders as Jerry points out above. I was thinking that I would take the feed line to the bypass from the oil pressure gauge fitting at the block and return it using the smaller threaded hole in the block next to the 1/2" return hole that is currently plugged.

If I convert to full flow and tee into the oil pressure gauge block fitting to feed the bypass, will I reduce the primary oil flow to the new filter too much and starve the engine? Would I be better to plumb the feed line to the bypass filter from the return line of the full flow filter? The return lines from both filters would go into the two separate, different size return holes that are next to each other on the block near the dowel.

Thanks,

Matt

Plumbing a bypass and a full flow filter is simple for anyone with more than three brain cells to rub together. Cummins Diesels ran that way for several decades. Ditto for operating a slide hammer. It's about as basic a tool as anything, and using one is a piece of cake for anyone who has ever made a living fixing cars.

Starving an engine for lubrication while pumping oil through a 1/16" restrictor orfice is about as likely as finding a chicken with lips.
Jerry

Jerry, I was hoping you'd respond...got my answer!

Working on cars has always been a hobby for me, so I appreciate and have a great respect for the knowledge from the professionals on this site.

Matt

Yeah, just remember that the front hose fittings are the pump outlet. In other words, oil is picked up from the oil pump and pushed into that front fitting, then through the filter, then to the back hose and inlet to lubricate all of the engine. Direction is sometimes important in planning these things. With full flow, nothing happens until the oil passes through the back inlet. Its a good idea to carry around a length of hose and fittings to bypass the spin-on filter in case of some unforeseen problem so you can connect them together to get where you are going.

In hooking them both up, I am not sure how much oil will make it through the bypass. Same as without a full flow connection, or much less to none since there is no restrictor in the full flow line. Depends on volume and pressure and I haven't tested to see if you would get any flow through the bypass without slightly restricting the full flow. Might look nice but it would be interesting to hear from others what they think would happen as far as functionality.

There's a subject in most high school and even engineering school curricula called "physics". It would be wise to spend some time studying it as it pertains to situations where pressure and volume is concerned. Why would the rate of flow through a bypass filter be different, given a particular amount of oil pressure and the same restrictor as before the full flow filter was added?
Jerry

I wouldn't be so sure. You are making a hole with more than 5 times the volume where there wasn't one before. I can't see that having no effect. The path of least resistance and all. No, I would want to test what happens since you are using the same pump with the same pump characteristics but asking it to move way more volume through a much bigger tube. Since a bypass system notoriously moves about 12%, adding a much larger opening HAS to reduce that number.

I would offer to do an experiment, but I am sorta busy these days with other things. Maybe someone else could?

Someone with a better vocabulary than I have needs to explain the difference between a "series" and a "parallel" circuit, and it works the same way whether it's happening with electricity or liquids. Of course, there's always the possibility that there's a little bit of deliberate obtuseness going on here, which I'd rather believe than the other, more serious possibility.
Jerry

I sent pre 68 Dave an PM ... hopefully, he can add to the discussion.

Peg

No, in Series or Parallel, there is a demand that takes place. It would matter depending on how you go about doing it. The 261 was designed EITHER full flow, or Bypass. As far as I know, nobody has ever tried them both at the same time. I love to learn new things, and from anyone who can contribute and be nice about it.

The simplest way I can understand plumbing both filters at the same time:

Plumb the two filter units in parallel - both units will get/take what they can handle (assuming basic physics applies).

DO NOT plumb the two filters in series.

Instead of continuing to rant, post a diagram of how either/both of you think this would work.

Otherwise, each of you might want to look in the mirror and privately rant to yourself.

As far as I am concerned:
- just use a full-flow filter, if your 261 is set up for one
- just use a by-pass filer, if your 261 is set for one

Unless, you do high-revving (4000+ RPMs) for extended periods in a dirty environment (maybe while sitting still, using a PTO).

Thanks,

I just took an oil pan off my Project1959235 engine after about 50 hours of operation. Since I modified it for Full Flow and put a Wix 51515 Spin On Filter on it, I wanted to see what was in the bottom of the pan after a brand new rebuild. If it were a standard bypass rebuild, one could expect a gray, bearing dust and crud at the bottom of the pan. This is perfectly normal. What I saw instead was a perfectly clean oil pan. Nothing but your normal yellowy oil (high zinc breakin oil). CLEAN CLEAN CLEAN. If all that full flow system does is filter bowling balls and marbles, its news to me. PROOF without any shadow of a doubt that full flow is clearly better in the long run. I credit the quality of the filter. WIX does the best job I think.

The proof is in testing, focusing on the issue using modern technology to ensure the process you use to test is legit, and not having blinders on.

I PROVE my results through additional tests, then provide the results both here and on my site.

(click on it - and, chill)

I had locked this thread down but thought there may be more constructive advice offered for the issues brought up in the initial and subsequent questions.

So, instead I edited out all the unnecessary, personal comments.

This topic was the subject of a thread back in 2008. Here are a couple excerpts:

_____________________

You could use the bypass filter in addition to your full flow filter if you wish. I personally don't think it would be worth the effort but it is interesting to note many heavy duty trucks have a bypass filter as well as a full flow filter.

You would need to find a source of pressurized oil somewhere on the engine and return it to the pan somehow. Again, I believe the work involved would be more than the benefit you will get from it.

_______________________________

Different engine, but here is a picture of just that:
http://rides.webshots.com/photo/2582718360080251109SqwKSM
The large white filter on the left is full flow, and has 1" lines to and from it. The black filter on the far right is a bypass filter, it gets pressure from the outlet of the full flow filter, and returns very clean oil to the engine via an extra dipstick hole.

__________________________

I was not able to open the pictures. Here is a link to the discussion--

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=454342

It makes sense to plumb it as described above. This should keep the flow the same as it would be if the full flow filter was used by itself.

Matt

Yeah, good job in doing the research. That is what all of us who try to organize documentation spend most of our time doing, but there are so many subjects to cover. I agree it probably isn't worth the trouble, but if you are set on doing it, looks like you have what you need!

The other alternative if you want it to look stock is to modify the old cannister for a spin-on adapter. We talked about this awhile back but never really engineered one that met everyones expectations. It would sure be nice not to have two filters to manage.

Matt,

Good on ya. I know searching thru these forums is a long-haul. Some of the guys are pretty good at it (you included). If we can get Zuckerburg to give us a grant, maybe he can send someone to organize it all.