The Stovebolt Site Forums The Shop Area Engine Shop 261 oiling to rockers

Some back ground information, according to the manufacture date on my 261 that I’m installing in my 1950 1 Ton it’s April 19 1955 and the head is a 848 head manufactured on May 5 1958 (see photos)

I had them hone the cylinders and install new block and cam bearings and the head was rebuilt with new guides, seal and resurfaced, they also did hot tank cleaning, magnafuxing (no cracks anywhere) decked the block top and bottom and shaved the head.
I’m very happy with the rebuild so far!
I’ve checked multiple sites, some that have great information and some not so much! I’m sure most on here know which is which!!!!!!
Can someone confirm for me that this is or is not a full pressure oil 261 or a bypass one? In one of the photos there is a screw on the exhaust/intake side beside the frost plug above the oil filter lines that I’m very curious if this has anything to do with my issue.
After installing the rocker assembly then using a drill to spin the oil pump I couldn’t get any oil to drip out of the rockers,( yes I did confirm the holes on the shaft are facing down). I also discovered that the engine needs to also be turning over so that the oil bypasses the solid lifters ( and yes they are the ones with the annulus indent).
I still couldn’t get oil up to the rockers so I pinched off around half way give or take the clear line (see the photo I used it just to have a visual that oil was flowing where the filter was going to be added).
I thinking that this oil filter line will need a restriction fitting installed which would mean it’s a bypass filtered oil right? I have to check the old lines but i don’t think there was any restriction in them.

Any help with identifying or clarifying or thoughts on this would be appreciated.

With that clear line connected, you're running oil right back into the oil pan, and putting little, or no oil into the passages to the crankshaft and elsewhere. Remove that line completely and plug the holes where it was attached. You have a "bypass" engine, since there are no big (1/2" NPT) ports that would identify a "full flow" engine. Even the later (1959-63) 261's would have probably been set up for bypass filtering unless the big dowel pin on the driver's side of the block was pushed in. If you choose to use a bypass oil filter (not necessary- - - -lots of engines had no filter at all) the restriction that controls oil flow through the filter element is built into the canister.
Jerry

Did you put the hollow head bolt back in the right place? If not, you'll never get oil up to the rockers. That has nothing to do with the filter connections.

Nothing to do with oiling, but has that 6848 head been drilled for the "steam holes" on a 261? Originally it would have a 6850 head.
(Just being nosey.)

You might need an oil line under the side cover .

Thanks Jerry, a bypass engine perfect explanation that’s what we deduced with me pinching off the clear line but still had me pondering exactly what engine I had, the clear line was never going to be permanent only for observation of flow seeing there was no dowel pin on this block.
When I got this engine from the scrap yard it did have an canister filter on but there were no obvious restrictions on the fittings or oil lines other than the small hole in the drain pipe inside, which makes me wonder why the rocker shafts were badly worn so I replaced them with the 216 shafts that showed no wear.
I do agree that it’s not necessary to have a filter and that’s probably the way I’ll go. I may just put it on for looks but plug it so it will have good flow to the rockers. Not like this truck will be worked very hard other than ice cream runs and shows.

848 head has the “steam holes” and the oil line was cleaned and reinstalled!

Oil does flow to the head without the head bolt with the hole in it as soon as I pinched the line off.
Fox Johnson a fellow bolter pulled a head bolt on his 57 261 and discovered a grove was cut in the threads as opposed to the hole being drilled, now that was definitely interesting but I’m thinking that could compromise the correct torquing of the head.
Thanks for the input everyone.

So a couple of things to check here. First, as Kevinski noted, the 55 block will have the steel line behind the lifter cover. Confirm your line is actually in place.

Second, and this is a little more complicated, 55-57 used a fitting at the steel tube with a 1/16 hole that feed the rockers. For 58, which fed the rockers from a main port, the block was drilled with a 1/16 feed hole. The 55-58 motors used rocker arms where the feed groove inside each arm intersected with the dribble hole of the arm.

In 59, GM made the last oiling change to these motors. Direct feed from the main galley, but the feed restriction was increased to 11/32. This created a sort of pressurized system. So to make sure the oil dribbled, the 59 and up rocker arms had the groove off set from the dribble hole. So with a 55 block, you will want to confirm you are using rockers with the early style intersecting groove. If you have the offset groove rockers, that may be part of your issue.

Lots of confusion on the "drilled bolt." So lets say you have a 56 truck and in 1961 discover that you need a new motor. You head down to the chevy dealer and order a fitted block. These replacement blocks were of the later 59 and up style motor with cast motor mounts to accommodate the mounting arrangements for the various years. The problem was that you could not just bolt on the 56 head and rocker arm assembly on to the 59-62 style block without getting too much oil to the rockers. So those fitted blocks came with a cap and a head bolt that was drilled through the center. When using the 55-58 head and rockers, you installed the cap in the block and blocked off the 59-62 style feed, and installed the drilled head bolt which was an alternate path for the oil to the rockers and had the correct restriction for the early style rockers. If you were using the fitted block with the later 59 and up head and rockers, you discarded the plug and bolt.

Hi Mike
Thanks for the further information.
As confirmed by my photo the steel line is installed!
The rockers are the early version with the grove in the centre not offset!
This engine cam out of a 56 GM truck that was supposed to have belonged to a old school mechanic so I don’t know if when he installed the 848 head if he didn’t know about the oil issues and just didn’t install the bolt with the hole drilled.

One of our own ‘bolters “Pre ‘68 Dave” is an expert on these Stovebolt engines and has a website that show the differences in the rockers and oil supply thru the years these engines were made.

Here is a link.

The steel line under the pushrod cover gets its oil from the rear camshaft bearing. It's not uncommon for that passageway to get sludged up and restrict, or stop oil flow to the rocker shaft altogether. Later model engines had a drilled passage in the block instead of the external line. One of the specialty tool makers (Lisle, maybe?) used to sell a wooden dowel that was a snug fit into the center head bolt hole. Remove the bolt, fill the hole with motor oil, insert the tool, and smack it HARD with a BFH. The hydraulic pressure would blow the crud out of the passages and reestablish oil flow to the rockers. I used a whittled-down piece of a broom stick to do the same thing- - - - -yep, I'm a cheapskate!
Jerry

He would not have to install the drilled bolt and cap if it was a 56 block. 56 was the first year for the 848 head so no drilled bolt necessary. You use that bolt and cap when installing a 59 and newer blocks and reinstalling the 54-58 head and rockers.

Its all about the rockers.

I’ll give it a try like Jerry mentioned for the bypass filter, block it off to the filter and confirm adequate oil to the rockers.

After removing the clear line and blocking the outlet fitting at the block with a plug the oil pressure went from just over 20 psi to over 50 and the flow to the head has increased significantly.
Thanks for the great advice.

"I love it when a plan comes together!" Does the oil pan on your engine have a straight passenger's side rail, or is there a slight offset in line with the distributor/oil pump area? That dogleg is there to clear a larger diameter oil pump housing on the 56-63 engine block. The bigger pump is a Melling M45 or the equivalent OEM part. 54 and early 55 235 and 261 engines run a Melling M29 with slightly smaller diameter gears and less volume output. With a little creative plumbing of inlet and outlet lines, the M29 pump can also be fitted to 216 engines. It's got a higher volume than the 216 pump.
Jerry

Yes it has the offset dog leg pan.
I will be starting off by using 30w conventional oil that I added about 25% Lucas oil stabilizer to for initial startup and break in. Then I’ll switch to Rottella 15/40 T4 conventional oil, I’m thinking that worked for me in the past with the 216 and for my diesel pickups as well as the Peterbuits I drove.

I am in the "drawing board" stages of a project to run Torrington roller bearings in stovebolt rocker arms, with full floating rocker shafts that don't wear on the bottom only. "Worn out" rocker shafts will be ground to a smaller diameter to match the ID of the needle bearing with a tool post grinder, and will be set up to rotate in the rocker shaft standoffs to equalize the wear all the way around the shaft.
Jerry

When I got a 48 pickup with a 55.2 235 in it, the rocker feed line from the rear cam bearing was plugged with sludge. There was an oil line Teed off the oil filter supply and run over top of the head to the pipe fitting in the middle of the head. Apparently, whoever did this didn't do it soon enough as the rockers and shafts were shot and noisy but they got lots of oil.

When assembling my 62 261 block with the 848 head of unknown year, I used the oil line under the side cover AND the drilled bolt. The block had the plugs in it. The oil line was was probably unnecessary but I found the instructions after assembly. So I have non-offset rockers and they don't get as much oil as with the earlier 235 block and the same head. But they get enough oil. Previously, the top end was more or less flooded with oil but that didn't seem to cause any oil consumption. Probably tended to heat up the oil though.