261 Head Removal Suggestions

[JSMvintage]

Hi all. Have a 1950 Chevy 3100 that was upgraded to a 261 engine and 848 head, but currently is not running. Diagnostics indicates the need for a valve job. Any suggestions that may be unique to the 261/848 that I should be aware of before taking this beast apart ? Chapter 3 of Deve's In-Line 6 book covers details of the head restore but not really removal from the block, so assuming nothing special to take note of.... but better to ask before than figure out how to fix something after the fact.

Thanks..

[Deve]

I would just keep the head gasket in tact so you can compare the new one to the old one. Always a good idea. Also, there may be a special bolt with a hole in the center that should go back in the place it was taken out of. The bolt would be the one nearest the brass loop in the center of the rocker train.

[JSMvintage]

Thanks. I'm taking lots of pictures of the break-down, I might post in case it helps someone else. Is it best to simply make a post with a dozen pictures and text, or have like a .doc with all included as a single file ?

So I'm thinking about adapting to the spin-on oil filter as per the book, but I'm a little confused over the need to change the plumbing in and out of the block to the new filter. I know the book was focused on a 235, it is possible that for the 261 that the existing plumbing would be OK with this conversion or are there other factors to consider.

Also, near as I can research, the 4 "steam holes" in the head should already be in this 848 head, correct... I think these additions are primarily for the 235 but can't get a clear understanding on this one.

Hopefully off to the machine shop today and back in business sometime next week.... we'll see.

Thanks for the help.

Joe

[JSMvintage]

So the center bolt, #2 according the Chevy's bolt pattern, is one of the long bolts and the #2 did not have a hole. The weep tube I guess it is, does have a direct connection into the head for oiling... so I'm assuming this is normal. As someone in the past did a rework on the engine though, if they screwed up and didn't put the right bolt back, would be good to know.

[JSMvintage]

So would like some advice, second viewpoint on the head and block after pulling the head. \

You can see from the pictures that the head definitely needs to be reworked, but the block is also a concern here. I was told by the previous owner that the truck had been left for a year a more and not run or even turned over... it seems there is some clogging around all the water ports/holes. Will do come patient cleaning around these to make sure to pulled clogging out rather than dropping into the block; and then do a full circulation cleaning fluid (any suggestions on brand/scheme would be appreciated... I plan on using Prestone radiator cleaner and run it for a short while before complete refresh and refill). Interestingly, when draining the antifreeze from the radiator and block it was mostly clean and see-thru green; however 99% came from the radiator and only a small amount from the actual block, which I thought was strange.

There are two (left and right) maybe 3/4 to 1 inch solid circles with what seems to be a thin brass ring around them... not sure their purpose but it looks sort of like a gunk collector... cleaned up nicely though.

Top of the pistons clean off nicely, and the cylinder walls are smooth and un-scored... so I think they are fine.

The head will be fully checked and redone, new valve seats, valves, etc. so should be no worries there. A couple of values don't look like they are seated though, which likely is why I got poor compression on the last two cylinders and decent but low leak results on the others. Redo job hopefully fixes all that.

[Deve]

What year 261?

[JSMvintage]

Sorry... I thought I had posted it. The engine and head decode as being from 1960. Unsure about the carb as someone rebuilt it and didn't replace the brass tag (although that isn't related to the head as such).

My machinist noticed a varnish type smell when I took the head in, which he thinks is why Intake #5 & 6 are somewhat stuck and not sealing correctly, we'll see after he takes it apart.

I did notice that one of my pushrods seems to be a replacement. It is mostly clean compared to the other 11 rods, but in particular I noticed that the ball side towards the lifter was solid and did not have the small hole in it like the others. I recall from your book that the hole is there to help with oiling and lubrication, so my question now is, has this idea been updated with better quality materials for the rods and so the holes are no long needed or made that way. We are ordering 6 rods (min order), but not sure if they'll be solid ends or with holes... so be good to know beforehand in case I need to keep searching for the correct rods (hopefully they'll be ok for $20/ea).

[Deve]

The hollow bolt may not be necessary for that engine. Always prime the oil pump after the rebuild to make sure there is oil getting to the rockers. To understand the oiling on that engine, read this article carefully:

http://devestechnet.com/Home/TheVenerable261

That will help you understand why the larger lines are needed. That is a solid lifter engine so the lifters all need to be the same height and so must the rods. You can put hydraulic lifters in that engine without problems but you have to decide which. The 848 head was never on the 261. The 261 came with an 850 head. If you have an 848 it has to have those holes drilled in it per that article. If the engine had the 848 head when you got it, chances are they are already drilled, but good idea to check.

[Carryall '51]

Deve, I have read and re-read information from the "Vernerable 261" article. Within a week or two, I will be taking my 235 head into my machinist to have the holes drilled and the valve line re-worked. I have a question concerning the steam hole cuts. Is the 12 degrees cut off of vertical or horizontal and is there any other info that might assist them? All the information you can give me will be immeasurable to the machinist that will be doing the work. I bow to your superior knowledge of all things Stovebolt.

[JSMvintage]

Thanks. Regarding the steam holes, the previous head pictures seem to show that 3 pairs of holes in these locations are indeed already there. But that suggests I actually need a 850 head gasket then, instead of the 848 I just ordered.... or the associated holes will be missing in the gasket, right ?

[Carryall '51]

JSM check your gasket as it arrives make sure the "steam holes" are in the gasket, if they are not I am afraid you have the wrong one & will suffer overheating in your head. A 235 head had been installed on my 261 block, my head had burnt valves, I suspect from not being drilled and the head gasket did not have the steam holes, we saw this after we pulled the head off. We suspect, the head not being drilled and the 235 head gasket not allowing the extra flow of coolant thru the head, was the cause of the failure.

[Deve]

I am not sure, it's been a long time if the holes are affected by the new gasket, but I DO know that I used an 848 gasket and do not remember there being a problem with it.

[Pre68Dave]

One must use a 261 head gasket no matter what head on a 261. Because of the bigger bore, a 235 gasket will not work/seal around the bore. All 261 gaskets will have the steam holes.

[Carryall '51]

I too Have a 848 head on a 261, after the tear down we noticed the "steam holes" were not cut into the 848 head. With the holes not cut we assumed that's why the vales were burnt. Can Anyone forward more details of this procedure to cut the holes...I would like my engine guy to have more info than he needs. I do know it needs to be cut 12 degrees from the port side. Is that 12 degrees off of vertical or horizonal? A HUGE difference, I ask these things because I am a newby to this stuff. My engine is a '54 and the head is a '56 (best we could tell on the head from the casting number.)

[JSMvintage]

Hi Carryall '51. So Deve's 261 book (Chevy Inline-6 Engine, a great resource) points to an article on the site "TheVenerable261" (http://devestechnet.com/Home/TheVenerable261) which has some info and some additional references. I recall a direct reference to details of drilling the steam holes, but unable to put my hands on it at the moment. Search the site, and for sure buy the book... its in one of the 2.

[Carryall '51]

Thanx JSMvintage, I have read the article you are referring to, I appreciate your response but it seems that article has "Limited Info" on preforming the procedure. I hoping others like yourself might enlighten me with that additional knowledge.

[Deve]

Dave will correct me if I am wrong... again.. thanks Dave, but I think the 850 is the only head the 261 came with? At least the 58-62 models? Anyhow, my machine shop always gives me the gasket set along with all the rebuild parts, so thanks Dave for clearing that up. You need a 261 head gasket because of the larger cylinders.

[Pre68Dave]

To my knowledge the only 848 head used on a 261 was the Canadian model.