The Stovebolt Site Forums The Shop Area Engine Shop 261 Head removal and feedback

Hi all, I'm still fairly new to the forum and hopefully will be able to eventually post some helps for some other newbies. Right now I am in the middle of a 1960 Chevy 261 engine revamp, redoing the heads due to low compression and leakage results. Below are some observations and questions I put to the forum for any insights and/or opinions as to my working assumptions... feel free to comment please. I could not find a thread that specifically addressed the 261 dismantling, but please redirect me if there is one.

So would like some advice, second viewpoint on the head and block after pulling the head. Hopefully the picture uploads will work... or else the rest of the post will be mostly meaningless :-). I'm mechanically inclined but not a mechanic by trade, a hobby mostly for getting old rides running, so all help and suggestions appreciated.

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 some patient cleaning around these to make sure to pull clogging out rather than dropping into the block; and then do a full circulation cleaning fluid once reassembled (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. Be interested in knowing exactly what these are for as I haven't seen them mentioned in searching.

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 near zero compression on the last two cylinders and decent but low leak results on the others.  Redo job hopefully fixes all that.

Thanks for your time folks... Joe

I can't tell from your photos, but it seems like you've got a couple of bent intake valves. That's not uncommon for a stovebolt engine that sits for some time without being turned over regularly. The valves that are open when the engine stops stick in their guides, and the pistons hit them when the engine is spun over with the starter to do a compression test. ALWAYS turn a stored engine by hand after checking all the valves for free movement before using the starter the first time. A valve job and a new head gasket will probably get you back in business.
Jerry

The brass is part of the head gasket. That is a composit head gasket. Originals were copper clad so someone has been in that motor before you. On the subject of valve guides for your head redo, there is a difference of opinion on this topic. Quite a few years ago I was having original valve guides removed and replaced with stock type new cast Iron guides. They have to be essentially pounded out and pounded in. The head that this process was being performed on cracked during the process and I turned a perfectly good 848 235 head into an instant boat anchor.

So I no longer replace them unless absolutly necessary. Instead, the stock guides get drilled out and bronze liners are installed. From there, a good machinist can dial in the correct clearance between the valve stem and the guide. This is important (even more so if you are going to use stock style guides) because if the clearance is too tight, you run the risk of overheating the guide and the valve stem and they sieze up. I believe the bronze is easier on the valve stems, helps with the lubricity better then cast iron, and is more forgiving if the clearance is not 100% spot on. On the other hand, too loose and you are drawing oil down the valve and smoking out the tail pipe. I also think the bronze guides are easier to replace and easier to service.

Valve seals are another area to discuss with your machinest. The stock type seals are these crappy O rings that get installed on the valves. They lasted about an hour back in the day, with todays rubber, they last about 10 minutes. There are two alternatives. The first is to use what is known as an umbrella seal that goeves over the guide. They work pretty good. But if you have a machinest that is decent, you can also machine the top of each valve guide to install a more modern teflon seal, or what you may hear referred to as a PC seal (PC stands for Perfect Circle who I think developed these types of seals). These work really well. The one caviat, you machinest has to be sure the seal is not over efficient. The valve stems need some lubricant.

If you are having trouble finding springs or retainers, no worries. Its the seat pressure that is the important factor. So if you can't locate proper 261 springs, your machinest can use springs from another application, even if a larger diameter spring, by simply enlarging the seat in the head. I dont know that this will be an issue as there always seems to be decent GM offerings on eBay. One piece of advice I will give you is do not buy springs from anyone, including ebay, if those springs have any corrosion on them. Its not worth the risk of having a failure, particularily on the intake side as a spring failure will result in a dropped intake valve that the piston will then hit and bend and you are back to square one.

\Look for GM springs with the paint completely intact. Different years took different spring pressures, and there are differences between 235 and 261 motors also even though they look identical, so be particular and get the correct springs for your 261 (i.e., find the correct part number for your application).

Just my own two cents and opinion.

JSMvintage Do more than a flush, while the head is off dig the 60 years of gunk out of your block. Screwdriver and a hammer thru any coolant holes especially to the rear of the block. Had one once with intakes bent from timing gear failure,just a beater wouldn't start like it should,so just ground the valves till they cleaned-up. Went ahead and put it all back start run ride and drive for a long time then. In your case get new valves if bent,as I said mine was just a beater !!

Get a stiff wire and push it into the block water drain to clean out. Often get filled up with dirt, etc., and will not drain.

Ed

A hammer and screwdriver around the cylinder walls is asking for trouble.
You don't know how thin the walls are (years of rusting) and you may crack them.

I had a 235 that was seriously blocked. No water out of the rear drain plug.
I could not get the area behind the plug clean enough for coolant to flow.
I'm sure that some of it was radiator stop-leak.
Had to remove the freeze plugs, water pump and drain plug(s) to get access.
Did the best I could with solid wires and long skinny screwdriver to clean the layers of crud from every opening I could find.
This worked good enough to get the coolant flowing again. Put everything back together with new head gasket.
Then did an engine flush with vinegar (or a store bought engine flush) until the water looked clean.
Final flush with water only.

Whatever was in the engine was also in the radiator. Took the radiator to the radiator shop for a boil.

The best solution would have been to pull the block and have it boiled-out at a rebuild shop.

Thanks for the tip. As for freeze plugs, I haven't seen any so far, or didn't recognize them. What are they near and how many are there.

Regarding the radiator, it flowed like a gusher are was very clean... so think the biggest issue is the antifreeze in block sat for so long in an already degraded state that now its gotten "globy". I'll yank the freeze plugs though and run some wire through as you suggest, along with removing the pepcock drain.

Thanks

Not sure about the 261, but the 216 has a couple casting plugs (aka freeze plugs) on the left side of the engine, and also one on the front and the back of the block. The rear one will be covered by the bell housing, and the front one may be covered by the water pump.
Here's a pic of the rear one (complete with sludge deposits.)

thanks all for the quick Feedback, this group is great.

A followup question.

I noticed 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 reading 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 longer needed or made that way.

Can you post a photo of your pushrods? None of the 235 or 261 had a hole in them. Some may have had an indentation, others a small groove. If you have a bent vavle like HRL seems to see in your photos, they you likely have a bent push rod. So check your push rods for that. Aftermarket push rods are avaiable and are better and stronger then the original push rods.

Suggestion. Send a picture of the pushrod ends and line all the them up together to compare their length.
Roll a pushrod on a flat surface to quickly check for bent ones.

Attached is a picture of the water jacket access points that I was talking about.
Freeze plugs can be removed by drilling a hole in the middle and using a screwdriver to twist them out.
It may be difficult for you to do this step so save it for last resorts.

Being that #5 & 6 intake valve are open some it highly probable.

That gunk is very likely radiator stop-leak added at some point, or several points in this truck's life to buy a few hundred more miles out of an expensive at the time radiator. Very common for these old farm relics.

BTW... here are the two types of push rod ends.

first is what 11 of the 12 look like. Second is a single, newer looking, rod.

Question is basically if the recessed hole version is required, or really a don't care as this stage of materials ?

So regarding the freeze plugs... I see them now, they are huge compared to what I'm used to. If it comes to it where I need to remove them, where do I get replacements ? I've done quite a bit of searching and so far haven't come up with a source.

Your FLAPS should have a selection of freeze plugs. I needed to have them order a couple for my engine that they didn't have on stock. They may have the size stamped on them if it's still readable.

I sold the truck but I replaced the rocker assembly and pushrods on a 235.
They were worn so badly it was difficult to adjust the gap accurately.
The new pushrods looked like the one you have without the indention or hole.
The rod's shaft diameter was slightly larger. It looked heftier.
No problems with working on solid lifters.

If you're working with the engine in the frame, new freeze plugs cam be very difficult to install. Try substituting rubber expansion plugs for the drive-in type.
Jerry

Yeah that one in the rear of the block covered by the bell housing would be especially tough. Kinda hard to put a rubber expansion plug in there too.

JSMvintage Listen to buoymaker,don't have to get too rough with hammer and screwdriver,just get the gunk out most suffer from stop leak.My 216 has a crack by the drain cock from sludge keeping the antifreeze away (maybe) keep it going by topping off with 50% antifreeze solution when needed.Shimmed the rods in 82 is still raring to go !!

JSMvintage You might want to use brass core plugs for better life on hard to change ones.

A lot of advice seems to be on here to do it halfways and just get something new when it fails, not sure why that is. They aren't making more of them, so I agree with you, do it the gentle way and save the engine and yourself a lot of headache.