261 Canadian Pontiac with 848 heads

loosenut · Veteran Member

261 Canadian Pontiac with 848 heads

long stroke · Canadian Poncho Superstar!

What i understand is that these heads only came on 235 motors. People have used these heads on 261's because of the slightly higher compression. Of course the steam hole situation can always be a serious factor in these 261's because of over heating with the 235 head, unless the steam holes are put in the 235 head.

loosenut · Veteran Member

That was my understanding as well but I thought it odd that all three that I have had have this head. All three of my heads have the "steam holes". One of the engines appeared to be a relatively fresh rebuild but due to not using the "head bolt with a hole" the rocker assembly had no oil and consequently failed. Does your 57 have the 848 head? Thank you for your input.

long stroke · Canadian Poncho Superstar!

Loosenut, thank you for getting my brain working. Here is what i know, all (Canadian) built (Oshawa) 261 in line six cylinder motors had the 848 casting numbers and of course they all had the steam holes because the 261 block had the steam holes. The confusion lies in the fact that the (American) 235 Chevrolet from 1954 to 1962 had the 848 head but it was an (American) casting and it did not have any steam holes in the head because obviously the 235 block did not have any steam holes. Ok, now what i learned is that the (American) 261 in line six had a very different cylinder head casting number it was a 850 casting number (the last three numbers). All these U.S.A. built 261's were for large Chevrolet trucks and they were slightly different than the Canadian 261's. U.S. built 261's had a real full flow oil filter as of 1958 and all the truck blocks had mechanical lifters. Our (Canadian) Pontiac 261's had no oil filters unless you ordered the useless by pass oil filters and all our motors were non solid lifter. 848 on a (Canadian) 261 was standard issue cylinder head with steam holes. 850 on a (American) issue truck 261 was standard issue, both having steam holes in the head and block. Now my question is what was the cylinder head number for a (Canadian) 235 in liner? I could not find this information. Why GM felt the need to confuse people with the same casting number for two very different heads, is any ones guess. Hope this helps you out. Cheers. George

loosenut · Veteran Member

Thank you George for the information. I have never heard about the two different 848 heads but am not surprised that all Canadian 261's had a 848 head. I am guessing it was an attempt to increase compression bur who knows. I mentioned earlier in this post about the "head bolt with the hole". Are you familiar with this, do you know if your engine has it and if so what is your understanding of why it is used?John PS I have no idea what the casting no. is for a Canadian 235. I have a friend who has a couple but do not know if US or Can. Will try to find out.

long stroke · Canadian Poncho Superstar!

Loosenut, you have to remind me about what year car and what year motor(s) you have. My 261 does not have the center bolt with the holes to allow oil flow to the rocker shafts. These special bolts were only used if you were useing 1958 and earlier rockers on a 1959 to 1962 block. With the change in 1959 all the rocker shaft oil supply tubes were pinched. This would be the (American) connection with 235/261 motors. I honestly do not know about the (Canadian) connection to these special (oil) through bolts. Tell us more about the 261 motors you have and what Canadian Pontiac you have one of these engines in. What i understand for sure is this, if you have a head with an (oil) through bolt then there is a reason for it. Putting in a regular bolt would kill the top end oiling in a real hurry. I will update if i learn anything else in this regard. Cheers. George

-- Edited by long stroke on Friday 11th of September 2015 10:54:04 PM

loosenut · Veteran Member

Hi: I have two complete 261's, one 58, one 59, (Canadian Pontiac) I have most of another engine but not the block (apparently it was bad and ditched before I arrived on the seen. All three have 848 heads and I believe all have the pinched off oil oil supply tube (going on bad memory). None of these engines are in a car but I have one in a stand (just fired it up couple weeks ago). This engine had the pinched off oil supply line to the rockers but no hole on the head bolt. It also had a toasted rocker arm assembly. It had been sitting for over 30 years when I acquired it. I took it apart and checked the bottom end. It looked real good and the bearing tolerances appeared good. I think it had been rebuilt and somehow oil system failed to get oil up top, hence the bad rocker arm assembly. Don't know if original head or not. It had been bored out +30. I cleaned it up and replaced the pistons, rings, new camshaft and bearings, I replaced the hydrolic lifters with solids as well.I had another head with a really nice rocker arm assembly so I did the valves seats (new valves). I went to my local machinist and had a head bolt drilled and assembled it. I also changed it to a full flow system. I installed a old set of Fenton split exhaust manifolds and a circ 1955 Nicson two X 1 intake manifold. I put a pair if matched Stromberg BXOV carbs on it. It has new points and condenser in original distributor, used starter on it. I have it on an engine stand so when a friend dropped in one day he asked "how soon to running". I said " let try it. We put gas in it and it fired on about the second turn. Was ideling in a few seconds. It has as yet no H2O in the system so have only run for few seconds each time but sounds like it is good. This is a project I started a year or so ago just because I wanted to build up an engine on my own. I really enjoyed this project and think I learned a bit along the way. Have a leaky H2O pump so not running it much until I get that sorted out.
Don't know where I go from here weither I will buy something to put it in or just sell it sometime. It is one of those "not the destination but rather the trip" sort of things.
I will check with my friend to see if his engines are Can. or US. If Can. I will get the head ser. #. George I really appreciate your input. John

loosenut · Veteran Member

I checked with my friend and they are both US engines with the 848 head. John

long stroke · Canadian Poncho Superstar!

loosenut wrote:
I checked with my friend and they are both US engines with the 848 head. John

Then that would make them both 235 motors and not 261's, if they were American castings with the 848 head. All american 261 motors had the 850 head, not the 848 head. There is some confusion here. Maybe the best thing to do here is to check the engine block casting numbers as well. Some one in the past might have mixed and matched some engine parts here. Cheers. George

drae_man · Veteran Member

my 261 has an 848 head also. Doubt it's ever been apart. it's in a 1962 canadian pontiac.
I also had marginal oil going to the rear set of rocker arms, I didn't do much about it except clean out the crud out, and die grind oil passages on the bottom side of the shaft, to ensure a path for oil.
works MUCH better now.
Cheers

loosenut · Veteran Member

Thanks for the input drae man.
George My friends engins are 235's. I was checking them in case they were Canadian 235's and I would get the head serial# but to no avail.

long stroke · Canadian Poncho Superstar!

drae_man wrote:
my 261 has an 848 head also. Doubt it's ever been apart. it's in a 1962 canadian pontiac.
I also had marginal oil going to the rear set of rocker arms, I didn't do much about it except clean out the crud out, and die grind oil passages on the bottom side of the shaft, to ensure a path for oil.
works MUCH better now.
Cheers

Wesley, this 848 (Canadian) casting would be correct for your Canadian 261. Could you please explain the grinding of oil passages on the bottom of your rocker shafts. I find this very interesting and would love to be informed on the matter. Cheers. George

long stroke · Canadian Poncho Superstar!

loosenut wrote:
Thanks for the input drae man.
George My friends engins are 235's. I was checking them in case they were Canadian 235's and I would get the head serial# but to no avail.

Loosenut, these would then be motors that do not have steam holes in the block or heads. They are completely different than 261 motor's, Canadian or American 261 motors have very little in common with 235 motors that were Chevrolet issue. 235 and 261 motors may look alike from the outside but there are many differences internally and even some parts externally. The 261 is a far superior motor to the 235 and i say this loving 235 engines in general. Cheers. George

loosenut · Veteran Member

Thanks George; I learnt some good stuff from your input. Thanks again, John

long stroke · Canadian Poncho Superstar!

loosenut wrote:
Thanks George; I learnt some good stuff from your input. Thanks again, John

Glad to help in any way and good luck with your motors and what ever vintage vehicles you put them in. Cheers. George

drae_man · Veteran Member

long stroke wrote:
drae_man wrote:
my 261 has an 848 head also. Doubt it's ever been apart. it's in a 1962 canadian pontiac.
I also had marginal oil going to the rear set of rocker arms, I didn't do much about it except clean out the crud out, and die grind oil passages on the bottom side of the shaft, to ensure a path for oil.
works MUCH better now.
Cheers
Wesley, this 848 (Canadian) casting would be correct for your Canadian 261. Could you please explain the grinding of oil passages on the bottom of your rocker shafts. I find this very interesting and would love to be informed on the matter. Cheers. George

Hi George, the shaft closest to the firewall was worn more than the front, the rockers had worn past the normal "flat" ground on the shaft. there was grooves etc. Instead of sleeving the rockers etc I cut a score leading from the oil supply hole, outwards in either direction, longitudinally.

The problem with leaving it worn like that was the oil was not going to travel up around the top of the rocker and out the top hole. this score I made was on the bottom of the shaft.... I can't believe I didn't take a picture.

long stroke · Canadian Poncho Superstar!

drae_man wrote:
long stroke wrote:
drae_man wrote:
my 261 has an 848 head also. Doubt it's ever been apart. it's in a 1962 canadian pontiac.
I also had marginal oil going to the rear set of rocker arms, I didn't do much about it except clean out the crud out, and die grind oil passages on the bottom side of the shaft, to ensure a path for oil.
works MUCH better now.
Cheers
Wesley, this 848 (Canadian) casting would be correct for your Canadian 261. Could you please explain the grinding of oil passages on the bottom of your rocker shafts. I find this very interesting and would love to be informed on the matter. Cheers. George
Hi George, the shaft closest to the firewall was worn more than the front, the rockers had worn past the normal "flat" ground on the shaft. there was grooves etc. Instead of sleeving the rockers etc I cut a score leading from the oil supply hole, outwards in either direction, longitudinally.
The problem with leaving it worn like that was the oil was not going to travel up around the top of the rocker and out the top hole. this score I made was on the bottom of the shaft.... I can't believe I didn't take a picture.

Wes, i hate to tell you this brother but that is not going to cut it. With all due respect, that is not going to fix the problem right. You are going to have to sleeve (all) of the rockers or try to find rockers in much better condition than the ones you have now. While you are at it, try to find healthier rocker shafts as well. I know for a fact that you are going to have issues down the road if you plan on putting any kind of mileage on that motor. If your car is going to be a trailer queen or a dust collector in the garage, then it does not matter. If you plan on putting some real miles on that motor, then you have to do it right. Cheers. George

drae_man · Veteran Member

Agreed, I wouldn't expect it to last forever. Once the dollar improves, if it does, I can get a set from the other side of the continent for $300 + but at the moment that's not in the budget. I appreciate the comments.